1. Variables

2. Variables A variable is a factor that can change during an experiment
Controlled variables  variables that need to stay the same during the experiment to keep it fair

3. Controlled experiments
Experiments should be controlled meaning that only one variable, the independent variable is allowed to vary.
All other factors should be kept controlled.
A fair test is an experiment where only one variable is allowed to change.

4. Types of variables
The independent variable is the one variable we change and is what we are investigating.
The dependent variable is what we are measuring during an experiment.
The dependent variable depends on the changes made to the independent variable,
Example if we wanted to examine how long different soft drinks stay fizzy
Our independent variable would be_______
Our dependent variable would be_________

5. Example – Plant growth

6. Does water effect the growth of the plant?
Dependent Variable (the variable we measure)
Plant growth
Independent Variable (the variable we want to test)
Water
Controls:
The amount of sunlight is kept the same
We use the same type of plant
We use the same potting mix
We use the same sized pot

7. Does Sunlight effect the growth of the plant?
Dependent Variable (the variable we measure)
Plant growth
Independent Variable (the variable we want to test)
Sunlight
Controls:
The amount of water is kept the same
We use the same type of plant
We use the same potting mix
We use the same sized pot

8. Planning an experiment
Good scientists only change one factor or variable at a time.
Otherwise they wouldn’t be able to work out which variable caused the effect.
All the other variables must be kept exactly the same.
To make sure you design an effective experiment you should know:
what you are trying to find out
exactly what you are going to measure
what you are going to change
what you are going to keep the same

9.
Log in to Into Science --> Activities --> Science-A journey of discovery --> The basketball experiment

10. Task Record your results in the table below
What is the independent variable?
What is the dependent variable?
What is the control variable?

11. Task

12. Dissolving Sugar Prac Aim Hypothesis:
Sugar grains come in a variety of sizes for different uses so a good scientist would take this into account when designing his/her experiment
Aim
To find out how quickly _______________ sugar grains dissolve in water
Hypothesis:
That sugar with a ______ grain will dissolve faster than sugar with a _______ grain.
different sized

13. Materials Icing sugar, white sugar, sugar cube Stop watch Stirring rod
Electronic balance
Spatula
Measuring cylinder
Plastic pipette
X3 beakers (medium)
X3 beakers (small)

14. Setting up
Method
Using a measuring cylinder, fill 3 medium sized beakers with 100ml of water
Using an electronic balance, weigh a sugar cube in a small beaker and record its weight (DON’T FORGET TO ZERO THE BEAKER)
3. Using a spatula, weigh THE SAME AMOUNT of icing sugar into one beaker and white sugar in the other. Record these exact weights into your table.

15. Running the Experiment
Method
4. Start the stopwatch AT THE SAME TIME YOU ADD THE SUGAR into the large beaker. 5. Stir slowly (do not crush the cube) 6. Record the time it took for all of the sugar cube to dissolve 7. Repeat steps 4-6 for the other two sugars

16. Results
Icing Sugar
White Sugar
Sugar Cubes
Weight (g)
Time
(sec)

17. Conclusion refer back to aim
Discussion
Which sugar dissolves the fastest and which is the slowest?
List all of the control variables? What is a control variable?
What is the thing we changed on purpose? What type of variable is this?
What is the dependent variable in this experiment?
Conclusion refer back to aim