A pupil releases the same toy car from the top of the same ramp, without a push. The ramp is raised from 10 cm to 20 cm. The pupil measures how far the car travels beyond the ramp on the same hard floor.
Which factor did the pupil deliberately change?
The pupil chooses the ramp height before each test: 10 cm, then 20 cm. The distance travelled is the result, not the factor deliberately changed.
A pupil releases the same toy car from the top of the same ramp, without a push. The ramp is raised from 10 cm to 20 cm. The pupil measures how far the car travels beyond the ramp on the same hard floor.
What result is recorded after the car rolls?
Measure the distance from the bottom of the ramp to the front of the stopped car. In these example results it is 40 cm, then 70 cm.
A pupil releases the same toy car from the top of the same ramp, without a push. The ramp is raised from 10 cm to 20 cm. The pupil measures how far the car travels beyond the ramp on the same hard floor.
Which should be kept the same to compare the effect of ramp height?
Use the same car, the same ramp and the same floor surface. Release the car from the top without a push each time. These choices help isolate the effect of ramp height.
A variable is a factor that can have different values or types. In one investigation, different variables do different jobs.
Which is the dependent variable in the car test?
Independent: ramp height. Dependent: distance travelled. Control variables include the car used and the floor surface. There can be several control variables.
A pupil tests a 10 cm ramp on a hard floor and a 20 cm ramp on carpet. The same car is used.
Why is it hard to tell whether ramp height caused a difference?
The floor surface could also affect the distance travelled. Test both ramp heights on the same floor surface, then compare the new measurements.
A pupil tests water held at 20 °C and 40 °C. Each test uses 100 cm³ of water and 5 g of the same sugar, with no stirring. The pupil measures the time until all the sugar dissolves.
What is the dependent variable here?
Change the water temperature. Measure the dissolving time. Keep the water volume, sugar mass and type, and stirring method the same.
Temperature does not always have the same job. Read what the pupil is testing.
Compare 20 °C and 40 °C water. Measure dissolving time.
Compare coarse and fine sugar. Keep water at 40 °C and measure dissolving time.
In Test B, what is the role of water temperature?
Test A changes water temperature, so it is independent. Test B holds it at 40 °C, so it is a control variable. A thermometer can check a control variable; being measured does not automatically make a factor the dependent variable.
A pupil tests water held at 20 °C and 40 °C. Each test uses 100 cm³ of water and 5 g of the same sugar, with no stirring. The pupil measures the time until all the sugar dissolves.
Keep the mass of sugar the same.
Use a balance to measure 5 g each time.
Sugar mass could also affect dissolving time.
Which explains why the sugar mass must stay at 5 g?
What: mass of sugar. How: weigh out 5 g of the same sugar for each test. Why: the amount of sugar could affect the dissolving time, making the effect of temperature harder to judge.
A pupil releases the same toy car from the top of the same ramp, without a push. The ramp is raised from 10 cm to 20 cm. The pupil measures how far the car travels beyond the ramp on the same hard floor.
Identify the independent variable.
Ramp height is deliberately changed from 10 cm to 20 cm. It is the independent variable.
A pupil releases the same toy car from the top of the same ramp, without a push. The ramp is raised from 10 cm to 20 cm. The pupil measures how far the car travels beyond the ramp on the same hard floor.
Identify the dependent variable.
The dependent variable is the outcome: distance travelled beyond the ramp, measured in cm.
A pupil releases the same toy car from the top of the same ramp, without a push. The ramp is raised from 10 cm to 20 cm. The pupil measures how far the car travels beyond the ramp on the same hard floor.
Which is a control variable?
Use the same floor surface because the surface could also affect the distance travelled.
A pupil releases the same toy car from the top of the same ramp, without a push. The ramp is raised from 10 cm to 20 cm. The pupil measures how far the car travels beyond the ramp on the same hard floor.
Which names a variable, rather than a piece of equipment?
A variable is a quantity or characteristic. Name what is measured, such as distance, rather than the measuring instrument.
A pupil compares a 10 cm ramp on a hard floor with a 20 cm ramp on carpet.
Which change would make this a better test of ramp height?
Keep the floor surface the same while changing the ramp height. Both tests must then be measured again.
A pupil tests water held at 20 °C and 40 °C. Each test uses 100 cm³ of water and 5 g of the same sugar, with no stirring. The pupil measures the time until all the sugar dissolves.
Identify the independent variable.
The pupil chooses different water temperatures and measures their effect on dissolving time.
A pupil tests water held at 20 °C and 40 °C. Each test uses 100 cm³ of water and 5 g of the same sugar, with no stirring. The pupil measures the time until all the sugar dissolves.
Identify the dependent variable.
Time is the dependent variable here because it is the outcome measured. The stopwatch is the equipment used.
A pupil tests water held at 20 °C and 40 °C. Each test uses 100 cm³ of water and 5 g of the same sugar, with no stirring. The pupil measures the time until all the sugar dissolves.
The pupil uses 100 cm³ of water each time. Which names this control variable precisely?
“Volume of water” is precise. “Water” alone does not say whether you mean its volume, temperature or another property.
A pupil tests water held at 20 °C and 40 °C. Each test uses 100 cm³ of water and 5 g of the same sugar, with no stirring. The pupil measures the time until all the sugar dissolves.
How should the pupil keep the volume of water constant?
Measure out the same 100 cm³ of water for each test, using suitable measuring equipment.
A pupil tests water held at 20 °C and 40 °C. Each test uses 100 cm³ of water and 5 g of the same sugar, with no stirring. The pupil measures the time until all the sugar dissolves.
Why should each test use the same mass of sugar?
Changing sugar mass as well as temperature would make it harder to judge the effect of temperature on dissolving time.
A pupil places the same piece of pondweed 10 cm, 20 cm and 30 cm from the same lamp. They record the volume of oxygen collected in 60 s. Water temperature is kept at 25 °C.
Which variable is deliberately changed?
The pupil moves the same lamp to different distances. The independent variable is the distance between lamp and pondweed.
A pupil places the same piece of pondweed 10 cm, 20 cm and 30 cm from the same lamp. They record the volume of oxygen collected in 60 s. Water temperature is kept at 25 °C.
Which is the dependent variable?
The outcome is the volume of oxygen collected in the fixed 60 s, measured in cm³.
A pupil places the same piece of pondweed 10 cm, 20 cm and 30 cm from the same lamp. They record the volume of oxygen collected in 60 s. Water temperature is kept at 25 °C.
What is the role of the 60 s collection time?
Time is controlled here so each gas volume is collected for the same duration. A variable can be kept constant in a particular test.
A pupil heats identical water samples for 30 s, 60 s and 90 s. Each sample starts at 20 °C. They measure the final water temperature.
Identify the independent variable.
Heating time is deliberately changed, so it is independent in this test. Time does not have a fixed role in every investigation.
A pupil compares coarse and fine sugar. They use a thermometer to check that the water remains at 40 °C, and measure the dissolving time.
What is the role of water temperature?
Water temperature is a control variable. Measuring a factor to keep it constant does not make it the dependent variable.
A pupil changes the ramp height and measures the distance travelled. Two tests happen to give the same distance.
Is distance travelled still the dependent variable?
The dependent variable is the outcome you measure, whether it changes or stays the same.
Every low-ramp test uses a hard floor. Every high-ramp test uses carpet. A pupil repeats each test five times.
Have the repeats removed the problem with this comparison?
Repeats can help assess variation in results. They cannot separate the effects of ramp height and floor surface when both differ together.
A pupil changes water temperature and measures sugar dissolving time. The water volume is already kept constant.
Should other relevant factors also be controlled?
Keep all relevant factors that could affect dissolving time constant, apart from the water temperature being tested.
A pupil compares cotton, wool and bubble wrap around identical beakers. Every beaker starts with 100 cm³ of water at 60 °C. They record the water temperature after 5 minutes. Insulation thickness and other conditions are kept the same.
Choose the role of each factor.
Change the insulating material. Measure the water temperature after 5 minutes. Keep the starting water volume at 100 cm³. Other control variables include starting temperature, insulation thickness and cooling time.
In the insulation test, every beaker starts with water at 60 °C. The pupil changes the insulating material and measures the temperature after 5 minutes.
Why must the starting temperature be the same?
Starting temperature could affect the final temperature. Keeping it the same helps the pupil compare the effect of the insulating material. This is more specific than only saying “to make it fair”.
Deliberately change one factor. Measure the outcome. Keep other relevant factors the same.
Use the first three steps before naming the variables. Ask pupils to point to what changes, what is measured and what stays the same. Then connect those jobs to the scientific names. Always use the full term “control variable”; a control treatment or comparison group is a different concept. Explanations are optional; questions move from the familiar car test to new situations.
All questions and example results are original. Scientific terminology follows the AQA GCSE science glossary. These activities focus on controlled experiments.