Mare is preparing an experiment using 3 cups, one made of paper, one of plastic and one of glass. She plans on pouring 50 ml of hot water from a pitcher into each of the 3 cups and record the temperature in 5 minute intervals. What is the independent variable in this investigation?
a. the time interval between measurements
b. the amount of water in each cup
c. the initial temperature of the water in the cups
d. the material the cups are made of
http://en.wikipedia.org/wiki/Dependent_and_independent_variables
The independent variable is the factor that the scientist changes or manipulates in an experiment. In this investigation, the independent variable is the material the cups are made of. Mare is using cups made of paper, plastic, and glass. By using different materials for each cup, she is manipulating the independent variable to observe any effects it has on the temperature of the water.
So, the correct answer is d. the material the cups are made of.