____11. Lorna would like to experiment on which design of paper plane A or B flies better. Which of
the following would be the best measure for a paper plane to be judged as flying better?
a.The distance of flight from the original point to its landing point
b.The time of flight from the original point to its landing point
c.The size of the airplane
d.Hard to tell

_____12. A student wanted to compare the energy value of some food. He burned different food
samples in the test tubes containing a fixed amount of water. He used the increase in water
temperature as a measure of relative energy value. Which of the following variables must be
kept the same to ensure validity of results?
a.Mass of food sample c. initial temperature of water
b.Volume of food sample d. final temperature of water

_____13. Some students wanted to test the best brand of dye in dyeing fabric. They dipped one
piece of identical fabric in each brand of dye. Then they washed and dried the fabric at the
same time. The pieces of fabric were then compared. Which of the following should be kept
constant if this is to be a fair experiment?
a.brand of dye, kind of fabric, amount of dye
b.kind of fabric, amount of dye, time of dyeing
c.time of dyeing, washing and drying, brand of dye
d.size of fabric, brand of dye, time of washing and drying