Fair testing (age 9+)

Question 1

Lena found that a 100 mL piece of ice melted in 6 minutes in a metal cup and in 9 minutes in a plastic cup at room temperature. She predicts that even in a colder place, like a refrigerator, the ice will still melt faster in the metal cup. Which follow‑up test would best check Lena’s prediction?

Accepted Answer

Put the same 100 mL of ice in each cup, put the cups in the refrigerator, and record how long the ice takes to melt.

Answer

Repeat the original test at room temperature with the same cups and ice amounts.

Answer

Only put the ice in the metal cup in the refrigerator and compare the melting time to the earlier plastic‑cup result.

Answer

Place 80 mL of ice in the metal cup and 120 mL of ice in the plastic cup, then leave both cups in the refrigerator.

Question 2

You tested two kinds of seeds to see which one sprouts faster. Both seeds were kept in the same light and given the same amount of water. After five days, Seed A had sprouted but Seed B had not. You now want to do another fair test to compare how the amount of water affects the two seeds. Which prediction is best based on your first test results?

Accepted Answer

Even with less water, seed A will still sprout before seed B.

Answer

Both seeds will sprout at the same time because they are getting the same amount of water.

Answer

Seed B will sprout before seed A because it needs less water.

Answer

Seed A will not sprout at all because it already sprouted in the first test.

Question 3

Mia investigated how the amount of water given to bean plants each week affects their height. She grew three groups of plants for four weeks, giving each group a different amount of water: 50 ml, 100 ml, and 150 ml per plant per week. At the end of the experiment the tallest plants were the ones that received 100 ml, the plants that received 150 ml were shorter than the 100 ml plants, and the plants that received 50 ml were the shortest. Based on these results, which prediction would be the most appropriate for Mia to test in a follow‑up investigation?

Accepted Answer

If the amount of water is increased from 150 ml to 200 ml per week, the plants will grow shorter than those receiving 150 ml, because giving too much water can hinder growth.

Answer

If the amount of water is decreased from 50 ml to 25 ml per week, the plants will grow taller than those receiving 50 ml.

Answer

If the amount of light is increased while keeping water at 100 ml per week, the plants will grow the same height as before.

Answer

If the amount of water is increased from 100 ml to 150 ml per week, the plants will grow taller than those receiving 100 ml.

Try three questions

Lena found that a 100 mL piece of ice melted in 6 minutes in a metal cup and in 9 minutes in a plastic cup at room temperature. She predicts that even in a colder place, like a refrigerator, the ice will still melt faster in the metal cup. Which follow‑up test would best check Lena’s prediction?

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