Year 8 Science · Unit 3 · Lesson 11

Variables in Change Investigations

Foundation Worksheet

Name

Date

Class

Learning Goals

Define independent variable, dependent variable, and controlled variable.
Explain what reliability and validity mean in an investigation.
Identify the variables in a chemical change investigation.

Warm Up

Match each term to its definition

Draw a line connecting each term on the left to its correct definition on the right. Or write the matching letter next to each term.

Term	Your answer	Definition
Independent variable		A. A testable prediction about the expected outcome of an investigation.
Dependent variable		B. What you deliberately change in an investigation.
Controlled variable		C. How confident you can be that your results represent the truth.
Reliability		D. What you measure to see the effect of the change.
Validity		E. A factor kept the same throughout the investigation to ensure a fair test.
Hypothesis		F. Whether an experiment actually tests what it claims to test.

Your Turn

Sort it!

An investigation asks: "Does temperature affect how quickly salt dissolves in water?" Write each factor from the pool into the correct category box below.

water temperature time for salt to dissolve amount of salt used volume of water stirring method type of container particle size of salt dissolving rate at each temperature type of salt used room air temperature

Independent Variable

Dependent Variable

Controlled Variables

Show What You Know

1. In your own words, explain why controlled variables are so important in a chemical change investigation. Give one example.

Recall 2 marks

2. A student repeats their experiment three times and gets very similar results each time. Which quality of their investigation does this demonstrate — reliability or validity? Explain how you know.

Recall 2 marks

Wrap Up

In one sentence, what was the main idea of this lesson?