You want to test the effect of water temperature on the rate of sugar
dissolution. Which of the following is an example of a controlled experiment
to test this?
A. The temperatures of five beakers of 250 mL of water are kept
constant, and 10 g of sugar is added to each beaker.
B. The temperatures of five beakers of 250 mL of water are varied,
and 10 g of sugar is added to each beaker.
C. The temperatures of five beakers of 250 mL of water are varied,
and 10 g of sugar is added to each beaker while three of the
beakers are stirred.
D. The temperatures of five beakers of 250 mL of water are varied,
and different amounts of sugar are added to each beaker.