Testing Materials for Uses

Question 1

A class performed a fair test to compare how quickly three different spoon materials—metal, wood, and plastic—heat up when their handles are placed in a pot of boiling water for 2 minutes. The metal spoon handle became very hot, the wooden spoon handle stayed cool, and the plastic spoon handle became slightly warm but began to soften. Based on this evidence, which of the following is the best reason for choosing a wooden spoon to stir a pot of hot soup?

Accepted Answer

Wood does not conduct heat well, so the spoon stays cool and is safe to hold while stirring hot soup.

Answer

Plastic does not melt when heated, making it the safest material for stirring hot soup.

Answer

Wood conducts heat quickly, allowing the soup to cool faster.

Answer

Metal is the cheapest material, which is why it is used for kitchen spoons.

Question 2

A student wants to find which material—metal, wood, or plastic—is strongest enough to be used for the tiny bridge beams in a classroom model. Which plan would be a fair test to compare the strength of the three materials?

Accepted Answer

Cut three strips that are all 30 cm long, 2 cm wide, and 0.5 cm thick—one metal, one wood, one plastic. Place each strip on the same two supports, then add identical 10‑gram weights one at a time to the middle of the strip until it bends or breaks, recording the total weight for each material.

Answer

Use a 30‑cm metal strip, a 25‑cm wood strip, and a 20‑cm plastic strip; place each on different tables and add the same 10‑gram weights to the middle of each until it bends, then compare the results.

Answer

Take three strips of the same length but make the metal strip twice as thick as the wood and plastic strips; put them on the same supports and add the same number of weights to each, noting which bends first.

Answer

Test the metal strip on a Monday, the wood strip on a Wednesday, and the plastic strip on a Friday, using the same supports and adding the same weights each day, then compare the weights needed to bend each strip.

Question 3

Lila tested three kinds of sticks to see which would be best for the frame of a kite that must stay thin and not bend much when the wind pushes it. She did a fair test by hanging each 30‑cm stick vertically and adding a 200‑gram weight to the end for 10 seconds. The bends she measured were: - Metal stick: bent 4 cm and weighed 150 g - Wood stick: bent 1 cm and weighed 35 g - Plastic stick: bent 2.5 cm and weighed 70 g Which material should Lila choose for the kite frame, based on these results?

Accepted Answer

Wood, because it bends a little and is the lightest

Answer

Metal, because it bends the least

Answer

Plastic, because it is in the middle for both bend and weight

Answer

Any material would work, because all bend some

Try three questions

A student wants to find which material—metal, wood, or plastic—is strongest enough to be used for the tiny bridge beams in a classroom model. Which plan would be a fair test to compare the strength of the three materials?

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