This science lesson discusses how to conduct a fair test to determine if hot or cold water works better for washing dishes. It provides an example of a student, Joseph, who wanted to find out if washing up liquid works better in hot or cold water. He prepared dirty plates and had his mother judge their cleanliness after washing. To ensure a fair test, Joseph needed to keep certain variables the same, such as the amount of washing up liquid used. The lesson evaluates Joseph's experiment and asks questions to help understand the importance of a fair test in science.

1. Science Grade 7 Lesson 22
Hot or Cold Water?

2. Science Grade 7 Lesson 22
Hot or Cold Water?

3. Q2. In your investigation you want to weigh 100 g of sugar accurately, what piece of equipment
would you use?
Q3. What do scientists mean by “a fair test”?
Component 1: Short Review
Q1. If you are about to start an investigation, what would you write under the heading
called ‘The Aim’?

4. Component 2: Lesson purpose /Intention
We want to be sure we know and understand what
makes it a ‘fair test’.

5. Component 3: Lesson Language Practice
Key words/terms:
Method

6. Component 4: Lesson Activity.
Component 4A
Hot or cold water
Joseph wanted to find out whether ‘washing up liquid’ worked better in
hot water or cold water.
He prepared some dirty plates to be used in his investigation and he
asked his mother to be the judge of whether they were clean after he
washed them. Joseph planned to use cold water from the tap and hot
water from a kettle.

7. Guide Questions
Component 4B
Q1. What should Joseph use to measure the amount of washing up liquid he will use?
Q2. How many dirty plates should Joseph get ready?
Q3. What is one important thing that Joseph needs to make sure stays the same
during his experiment so that it’s a fair test?

8. Component 4C
Q1. If Joseph wrote down his results in a table how many columns should it have?
Q2. How could Joseph’s mother judge the cleanliness of the plates?
Q3. At the end of the investigation Joseph‘s results showed that all three plates washed
in the hot water were: 1. ‘very clean’ but that in the cold water two plates were 2. ‘a
bit cleaner’ and one plate was 3. ‘not clean’. What should he write in his conclusion?

9. Component 5: Lesson Conclusion
Q1. Has this lesson helped you to better understand what a fair test is
in science? If so, how?
Q2. Has this lesson encouraged you to do a scientific investigation
yourself? If so, how?