Question

a student conducts an experiment to determine the effect of adding salt on the boiling temperature of water

sample	amount of salt	boiling temperature
sample 2	2g	102.3°c
sample 3	5g	104.8°c
sample 4	10g	107.5°c

which variable should be kept constant during the experiment?

a) boiling temperature
b) amount of salt added
c) volume of water
d) time required for water to boil

Explanation:

In an experiment investigating the effect of one variable (amount of salt, the independent variable) on another (boiling temperature, the dependent variable), other factors that could affect the dependent variable must be kept constant (controlled variables). The boiling temperature is the dependent variable being measured, so it changes (A is wrong). The amount of salt is the independent variable being manipulated, so it changes (B is wrong). The time to boil is a result of the experiment and depends on other factors (D is wrong). The volume of water can affect boiling temperature, so to isolate the effect of salt, it must be kept constant (C is correct).

Answer:

C) volume of water