S3 Science: Scientific Investigation And Fair Tests (Paper 1 (basics))

S3 Science: Scientific Investigation and Fair Tests (Paper 1 (basics))

2026-11-14

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Tutor Prep Guide · the steps of a scientific investigation, hypotheses and testable predictions, independent and dependent variables, controlled variables, fair tests, control groups, repeated measurements and the mean, range, percentage error, accuracy and precision

S3 Science: Scientific Investigation and Fair Tests (Paper 1 (basics))

This paper starts from the definition of a fair test and practises changing only one variable, identifying independent and dependent variables, controlling the other conditions, comparing against a control group, averaging repeated readings, the range, percentage error, and proportional prediction with a spring.

Direct answers　A fair test changes one variable; the independent variable is deliberately changed; the dependent variable is measured; everything else stays the same; the range is largest minus smallest; percentage error is error over accepted value times one hundred.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	20
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: S3 Science: Scientific Investigation and Fair Tests
Level	S3

02　Questions (10 items)

FoundationWhat do we call an experiment in which only one variable is changed and all the others are kept the same?
FoundationWhat is usually the first step of a scientific investigation?
FoundationThe boiling point of water is measured three times as 99.8, 100.1 and 100.0 degrees. What is the mean?
IntermediateA study looks at how the amount of fertiliser affects tomato growth. Which is the independent variable?
IntermediateWhen comparing the grease removing power of two washing up liquids, what should happen to the water temperature, the volume of water and the amount of oil?
IntermediateThe control plants are 12.0 cm tall and the experimental plants are 15.6 cm tall. By what percentage is the experimental group taller?
ChallengeAn electronic balance reads 12.4 g while the accepted value is 12.35 g. What is the percentage error?
ChallengeSix length readings are 2.05, 2.04, 2.06, 2.05, 2.07 and 2.03 cm. What is the range?
ChallengeA spring stretches 1.2 cm under 2 N and 2.4 cm under 4 N. How much does it stretch per newton, and what is expected under 12 N?
Error redoTwo plants are compared: one by the window watered with tap water, the other in the dark watered with distilled water. The student concludes that light affects growth. What is wrong?

03　Answers and one-line notes

#	Answer	One-line note
1	A fair test	With only one variable changing, the result can be blamed on that variable.
2	Observing a phenomenon and asking a question that can be investigated	Only with a question can you write a hypothesis and design an experiment.
3	99.97 degrees	The three readings add up to 299.9 and dividing by three gives 99.97.
4	The amount of fertiliser	The amount of fertiliser is deliberately changed, so it is the independent variable; plant height is the measured dependent variable.
5	All three must be kept the same	Only the type of washing up liquid may change; everything else must be identical for a fair test.
6	3.6 cm taller, which is 30.0 percent	Subtract to get 3.6, then divide by the control value 12.0 and multiply by one hundred.
7	0.40 percent	The error of 0.05 is divided by the accepted value 12.35 and multiplied by one hundred.
8	0.04 cm	The range is the largest reading 2.07 minus the smallest 2.03.
9	0.6 cm per newton, so 7.2 cm under 12 N	Divide 1.2 by 2 to get 0.6, then multiply 0.6 by 12 to predict the stretch.
10	Two variables, light and water quality, were changed at the same time, so it is not a fair test	To test light, the water quality and amount must be identical for both plants.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

For any investigation ask three questions: what is changed (independent variable), what is measured (dependent variable), and what must stay the same (controlled variables); two changes at once means it is not a fair test.Tutor Registration →

Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.