Identifying variables designing experiments

8 April 2023

How Science WorksIdentifying Variables and Designing Investigations

8 April 2023

Identifying variables and Designing InvestigationsLearning outcomes:By the end of the lesson you should be able to• Explain what the different types of variables are.• Recognise different variables in example experiments.• Understand why the consideration of variables is

important when designing an experiment.

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Identifying variables and Designing InvestigationsThe INDEPENDENT VARIABLE

• Also known as the INPUT variable.

• This is the thing that you change or manipulate, the thing you are testing.

8 April 2023

Identifying variables and Designing InvestigationsThe DEPENDENT VARIABLE

• Also known as the OUTPUT variable.

• This is the thing that you measure or observe, it’s the results of the experiment.– You expect the dependent variable to be

affected by the independent variable.

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Identifying variables and Designing InvestigationsThe CONTROL VARIABLES

• Any variable that you keep the same in order to allow for a ‘fair test’.

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Identifying variables and Designing InvestigationsExample No. 1

• A student thinks that year 10 students will be better at doing a quiz than year 8 students.– Task 1: Task 1: Write down the independent,

dependent and control variables in this experiment.

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Identifying variables and Designing InvestigationsExample No. 1• Independent variable = the year group the

students are in (year 10 or year 8)

• Dependent variable = the students scores on the quiz

• Control variables = the same quiz should be used, students should have the same amount of time to complete it.

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Identifying variables and Designing InvestigationsExample No. 2

• A student has made the following prediction for an experiment; “the more caffeine I drink the quicker my reaction times will be.”– Task 2: Task 2: What are the independent, dependent

and control variables in this experiment.

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Identifying variables and Designing InvestigationsExample No. 2• Independent variable = the amount of caffeine

drunk by the student (e.g. number of cups of cola)

• Dependent variable = the students reaction times (e.g. how quick they can catch a ruler)

• Control variables = the same type of drink, same method of measuring reaction time.

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Identifying variables and Designing InvestigationsExample No. 3

• The light intensity was measured at different points moving away from the trunk of a large tree in full leaf.– Task 3: Task 3: What are the independent, dependent

and control variables in this experiment.

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Identifying variables and Designing InvestigationsExample No. 3• Independent variable = the distance from the

tree trunk.

• Dependent variable = the light intensity.

• Control variables = the same tree used for all measurements, the same light intensity meter, the same day/weather conditions.

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Identifying variables and Designing InvestigationsExample No. 4

• Listening to music impairs your ability to study.– Task 4: Task 4: What are the independent, dependent

and control variables in this experiment.

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Identifying variables and Designing InvestigationsExample No. 4• Independent variable = whether the student is

listening to music or not.

• Dependent variable = the students ability to recall information leant while listening to music (e.g. score on a memory test).

• Control variables = the same type of music, the same information to be learnt.

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Identifying variables and Designing InvestigationsDesigning an experiment.• The larger the surface area of a parachute,

the slower the object will fall.– Task 5: Task 5: design an experiment to test this

hypothesis• Identify the variables – what are you going to

change? How will you change it? What will you measure? How will you measure it? What needs to be kept the same to make the experiment a fair test?

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Identifying variables and Designing InvestigationsDesigning an experiment.

• What is the optimum temperature needed for the enzyme amylase to work?– Task 6: Task 6: design an experiment to test this

hypothesis• What are the independent and dependent

variables? How will you make it a fair test? How many different temperatures will you test? How will you measure the results?

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Identifying variables and Designing InvestigationsPlenary: Revisiting the learning outcomes

• Show me, using your traffic lights, how well you think you have met each of the learning outcomes.– Explain what the different types of variables are.– Recognise different variables in example experiments.– understand why the consideration of variables is

important when designing an experiment.