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GCSE Biology · GCSEChapter 1 · Working scientifically and practical skills
GCSE · Chapter 1

Working scientifically and practical skills

By the end of this chapter you will be able to

  • Name the independent, dependent and control variables in a practical
  • Write a risk assessment with a hazard, a risk and a control measure
  • Calculate a mean, decide whether an anomaly should be removed, and explain precision and accuracy
  • Convert units, write numbers in standard form and calculate a percentage change
  • Read values from a graph, describe a pattern, and evaluate a conclusion

You should already know

  • Working with units, means and graphs at KS3 (Year 9 Science and Maths)

Where this leads

  • Every required practical in the course (Chapters 2 to 18)
  • Cell sizes in standard form (Chapter 2)

GCSE Biology. Content follows the GCSE (9-1) subject content for England (Edexcel and AQA). Content references: Identify independent, dependent and control variables, and plan a fair test, Assess the risks of a practical and describe control measures, Calculate means, identify anomalies, and explain precision, accuracy and reliability, Use units and standard form, and calculate percentage change, Draw and read tables and graphs, and evaluate a method and a conclusion.

Exercise P  Do you remember?

1
FWhat is the mean of 4, 6 and 8? Write the number.
2
FHow many millimetres are there in 1 centimetre? Write the number.
3
FWhat is 100 multiplied by 10? Write the number.
4
FWhich is the independent variable: the one you change on purpose, or the one you measure? Write the words.
5
FWhat does a line graph show best? Write the words.
1.1

Variables and fair tests

GCSE
Identify independent, dependent and control variables, Plan a fair test
Video lesson: Variables and fair testsComing soon
Context. Ravi wants to know whether pondweed gives off more bubbles when the lamp is closer. “I will move the lamp,” he says, “and count the bubbles. The pondweed, the water and the time must stay the same.”

In a practical, the independent variable is the one you change on purpose. The dependent variable is the one you measure to see its effect. A control variable is any other factor that could change the result, so it is kept the same. A test is fair when only the independent variable is changed.

A testable hypothesis is a prediction that can be checked by measuring or counting. “Pondweed looks nice” cannot be tested. “More light gives more bubbles” can be tested.

Type of variableIn the pondweed test
Independent (changed on purpose)distance from the lamp (cm)
Dependent (measured)bubbles per minute
Control (kept the same)type of pondweed, water temperature, length of the cut stem
The variables in a pondweed test under a lamp

Key ideas

  • The independent variable is changed on purpose.
  • The dependent variable is measured to show the effect.
  • Control variables are kept the same so the test is fair.
  • Change only one variable at a time.
Worked example 1.1.1
Ravi changes the distance of the lamp from the pondweed. Name the independent variable. Write the words.

Method. Find the variable that is changed on purpose.

  1. Find the change. Ravi moves the lamp on purpose.
    moves the lamp
  2. Name the variable. The distance from the lamp is the variable being changed.
    distance from the lamp
  3. Write the answer.
    distance from the lamp

Check. The distance is set before each count. ✓

Worked example 1.1.2
Ravi counts the bubbles in one minute. Name the dependent variable. Write the words.

Method. Find the variable that is measured.

  1. Find the measurement. Ravi counts the bubbles, so the count is measured.
    counts the bubbles
  2. Name the variable. The number of bubbles per minute is the dependent variable.
    bubbles per minute
  3. Write the answer.
    bubbles per minute

Check. The bubbles depend on the distance from the lamp. ✓

Worked example 1.1.3
Name one control variable in Ravi’s test. Accept any one: type of pondweed, water temperature, or length of the cut stem.

Method. Find a factor that must stay the same.

  1. Think. A control variable stays the same for every reading.
    stays the same
  2. Name one. If the water temperature changed, the test would not be fair.
    water temperature
  3. Write the answer.
    Accept any one: type of pondweed, water temperature, or length of the cut stem.

Check. Keep each control the same for every distance. ✓

Watch out

Watch out: if Ravi moves the lamp and also changes the water temperature, he cannot say which change caused the result.

Exam tip

Exam tip. Name a variable in full, for example “distance from the lamp”, not just “distance”.

Try it (with your teacher). Set up pondweed in water under a lamp at two distances. Keep the pondweed type, the water and the time the same. Count the bubbles for one minute at each distance. Name the independent, dependent and control variables.

Exercise 1A  Variables and fair tests

1
FA pupil changes the distance of a lamp from pondweed to change the light. Name the independent variable. Write the words.
2
FIn the same test, name the dependent variable. Write the words.
3
FIn the same test, name one control variable. Accept any one: type of pondweed, water temperature, or length of the cut stem.
4
FIn a test of how temperature changes the number of bubbles from pondweed, which variable is measured? Write the words.
5
FWhich of these is a testable hypothesis? Write a or b. (a) Pondweed is an interesting plant. (b) More light gives more bubbles from pondweed.
6
FAli changes the lamp distance and the water temperature at the same time. Is this a fair test? Write yes or no.
7
PSA bean test keeps the number of seeds, the water and the light the same, and changes only the temperature. Name one control variable. Accept any one: number of seeds, amount of water, or light.
8
PSA pupil plans to plot the height of a bean plant against time. Which variable goes on the x-axis? Write the words.
9
PSWrite a testable hypothesis about pondweed and light. Accept any sentence that says more light gives more bubbles, or less light gives fewer bubbles.
10
RRuth says her result proves that light causes bubbles. Explain in one sentence why one test cannot prove this. Accept any sentence that says the result shows a link, but other factors or chance could also explain it, so more controlled tests are needed.
1.2

Risk assessment and safe practice

GCSE
Assess the risks of a practical and describe control measures
Video lesson: Risk assessment and safe practiceComing soon
Context. Hana’s class is going to look at prepared slides under a microscope, test pondweed under a lamp and use iodine solution. Before the lessons, the teacher asks: “What could go wrong, and how will you stop it?”

A hazard is something that could cause harm. The risk is the chance that the harm happens, and how serious it could be. A control measure is an action that reduces the risk. A risk assessment lists the hazards, the risks and the control measures before any practical starts.

Pupils use only safe living material, such as pondweed, bean plants and prepared slides. Microorganisms are handled only under the school’s microbiology rules, and some are used by the teacher as a demonstration only. Anything involving a flame, hot water or electricity is controlled by the teacher.

ActivityHazardRiskControl measure
Heating water in a beaker for a teacher demonstrationhot water and a flameburns and scaldsthe teacher lights and controls the burner; tie back hair; use a heatproof mat
Looking at prepared slides with a microscopea glass slide and the lampcut fingers; hot lamphandle slides by their edges; switch the lamp off when finished
Testing pondweed under a lampan electrical lamp near waterelectric shockkeep the lamp dry and at a safe distance; a teacher checks the set-up
Testing starch with iodine solutioniodine stains skin and clothes and is harmful if swallowedstained clothes; skin irritationwear eye protection and an apron; wipe up spills at once
A risk assessment for four practicals

Key ideas

  • A hazard could cause harm; a risk is the chance and seriousness of harm.
  • A control measure reduces a named risk.
  • Use only safe living material, such as pondweed and bean plants.
  • Keep electricity, flames and hot water under teacher control.
Worked example 1.2.1
In a practical with hot water and a flame, name the hazard. Write the words.

Method. Find what could cause harm.

  1. Look at the set-up. Hot water and a flame can cause burns.
    hot water and a flame
  2. Name it. The hazard is the hot water and the flame.
    hot water and a flame
  3. Write the answer.
    hot water and a flame

Check. The hazard is the thing that could cause harm. ✓

Worked example 1.2.2
In the same practical, name the risk. Write the words.

Method. Think about the harm that could happen.

  1. Think. Touching the hot beaker or the flame could hurt a person.
    could hurt a person
  2. Name it. So the risk is burns and scalds.
    burns and scalds
  3. Write the answer.
    burns and scalds

Check. A risk is the chance of harm and how serious it could be. ✓

Worked example 1.2.3
Name a control measure for the flame and hot water. Accept any one: a teacher lights and controls the burner, or tie back long hair.

Method. Choose an action that reduces the risk.

  1. Think. An action that reduces burns is a control measure.
    reduces burns
  2. Name one. A teacher who lights and controls the burner reduces the risk.
    teacher lights
  3. Write the answer.
    Accept any one: a teacher lights and controls the burner, or tie back long hair.

Check. Each control measure must match a named risk. ✓

Watch out

Watch out: a risk is not the same as a hazard. “The beaker is hot” is a hazard. “Burns and scalds” is the risk.

Exam tip

Exam tip. A control measure must match the risk. “Be careful” does not name an action, so it does not earn the mark on its own.

Try it (with your teacher). With your teacher, write a risk assessment for looking at prepared slides under a microscope. Make columns for the activity, hazard, risk and control measure. Check that every control measure reduces a named risk.

Exercise 1B  Risk assessment and safe practice

1
FWhat is a hazard? Write the words.
2
FWhat is a risk? Write the words.
3
FA glass microscope slide could break. Name the risk. Write the words.
4
FWhich of these is a control measure? Write a or b. (a) The slide could break. (b) Handle slides by their edges.
5
FWhy should pupils use a lamp only in the way the teacher shows? Write one sentence. Accept any sentence that says the lamp near water could cause an electric shock, so the set-up must be checked.
6
PSWhich of these is safe for a pupil practical? Write a or b. (a) pondweed from a pond (b) an unknown mould from a damp wall
7
PSA hot lamp filament could burn a pupil. Name one control measure. Write the words.
8
PSA risk for iodine solution is stained clothes. Name a control measure that matches this risk. Write the words.
9
RA pupil writes “be careful” as the control measure for iodine solution. Explain why this is not enough. Write one sentence. Accept any sentence that says it names no specific action to reduce a named risk, such as wearing an apron and eye protection.
10
RChallenge: write a risk assessment row for testing pondweed under a lamp. Give the hazard, the risk and one control measure. Accept any row that names an electrical hazard, electric shock as the risk, and a named action such as keeping the lamp dry.
1.3

Means, anomalies, precision and accuracy

GCSE
Calculate means and identify anomalies, Explain precision, accuracy and reliability
Video lesson: Means, anomalies, precision and accuracyComing soon
Context. Ravi counts the bubbles from pondweed at 20 cm four times. The counts are 14, 16, 15 and 24. The last count is much higher than the others. “Should I leave it out?” he asks.

The mean is the total of the results divided by the number of results. Repeat each reading several times to find a mean that you can trust. An anomaly is a result that does not fit the pattern of the others. An anomaly is left out of the mean only when there is a clear reason, such as a measuring mistake, and the reason is written down.

Precision is how close repeat results are to each other. Accuracy is how close a result is to the true value. A reliable result is one that gives the same answer when repeated, and that other people can also get using the same method.

RepeatBubbles per minute at 20 cm
114
216
315
424
Four repeat counts of bubbles at 20 cm

Key ideas

  • Mean = total of the results divided by the number of results.
  • An anomaly is left out only with a stated reason.
  • Precision is closeness of repeats; accuracy is closeness to the true value.
  • Uncertainty for a scale reading is half the smallest division.
Worked example 1.3.1
Find the mean of the four repeat counts, 14, 16, 15 and 24. Write the number.

Method. Add the results, then divide by the number of results.

  1. Add. Add the four counts: 14 + 16 + 15 + 24 = 69.
    14 + 16 + 15 + 24 = 69
  2. Divide. Divide the total by 4, the number of counts.
    69 / 4 = 17.25
  3. Write the answer.
    17.25

Check. 17.25 x 4 = 69. ✓

Worked example 1.3.2
Leave out the anomaly, the count of 24, and find the mean of the other three. Write the number.

Method. Remove the anomaly, then find the mean of the rest.

  1. Remove. The count of 24 does not fit the pattern. Leave it out only because a reason is recorded, for example a counting mistake.
    remove 24
  2. Add. Add the three remaining counts: 14 + 16 + 15 = 45.
    14 + 16 + 15 = 45
  3. Divide. Divide by 3.
    45 / 3 = 15
  4. Write the answer.
    15

Check. 15 x 3 = 45. ✓

Worked example 1.3.3
A set of readings is very close together but all are 5 cm below the true value. Write the words: precise but not accurate, or accurate but not precise.

Method. Compare the spread with the distance from the true value.

  1. Spread. The readings are close together, so they are precise.
    close together
  2. Distance. They are far from the true value, so they are not accurate.
    far from the true value
  3. Conclude. The result is precise but not accurate.
    precise but not accurate
  4. Write the answer.
    precise but not accurate

Check. Precision and accuracy are separate ideas. ✓

Watch out

Watch out: do not remove a result just because it is high. Remove an anomaly only when you have a clear reason, and say what the reason is.

Exam tip

Exam tip. A mean can be a decimal. Leave it as a decimal rather than rounding it to a whole number.

Try it (with your teacher). With your teacher, count the bubbles from pondweed for one minute, three times, at one distance. Work out the mean. Look for an anomaly and decide whether there is a reason to leave it out.

Exercise 1C  Means, anomalies, precision and accuracy

1
FFind the total of 5, 7 and 9. Write the number.
2
FFind the mean of 5, 7 and 9. Write the number.
3
FFind the mean of 12, 15, 18 and 21. Write the number.
4
FThree readings of a scale are 0.31 A, 0.29 A and 0.30 A. Find the mean. Write the number.
5
FThe counts are 14, 16, 15 and 24. Which count is the anomaly? Write the number.
6
FWithout the anomaly, the counts are 14, 16 and 15. Find the mean. Write the number.
7
FFind the range of the repeats 8, 9 and 10 bubbles per minute. Write the number.
8
FWhich describes precision? Write a or b. (a) The repeats are close together. (b) The result is close to the true value.
9
FWhich describes accuracy? Write a or b. (a) The repeats are close together. (b) The result is close to the true value.
10
PSA ruler has a smallest division of 1 mm. Write the uncertainty of one reading, in mm. Write the number.
11
PSA pupil measures three bean leaves: 20 mm, 22 mm and 24 mm. Find the mean length. Write the number.
12
RRavi says the mean of 14, 16, 15 and 24 is 15 because the anomaly must be removed. Write one sentence explaining why he is wrong. Accept any sentence that says the anomaly is left out only with a stated reason, so the mean of all four counts is 17.25.
1.4

Units, standard form and percentage change

GCSE
Use units and convert between them, Write numbers in standard form, Calculate percentage change
Video lesson: Units, standard form and percentage changeComing soon
Context. Hana measures a bean leaf and writes its length as 6 cm. Her partner writes the same length as 60 mm. They both agree, but they need to use the same units to compare the leaves.

Biology uses the metre and its smaller units. Each step in the length units is a multiplication or division by 10 or 1000. Standard form writes a number as a number between 1 and 10, multiplied by a power of 10, for example 4500 = 4.5 x 103. A percentage change is the change divided by the original value, multiplied by 100.

Percentage change = (change / original value) x 100.

UnitEqual to
1 cm10 mm
1 m100 cm
1 m1000 mm
1 mm0.001 m
Length units used in biology

Key ideas

  • 1 cm = 10 mm; 1 m = 100 cm = 1000 mm.
  • Standard form: a number between 1 and 10, times a power of 10.
  • Percentage change = change / original value x 100.
  • Always write the unit in the answer.
Worked example 1.4.1
Convert 2.5 cm into mm. Write the number of mm.

Method. Use 1 cm = 10 mm, so multiply by 10.

  1. Multiply. Each centimetre is ten millimetres, so multiply by 10.
    2.5 x 10
  2. Calculate. Multiply 2.5 by 10 to get the number of millimetres.
    2.5 x 10 = 25
  3. Write the answer.
    25

Check. 25 mm divided by 10 is 2.5 cm. ✓

Worked example 1.4.2
Write 4500 in standard form.

Method. Move the decimal point to make a number between 1 and 10, and count the places moved.

  1. Place the point. Move the point to make 4.5, which is between 1 and 10.
    4.5
  2. Count the places. The point moved three places to the left, so the power is 3.
    3 places
  3. Write it. So 4500 = 4.5 x 103.
    4.5 x 103
  4. Write the answer.
    4.5 x 103

Check. 4.5 x 1000 = 4500. ✓

Worked example 1.4.3
A plant grows from 12 cm to 15 cm. Find the percentage change.

Method. Find the change, then divide by the original value and multiply by 100.

  1. Find the change. The change is 15 - 12 = 3 cm.
    15 - 12 = 3
  2. Divide. Divide the change by the original value, 12.
    3 / 12 = 0.25
  3. Multiply. Multiply by 100 to give a percentage.
    0.25 x 100 = 25
  4. Write the answer.
    25%

Check. 25% of 12 is 3, so 12 + 3 = 15. ✓

Watch out

Watch out: 1 cm is 10 mm, not 100 mm. For percentage change, divide by the original value, not the new value.

Exam tip

Exam tip. Write the unit with your answer, for example “25 mm”, so the marker can see it is correct.

Try it (with your teacher). With your teacher, measure one bean leaf in millimetres. Convert the length to centimetres and check the answer using 1 cm = 10 mm. Then measure it again the next day and work out the percentage change.

Exercise 1D  Units, standard form and percentage change

1
FConvert 3 cm into mm. Write the number.
2
FConvert 5000 mm into m. Write the number.
3
FConvert 2 m into cm. Write the number.
4
FConvert 0.5 m into cm. Write the number.
5
FWrite 6000 in standard form. Write the answer using x 10^ for the power.
6
FWrite 0.04 in standard form. Write the answer using x 10^ for the power.
7
FWork out 2 x 10^3. Write the number.
8
FWrite 3 x 10^-1 as a decimal. Write the number.
9
FA plant grows from 40 mm to 50 mm. Find the percentage change. Write the number, with the percentage sign.
10
PSA leaf shrinks from 80 mm to 60 mm. Find the percentage change. Write the answer as a decrease.
11
PSA leaf is 6 cm long. Write its length in mm. Write the number.
12
PSA stem grows from 150 mm to 165 mm. Find the percentage change. Write the number, with the percentage sign.
13
RAli writes 4500 as 45 x 102 and calls it standard form. Is this correct? Write yes or no.
14
RChallenge: a cell is measured as 0.02 mm across. Write this in standard form, then explain why standard form is useful for very small or very large numbers. Accept any answer that gives 2 x 10^-2 mm and a sentence saying it avoids long strings of zeros.
1.5

Tables, graphs and conclusions

GCSE
Draw and read tables and graphs, Describe patterns and evaluate a conclusion
Video lesson: Tables, graphs and conclusionsComing soon
Context. Ravi plots his results on a line graph. He sees that the mean number of bubbles falls as the lamp moves away. “So light makes the pondweed give off more bubbles,” he writes. “Is that a fair conclusion?” asks the teacher.

Choose the graph type from the data. A bar chart shows separate groups or categories. A line graph joins points to show how a value changes, usually over time or over a range of a variable. A scatter graph shows two linked numbers as separate points.

Put the independent variable on the x-axis, label both axes with units, and choose a scale that uses most of the grid. A conclusion says what the data show, how the data support the idea, and how far the test can be trusted.

Mean bubbles per minute010203040010203040distance from the lamp (cm)bubbles per minute
Line graph of mean bubbles per minute against distance from the lamp

Key ideas

  • Bar chart: separate groups. Line graph: change over a range. Scatter graph: two linked numbers.
  • Independent variable on the x-axis; dependent variable on the y-axis.
  • A conclusion matches the data and says how far it is supported.
  • An evaluation names a weakness and a specific improvement.
Worked example 1.5.1
Read the mean number of bubbles at 20 cm from the graph. Write the number.

Method. Find 20 on the x-axis, go up to the line, then read across to the y-axis.

  1. Find 20. Find 20 cm on the x-axis.
    20 cm
  2. Read across. The point at 20 cm is at 15 on the y-axis.
    point at 15
  3. Write the answer.
    15

Check. This matches the mean of the three counts from earlier. ✓

Worked example 1.5.2
Describe the pattern shown by the graph. Accept any sentence that says the number of bubbles falls as the distance from the lamp increases.

Method. Describe the change in y as x increases.

  1. Look at the trend. As the distance increases, the points go down.
    points go down
  2. Describe it. So the number of bubbles falls as the distance increases.
    falls as the distance increases
  3. Write the answer.
    Accept any sentence that says the number of bubbles falls as the distance from the lamp increases.

Check. The pattern uses the values: 40 at 10 cm, down to 5 at 40 cm. ✓

Worked example 1.5.3
Use the bean plant graph to find the change in height from week 1 to week 3. Write the number, in cm.

Method. Find the height at each week, then subtract.

  1. Read week 1. The plant is 6 cm tall at week 1.
    6 cm
  2. Read week 3. The plant is 11 cm tall at week 3.
    11 cm
  3. Subtract. The change is 11 - 6 = 5 cm.
    11 - 6 = 5
  4. Write the answer.
    5

Check. 6 + 5 = 11. ✓

Watch out

Watch out: the x-axis carries the independent variable and the y-axis the dependent variable. A conclusion that says “light causes” needs more than one test.

Exam tip

Exam tip. A conclusion should use the data values, for example “5 bubbles at 40 cm and 40 at 10 cm”, not only the words “it went down”.

Try it (with your teacher). With your teacher, plot a line graph of the mean number of bubbles against distance, with the distance on the x-axis. Describe the pattern, and write one improvement to the test.

Exercise 1E  Tables, graphs and conclusions

1
FIn the pondweed test, which variable goes on the y-axis? Write the words.
2
FWhich kind of graph shows separate groups, such as the number of plants in four areas? Write the words.
3
FWhich kind of graph joins points to show how plant height changes over time? Write the words.
4
FWhich kind of graph shows two linked numbers as separate points? Write the words.
5
FRead the mean number of bubbles at 10 cm from the graph. Write the number.
6
FRead the mean number of bubbles at 30 cm from the graph. Write the number.
7
FThe height of a bean plant at week 4 is shown in the graph. Write the height in cm. Write the number.
8
FFind the change in height of the bean plant from week 0 to week 2. Write the number, in cm.
9
FCompare the mean bubbles at 40 cm with those at 10 cm. Write fewer or more.
10
PSComplete the sentence: the number of bubbles ... as the distance from the lamp increases. Write the word that fits.
11
PSName one improvement to the pondweed test. Accept any sensible improvement, for example more repeats at each distance, or counting for a longer time.
12
PSRavi says the data prove that light causes bubbles. Write yes or no.
13
RChallenge: write a conclusion for the pondweed test in one sentence. It must use two data values and say how far the test supports the idea. Accept any sentence that uses data such as 40 and 5 bubbles per minute and says the result supports the idea, but more controlled tests would confirm it.

Chapter summary

SkillMethod
Fair testChange only the independent variable; measure the dependent variable; keep the control variables the same.
RiskHazard (what could cause harm), risk (chance and seriousness), control measure (reduces the risk).
Mean and anomalyTotal divided by the number of results; leave out an anomaly only with a stated reason.
Precision and accuracyPrecision: repeats close together. Accuracy: close to the true value.
Units1 cm = 10 mm; 1 m = 100 cm = 1000 mm; standard form is a number from 1 to 10 times a power of 10.
Percentage changeChange divided by the original value, times 100.
GraphsBar chart for groups; line graph for change; scatter graph for two linked numbers.

Can you…?

  • I can name the independent, dependent and control variables in a practical
  • I can write a risk assessment with a hazard, a risk and a control measure
  • I can calculate a mean and explain when an anomaly may be left out
  • I can explain precision, accuracy and reliability
  • I can convert units, write numbers in standard form and calculate a percentage change
  • I can read a graph, describe a pattern and evaluate a conclusion

Key terms

independent variable
the variable that is changed on purpose
dependent variable
the variable that is measured to show the effect
control variable
a variable that is kept the same so the test is fair
hazard
something that could cause harm
risk
the chance that harm happens, and how serious it could be
control measure
an action that reduces a named risk
anomaly
a result that does not fit the pattern of the others
precision
how close repeat results are to each other
accuracy
how close a result is to the true value
standard form
a number from 1 to 10 multiplied by a power of 10
percentage change
the change divided by the original value, multiplied by 100

Exercise 1Z  Check-up

1
Name the dependent variable in a test of how the distance of a lamp changes pondweed bubbles. Write the words.
2
Find the mean of 10, 12 and 14. Write the number.
3
Which describes a hazard? Write a or b. (a) hot water and a flame (b) burns and scalds
4
Find the anomaly in the counts 8, 9, 9 and 20. Write the number.
5
Convert 4 m into cm. Write the number.
6
Write 7000 in standard form. Write the answer using x 10^ for the power.
7
A plant grows from 20 cm to 26 cm. Find the percentage change. Write the number, with the percentage sign.
8
Which graph should be used to show the number of leaves on four different plants? Write the words.
9
Name one control measure for a hot coil or hot lamp. Accept any one: switch it off between readings, or let it cool.
10
Explain in one sentence why a fair test keeps the control variables the same. Accept any sentence that says other factors could change the result, so only the independent variable should change.

Total 19 marks. Allow about 19 minutes.

Exercise 1X  Exam-style questions

1
FName the independent variable in a test of how the length of a wire changes its resistance. Write the words.[1 mark]
2
FFind the mean of 5, 7 and 9. Write the number.[1 mark]
3
FName the independent variable in a test of how the temperature of water changes the number of bubbles from pondweed. Write the words.[1 mark]
4
PSWrite one hazard and one control measure for using a hot water bath. Accept any sensible pair, for example hot water and keeping the water bath away from edges.[2 marks]
5
PSConvert 1.2 km into m. Write the number. (1 km = 1000 m)[2 marks]
6
PSThree readings of a scale are 0.22 A, 0.26 A and 0.28 A. Find the mean. Write the number.[2 marks]
7
PSA plant grows from 40 mm to 46 mm. Find the percentage change. Write the number, with the percentage sign.[2 marks]
8
PSA pupil counts the bubbles from pondweed at four distances: 40, 15, 9 and 5 bubbles per minute. Describe the pattern in one sentence. Accept any sentence that says the number of bubbles falls as the distance increases.[2 marks]
9
RA pupil uses three repeat readings of 20, 22 and 35 mm. Explain whether the 35 mm reading should be left out. Accept any answer that says it should only be left out with a stated reason, and that the mean is not changed unfairly without one.[3 marks]
10
RA student says her results are accurate because all her repeat readings are close together. Explain the mistake in one sentence. Accept any sentence that says close repeats show precision, not accuracy, because accuracy needs closeness to the true value.[3 marks]
Chapter 2: Cell structure and microscopy →

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