Reversible Changes

Question 1

Which of the following describes a reversible change and also explains how to reverse it?

Accepted Answer

Melting ice into water; to reverse it, place the water in a freezer so it freezes back into ice.

Answer

Burning a candle; to reverse it, blow out the flame and the candle will become whole again.

Answer

Evaporating water from a puddle; to reverse it, sprinkle salt on the puddle.

Answer

Dissolving sugar in water; to reverse it, add more sugar to the solution.

Question 2

Sam tried four different things with everyday items. Which three of the following can be undone so that the original material is exactly the same as before?

Accepted Answer

Melted a chocolate chip, froze a cup of orange juice into a popsicle, dissolved a spoonful of sugar in water

Answer

Melted a chocolate chip, dissolved a spoonful of sugar in water, burned a small piece of cardboard

Answer

Froze a cup of orange juice into a popsicle, dissolved a spoonful of sugar in water, burned a small piece of cardboard

Answer

Melted a chocolate chip, froze a cup of orange juice into a popsicle, burned a small piece of cardboard

Question 3

Lila performed four different experiments, each starting with a single material. Which experiment can be completely reversed so that every original material she began with is recovered exactly as it was before?

Accepted Answer

She melted a piece of chocolate in a warm pan and then let it harden again at room temperature.

Answer

She mixed sand with water, stirred, then poured the mixture through a filter paper and collected the dry sand.

Answer

She burned a small piece of paper until it turned to ash and then crushed the ash into a fine powder.

Answer

She stirred sugar into a cup of water until it dissolved, poured the mixture into a shallow dish, and let the water evaporate, leaving a crust of sugar.

Try three questions

Which of the following describes a reversible change and also explains how to reverse it?

Sam tried four different things with everyday items. Which three of the following can be undone so that the original material is exactly the same as before?

Lila performed four different experiments, each starting with a single material. Which experiment can be completely reversed so that every original material she began with is recovered exactly as it was before?

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