Question

A group of students is investigating whether copper is a better thermal conductor than steel. The students take a copper wire and a steel wire of the same length and diameter. They put equal lengths of wax on one end of each wire and dip the other end into a beaker of hot water. The length of wax left on the wires after 10 minutes is shown.
Experimental Observations:
- Original length of wax
- Copper: 3 cm
- Steel: 3 cm
- Length of wax after 10 minutes
- Copper: 0.7 cm
- Steel: 1.8 cm
What was the dependent variable in this experiment?
a. Type of wire used
b. Original length of wire
c. Original length of wax
d. Thermal conductivity of wire

Answer 1

Answer: Option c: original length of wax.

In an experiment, there are three types of variables: independent, dependent, controlled or constant.

Independent variables are the ones which do not change but can be changed by the scientist. dependent variables are the ones which change when the independent variables change. This is what a scientist observes. Constant variables are the conditions which are kept the same through out the experiment.

In the given experiment, the type of wire used, the length of the wire, thermal conductivity of the wire are independent variables. The time for which the wire is dipped in the hot water, the temperature of the water are controlled variables.

The original length of the wax is a dependent variable. This is because, as the wire is changed, depending upon the thermal conductivity of the wire, the original length of the wax changes.

Answer 2

The dependent variable is clearly the original length of wax because the amount the wax melted determined which type of metal was a better heat conductor. The best heat conductor was steel because it held heat for longer thus making the wax continue to melt for longer than the steel wire resulting in a longer piece of melted wax left on the wire.