**Revision**

When revising, many people find it helpful to write as they work. You are more likely to remember something that you have written than something that you have just looked at in a book. You will also find that you can concentrate better and learn faster if you revise hard for a few short sessions rather than for one long one. You will find that you get more revision done in three half-hour sessions with five minute breaks in-between than in one session of 1½ hours. When you take a break, do something completely different – preferably physical. Go for a walk, jump up and down, run around the garden or kick a ball.

Your memory recall of the work you have learned will be improved immensely if you go through it at regular intervals. People who have studied memory talk about the ‘forgetting curve’. Suppose you have done an hour’s revision and have learned a

summary of a topic. The forgetting curve shows that whatever you are going to forget of that summary, you are likely to forget as much as half of it in the next 24 hours. If you spend just five minutes quickly going through that same summary the next day, and another five minutes a few days later, your memory recall at a later date when you write the exam will be much better.

**How to tackle exam questions**

**Multiple choice questions**

You probably will have to answer the questions by filling in blocks on an answer sheet. Use a pencil to fill in the blocks, so that you can rub it out if you wish to change an answer. If the examination requires you to use a pen, go over them again at the end when you are satisfied with your answers.

There will usually be four options to choose from in a multiple choice question. When you read the question, try to answer it in your mind without looking at the choices, then see if your answer is one of them. Sometimes the wrong choices can confuse you. There is always only one correct answer, so never fill in two blocks. If you do that, your answer will be marked wrong.

You do not lose marks if you get a multiple choice question wrong, so never leave out a question simply because you are not sure of an answer. Try to eliminate some choices that you think are definitely wrong, and then guess and hope for the best. Do not go on to the next question without committing yourself to an answer to the previous question, even if you are not sure of it. Answer it, but make a mark on the question paper so that, if you have time, you can come back to it when you have finished the rest of the examination.

**Calculations**

Any answer to a question that requires a calculation must start with a statement of the principle, law or equation that is required for the calculation. If you do not state the formula first and only write down numbers and an answer, you will get no marks, even if your answer is correct.

We use the SI system of units. If you are given a value in another unit, it first must be converted into the relevant SI unit before you substitute it into the equation. It is not necessary to write the unit with each substitution in the equation, provided each is in the correct SI units. You must write the correct SI unit with you final answer.

So the procedure is as follows:

- Ensure that all given quantities are in SI units.
- Write the relevant equation for the calculation. If necessary, change the subject of the formula.
- Substitute the given values. It is not necessary to write the unit with the substitution.
- Carry out the calculation.
- Write the answer, with the correct SI unit. If the quantity is a vector quantity, write the direction.

**Mark allocation**

Marks are usually allocated as follows:

- One mark for the equation for the calculation.
- One mark for each correct substitution, in SI units.
- One mark for the correctly calculated answer, with the unit. If the unit is missing or incorrect, this mark is lost.
- One mark for the statement of the correct direction, if it is a vector quantity.

**Positive marking**

Very often questions requiring calculations are structured so that an answer to one part of the question is used in another part of the question. If you make a mistake in the first part so that the answer to that part is wrong, you will not be penalised for an incorrect answer in the later part, provided your calculations are correct. This is often called ‘positive marking’. Nevertheless, what should you do if you have no idea how to answer (say) question 2.1, but know that if only you had the answer to 2.1 you could answer 2.2? Simply assume an answer to 2.1. Write ‘2.2 Assume the answer to 2.1 is …’. Write any number with the correct unit and carry on.

**How to use this study guide**

Each topic is presented as a summary followed by a selection of examination-type questions. The summaries are the ‘bare bones’ of what you need to know for each topic. Do not try simply to learn the summaries off by heart. You must make sure that you understand each statement in the summary. If not, then refer to the Learner’s Book and study the relevant section. Once you are sure that you understand the statements, you can concentrate on learning the summary. It will be useful for you to write down the key words as they appear in the summary, then test yourself to see if you can state what is in the summary. Then work through the questions set on the topic. The answers are given at the back of the book, with an indication of how marks would be allocated in an exam.

A full sample Physics examination and a full sample Chemistry examination are also provided, with answers for you to test yourself before the final exams at the end of the year.

**Prefixes and units**You will encounter the prefixes given in the table below as you study Physical Science. You will see from the table that the prefixes that are used in science all relate to exponents that are multiples of 3. While there are prefixes for numbers bigger than 106 and also smaller than 10-15, it is sufficient for you to learn only those that are in this table.

| mega- | kilo- | unit | milli- | micro- | nano- | pico- | femto- |

Factor | × 106 | × 103 | 1 | × 10–3 | × 10–6 | × 10–9 | × 10–12 | × 10–15 |

Symbol | M | K | m | μ | n | p | f | |

| MW º megawatt | kW kilowatt | W Watt | mW milliwatt | μW microwatt | nW nanowatt | pW picowatt | fW femto- watt |

- Micro uses the Greek symbol μ (pronounced ‘mew’).
- All prefix symbols are small letters except for mega. This is to distinguish mega from milli.
- When writing the symbol for the prefix with the symbol for the unit (for instance, mW) there is no space or dot between the prefix and the unit.

**SI units used in the Grade 10 curriculum**

Here is a list of the symbols and SI units for quantities that you will come across in the Grade 10 curriculum. Test yourself to see that you know the symbol and unit for the quantity and the quantity for the unit.

Temperature |
| K (kelvin) |

Distance |
| m |

Amplitude |
| m |

Frequency |
| Hz (hertz) |

Time |
| s |

Period |
| s |

Speed, velocity |
| m.s |

Wavelength | λ | m |

Energy |
| J (joule) |

Planck’s constant |
| J.s |

Charge |
| C (coulomb) |

Potential difference |
| V (volt) |

Emf |
| V (volt) |

Current |
| A (ampere) |

Resistance |
| Ω (ohm) |

Quantity of matter |
| mol |

Volume | V | m |

Concentration |
| mol·dm |

Pressure |
| Pa (pascal) |

Acceleration |
| m.s |