Friday, 24 September 2021 08:39

OVERVIEW GRADE 12 NOTES - PHYSICAL SCIENCE PAPER 2: CHEMISTRY STUDY GUIDES

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Colour Diagrams: Acid-base Indicators*

color diagrams kghjs

Overview

Dear Grade 12 learner

This Mind the Gap study guide helps you to prepare for the end-of-year CAPS Grade 12 exam.
The study guide does NOT cover the entire curriculum, but it does focus on core content of each knowledge area and points out where you can earn easy marks.
You must work your way through this study guide to improve your understanding, identify your areas of weakness and correct your own mistakes.
To ensure a good pass, you should also cover the remaining sections of the curriculum using other textbooks and your class notes.

Overview of the Grade 12 exam
The following topics make up each of the TWO exam papers that you write at the end of the year:

Cognitive level

Description

Paper 2
(Chemistry)

1

Remembering/Recall

15%

2

Understanding/Comprehension

40%

3

Applying and analysing

35%

4

Evaluating and creating (synthesis)

10%

Paper Type of questions Duration  Total  Date  Marking 

Chemistry 

  • 10 multiple-choice questions – 20 marks
  • Structured questions – 130 marks 
3 hours 150 October/November External
Paper 2: Chemistry Focus        
Content Marks Total  Duration  Weighting of cognitive levels 
Chemical change 84 150 marks 3 hours 15 40 35 10

How to use this study guide

This study guide covers selected parts of the different topics of the CAPS Grade 12 curriculum in the order they are usually taught during the year. The selected parts of each topic are presented in the following way:

  • An explanation of terms and concepts;
  • Worked examples to explain and demonstrate;
  • Activities with questions for you to answer; and
  • Answers for you to use to check your own work.

The activities are based on exam-type questions. Cover the answers provided and do each activity on your own. Then check your answers. Reward yourself for things you get right. If you get any incorrect answers, make sure you understand where you went wrong before moving on to the next section. In these introduction pages, we will go through the mathematics that you need to know, in particular, algebra and graphs. These are crucial skills that you will need for any subject that makes use of mathematics. Make sure you understand these pages before you go any further. Go to www.elimuza.com to download past exam papers for you to practice.

Top 10 study tips

  1. Have all your materials ready before you begin studying – pencils, pens, highlighters, paper, etc. 
  2. Be positive. Make sure your brain holds on to the information you are learning by reminding yourself how important it is to remember the work and get the marks.
  3. Take a walk outside. A change of scenery will stimulate your learning. You’ll be surprised at how much more you take in after being outside in the fresh air.
  4. Break up your learning sections into manageable parts. Trying to learn too much at one time will only result in a tired, unfocused and anxious brain.
  5. Keep your study sessions short but effective and reward yourself with short, constructive breaks.
  6. Teach your concepts to anyone who will listen. It might feel strange at first, but it is definitely worth reading your revision notes aloud.
  7. Your brain learns well with colours and pictures. Try to use them whenever you can.
  8. Be confident with the learning areas you know well and focus your brain energy on the sections that you find more difficult to take in.
  9. Repetition is the key to retaining information you have to learn. Keep going – don’t give up!
  10. Sleeping at least 8 hours every night, eating properly and drinking plenty of water are all important things you need to do for your brain. Studying for exams is like strenuous exercise, so you must be physically prepared.

Mnemonics

A mnemonic code is a useful technique for learning information that is difficult to remember. Here’s the most useful mnemonic for Mathematics, Mathematical Literacy, and Physical Science:
BODMAS:

B– Brackets
O– Of or Orders: powers, roots, etc.
D– Division 
M– Multiplication
A– Addition
S– Subtraction

Throughout the book you will be given other mnemonics to help you remember information. The more creative you are and the more you link your ‘codes’ to familiar things, the more helpful your mnemonics will be.

Mind maps

There are several mind maps included in the Mind the Gaps guides, summarising some of the sections.
mind maps ajhbjh
Mind maps work because they show information that we have to learn in the same way that our brains ‘see’ information. As you study the mind maps in the guide, add pictures to each of the branches to help you remember the content. You can make your own mind maps as you finish each section.
How to make your own mind maps:

  • Turn your paper sideways so your brain has space to spread out in all directions.
  • Decide on a name for your mind map that summarises the information you are going to put on it.
  • Write the name in the middle and draw a circle, bubble or picture around it.
  • Write only key words on your branches, not whole sentences.
  • Keep it short and simple.
  • Each branch should show a different idea.
  • Use a different colour for each idea.
  • Connect the information that belongs together.
  • This will help build your understanding of the learning areas.
  • Have fun adding pictures wherever you can. It does not matter if you can’t draw well.

On the day of the exam

  1. Make sure you have all the necessary stationery for your exam, i.e. pens, pencils, eraser, protractor, compass, calculator (with new batteries). Make sure you bring your ID document and examination admission letter.
  2. Arrive on time, at least one hour before the start of the exam.
  3. Go to the toilet before entering the exam room. You don’t want to waste valuable time going to the toilet during the exam.
  4. Use the 10 minutes reading time to read the instructions carefully. This helps to ‘open’ the information in your brain. Start with the question you think is the easiest to get the flow going.
  5. Break the questions down to make sure you understand what is being asked. If you don’t answer the question properly you won’t get any marks for it. Look for the key words in the question to know how to answer it. Lists of difficult words (vocabulary) is given a bit later on in this introduction.
  6. Try all the questions. Each question has some easy marks in it so make sure that you do all the questions in the exam.
  7. Never panic, even if the question seems difficult at first. It will be linked with something you have covered. Find the connection.
  8. Manage your time properly. Don’t waste time on questions you are unsure of. Move on and come back if time allows. Do the questions that you know the answers for, first.
  9. Write big and bold and clearly. You will get more marks if the marker can read your answer clearly.
  10. Check weighting – how many marks have been allocated for your answer? Take note of the ticks in this study guide as examples of marks allocated. Do not give more or less information than is required.

Question words to help you answer questions

It is important to look for the question words (the words that tell you what to do) to correctly understand what the examiner is asking. Use the words in the table below as a guide when answering questions.

Question word

What is required of you

   

Analyse

Separate, examine and interpret

   

Calculate

This means a numerical answer is required – in general, you should show your working, especially where two or more steps are involved

   

Classify

Group things based on common characteristics

   

Compare

Point out or show both similarities and differences between things, concepts or phenomena

   

Define

Give a clear meaning

   

Describe

State in words (using diagrams where appropriate) the main points of a structure/process/phenomenon/ investigation

   

Determine

To calculate something, or to discover the answer by examining evidence

   

Differentiate

Use differences to qualify categories

   

Discuss

Consider all information and reach a conclusion

   

Explain

Make clear; interpret and spell out

   

Identify

Name the essential characteristics PAY SPECIAL ATTENTION

   

Label

Identify on a diagram or drawing

   

List

Write a list of items, with no additional detail

   

Mention

Refer to relevant points

   

Name

Give the name (proper noun) of something

   

State

Write down information without discussion

   

Suggest

Offer an explanation or a solution

   

Tabulate

Draw a table and indicate the answers as direct pairs

   

Vocabulary

The following vocabulary consists of all the difficult words used in Mind the Gap Mathematics, Mathematical Literacy, and Physical Science. We suggest that you read over the list below a few times and make sure that you understand each term. Tick next to each term once you understand it so you can see easily where the gaps are in your knowledge.

(adj)

adjective: describing word such as “big”

(adv)

adverb: describing word for verbs, such as “fast”

(prep)

preposition: a word describing a position, such as “on”, “at”

(sing)

singular: one of

(pl)

plural: more than one of

(abbr)

abbreviation

General terms

Term

Meaning

A

 
   

abbreviate

(v). Make shorter.

abundant

(adj). Having plenty of something.

accept

(v). Agree to receive something; say yes to; believe; tolerate something.

account for

(v). Explain why.

adjacent

(adj). Next to something.

affect

(v). Make a difference to; touch the feelings of. Do not confuse with effect. See effect.

analyse

(v). Examine something in detail.

ante-

(prep). Before (e.g., ante-natal – before birth)

anti-

(prep). Against (e.g., anti- apartheid – against apartheid).

apparent

(adj). Clearly visible; the way something seems to be or the way it appears.

appear

(v). Come into sight; seem to be.

approximate

(v. & adj.). Come close to (v); roughly, almost, not perfectly accurate, close but not exact. The verb is pronounced “approxi-mayt” and the adjective is pronounced “approxi-mitt”.

aquatic

(adj). Growing or living near or in water.

arbitrary

(adj). Based on random choice; unrestrained and autocratic.

C

 
   

category

(n). Class or group of things.

cause

(v). Make something happen.

cause

(n). The person or thing that makes something happen; an aim or movement to which a person is committed.

causality

(n). Someone or something responsible for a result.

collide

(v). To crash into; to hit.

complex

(adj). Consisting of many different parts; not easy to understand (n) a group or system of things connected in a complicated way.

component

(n). A part.

compose

(v). To make up from parts.

composite

(n). Something made up of parts; (adj) made up of several parts.

condition

(n). The state something is in; the situation that must exist before something else is possible.

conjunction

(n). When two or more things come together at the same point; in grammar, a part of speech that connects words, sentences, phrases or clauses, e.g.: “and”

consider

(v). Think about.

contrast

(v). Show the difference between;

 

(n). something that is very different from what it is being compared with.

conversely

(adv). The opposite of.

counteract

(v). Act against something in order to stop it.

D

 
   

data (pl),

datum (sing)

(n). Information given or found.

deduce

(v). To work something out by reasoning.

deduction

(n). Conclusion or idea that someone has worked out.

define

(v). Give the meaning of a word or words.

definition

(n). The meaning of a word or words.

deliver

(v). To bring and hand over.

denote

(v). To refer to or mean something.

determine

(v). Work out, usually by experiment or calculation.

discreet

(adj). Careful, polite.

discrete

(adj). Single, separate, distinct, a part.

E

 

effect

(n). Result.

effect

(v). Carry out, do, enact.

eject

(v). Force or throw something or someone out violently or suddenly.

elapse

(v). Pass by or finish, e.g., time.

establish

(v). Show or prove, set up or create.

exceed

(v). Go beyond.

excess

(n). More than necessary.

excluding

(prep). Not including.

exclusive

(adj). Excluding or not admitting other things; reserved for one particular group or person.

exemplar

(n). A good or typical example.

exempt

(v). To free from a duty.

exempt

(adj). Be freed from a duty.

exemption

(n). Being freed from an obligation.

exhibit

(v). To show or display.

exhibit

(n). A part of an exhibition.

expel

(v). Force someone or something to leave a place. Eject.

extent

(n). The area covered by something.

F

 

factor

(n). A circumstance, fact or influence that contributes to a result; a component or part.

factory

(n). A place where goods are made or put together from parts.

find

(v). Discover or locate.

find

(n). Results of a search or discovery.

finding

(n). Information discovered as the result of an inquiry.

fixed

(adj). Not able to move, attached; or repaired, not broken.

format

(n). Layout or pattern; the way something is laid out.

G

 

global

(adj). Found all over the world (globe).

H

 

hazard

(n). Something dangerous.

heterogeneous

(adj). Made up of many different parts.

homogeneous

(adj). Uniform, made up of the same types of parts.

hypothesis

(n). A theory or proposed explanation.

hypothetical

(adj). Theoretical or tentative; waiting for further evidence.

I

 

identify

(v). Recognise or point out.

illustrate

(v). Give an example to show what is meant; draw.

impair

(v). Weaken or damage.

imply

(v). Suggest without directly saying what is meant.

indicate

(v). Point out or show.

initial

(n). First.

initiation

(n). The action of beginning something; the action of admitting somebody into a group or organisation.

insufficient

(adj). Not enough.

interchange-

(adj). Can be swapped or

able

exchanged for each other.

investigate

(v). Carry out research or a study.

issues

(v). Comes out of.

issues

(n). An important problem or a topic for debate.

M

 

macroscopic

(adj). Visible without being made bigger.

manipulate

(v). Handle or control (a thing or a person).

microscopic

(adj). Very small, not visible without being made bigger.

motivate

(v). Give someone a reason for doing something.

multiple

(adj). Many.

N

 

negligible

(adj). Small and insignificant; can be ignored. From “neglect” (ignore).

numerical

(adj). Relating to or expressed as a number or numbers.

numerous

(adj). Many.

O

 

observe

(v). Look at; watch carefully.

obtain

(v). Get.

occur

(v). Happen.

operate

(v). Work; drive; control.

optimal

(adj). Best; most favourable.

optimum

(adj). Best; (n) the most

 

favourable situation for growth or success.

overabundance

(n). More than enough; too much.

P

 

phenomenon

(n). A fact or situation that is seen to exist or happen.

phenomena

(n). Plural of phenomenon.

prefix

(n). Part of a word that is attached to the beginning of many different words, changing their meaning, e.g., prehistoric – before written records were kept.

prepare

(v). Make ready before an event; set things up.

principal

(n). Head of a school.

principal

(adj). Main or most important.

principle

(n). A basic truth that guides the way a person behaves.

provide

(v). Make available for use; supply.

Q

 

quality

(n). The standard of something compared to other similar things; a characteristic of someone or something.

R

 

reciprocal

(adj). Given or done in return.

record

(v). Make a note of something in order to refer to it later (pronounced ree-cord).

record

(n). A note made in order to refer to it later; evidence of something; a copy of something (pronounced rec-cord.

relative

(adj). Considered in relation to something else; compared to.

relative

(n). A family member.

represent

(v). Be appointed to act or speak for someone; amount to.

resolve

(v). Finalise something or make it clear; bring something to a conclusion.

respect

(v). Admire something or someone; consider the needs or feelings of another person.

respectively

(adj). In regards to each other, in relation to items listed in the same order.

S

 

simultaneously

(adv). At the same time.

site

(n). Place.

suffice

(v). Be enough.

surplus

(adj). More than is needed.

survey

(n). A general view, examination, or description of someone or something.

survey

(v). Look closely at or examine; consider a wide range of opinions or options.

T

 

tendency

(n). An inclination to do something in a particular way; a habit.

tertiary

(adj). Third level.

U

 

uniform

(n). Standardised clothing.

uniform

(adj). Remaining all the same at all times; unchanging.

V

 

verify

(v). Show to be true; check for truth; confirm.

vice versa

(adv). The other way round.

versus

(prep). Against. Abbreviated “vs” and sometimes “v”.

Technical terms

A  

absorption

(n). To take into; the process of

 

taking something in.

account

(n. & v.). Finance: A record of

 

income and expenditure. To

 

explain (v), e.g. “Account for why

 

the sky is blue”.

acetic

(adj). Pertaining to vinegar; an

 

organic molecule containing two

 

carbons. See organic, eth- for

 

more.

acetone

(n). Propanone. CH3COCH3; the

 

ketone of acetic acid. See ketone

 

for more.

acetylene

(n). Ethyne, C2H2. Used in welding

 

torches (blowtorches). See also

 

alkene.

acid

(n). A proton donor or substance

 

that ionises into H+ or H3O+ when

 

dissolved in water; sour-tasting

 

substance; corrosive; pH below 7.

 

See also base and alkali.

acidified

(adj). To have been made acidic.

acidity

(n). How acid something is.

activated

(adj). Made to function. Chemistry:

 

something moved into an unstable

 

higher-energy level or state.

 

Usually “activated complex”, the

 

combination of reactants just

 

before they turn into products. See

 

also reactant, reagent, product.

activation

(n). The process of activating

 

something. “Activation energy”,

 

the required energy to create an

 

activated complex.

aerosol

(n). A solution of substances in air or

 

other gas, e.g. as in an aerosol can.

affinity

(n). A liking for something;

 

an attraction to something; a

 

tendency to react with something

 

(chemistry). See also paraffin.

alcohol

(n). In common usage, ethanol

 

C2H5OH. Technically, any organic

 

substance or molecule containing

 

an -OH group. See organic.

aldehyde

(n). Any organic molecule containing

 

-CHO, formed by oxidising alcohols.

 

See alcohol and organic.

algae

(n). Adjective: algal (pertaining to

 

algae); an aquatic plant (lives in

 

water), which lacks leaves, stems,

 

roots.

algebra

(n). A mathematical system

 

where unknown quantities are

 

represented by letters, which

 

can be used to perform complex

 

calculations through certain rules.

alkali

(n). See base.

alkane

(n). An organic molecule or

 

compound or substance which

 

contains only single bonds

 

between carbons. See organic.

alkene

(n). An unsaturated organic

 

molecule, compound or substance,

 

which contains at least one double

 

bond between carbons. See

 

organic and unsaturated.

alkyl

(n). A prefix (word part) which shows

 

that the word after it has an alkane

 

group attached to it, by removing

 

one hydrogen from the alkane.

alkyne

(n). An unsaturated organic

 

molecule, compound or substance,

 

which contains at least one triple

 

bond between carbons. See

 

organic and unsaturated.

amalgam

(n). General use: a mixture. In

 

chemistry, specifically a mercury

 

alloy.

amide

(n). An organic compound

 

containing the group -C(O)NH2; an

 

inorganic compound containing

 

the group NH2.

amine

(n). The same as an amide except

 

the -NH2 can be attached to

 

anything, and does not have the

 

CO group shown above.

ammonia

(n). NH3.

ammonium

(adj). NH4+, found as a cation or as

 

part of a salt. See salt and cation.

amphiprotic

(n). See ampholyte.

ampholyte

(n). A substance that can act as an

 

acid or base. See acid, base.

anions

(n). A negative ion. See cation, ion.

anode

(n). The negative electrode of

 

a cell or current supplier; the

 

positive electrode of an electrolytic

 

system; attracts negative ions. See

 

electrode, cathode.

antacid

(n). A substance used to neutralise

 

(react with) acid. E.g. chalk. See

 

acid, neutralise.

apparatus

(n). Equipment; parts of a scientific experiment.

aqueous

(n). Dissolved in water.

Arrhenius

(n). Arrhenius’ theory of acids and bases: That acids produce H+ or H3O+ in water, and bases produce OH–. See Brønsted-Lowry.

asbestos

(n). A fireproof fibrous substance containing silicon used for fireproofing.

asbestosis

(n). A lung disease caused by inhaling asbestos fibres, can lead to cancer.

atm

(n). Abbreviation: atmospheres of pressure (1 atm = 101,3 kPa). The pressure of the air at sea level. Same as “bar” (barometric pressure).

ATM

(n). Abbreviation: automatic teller machine.

atmosphere

(n). The air or the gases surrounding a planet; the sky; as a unit of measurement, see atm.

atmospheric

(adj). To do with the atmosphere.

atom

(n). The smallest unit of a chemical element, which, if broken down further, no longer behaves in the same way chemically. Consists of a nucleus or centre part which is positively charged, and an electron cloud (negatively charged) which surrounds the nucleus. See nuclear.

attract

(v). To bring something closer.

average

(n). Mathematics: The sum of parts divided by the quantity of parts. In common use: neither very good, strong, etc., but also neither very weak, bad, etc; the middle. In Physical Science and Mathematics: if you are asked to find the average, you always have to calculate it using the information you have. For example, the average of (1;2;3) is 2, because (1+2+3)/3 = 2. See also mean, median and mode.

avogadro (constant or number)

(n). 6,023 × 1023 particles; one mole. See mole and mol.

axis (sing), axes (pl, pronounced “akseez”)

(n). A line along which points can be plotted (placed), showing how far they are from a central point, called the origin. See origin. “Vertical axis” or “y-axis” refers to how high up a point is above the origin (or how far below). “Horizontal axis” or “x-axis” refers to how far left or right a point is away from the origin.

B

 
   
   

bakelite

(n). A type of hard, brittle plastic

 

that can’t melt once it has set

 

or taken shape (thermosetting),

 

made from phenol C6H5OH, and

 

formaldehyde (methanal), CH2O.

balance

(v. & n.). To make two things equal

 

(v); a scale to weigh objects (n).

 

Chemistry: to compare two sides

 

of a chemical equation and make

 

sure that there are the same

 

numbers of atoms on both sides.

base

(n). A proton acceptor, or substance

 

that ionises into OH– when

 

dissolved in water; a bitter-tasting

 

substance, corrosive, pH above 7.

 

See also acid. Do not confuse with

 

common everyday use, meaning

 

“the bottom” or “low”.

basic

(n). Bitter or made of a base. Do not

 

confuse with popular use, meaning

 

“low” or “simple” or “crude”.

battery

(n). A collection of cells connected

 

in series (end-to-end). See cell. In

 

common use, “battery” is used to

 

mean the same as “cell” (e.g. a

 

penlight or AA cell), but this use is

 

incorrect except for a car battery,

 

which consists of a series of cells.

benzoic

(adj). Contains benzene or a

 

benzene ring.

bi-

(prefix). Two.

bicarbonate

(n). Any salt containing the ion

 

-HCO –. So called because the

 

3

 

carbonate (CO32–) attaches to

 

another ion and the hydrogen

 

(two bonds). The name “hydrogen

 

carbonate” is now preferred.

biodegradable

(adj). Can be broken down by

 

natural processes e.g. involving

 

bacteria, moulds, fungus, etc.

biodiesel

(n). Diesel (a type of petrol) made

 

from plants rather than fossil fuels

 

(coal, oil).

BODMAS

(abbr). Brackets, of/orders

 

(powers, squares, etc), division,

 

multiplication, addition, subtraction.

 

A mnemonic (reminder) of the

 

correct order in which to do

 

mathematical operations.

boil

(v). Physics: to cause a liquid’s

 

vapour pressure to exceed

 

the pressure of the gas in the

 

container, usually by heating it,

 

but it can be done by lowering

 

the pressure of the gas in the

 

container, too. See vapour

 

pressure. In common usage, to

 

make a liquid hot until it bubbles.

bond

(n). A connection. In physics and

 

chemistry, between atoms and

 

molecules.

breadth

(n). How wide something is. From

 

the word “broad”.

brine

(n). A saturated salt solution (a

 

mixture of water and salt which

 

can’t dissolve any more salt).

bromide

(n). Something containing bromine,

 

usually one ion. See ion.

bromo-

(prefix). Something containing

 

bromine.

bromothymol

(n). A type of acid-base indicator

(blue)

used to tell whether something

 

is an acid or base. Turns blue (in

 

base) or yellow (in acid).

Brønsted-Lowry

(n). A theory of acids and bases

 

which says that acids are proton

 

donors (they give away protons),

 

and bases are proton acceptors

 

(they take protons). Since H+ is

 

just a proton, this does not mean

 

something different from the

 

Arrhenius theory that an acid is a

 

substance that dissolves into H+ in

 

water. See proton, Arrhenius.

but-

(prefix). Four carbons. Pronounced

 

“beaut”. E.g. butane is a four-

 

carbon alkane.

   

C

 
   

calibrate

(v). To adjust a measuring tool

 

or measurement against a

 

known accurate measurement to

 

ensure that the measuring tool or

 

measurement is accurate; to check

 

a measurement or measuring

 

tool’s accuracy; to mark with

 

accurate measurements using a

 

standard scale like cm, mm, mℓ,

 

etc. Common use: to assess or

 

evaluate carefully.

carbohydrate

(n). Organic compounds containing

 

carbon and hydrogen, occurring

 

in foods and living tissues and

 

including sugars, starch, and

 

cellulose. They contain hydrogen

 

and oxygen in the same ratio

 

as water (2:1). Not the same

 

as hydrocarbons, which are any

 

substances containing mostly

 

hydrogen and carbon.

carbonate

(n). -CO32–

carbonic

(adj). Anything containing carbon,

 

or more specifically, CO2

carbonyl

(adj). Containing double bonded

 

carbon and oxygen: =C=O.

carboxyl

(adj). Containing -COOH.

carboxylic

(adj). Carboxyl-containing.

Cartesian

(adj). Anything believed or

 

proposed by Rene Descartes.

 

In particular, the x-and-y axis

 

coordinate system.

catalyst

(n). A substance that alters the

 

rate of a chemical reaction without

 

itself being consumed in the

 

reaction. Without qualification, or

 

as “positive catalyst”, something

 

that starts or speeds up a reaction.

 

A “negative” catalyst slows down a

 

reaction.

catalytic

(n). Containing or using a catalyst.

cathode

(n). The positive electrode of a cell

 

or current supplier; the negative

 

electrode of an electrolytic

 

system; attracts positive ions. See

 

electrode, anode, ion.

cathodic

(adj). Involving a cathode. Cathodic

 

protection: To use a more reactive

 

metal to protect a less reactive

 

metal from oxidation. See anode,

 

cathode, oxidise.

cation

(n). A positively charged ion. See

 

anion, ion.

caustic

(adj). Basic; a base.

cell

(n). An apparatus that generates

 

electricity using electrochemistry.

 

An AA or Penlight battery, as it is

 

commonly called, is a cell. A car

 

battery consists of a number of

 

cells inside a single container.

CFC

(n). A chlorofluorocarbon. A

 

substance containing carbon,

 

chlorine and fluorine. Responsible

 

for breaking down ozone (O3) which

 

protects us from too much UV

 

radiation from the sun.

chain

(n). Chemistry: a long series of

 

atoms bonded together, usually

 

carbon.

charge

(n). Chemistry: having too

 

many or too few electrons

 

(most commonly), resulting in

 

a substance ionising. A positive

 

charge results from too few

 

electrons, and a negative charge

 

from too many electrons. Physics:

 

a basic feature of all physical

 

electromagnetic particles, except,

 

e.g. neutrons and photons, which

 

have zero charge. All protons have

 

a positive charge, all electrons

 

have a negative charge.

chart

(v). To draw a diagram comparing

 

values on Cartesian axes.

Le Châtelier’s

(n). That in reversible reactions,

Principle

chemical systems will favour the

 

forward or reverse reaction to

 

minimise the change imposed

 

on the system. If a chemical

 

equilibrium is disturbed by

 

changing the conditions, the

 

position of equilibrium moves to

 

counteract the change.

chloro-

(prefix). Containing chlorine.

chlorofluoro-

See CFC.

carbons

 

chloroform

(n). CHCℓ2. A liquid formerly used

 

as an anaesthetic.

chlorophyll

(n). A green substance found

 

in plants which enables

 

photosynthesis (broadly,

 

generating food from CO2). See

 

photosynthesis.

coefficient

(n). A constant value placed

 

next to an algebraic symbol as a

 

multiplier. Same as constant (see

 

below). Or: a multiplier or factor

 

that measures a property, e.g.

 

coefficient of friction.

combustion

(n). The process of burning, usually

 

in oxygen. Rapid oxidation.

completion

(n). Chemistry: when a reaction

 

no longer proceeds (continues)

 

because it has run out of one

 

or more of the reactants. See

 

reactant, reaction.

complex

(n). See activated.

(activated)

 

compound

(n). A substance made up of

 

molecules consisting of more

 

than one different type of atom,

 

chemically bonded in a constant

 

ratio. E.g. Water (H2O) is a

 

compound, but Sulphur powder

 

(S) is not. In a compound, the

 

original chemicals (reactants) have

 

reacted or merged to form a new

 

substance. Compare to mixture.

compressed

(adj). Subjected to pressure,

 

squashed.

concentration

(n). The number of moles of

 

substance per unit volume.

 

See mol, moles. How “strong” a

 

solution is. See solution.

condensation

(n). When a vapour or gas cools

 

down and starts to collect into

 

larger droplets; changing phase

 

from vapour or gas to liquid.

 

Condensation reaction: to produce

 

a larger molecule from two smaller

 

ones.

conditions

(n). Physics and Chemistry: how

(STP)

the environment is: temperature

 

and pressure. STP (Standard

 

Temperature and Pressure is 25°C

 

and 1 atm).

conjugate

(n). To join together. Chemistry: two

 

things that belong together, e.g.

 

conjugate acid-base pairs.

conservation

(n). A law which describes

 

something that does not change.

 

E.g. the conservation of matter-

 

energy says that matter-energy

 

cannot be created or destroyed,

 

only transformed from one form

 

into another. There are a number

 

of other conservations, e.g.

 

momentum and torque.

constant

(n). See coefficient. Means

 

“unchanging”.

contaminate

(v). Chemistry: to introduce

 

impurities or other substances

 

which are not meant to be part of

 

a reaction.

control

(n. and v.). To ensure something

 

does not change without

 

being allowed to do so (v);

 

an experimental situation to

 

which nothing is done, in order

 

to compare to a separate

 

experimental situation, called the

 

‘experiment’, in which a change

 

is attempted. The control is then

 

compared to the experiment to see

 

if a change happened.

control variable

(n). A variable that is held constant

 

in order to discover the relationship

 

between two other variables.

 

“Control variable” must not be

 

confused with “controlled variable”

 

(see independent variable).

coordinate

(n). The x or y location of a point on

 

a Cartesian graph, given as an x or

 

y value. Coordinates (pl) are given

 

as an ordered pair (x, y).

correlate

(v). To see or observe a

 

relationship between two things,

 

without showing that one causes

 

the other.

correlation

(n). That there is a relationship

 

between two things, without

 

showing that one causes the other.

correspond

(v). To pair things off in a

 

correlational relationship. For two

 

things to agree or match. E.g. A

 

corresponds to 1, B corresponds to

 

2, C corresponds to 3, etc.

corrode

(v). Chemistry: to destroy by

 

gradual chemical action. Usually

 

refers to acidic action. Compare

 

to erode. General use: to destroy

 

gradually.

corroding

(adj). A process or substance

 

that corrodes; to be subject to

 

corrosion.

corrosion

(n). To corrode.

corrosive

(adj). To be capable of corroding

 

something.

counteract

(v). Oppose or resist.

covalent

(adj). Chemistry: a bond which

 

results from sharing electrons

 

between atoms. Compare ionic

 

bond.

cracking

(n). A process of breaking a

 

complex organic molecule into

 

simpler parts using heat and

 

pressure.

cubed

(adj). The power of three;

 

multiplied by itself three times.

cubic

(adj). Shaped like a cube; having

 

been multiplied by itself three

 

times.

current

(n). Flowing electrons.

   

D

 
   

decompose

(v). To break down into

 

components.

degradable

(adj). Capable of breaking down or

 

being broken down.

dehydrating

(adj). To remove water from. A

(agent)

“dehydrating agent” is a substance

 

which can remove water from

 

another substance. E.g. H2SO4,

 

ethanol.

dehydration

(n). The process of removing water

 

from a substance.

dehydrogena-

(n). The process of removing

tion

hydrogen from a substance.

dehydrohalo-

(n). To remove hydrogen and a

genation

halogen from a substance. See

 

halogen.

denominator

(n). See divisor. In popular speech:

 

a common factor.

depend

(v). To be controlled or determined

 

by something; to require something

 

to happen or exist first.

dependent

(adj/n). A variable whose value

(variable)

depends on another; the thing

 

that comes out of an experiment,

 

the effect; the results. See also

 

independent variable and control

 

variable. The dependent variable

 

has values that depend on the

 

independent variable, and we plot

 

it on the vertical axis.

depleted

(adj). Having been used up; run

 

out of.

deposit

(n). Finance: to place money into

 

an account. Physical Science: to

 

cover a surface of one substance

 

with another substance, e.g. metal

 

plating on an electrode.

determine(s)

(v). To cause; to ensure that; to set

(causation)

up so that; to find out the cause of.

di-

(prefix). Two.

diamine

(n). A substance containing two

 

amine groups. See amine.

diammonium

(n). Having two ammonium (NH4)

 

groups. See ammonium.

diaphragm

(n). A thin sheet of any substance

 

covering a gap. Biology: the muscle

 

below the lungs which moves to

 

cause breathing. Electrochemistry:

 

a thin sheet inside a cell which

 

separates the electrodes. It is

 

porous and allows solutions

 

containing ions through, but serves

 

to separate gas products.

difference

(n). Mathematics: subtraction.

 

Informally: a dissimilarity. How

 

things are not the same.

dilute

(adj. & v). To lower the

 

concentration of a solution. See

 

solution and concentration (v):

 

a solution which has had its

 

concentration lowered (adj).

dilution

(n). The opposite of concentration;

 

how low a concentration is,

 

measured in mol/dm3; the process

 

of diluting.

dimer

(n). A molecule made of two

 

identical parts. See also polymer.

diode

(n). A semiconductor device with

 

two terminals (electrodes), usually

 

allowing current to flow in one

 

direction only.

diol

(n). A molecule with two alcohol/

 

hydroxyl (OH) groups.

dipole

(n). A polarised molecule with a

 

distinctly positive and distinctly

 

negatively-charged end.

diprotic

(n). Having two protons.

displace

(v). To move or relocate something.

dissipate

(v). To disperse or scatter (e.g.

 

gas). Thermodynamics (Energy):

 

to cause energy to be lost as heat.

 

Popular use: to disappear.

dissociate

(v). To break apart; to no longer be

 

associated with.

dissolve

(v). To break up into ions within a

 

solution (usually water); to mix a

 

solid (usually powder) into a liquid,

 

to form a solution. See solution,

 

ion. Alternative popular use: to

 

bring to an end.

distil(l)

(v). To purify through repeated

 

heating of a liquid and collection

 

of condensation. The heating

 

process causes the liquid to form

 

gas or vapour, which condenses

 

on the side of the heating vessel

 

(container) or an exit tube, leaving

 

impurities behind in the heating

 

vessel.

distribution

(n). How something is spread

 

out. Mathematics: the range and

 

variety of numbers as shown on a

 

graph.

disturb

(v). Chemistry: to mix or stir a liquid

 

or solution; to shake it up.

divisor

(n). The number below the line

 

in a fraction; the number that is

 

dividing the other number above

 

the fraction line. See numerator,

 

denominator.

domain

(n). The possible range of x-values

 

for a graph of a function. See

 

range.

durable

(adj). Tough; something that can

 

endure.

dynamic

(adj). Changing often. Relating

 

to forces that produce motion.

 

Opposite of static. See static and

 

electrostatic.

   

E

 
   

ecosystem

(n). An integrated, complex,

 

interacting, mutually dependent

 

living system or environment.

electric

(adj). Containing electricity

 

(electrons).

electro-

(adj). Where chemical reactions

chemical

cause the release of electrons,

 

usually into a circuit. General use:

 

anything relating to electrical and

 

chemical phenomena.

electrode

(n). General use: the point where

 

electrons enter or exit a power

 

source or a circuit. Specifically

 

(Electrochemistry): Part of a circuit

 

dipped into a solution to receive or

 

release electrons. See anode and

 

cathode.

electrolysis

(n). The splitting of a chemical

 

into ions. (The chemical is usually

 

dissolved in water or another

 

solution.) It is done by means of

 

electricity. See electrochemical.

electrolyte

(n). A substance (usually liquid

 

or gel solution) which contains

 

a compound that will be split by

 

electricity. Ionisable solutions or

 

components.

electromotive

(adj). Usually electromotive force

 

or emf. The potential difference

 

caused by electromagnetism,

 

which causes current to flow.

 

Producing a current with

 

electromagnetism. See emf.

electron

(n). A fundamental physical

 

particle bearing a negative charge,

 

weighing approximately 9 × 10−28g,

 

which is found around atomic

 

nuclei in areas called ‘orbitals’.

 

Responsible for electricity and

 

chemical reactions. Symbol e–. See

 

proton, nucleus.

electroplate

(v). To cover a surface of a less

 

valuable substance with a more

 

valuable metal, using electrolysis.

element

(n). Mathematics: part of a set

 

of numbers. Physics: a pure

 

substance made only of atoms of

 

one type, with the same number

 

of protons in each nucleus. An

 

element cannot be broken down

 

further without losing its chemical

 

properties. Each element has a

 

unique atomic number which is the

 

number of protons in the nucleus.

 

See nucleus, atom, isotope.

 

Popular use: part of.

eliminate

(v). To remove or get rid of.

 

Mathematics: to cancel a factor

 

out of one side of an equation by

 

dividing by that factor throughout,

 

or by substituting in another

 

formula or value that is equal.

 

Chemistry: to produce a smaller

 

substance as a by-product

 

from reacting more complex

 

substances, usually water or CO2;

 

in the sense of: to remove those

 

molecules from the reaction.

emf

(abbr). Same as electromotive

 

force. Always written in lowercase

 

(small letters).

emission

(n). Something released, e.g. gas,

 

light, heat.

emit

(v). To release.

empirical

(adj). Relating to the senses or to

 

things that you can see, touch,

 

taste, etc. Chemistry: empirical

 

formula: a formula giving the

 

proportions of the elements

 

present in a compound but not the

 

actual numbers or arrangement

 

of atoms; the lowest ratio of

 

elements without giving structure

 

or quantities.

emulsion

(n). Small particles or droplets of

 

a substance or liquid which do

 

not dissolve in a different liquid;

 

suspended or floating within that

 

liquid, e.g. to mix oil and water by

 

shaking them up.

endothermic

(adj). Taking in heat, ΔH > 0. See

 

enthalpy, exothermic.

energetic

(adj). Having a lot of energy;

 

performing a lot of work.

energy

(n). Work or the ability to do

 

work. There are various forms of

 

energy: motion (Ek), light energy

 

(photons), electrical energy, heat,

 

etc. Energy can neither be created

 

nor destroyed, but only converted

 

from one form to another. See

 

conservation.

enthalpy

(n). The total heat content of a

 

system, H, including the chemical

 

energy.

equilibria (pl),

(n). The state of being in balance.

equilibrium

Chemistry: when the forward

(sing)

reaction rate is equal to the

 

reverse reaction rate. See Le

 

Châtelier’s Principle.

erode

(v). To wear away by means of

 

friction (rubbing).

ester

(n). An organic compound

 

produced by bonding an alcohol

 

to a carboxylic (organic) acid,

 

by means of dehydration. See

 

carboxylic, organic, alcohol,

 

dehydration. Responsible for fruit

 

flavours and many pleasant odours

 

(smells).

esterfication

(n). The production of esters.

estimate

(n., v.). To give an approximate

 

value close to an actual value; an

 

imprecise calculation.

eth-

(prefix). Containing two carbons.

eutrophication

(n). Excess nutrients in water

 

causing excessive plant growth and

 

strangulation of a waterway.

evaporate

(v). To change phase of matter

 

from liquid to gas. Compare

 

sublimate and boil.

excited

(n). The state of being in a higher

 

energy level (higher than ground

 

state).

exo-

(prefix). Outside of.

exothermic

(adj). Giving off heat, ΔH < 0. See

 

enthalpy, endothermic.

exponent

(n). When a number is raised to a

 

power, i.e. multiplied by itself as

 

many times as shown in the power

 

(the small number up above the

 

base number). So, 23 means

 

2 × 2 × 2. See also cubed.

exponential

(adj). To multiply something many

 

times; a curve representing an

 

exponent.

extrapolation

(n). To extend the line of a graph

 

further, into values not empirically

 

documented, to project a future

 

event or result. In plain language:

 

to say what is going to happen

 

based on past results which were

 

obtained (gotten) by experiment

 

and measurement. If you have

 

a graph and have documented

 

certain results (e.g. change vs

 

time), and you draw the line further

 

in the same curve, to say what

 

future results you will get, that is

 

called ‘extrapolation’. See predict.

extrude,

(v., n.). To push something through

extrusion

a mould or shape, usually a liquid

 

or gel through a hole, to create a

 

new shape.

   
       

F

     
   

fahrenheit

(n). A temperature scale based

 

on human body temperature.

 

Water freezes at 32°F and boils

 

at 212°F under standard

 

conditions. The conversion

 

formula to centigrade/celcius is:

 

(˚F – 32) × 5/

9

= ˚C

     
   

favoured

(adj). Preferred. Chemistry: in a

 

chemical reaction, the direction of

 

the reaction after the equilibrium

 

is broken.

   

fermentation

(n). The conversion of a sugar or

 

carbohydrate to an alcohol, usually

 

by yeast or bacteria.

fertilisation

(n). The process of adding

 

nutrients to soil. Biology: the fusion

 

of male and female gametes (sex

 

cells) into a zygote (group of cells

 

that will become a foetus or other

 

living organism).

fertiliser

(n). A substance added to soil for

 

nutritional reasons.

fixation

(n). The process of fixing on

 

something or someone.

fixed

(n). The process of attaching one

(chemistry)

chemical or compound to another.

 

E.g. nitrogen fixing is the bonding

 

of free N2 to organic chemicals.

fluid

(n). Any substance that can flow

 

and take the shape of a container;

 

liquid, some gels, and gas.

fluorescent

(n). Bright, colourful, due to

 

changes in energy levels of

 

electrons, as seen in fluorescent

 

tubes, ink, etc. See reflective.

formic

(prefix). Same as meth-. Contains

 

one carbon. From Latin “formica”:

 

ant, referring to formic acid, which

 

is found in an ant’s sting.

fraction

(n). Mathematics: Not a whole

 

number; a representation of a

 

division. A part. E.g. the third

 

fraction of two is 0,666 or ⅔.

 

meaning two divided into three

 

parts. Chemistry: a part of a

 

solution or mixture separated out

 

by distillation. See distil.

function

(n). Mathematics: when two

 

attributes or quantities correlate.

 

If y changes as x changes, then

 

y = f(x). See correlate, graph,

 

Cartesian, axis, coordinate. Also:

 

a relation with more than one

 

variable (mathematics). Chemistry:

 

functional group: part of a

 

molecule that gives the substance

 

its chemical properties in common

 

with other similar chemicals.

   

G

 
   

galvanic

(adj). Relating to currents caused

 

by a chemical reaction. See

 

electrochemistry.

galvanising

(n). To electroplate so as to protect,

 

e.g. cover iron with zinc to prevent

 

rust.

gas

(n). The third phase of matter.

 

When a solid is heated it turns into

 

liquid, and when a liquid is heated

 

it turns into gas.

gaseous

(adj). In a gas form.

gradient

(n). A slope. An increase or

 

decrease in a property or

 

measurement. Also the rate of such

 

a change. In the formula for a line

 

graph, y = mx + c, m is the gradient.

gradually

(adv). To change or move slowly.

graph

(n). A diagram representing

 

experimental or mathematical

 

values or results. See Cartesian.

graphic

(n., adj.). A diagram or graph

 

(n). Popular use: vivid or clear or

 

remarkable (adj.).

graphically

(adv). Using a diagram or graph.

 

Popular use: to explain very clearly.

groundwater

(n). Water held in the earth

 

(underground).

gypsum

(n). Calcium sulphate.

   

H

 
   
   

Haber (process)

(n). An industrial process to produce

 

ammonia from nitrogen and

 

hydrogen, using an iron catalyst at

 

high temperature and pressure.

haemoglobin

(n). A compound containing

 

iron, found in red blood cells,

 

responsible for carrying oxygen.

half-cell

(n). One of the sides of an

 

electrochemical cell; one of the

 

electrodes and the chemical

 

solution around it.

half-reaction

(n). The equation for the chemical

 

reaction occurring in a half-cell.

halide

(n). A compound containing a single

 

halogen, e.g. NaCℓ. See halogen.

halo-

(prefix). Containing a halogen. See

 

halogen.

haloalkane

(n). An alkane bonded to a

 

halogen. See halogen.

halogen

(n). Any of the elements fluorine

 

(F), chlorine (Cℓ), bromine (Br),

 

iodine (I), and astatine (At), in

 

group VIIA (17) of the periodic

 

table. They combine with metals to

 

produce salts. See salt.

halogenation

(n). Adding a halogen.

hardness

(n). (Water). Containing salts, usually

 

calcium carbonate. If water contains

 

too many such salts, soap does

 

not function properly and doesn’t

 

produce bubbles or foam. “Water’s

 

hardness is determined by the

 

concentration of multivalent cations

 

in the water. Multivalent cations are

 

cations (positively charged metal

 

complexes) with a charge greater

 

than 1+. Usually, the cations have

 

the charge of 2+. Common cations

 

found in hard water include Ca2+

 

and Mg2+.” (Wikipedia).

heat

(n). Physics: a measure of the

 

average kinetic energy of the

 

molecules or atoms in a substance;

 

enthalpy; the energy of an object

 

as molecular motion. Alternatively,

 

infra-red radiation (heat radiation)

 

coming off a body. See body.

homologous

(n). Belonging to the same group

 

of things; analogous. Biology:

 

a flipper is homologous with a

 

leg or arm. Chemistry (organic):

 

belonging to the same series of

 

molecules, e.g. alkanes: methane,

 

ethane, propane; having the same

 

functional group.

hydrate

(n). To add water to.

hydration

(n). Having had water added.

 

Some salts are hydrated, meaning

 

that they have a number of water

 

molecules bonded to them, which

 

can be removed by heat. Heating

 

a hydrated salt changes its colour

 

but not the chemical reactions it

 

will undergo. See salt.

hydrocarbon

(n). Any compound consisting

 

mainly of hydrogen and carbon.

 

Compare carbohydrate.

hydrochloric

(adj). Any chemical containing HCℓ.

hydrohalogen-

(n). Adding a hydrogen and halogen

ation

atom to a molecule.

hydrolysis

(n). Splitting by reacting with

 

water. Applies to salts and organic

 

chemicals. E.g. A haloalkane plus

 

water or a dilute NaOH gives an

 

alcohol and either a hydrohalide

 

or sodium salt. Dissolving a

 

salt in water can be considered

 

hydrolysis.

hydronium

(n). H

O+ ion.

 

3

 

hydroxide

(n). OH– ion. This usage applies

 

specifically to bases (see acid,

 

base). In organic molecules, OH– is

 

an alcohol functional group called

 

the hydroxyl group. See alcohol,

 

hydroxyl, diol.

hydroxyl

(n). See hydroxide.

hydroxylamine

(n). An amine with a hydroxyl

 

group.

     

I

   
   

ideal

(adj). Not as seen in real

 

life; theoretical. Ideal gas: a

 

hypothetical gas whose molecules

 

occupy negligible space and

 

have no interactions, and which

 

consequently obeys the gas laws

 

(PV = nRT) exactly.

ignition

(n). The start of a combustion

 

reaction. Common use: to start

 

a car (which has an internal

 

combustion engine). See engine,

 

combustion.

illuminate

(v). To explain or light up.

immerse

(v). To cover in liquid.

impair

(v). Prevent; hinder; slow down.

impure

(adj). Containing a variety of

 

additional chemicals in smaller

 

amounts in addition to the main

 

chemical.

incandescent

(adj). Giving off light as a result of

 

being heated.

independent

(n). The things that act as input

(variable)

to the experiment, the potential

 

causes. Also called the controlled

 

variable. The independent variable

 

is not changed by other factors, and

 

we plot it on the horizontal axis. See

 

control, dependent variable.

indicator

(n). Chemistry: a substance used

 

to check for pH levels, which

 

changes colour according to pH.

 

See acid, base, pH.

indigo

(n). The colour between violet and

 

blue; purplish-blue.

inert

(adj). Chemistry: a chemical or

 

element which does not react or is

 

difficult to cause to react, e.g. Ne,

 

Xe, He. N2 is sometimes described

 

as inert but it’s not in the group of

 

Noble Gases. Common use: lazy,

 

unwilling to move.

inflammable

(adj). Same as flammable; easily

 

set on fire (combustion).

inhibitor

(n). Something that slows down or

 

prevents.

inorganic

(adj). Not containing carbon;

 

mineral. Exceptions are C, CO, CO2,

 

which, whilst they contain carbon,

 

are not considered organic as they

 

can be produced during inorganic

 

chemical reactions.

insoluble

(adj). Not able to dissolve.

insufficient

(adj). Not enough.

interact

(v). To affect each other, to be

 

directly involved with or act on

 

each other.

intermediate

(adj). A state in between.

intermolecular

(adj). Between molecules. See

 

molecule, intramolecular.

intramolecular

(adj). Within or inside a molecule.

 

See molecule, intermolecular.

inversion

(n). Chemistry: turning something

 

upside down.

ion

(n). An atom or molecule or part of

 

a molecule which has an electrical

 

charge due to gaining or losing one

 

or more electrons.

ionic (bond)

(adj.). A bond in which electrons

 

have been transferred from one

 

side of the molecule to another

 

resulting in a cation and anion,

 

which then attract. E.g. NaCℓ.

ionisation

(n). The process of ionising. See

 

ionise.

ionise

(v). To turn into an ion. See ion.

irreversible

(adj). Cannot be reversed. Said

 

of certain chemical reactions,

 

in which case it specifically

 

means that the reaction does not

 

spontaneously reverse (not an

 

equilibrium reaction). The reaction

 

only proceeds in one direction.

 

Example: combustion.

isolate

(v). To separate from. Usual use

 

in Physical Science means to

 

separate one chemical from

 

another. Compare insulate, distil.

isomer

(n). A substance with the same

 

empirical formula but a different

 

structural formula. See empirical,

 

structural.

isotope

(n). An element which has a

 

different number of neutrons from

 

the usual number of neutrons in the

 

element. E.g. 12C has 6 protons and

 

6 neutrons, but 14C has 8 neutrons

 

and 6 protons, and is radioactive.

IUPAC

(abbr). International Union of Pure

 

and Applied Chemistry. Standardised

 

naming conventions for chemicals.

   

J

 
   

joule

(n). Unit of energy.

   

K

 
   
   

kelvin

(n). Unit of temperature, with

 

absolute zero being the point where

 

no molecular motion occurs, at

 

-273,15˚C. Hence, the freezing point

 

of water is 273,15 K. Note that there

 

is no degree sign before K.

ketone

(n). An organic compound with the

 

carbonyl group = C = O. Made by

 

oxidising secondary alcohols. E.g.

 

acetone.

   

L

 
   
   

law

(n). In Physical Science, a

 

formula or statement, deduced

 

(discovered) from observation

 

(watching). The formula or

 

statement will then predict that

 

under the same conditions the

 

same thing will always happen. E.g.

 

the first law of thermodynamics

 

says that matter and energy

 

cannot be destroyed, but only

 

changed from one form to another.

leach

(v). When a substance drains out

 

of soil, e.g. into rivers. Similar to

 

“leak”.

litmus

(n). A type of acid/base indicator.

 

See indicator. It is red when

 

exposed to acid and blue when

 

exposed to a base.

   

M

 
   

macromolecule

(n). A large molecule, usually a

 

polymer or protein.

macroscopic

(adj). Large enough to be visible

 

to the unaided human eye; big

 

enough to be seen.

magenta

(n). A bright purple/pink colour.

manipulate

(v). To change, or rearrange

 

something. Usually in Mathematics

 

it means to rearrange a formula to

 

solve for (to get) an answer.

material

(n). Any substance, not just cloth.

matter

(n). Substance; stuff. Opposite of

 

vacuum (nothing).

mean

(n). See average.

median

(n). Mathematics: the number in

 

the middle of a range of numbers

 

written out in a line or sequence.

metal

(n). A substance which is malleable

 

(can be hammered flat), is ductile

 

(can be drawn into a wire), which

 

conducts electricity and heat well

 

and which is reflective (most light

 

striking it is emitted again). Most

 

elements are metals except the

 

few on the right hand side of the

 

periodic table starting at Boron (B)

 

and running diagonally down to

 

Astatine (At).

meth-

(prefix). Having one carbon. See

 

formic.

methylated

(adj). Having had a single carbon

 

or methyl group added.

metric

(adj). A measurement system,

 

using a base of 10 (i.e. all the

 

units are divisible by 10). The USA

 

uses something known as the

 

Imperial system, which is not used

 

in science. The Imperial system is

 

based on 12. Examples: 2,54 cm

 

(metric) = 1 inch (imperial).

 

1 foot = 12 inches = approx.

 

30 cm; 1 metre = 100 cm. 1 Fl.Oz

 

(fluid ounce) = approx 30 mℓ.

microscopic

(adj). Too small to be seen by the

 

unaided human eye.

minimum

(n). The smallest amount possible.

mixture

(n). When you mix or combine

 

substances without them

 

undergoing a chemical reaction. In

 

other words, the substances mixed

 

stay separate (chemically) and do

 

not bond. Different to compound.

 

See compound, reaction.

modal

(adj). Pertaining to the mode, or

 

method. Can mean: about the

 

mathematical mode or about the

 

method used. See mode.

mode

(n). Mathematics: the most

 

common number in a series of

 

numbers. See also mean, median.

mol

(abbr). Mole.

molar

(adj). About a mole. See mole.

mole

(n). A unit describing an amount

 

of substance. 6,023 × 1023

 

molecules or atoms of the

 

substance.

 

E.g. 18 g of water is 1 mol of

 

water (H = 1, O = 16, H2O = 18).

molecular

(adj). About molecules. See

 

molecule.

molecule

(n). The smallest amount of a

 

compound; a single particle

 

composed of the elements that

 

make up the compound. E.g. in

 

water, a single particle consisting

 

of two hydrogen atoms and one

 

oxygen atom.

mono-

(prefix). One.

monomer

(n). Part of a macromolecule; the

 

simplest repeating unit. Monomers

 

bond to form polymers. See

 

polymer, isomer.

monoprotic

(adj). Having one proton.

   

N

 
   

neutral

(adj). Chemistry: pH 7,0. Neither

 

acid nor base. E.g. water. In

 

common use: not biased. See bias.

neutralise

(v). To make something neutral; to

 

complete an acid/base titration.

neutron

(n). A subatomic particle with

 

no charge, mass approximately

 

the same as a proton, found in the

 

nucleus of an atom. Symbol n0.

 

If there are too many protons in

 

a nucleus, the substance will be

 

radioactive as it releases

 

alpha particles (helium nuclei,

 

2p+ + 2n0).

nitrate

(n). Containing NO −.

 

3

nitrite

(n). Containing NO −.

 

2

nomenclature

(n). A system of describing things;

 

a naming system, designed to

 

make a name unambiguous or

 

unique.

nonmetal

(n). Any of the elements that are

 

not metals, e.g. Boron (B), Silicon

 

(Si), Sulphur (S), Oxygen (O), etc.

nucleus (sing),

(n).The centre of something

nuclei (pl),

(generally), specifically the centre

nuclear (adj)

of an atom, consisting of at least

 

one proton (hydrogen), or two

 

protons and two neutrons (helium).

 

Plural nuclei is pronounced “noo-

 

klee-eye”.

numerator

(n). The opposite of a denominator;

 

the number on top in a fraction.

   

O

 
   

-oate

(suffix). An ester.

odour

(n). A smell.

optimal

(adj). Best, most.

organic

(adj). Containing carbon, except C,

 

CO, CO2.

origin

(n). Mathematics: the centre of

 

a Cartesian coordinate system.

 

General use: the source of

 

anything, where it comes from.

outlier

(n). Statistics: a data point which

 

lies well outside the range of

 

related or nearby data points.

oxalic (acid)

(n). Ethanedioic acid; chem.

 

formula: (COOH)2.

oxidation

(n). Specifically, adding an oxygen

 

atom to a molecule, but more

 

general use: losing electrons from

 

any substance in a redox reaction.

 

See redox.

oxide

(n). A compound containing

 

an oxygen atom, especially if it

 

previously did not contain one, e.g.

 

iron (metal), vs iron oxide (rust).

oxidise

(v). To add an oxygen or remove

 

electrons from a substance.

   

P

 
   

paraffin

(n). Any waxy organic substance,

 

previously the general name for

 

alkanes. Formula ranges from

 

C20H42 to C40H82.

parallel

(adj). Keeping an equal distance

 

along a length to another item

 

(line, object, figure). Mathematics:

 

two lines running alongside each

 

other which always keep an equal

 

distance between them.

particle

(n). Any small part, e.g. a proton,

 

an atom, a molecule.

pascal

(n). The unit of pressure,

 

abbreviated Pa, units: N/m2

pent-

(prefix). Five.

per

(prep). For every, in accordance

 

with. Chemistry: the maximum

 

amount of an element possible

 

for the number of bonds available.

 

See e.g. peroxide.

peroxide

(n). H2O2.

perpendicular

(adj). Normal; at right angles to

 

(90˚).

phase

(n). Time, period; a state of matter

 

(solid, liquid, gas); the relationship

 

in time between the cycles of a

 

system (such as an alternating

 

electric current or a light or sound

 

wave) and either a fixed reference

 

point or the states or cycles of

 

another system with which it

 

may or may not be synchronised

 

(simultaneous). I.e. if two systems

 

vibrate at the same time at the

 

same rate, they’re “in phase”.

photosynthesis

(n). The process of converting

 

CO2 into carbohydrates using

 

atmospheric CO2, chlorophyll, and

 

light.

pi

(n). π, the Greek letter p, the

 

ratio of the circumference of a

 

circle to its diameter. A constant

 

without units, value approximately

 

3,14159.

plastic

(n., adj.). An artificial substance

 

made from hydrocarbon polymers

 

which is often flexible and able to

 

be moulded and is often a poor

 

electrical conductor (n); flexible

 

(adj).

plot

(v). To place points on a Cartesian

 

coordinate system; to draw a

 

graph.

poly-

(prefix). Many.

polyester

(n). A polymer made from esters.

polymer

(n). A synthetic substance made

 

from many monomers (repeating

 

units). See monomer.

polymerisation

(n). Making a polymer.

polyprotic

(adj). Having many protons.

porous

(adj). Having many holes that allow

 

fluids through.

positive

(adj). Having many protons not

 

paired with electrons; a lack of

 

electrons.

potential

(n). Having the ability to do work, in

 

particular, Ep (potential energy, the

 

tendency to fall or start moving,

 

as in a spring), or emf (voltage).

 

General use: potential exists when

 

there is an energy difference

 

between two points, e.g. due to

 

gravity or electrical charge. In the

 

context of electricity, read it as

 

“voltage”.

precipitate

(n). Chemistry: A product of a

 

reaction that cannot dissolve in the

 

solution and settles at the bottom

 

of the reaction vessel (container).

predict

(v). General use: to foresee.

 

Physical Science: to state what will

 

happen, based on a law. See law.

pressure

(n). A continuous force exerted on

 

an object over a certain area, in

 

pascals, Pa. N/m2. See pascal.

product

(n). Chemistry: the substance or

 

compound made as a result of a

 

chemical reaction. See reaction.

 

Mathematics: the result of

 

multiplying two numbers.

project

(n. & v.). A project (n., pronounced

 

PRODJ-ekt) is a plan of action

 

or long-term activity intended to

 

produce something or reach a goal.

 

To project (v., pronounced prodj-

 

EKT), is to throw something, or to

 

guess or predict (a projection). To

 

project a result means to predict a

 

result. See extrapolate.

prop-

(prefix). Three carbons.

 

Pronounced “prope” (rhymes with

 

“rope”).

proportion

(n). To relate to something else

 

in a regular way, to be a part of

 

something in relation to its volume,

 

size, etc; to change as something

 

else changes. See correlate and

 

respectively.

protein

(n). A large, complex organic

 

molecule containing nitrogen,

 

usually making up structural

 

elements of living things (building

 

blocks of cells, antibodies, etc).

protolytic

(adj). Capable of removing a

 

proton; proton transfer. Compare

 

acid.

proton

(n). The positively-charged particle

 

that forms the centre of an atomic

 

nucleus, weighing 1 836 times as

 

much as an electron, but having

 

the same and opposite charge.

 

Symbol p+. See also nucleus,

 

neutron, electron.

pump

(n). A machine that uses energy

 

to transfer a fluid from one

 

place to another. In Biology one

 

finds cellular pumps, which are

 

biological machines for transferring

 

ions and nutrients.

pure

(adj). Containing only the

 

compound or element in question,

 

without any other compounds or

 

elements mixed in. See impure.

purification

(n). The process of removing

 

impurities. See distil.

   

Q

 
   

qualitative

(adj). Relating to the quality

 

or properties of something. A

 

qualitative analysis looks at

 

changes in properties like colour,

 

that can’t be put into numbers.

 

Often contrasted with quantitative.

quantitative

(adj). Relating to, or by comparison

 

to, quantities. Often contrasted

 

with qualitative. A quantitative

 

analysis is one in which you

 

compare numbers, values and

 

measurements.

quantity

(n). Amount; how much.

   

R

 
   

rancid

(n). Having an unpleasant smell due

 

to having started to ferment or rot,

 

usually said of meat, oil or butter.

random

(n). Unpredictable, having no cause

 

or no known cause. Done without

 

planning.

range

(n). Mathematics: the set of values

 

that can be supplied to a function.

 

The set of possible y-values in a

 

graph. See domain.

rate

(n). How often per second (or per

 

any other time period). Physics:

 

number of events per second; see

 

frequency.

   

ratio

(n). A fraction; how one number

 

relates to another number; exact

 

proportion. If there are five women

 

for every four men, the ratio of

 

women to men is 5:4, written

 

with a colon (:). This ratio can be

 

represented as the fraction 5/4 or

 

1¼ or 1,25; or we can say that

 

there are 25% more women than

 

men.

react

(v). Chemistry: when two or more

 

elements or compounds are

 

brought into a mixture and form

 

chemical bonds, creating new

 

compounds.

reactant

(n). A chemical before it bonds with

 

another chemical. See reagent.

reaction

(n). Chemistry: The process

 

of reacting; a state in which

 

chemicals react. See endothermic

 

and exothermic. Physics (nuclear):

 

When a nucleus of an atom breaks

 

down and subsequently releases

 

energy and/or bonds with another

 

nucleus. In the first case, it is a

 

fission (splitting) reaction, in the

 

second case a fusion (joining)

 

reaction.

reactive

(adj). Tending to react easily.

reactivity

(n). How reactive a substance is

 

(unreactive or reactive).

reagent

(n). A reactant when it is still in its

 

bottle or container, before being

 

mixed.

redox

(abbr). Chemistry: reduction-

 

oxidation reaction; a chemical

 

reaction in which one substance

 

is reduced (gains electrons), and

 

another is oxidised (loses electrons).

 

See reduce, oxidise, anode, cathode,

 

electrode, electrochemistry.

reduce

(v). To make smaller. Chemistry: to

 

gain electrons (negative charges).

reflux

(n., v.). A substance that flows back

 

into its container after coming out.

 

Chemistry: the process of boiling a

 

liquid so that any vapour is liquefied

 

and returned to the stock (source).

refraction

(n). Bending light when it travels

 

from one medium (e.g. air) into

 

another medium (e.g. water or

 

glass). Changing the direction of

 

propagation of any wave as a result

 

of its travelling at different speeds at

 

different points along the wave front.

 

See Huygens’ principle, diffraction.

S

 
   
   

salt

(n). In common usage, NaCℓ.

 

Chemistry: any compound formed

 

from the reaction of an acid with

 

a base, with the hydrogen of the

 

acid replaced by a metal or other

 

cation. A non-metal ion bonded to

 

a metal ion.

saturated

(adj). Organic chemistry: Having

 

no available bonds or only single

 

bonds. Common use: cannot take

 

any more, usually said of a cloth

 

and liquid.

SI

(abbr). Système International. The

 

international system of metric

 

units used by scientists. See

 

metric, IUPAC.

simplify

(v). To make simpler. Mathematics:

 

to divide throughout by a common

 

factor (number or algebraic letter)

 

that will make the equation easier

 

to read and calculate.

slaked (lime)

(n). Calcium Hydroxide, Ca(OH)2.

solubility

(n). How easily something dissolves

 

(mixes into a liquid).

soluble

(adj). See solubility.

solute

(n). The substance that you place

 

in a liquid (the solvent) so as to

 

dissolve it. E.g. salt. See solvent.

solution

(n). A mixture of a solute and a

 

solvent. A liquid which has had

 

something dissolved in it (mixed).

 

Mathematics: the step-by-step

 

displaying of calculations to

 

arrive at answers. Common use:

 

the answer to a problem, in the

 

sense of dissolving (removing) a

 

problem.

solvent

(n). The liquid that dissolves the

 

substance placed into it. E.g. water.

spectator

(n). Chemistry: a compound or

 

chemical which does not get

 

involved in a chemical reaction.

spontaneous

(adj). Randomly, without

 

provocation or cause or prior

 

planning.

stable

(adj). Chemistry and Nuclear

 

Physics: not likely to break down or

 

react further.

standardised

(adj). Chemistry: a solution of

 

known concentration, e.g. 1 molar

 

(1 mol/dm3).

steam

(n). Water vapour, microscopic

 

droplets of water. Not a gas, a

 

suspension of water droplets in air.

 

See suspension, gas, liquid, phase,

 

aerosol.

STP

(abbr). Standard temperature and

 

pressure; 101,3 kPa and 25˚C.

structural

(adj.). Pertaining to structure;

(isomer)

a series of molecules whose

 

structures are different but their

 

chemical or empirical formulae are

 

the same.

sublimate

(v). To change phase of matter

 

from solid straight to gas without

 

the intermediate phase of liquid.

 

See the case of dry ice (CO2).

subscript

(n). A number placed below the

 

rest of the line, e.g. CO2.

substance

(n). Matter. Physical things.

substituent

(n). Chemistry: an ion or functional

 

group or group of atoms that

 

replaces a hydrogen on an organic

 

molecule.

substitute

(v). To replace.

substitutents

(n). Something that gets replaced.

substitution

(n). The process of substituting.

 

Mathematics: to replace an

 

algebraic symbol in a formula with

 

a known value or another formula,

 

so as to simplify the calculation.

 

See simplify. Chemistry: to

 

cause a substituent to bond to a

 

substance.

superscript

(n). A number placed above the

 

rest of the line, e.g. πr2.

synthesis

(n). The process of

 

manufacturing (making)

 

something. Chemistry: to bond

 

smaller molecules together

 

to create a larger molecule,

 

e.g. methanol from CO and H .

 

Synthesis gas: a gas mixture 2

 

(e.g. CO, H2), which when heated

 

produces a new compound, e.g.

 

methanol.

synthetic

(adj). Artificial, man-made.

system

(n). Any closely associated and

 

inter-related or inter-dependent

 

group of things; a set of things

 

working together. Chemistry: a

 

vessel (container) which contains a

 

chemical reaction.

T

   
   
   

terminal

(n). Final; end point.

termination

(n). Coming to an end.

tetra-

(prefix). Four.

theory

(n). A usually mathematical

 

representation of an explanation

 

for something in the sciences,

 

which does not depend on the

 

thing being explained. A theory

 

differs from a law in that theories

 

are prone to empirical (visible

 

or measurable) refutation

 

(rejection); meaning that they

 

can be discarded if evidence

 

comes in that they are wrong.

 

See law.

thermoplastic

(n). Chemistry: will melt if heated.

thermoset

(n). Once set into a shape it cannot

 

melt again.

thiosulphate

(n). A salt containing the anion

 

S

O 2−.

 

2

3

threshold

(n). Physical Science: the

 

magnitude or limit of something,

 

which, if exceeded, will cause

 

something else, e.g. release of

 

radiation, a chemical reaction, etc;

 

the minimum amount of energy

 

required to cause something.

 

Medicine: the maximum safety

 

level of a dose.

titrate

(v). To measure off a reagent

 

precisely drop by drop into a vessel

 

(container) containing another

 

reagent, so as to work out the

 

concentration of the reagent in the

 

vessel.

toxic, toxin

(adj., n.). Poisonous, poison.

transfer

(n). To move from one place to

 

another. Chemistry: usually refers

 

to moving an electron from one

 

compound to another. Finance:

 

usually refers to a payment

 

or credit. See credit, debit,

 

transaction.

trends

(n). Mathematics: regular patterns

 

within data.

tri-

(prefix). Three.

trial

(n). Chemistry: to repeat an

 

experiment, an iteration,

 

or particular attempt at an

 

experiment. (From “try”, to try

 

once).

triprotic

(n). Having three protons.

turbidity

(n). How muddy, muddled or

 

opaque or disturbed a liquid is.

   

U

 
   

unit

(n). A subdivision of a scale. See

 

scale.

universal

(n). A chemical which can indicate

(indicator)

how acid or basic a solution is,

 

ranging from reds (acidic) to violets

 

(basic), including most of the

 

colour spectrum.

unsaturated

(n). Organic chemistry: having

 

double or triple bonds present.

unstable

(n). Chemistry or Nuclear Physics:

 

prone to disintegrating or reacting.

urea

(n). CO(NH2)2. The substance used

 

to remove excess nitrogen from

 

animals via urination. Useful as a

 

fertiliser.

   

V

 
   
   

vapour

(n). The pressure above a liquid

pressure

caused by molecules evaporating

 

from the surface of its liquid form,

 

when in phase equilibrium (i.e. as

 

many molecules leaving the liquid

 

surface are condensing back into

 

the liquid).

variable

(n., adj.). A letter used to represent

 

an unknown quantity in algebra

 

(n); a quantity that changes (n);

 

subject to change (adj).

vessel

(n). Any container. Common use: a

 

container or ship.

visible

(adj). Able to be seen by the human

 

eye, opposite of invisible. Compare

 

microscopic, macroscopic.

viscosity

(n). The thickness of a fluid. A

 

viscous fluid flows slowly, e.g.

 

syrup. Pronounced “viss-KOSS-

 

itee” and “viss-k’s”.

volatility

(n). How easily something

 

evaporates. E.g. Ether (C2H5OC) is

 

more volatile than water.

volt

(n). Unit of potential difference

 

in electricity. The difference of

 

potential (Ep) that would carry one

 

ampere of current against one

 

ohm resistance. Same as emf. See

 

emf, resistance, ohm, ampere.

voltage

(n). The measurement of volts.

voltaic

(n). The production of electricity

 

in a cell. See battery, cell,

 

electrochemistry, electrode,

 

cathode, anode, galvanic.

volume

(n). A measure of the space

 

occupied by an object, equal to

 

length x breadth x height.

   

Y

 
   

yield

(n., v.). The amount of substance

 

produced in a chemical reaction

 

(n); products of a process (n); to

 

hand over or give up (v).

The maths you need

This section gives you the basic mathematical skills that you need to pass any subject that makes use of mathematics. Whether you’re studying for Physical Science, Mathematics, or Mathematical Literacy, these basic skills are crucial. Do not go any further in this book until you have mastered this section.

1. Basic pointers

  • If a formula does not have a multiplication (×) sign or a dot-product (·), and yet two symbols are next to each other, it means “times”. So, m1m2 means mass 1 times mass 2. You can also write it as m1 × m2, or m1·m2
  • Comma means the same as decimal point on your calculator (i.e. 4,5 = 4.5). Do not confuse the decimal point with dot product (multiply): 4.5 = 412​but 4·5 = 20. Rather avoid using the dot product for this reason.
  • In science it is common to write divisors with an exponent. This means, for example, that 0,5 metres per second is usually written 0,5 m·s–1 rather than 0,5 m/s. Both notations are perfectly correct, however, and you may use either. It is important, however, that you either use –1 or / . If you just put 0,5 ms, that means 0,5 milliseconds, which is not a velocity (speed in a direction); it is a time. A variable is something that varies (means: changes). So, for example, the weather is a variable in deciding whether to go to the Variables in science and mathematics are represented with letters, sometimes called algebraic variables. The most common you see in maths is x, probably followed by y, z. In science, variables are given their letter symbols specifically depending on what they stand for; so, for example, M or m are used for mass (amount of substance in kilograms); v is used for velocity (speed in a certain direction); a is used for acceleration (change in velocity), etc. You can guess for the most part what a variable is for by what its letter is; so V is voltage, R is resistance, P is pressure, and so on.

2. Subject of formula or solving for
Very often you have to “make something the subject of a formula” or “solve for something”. This refers to finding the value of an unknown quantity if you have been given other quantities and a formula that shows the relationship between them.

Worked example 1
If John has 5 apples, and he gives some to Joanna, and he has two apples left, how many did he give to Joanna? Well, the formula would be something like this:

  • 5 – x = 2

To solve for x, we simply have to swap the x and the 2. What we’re actually doing is adding “x” to both sides:

  • 5 – x + x = 2 + x

this becomes:

  • 5 = 2 + x

then we subtract 2 from both sides to move the 2 over:

  • 5 - 2 = 2 - 2 + x 
    5 - 2 = x 
    3 = x  ... so John gave Joanna three apples.

The same procedures apply no matter how complex the formula looks. Just either add, subtract, square, square root, multiply, or divide throughout to move the items around.

Worked example 2
Let’s take an actual example from Electricity: V = IR. This means, the voltage in a circuit is equal to the current in the circuit times the resistance.
Suppose we know the voltage is 12 V, and the resistance is 3 Ω. What is the current?

  • V=IR
    12=3 × I

divide throughout by 3 so as to isolate the I

  • 12 = (30)I
     3    ( 3 )

remember that anything divided by itself is 1, so:

  • 12 = (1) × I ... and 12 = 4 ...so
     3                            3
    4 =  I  or 
    I = 4 A ... The circuit has a current of 4 amperes.

It is possible to remember how to solve for these equations using a triangle mnemonic as follows:
If you’re solving for V, cover V with your hand. Then, I next to R means I times R, or IR. So, V = IR. If you’re solving for R, cover R with your hand. V is over I. So R = VI ​. While this is an easier way to do it, remember that many formulas do not consist of only three parts, so it is better to know how to make something the subject of a formula, or solve for something.
vir kghakjghd

Worked example 3
Here’s a more tricky example. Given

  • Kc = 4,5
    [SO3] = 1,5 mol/dm3
    [SO2] = 0,5 mol/dm3
    [O2] = (X - 48) mol/dm3

Solve for x: 

  • kc kbhkajghd
    ∴x
    = 176 g

How did we get that answer?

Step by step
Let’s see how it works.First, solve for the exponents (powers):
step by tsep

 

Now we multiply both sides by 576 to remove the 576 from the bottom row

  • 576 = (x – 48) 576
    4,5         576 

and we cancel the 576’s on the right hand side as shown above.
Now, if 576 ÷ 4,5 = 128, then

  • 128 = x – 48

Now we add 48 to both sides to move the 48 across

  • 128 + 48 = x – 48 + 48 ... hence, 128 + 48 = x = 176.

3. Statistics
Many experiments in science use statistics. You should therefore at least know the following:
Dependent variable: The thing that comes out of an experiment, the effect; the results.
Independent variable(s): The things that act as input to the experiment, the potential causes. Also called the controlled variable.
Control variable: A variable that is held constant in order to discover the relationship between two other variables. “Control variable” must not be confused with “controlled variable”.
It is important to understand that in science, correlation does not mean causation. That is, if two variables seem to relate to each other (they seem to co-relate), it doesn’t mean that one causes the other. A variable only causes another variable if one of the variables is a function f(x) of the other. We will see more about this when we look at graphs, below.

  • Mean: The average. In the series 1, 3, 5, 7, 9, the mean is 1 + 3 + 5 + 7 + 9 divided by 5, since there are 5 bits of data. The mean in this case is 5.
  • Median: The datum (single bit of data) in the precise middle of a range of data. In the series 1, 3, 5, 7, 9, the median value is 5.
  • Mode: The most common piece of data. In the series 1, 1, 2, 2, 3, 3, 3, 4, 5, the mode is 3.

Often in scientific formulas it is said that things are proportional to each other. However, we cannot calculate the value of a force or energy output or mass etc., if we only know what things are in proportion (i.e. which things correlate).
Let’s take momentum for example. Momentum (how forcefully something moves, more or less), is proportional to velocity (speed in a direction). So the faster something’s moving, the more momentum it has. But p (momentum) can’t be calculated if we only know velocity; we need to know mass as well. Why? Because momentum is also proportional to mass; the more massive something is, the more momentum it has. Thus, to get rid of the proportionality sign (∝), we have to come up with a formula. Many experiments in science serve to find out what the relationship is between two variables, i.e. if they’re merely correlated — proportional — or if they’re causally related. In the case of momentum, it’s easy, because there are no further variables: p = mv. However, in the case of gravity or electric or magnetic field strengths, it’s not that easy. In those cases, we have to introduce something called a “constant”. A constant is a fixed value that is always multiplied into an equation. Constants are often written k. However, some specific constants, such as in the Law of Gravity, have their own symbol, in this case, G. These constants are given in the tables later in this book.

4. Graphs
A lot of work in science involves interpreting graphs. You get graphs of motion, graphs of rates of chemical reactions, graphs of distance-relative strengths of force fields, and so on. Before you can understand these graphs, it’s probably best to start from scratch with Cartesian Coordinates. “Coordinates” are numbers that refer to the distance of a point along a line, or on a surface, or in space, from a central point called the “origin”. Graphs that you will use have only two dimensions (directions). The positions of points on these graphs are described using two coordinates: how far across (left-to-right) the point is, called the x-coordinate, and how far up-or-down on the page the point is, called the y-coordinate.

Worked example 4
Consider the following graph. It shows six points in a straight line.


graphs
The coordinates shown can be described using what are called “ordered pairs”. For example, the furthest point in this graph is 3 units across on the “x-axis” or horizontal line. Likewise, it is also 3 units up on the y-axis, or vertical (up and down) line. So, its coordinates are (3;3). The point just below the midpoint or “origin”, is one unit down of the x-axis, and one unit left of the y-axis. So its coordinates are (-1;-1). Note that anything to the left or below of the origin (the circle in the middle), takes a minus sign. In most cases in science, you’ll only have graphs showing positive axes (plural of axis, pronounced aks-eez), since most graphs are of time 
This series of dots look like they’re related to each other, because they’re falling on a straight line. If you see a result like this in an experimental situation, it usually means that you can predict what the next dot will be, namely, (4;4). This kind of prediction is called “extrapolation”. If you carry out the experiment, and find that the result is (4;4), and then (5;5), you’ve established that there is a strong relation or correlation. You can therefore start thinking about a formula to describe your findings. For example, this might be a graph showing a measurement of voltage (x) against a measurement of resistance (y).
Now, another way of saying that x relates to y, or x is proportional to y, is to say that y is a function of x. This is written y = f(x). So, in the example given above, voltage is a function of resistance. But how is y related to x in this graph? Well, it seems to be in a 1 to 1 ratio: y = x. So the formula for this graph is y = x. In this case, we’re only dealing with two factors; x and y. In other graphs you’ll find that sometimes more factors are involved, such as acceleration graphs, which have units of m/s2. Don’t worry about that; you treat them the same way (for example, m/s2 vs. time).

Worked example 5
Now, let’s take a slightly more complex case, illustrated next to this paragraph. In this graph, we see that wherever x is equal to something, y is one more. So, trace your finger from the bottom left dot upwards. It meets the x-axis at the point -3. Do the same for the same point towards the y-axis. You’ll see it meets the y-axis at -2. You’ll see the next coordinates are (–2;–1), then (–1;0), then (0;1), (1;2), and finally (2;3). From this we can see that whatever x is, y is one more. So, y = x + 1 is the formula for this line.
worked example 5 jgjad

Worked example 6
Let’s take another case. In this next case, we see the following values: where x has a certain value, y has double that value. Let’s tabulate it.
worked exapmple 6 jkayhgda

x

y

1,5

3

1

2

0,5

1

0

0

–0,5

–1

1

–2

–1,5

–3

So, when x is 1,5, y is 3, when x is 1, y is 2. Thus, the formula for this line is: y = 2x. This value next to x is called the “gradient” or “slope” of the line. The larger the value next to x is, i.e. the larger the gradient, the steeper the slope. The gradient is usually abbreviated as “m” when it is unknown.
Now, how this applies to science is simple: if we are looking, for example, at a case of a graph of a chemical reaction, we will usually have the x-axis as time. And the y-axis will usually be the quantity (amount) of substances produced. So, if we have a graph of a chemical reaction with a large gradient, it means that the reaction is fast; a lot of substance (y) i s produced in a short time (x). If, for example, we heated the reaction, and saw that the gradient increased even more, that would show that the chemical reaction was sped up by heat, or, that reaction rate is proportional to heat. Likewise, if the gradient sloped downwards, it would show that the reaction slowed down over time, because y, the amount of substance produced, was decreasing, as x (time) increased, e.g. because the reactants were being used up.

Worked example 7
Let’s do one more case. In this case, we can see that y is a function of x, since it’s a straight line graph. However, it’s not that easy to see the relationship between x and y. We can see that the slope is the same as the previous graph, so it must be something like y = 2x. However, it doesn’t quite make sense, since 2(–1,5) is not –2. We see that where x is zero (at the origin), y is at 1. But the slope is the same, so it must be y = 2(0) + 1. So the formula is: y = 2x + 1.
worked example 7 jygyuad

 x 2x + 1 
 -1,5 -2  2(–1,5)+1 = –3+1 = –2
 -1  -1  2(–1)+1 = –2+1 = –1
 -0,5  0  2(–0,5) +1 = –1+1 = 0
 0  1  2(0)+1 = 0+1 = 1
 0,5  2  2(0,5)+1 = 1+1 = 2
 1  3  2(1)+1 = 2+1 = 3 

Resource sheets

The following information sheets will be supplied to you in the exam. You do not need to memorise them.

SI Units: Multipliers

Prefix

Symbol

Value

Value written in full

tera

T

1012

1 000 000 000 000

giga

G

109

1 000 000 000

mega

M

106

1 000 000

kilo

k

103

1 000

hecto

h

102

1 00

deka

da

101

1

deci

d

10–1

0,1

centi

c

10–2

0,01

milli

m

10–3

0,00 1

micro

µ

10–6

0,00 000 1

nano

n

10–9

0,00 000 000 1

pico

p

10–12

0,00 000 000 000 1

femto

f

10–15

0,00 000 000 000 000 1

Constants

Name  SI Unit Symbol  Approximate Value  Easier to Understand 
STP (Standard Temperature and  Pressure), (in Physics).  not applicable, two conditions 1 ATM (101,3 kPa), 25°C (298 Kelvin (K)) You generally put two ATM (bar) pressure in car tyres, i.e. the pressure in a car tyre is twice atmospheric pressure
Standard Conditions (Chemistry) not applicable, three conditions STP plus 1 mol/dm3 As above
Gas constant R 8,3 J / mol⋅K The R in PV = nRT
Molar gas volume at STP V0 22,4 dm3 / mol 22,4 Litres of gas is made by a mole of a substance
Avogadro’s constant NA 6,022045 × 1023 units/mol 6 022 000 000 000 000 000 000 00 particles is one mole

period table asdshbji

Formulas

Moles, Gas Laws, Chemical Equilibria:

= gas constant
= number of moles

m = mass
T= temperature
V= volume
c= concentration, also [ ]

  • n =    c =   c =
          M           V         MV 
  • PV = nRT    P1V1  =  P2V2   
                         T1            T2

formulas

Where [S] is the concentration of S in mol/dm3
Notes:
In most cases in chemistry, subscripts refer to how many atoms there are; e.g. H2O = two atoms of H & 1 atom of O.

Standard reduction potentials

standard reduction potential hufthtugfad

Notes:

  • Eθ means the same as E0.
  • There are two versions of this table; they are identical except one is upside-down. Just memorise that Fluorine (F) has the greatest oxidising ability.
  • A strong reducing agent will displace a weaker reducing agent from its salt.
  • Always start with the oxidation half reaction.
  • A redox reaction will take place when a reducing agent reacts with an oxidising agent.
  • Balance the electron charge of each half-reaction by multiplying each with a suitable coefficient.
  • Add the two half-reactions together, eliminating electrons from both sides.
  • Eliminate common ions or molecules from both sides of the equation e.g. H+ and H2
  • You can then combine the E0 voltages to get the total voltage of a cell. Use the values exactly as they are; do not round off.
    • E0cell = E0cathode – E0anode
      OR
    • E0cell = E0oxidising agent – E0reducing agent
  • A positive answer means that the reaction will proceed spontaneously from left to right. A negative value means that it is not spontaneous.
Last modified on Monday, 27 September 2021 06:45