Planning, evaluating and improving experiments

Measurement, maths and practical skills · Lesson 5 of 5

Lesson 5 of 5

Lesson 5 of 5 · Measurement, maths and practical skills

Planning, evaluating and improving experiments

8 min read · about 1 h 30 min with practice3 quick checks≈2% of the testStretch

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Planning and evaluation marks separate A from A*. Cambridge Paper 5 opens with a 15-mark plan for an experiment you have never seen. AQA Paper 3 Section A, Edexcel Paper 3, the IAL practical units, OCR’s practical questions and the WJEC/CCEA practical papers all ask you to criticise a method, pick out the biggest uncertainty and judge whether data really support a claim. The marks go to specific, justified, quantitative statements, never to vague ones.

By the end you’ll be able to

Identify independent, dependent and control variables and explain how each control is achieved
Write a workable, safe, sequenced method with named apparatus, ranges and numbers of readings
State in advance which graph to plot to test a proposed relationship and how the constants follow from gradient or intercept
Evaluate a procedure: identify the largest source of uncertainty and propose specific, justified improvements
Critically assess whether data support a hypothesis, including the effect of systematic errors on the conclusion

What the exam asks

Plan: “Design a laboratory experiment to test the relationship between $x$ and $y$ ” (Cambridge P5), or a 6-mark “Describe how you would investigate…” (AQA, Edexcel, OCR A).
Variables: name the independent, dependent and control variables, and say how each control is kept constant.
Analysis plan: “What graph would you plot? How would you determine $k$ and $n$ ?”, including units.
Evaluate: identify the largest source of uncertainty, suggest a specific improvement and explain why it helps.
Conclude: “Do the data support the hypothesis?”, with a quantitative argument that uses uncertainties.

Core ideas

Variables and controls

Check your understanding

3 questions on planning, evaluating and improving experiments. Every option is explained once you answer.

Answers are checked on our side, every option is explained, and your result feeds your mastery for this topic. It’s free.

Flashcards

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PromptCard 1 of 3

Independent, dependent and control variables?

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Planning, evaluating and improving experiments

Measurement, maths and practical skills · Lesson 5 of 5

Lesson 5 of 5

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Lesson 5 of 5 · Measurement, maths and practical skills

Planning, evaluating and improving experiments

8 min read · about 1 h 30 min with practice3 quick checks≈2% of the testStretch

Reading is free. Sign in to tick off lessons, keep your place and track your mastery.

By the end you’ll be able to

Identify independent, dependent and control variables and explain how each control is achieved
Write a workable, safe, sequenced method with named apparatus, ranges and numbers of readings
State in advance which graph to plot to test a proposed relationship and how the constants follow from gradient or intercept
Evaluate a procedure: identify the largest source of uncertainty and propose specific, justified improvements
Critically assess whether data support a hypothesis, including the effect of systematic errors on the conclusion

What the exam asks

Plan: “Design a laboratory experiment to test the relationship between $x$ and $y$ ” (Cambridge P5), or a 6-mark “Describe how you would investigate…” (AQA, Edexcel, OCR A).
Variables: name the independent, dependent and control variables, and say how each control is kept constant.
Analysis plan: “What graph would you plot? How would you determine $k$ and $n$ ?”, including units.
Evaluate: identify the largest source of uncertainty, suggest a specific improvement and explain why it helps.
Conclude: “Do the data support the hypothesis?”, with a quantitative argument that uses uncertainties.

Core ideas

Variables and controls

Check your understanding

3 questions on planning, evaluating and improving experiments. Every option is explained once you answer.

Answers are checked on our side, every option is explained, and your result feeds your mastery for this topic. It’s free.

Flashcards

The first 3 of 10 cards for this topic. Sign in and finish the lesson to review them with spaced repetition.

PromptCard 1 of 3

Independent, dependent and control variables?

0% read · 8 min left

Role	Meaning	Example: pendulum period against length
Independent (IV)	what you change deliberately	length $l$ , measured with a metre rule to the centre of the bob
Dependent (DV)	what you measure as a result	period $T$ , from 20 oscillations timed with a stopwatch
Control	kept constant, because it could also affect the DV	amplitude kept small (under 10°) by starting from the same angle each time; same bob

Proposed relationship	Plot	Gradient	Intercept	Relationship holds if
$y = kx^n$	$\lg y$ against $\lg x$	$n$	$\lg k$	straight line
$y = A e^{-kx}$	$\ln y$ against $x$	$- k$
$T = 2\pi\sqrt{l/g}$	$T^2$ against
$v^2 = u^2 + 2as$	$v^2$ against
$\varepsilon = V + Ir$	$V$ against $I$	$-r$

Vague (no credit)	Specific (credit)
“Use more accurate equipment”	“Use light gates connected to a data logger to time the trolley, which removes the reaction-time uncertainty of about 0.2 s”
“Repeat it”	“Repeat each reading three times and average, discarding anomalies, to reduce random error in $T$ ”
“Use a better ruler”	“Use a micrometer (0.01 mm) instead of vernier calipers (0.1 mm): the percentage uncertainty in a 0.30 mm diameter drops from 33% to about 3%”
“Avoid heat loss”	“Lag the beaker and fit a lid, so less energy is lost and the measured temperature rise is not too small”

-k

Planning, evaluating and improving experiments

By the end you’ll be able to

What the exam asks

Core ideas

Variables and controls

Check your understanding

Flashcards

Planning, evaluating and improving experiments

By the end you’ll be able to

What the exam asks

Core ideas

Variables and controls

Check your understanding

Flashcards

Writing a workable method

Choosing the graph before you take data

Evaluating a procedure

Judging a conclusion

Worked examples

Exam technique

Common mistakes

Quick recap

By the end you’ll be able to

What the exam asks

Core ideas

Variables and controls

vii.Check your understanding

viii.Flashcards

By the end you’ll be able to

What the exam asks

Core ideas

Variables and controls

vii.Check your understanding

viii.Flashcards

Writing a workable method

Choosing the graph before you take data

Evaluating a procedure

Judging a conclusion

Worked examples

Exam technique

Common mistakes

Quick recap

Check your understanding

Flashcards

Check your understanding

Flashcards