1. Welcome to Natural Science
Concept 3: Planning Scientific Investigations
By the end of this lesson, you will be able to…
Identify factors to be considered in investigations
Plan ways to collect data across a range of values
Replace italicised words to fit lesson
Activities:
Thinking: Identifying factors
Hypothesizing
Planning an investigation
Writing a plan

2. Thinking: Identifying Factors
For each investigation question, identify the:
Independent variable (the factor that is being changed)
Dependent variable (the factor being measured or observed)
Control variables (factors that remain constant)
How does the size of a beaker affect how quickly water boils?
How does the number of open windows in a room affect the air temperature?
How does the mass of flour in a cake affect it’s thickness?
How do different types of exercise effect pulse rate?
Independent variable =
Size of beaker
Dependent variable =
Time to boil water
Control variables =
Volume of water, type of water, heat source, etc.
Independent variable =
Dependent variable =
Control variables =
No. of windows
Air temperature
Size of room, environmental conditions, etc
Independent variable =
Dependent variable =
Control variables =
Mass of flour
Height of cake
Size of cake tin, mass of other ingredients, etc
Independent variable =
Types of exercise
Dependent variable =
Pulse rate
Control variables =
Time to exercise, rest periods, etc

3. Conclusion Theory Hypothesizing Is it……
What is the definition of a hypothesis?
Is it……
a. ….the answer to a question based on data (or evidence) and argument?
Conclusion
b. ….an idea based on multiple observations or investigations?
Theory
c. …. a suggested explanation for the conclusion to an experiment based on initial observations?

4. Hypothesizing
For each of the investigation questions, choose the best hypothesis provided:
How does the size of a beaker affect how quickly water boils?
How does the number of open windows in a room affect the air temperature?
How does the mass of flour in a cake affect it’s thickness?
How do different types of exercise effect pulse rate?
a. To find out if bigger beakers heat water more quickly than small beakers
b. Big beakers will heat water more quickly than small beakers
c. I think that big beakers are the best at boiling water
a. The more open windows, the lower the temperature of the room.
b. To investigate windows and room temperature
c. I think that the number of windows will affect room temperature
a. The thickness of a cake is affected by the mass of flour
b. I think that the mass of flour will not affect cake thickness
c. The more flour added to a cake recipe, the thinner the cake will be
a. To increase your pulse rate you must exercise regularly
b. Aerobic exercises, such as running, increases pulse rate more than stretching exercises
c. I think that playing rugby is the best exercise to increase pulse rate

5. Planning an Investigation
In groups, you will be given a beaker of lemonade and some raisins.
Drop the raisins in the lemonade and see what happens.
What could you investigate?

6. Planning an Investigation
Use ‘Sieve Thinking’ to record your ideas and narrow them down until you have an investigation question which includes both the independent and dependent variables.

7. Sieve Thinking Learning Objective:
To identify the independent variable
My thoughts:
1st sieve
2nd sieve
My investigation question
Sieve Thinking

8. Writing a plan What are you going to investigate?
Use the questions below to help you structure your investigation plan.
What are you going to investigate?
Which variable are you changing (independent variable)?
Which variable are you going to measure (dependent variable)?
List the variables that will need to remain the same (control variables)
Write a hypothesis for your investigation.
Now write a brief step by step plan of what you will do. Include:
- all the equipment you will use
- the number and range of measurements you will take
- how you will take the measurements
- any suitable diagrams of how you will set up equipment
- what you will need to do to make your experiment a safe one

9. Homework Plan an experiment to provide data that are accurate and
The 17th Century scientist and philosopher Galileo attended church and watched the huge light fitting gently swing. He timed how long it took to swing left to right and back again. He thought, ‘Does the swing time change if the chain length changes, or if the mass of the light changes?’
Plan an experiment to provide data that are accurate and
would impress Galileo.
Remember: you can only have one independent variable in
any one experiment i.e. by changing more than one variable
your experiment will not be a fair test.