Hayley would like to investigate which type of cellphone battery last the longest.

Identify the independent variable in her investigation.

• How many apps are running.

• The type of cellphone.

• The number of hours before the battery runs out.

• The number of phone calls made.

• If music is played on the cellphone.

Musa would like to know which type of fridge is the most energy efficient. She measures how much energy two different brands of fridges use and compares the results. Select all the variables that must be controlled.

• The amount of food that is in the fridge and must be kept cold.

• The energy used by the fridge.

• The time over which the fridge's energy usage is recorded.

• The number of times the fridge is opened and the length of time for which the door is open.

• The type or make of the fridge.

Many people invest their money with different banks. They find that the longer they invest their money for, the more interest they earn. Which of the following is the correct investigative question?

• How can you earn the most interest?

• Which bank is the best bank to invest in?

• How does the length of time for which the money has been invested, affect the amount of interest earned?

• Why do people invest their money?

• How does the amount of interest earned affect the time for which your money was invested?

A birdwatcher records how many fruit the male hornbill bird brings to his mate every day for a week.

The independent variable is:

• The bird's gender (male or female).

• The number of fruit.

• The day of the week.

• The type of bird.

• The number of chicks.

How does the amount of salt (concentration) affect the boiling point of salt water?

Select all the control variables.

• The amount of salt.

• The amount of water.

• The temperature at which the salt water boils.

How does the your blood sugar level change over time after you have eaten a meal?

This is an example of:

• An observation.

• An aim.

• An investigative question.

• An hypothesis.

Which types of plants grow best in the shade?

Click on all the controlled variables.

• The type of plant which grows.

• The amount of sun.

• The soil pH.

• The amount of water the plants get.

• The day of the week.

A scientist wants to see how the soil pH affects the types of plants that grow. The independent variable is:

• The scientist.

• The soil.

• The pH of the soil.

• The types of plants that grow.

How does the amount of water in the atmosphere affect the chance that it will rain?

The chance of rain is the:

• independent variable.

• dependent variable.

• controlled variable.

How quickly does milk go sour in the fridge when the fridge is at different temperature settings.

The independent variable is:

• The time taken for milk to go sour.

• The fridge.

• The temperature setting.

• Which house you are in.