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Investigation: Different masses of baking soda are added to 50 mL of vinegar each time, and the volume of gas collected is measured. In this investigation, which is a controlled variable?
the volume of vinegar
the mass of baking soda
the volume of gas collected
Answer and explanation
the volume of vinegar
Independent variable: what the investigator deliberately changes. Dependent variable: what is measured in response. Controlled variables: what is kept the same so the test is fair.
Grades 9–12 · Measurement & evidence
Investigation: A sugar cube is dropped into 200 mL of water at 10 °C, 25 °C, 40 °C and 55 °C without stirring, and the time to dissolve is recorded. In this investigation, which is a controlled variable?
the water temperature
the volume of water
the time to dissolve
Answer and explanation
the volume of water
Independent variable: what the investigator deliberately changes. Dependent variable: what is measured in response. Controlled variables: what is kept the same so the test is fair.
Grades 9–12 · Measurement & evidence
Investigation: Salt is stirred into water at different stirring speeds, using 5 g of salt each time, and the time to dissolve is recorded. In this investigation, which is the dependent variable?
the time to dissolve
the stirring speed
the mass of salt
Answer and explanation
the time to dissolve
Independent variable: what the investigator deliberately changes. Dependent variable: what is measured in response. Controlled variables: what is kept the same so the test is fair.