A fair test shows one metal strip holds more weight than one plastic strip before bending. What does the evidence support?

• These samples resist bending differently.
• Every plastic strip is too weak for any job.
• Every metal strip is best for every possible job.

In a set-time test comparing how well materials block water, which things should stay the same?

• Water amount only; change time and size
• Water amount, test time, sample size
• Test time only; change water and size

Some pans use heat-resistant plastic handles because plastic carries heat more slowly than metal.

Ali compares how easily metal and plastic strips bend. He supports them in the same way. What else makes the comparison fair?

• Use a thick metal strip and thin plastic.
• Use equal strips and the same force.
• Use more force on metal than on plastic.

These example results compare equal-sized strips tested the same way. Which sample fits a model bridge that must hold a load without bending?

• Plastic: it bent under the smallest load.
• Wood: it held a load between the others.
• Metal: it held the greatest load.

The chart shows example loads held before bending. How many more kilograms did the metal sample hold than the plastic sample?

Fair tests compare samples for a folding rain cover. Wood lets water through. Metal blocks water but stays stiff. Plastic blocks water and bends without breaking. Which sample meets both needs: keeping rain out and folding?

• Wood: it lets water through in the test.
• Metal: it blocks water but stays stiff.
• Plastic: it blocks water and folds.

Mia uses equal-sized samples. She tests cloth with 100 mL of water for 2 minutes and plastic with 50 mL for 2 minutes. Why is this comparison unfair?

• She changed the amount of water.
• She kept the test time the same.
• She used two materials in the test.