Heating and Cooling of Matter

Cookies turn brown and become a solid after baking them in the oven. Popsicles melt in the sun on a hot day. Which statement is true about the changes?

• The changes caused to the cookies and popsicles when heater can be reversed by cooling them.
• The change to the popsicle when heated cannot be changed by cooling, but the cookies can be changed back.
• The changes to the popsicle and cookies when heater cannot be reversed if cooled.
• The change caused to the popsicle when heated can reversed by cooling, but the change to the cookies cannot be changed.

Observations below show four changes that occurred when heat was added. Which student makes the correct claim?

• Student A says, “Change 1 is irreversible because cooling the butter in a pan will not make it solid again."
• Student B says, "Change 2 is irreversible because the chocolate will not be the same shape once it is solid again."
• Student C says, “Change 3 is irreversible because cooling the ice cream cone will not make it a solid again."
• Student D says, “Change 4 is irreversible because the newspaper pieces have turned to ash."

Becca claims that some changes in states of matter can be reversed. She gives the example of melting butter. She says that you can turn a solid piece of butter into a liquid and then turn it back to a solid. Her friend Mel disagrees and says changes in butter are irreversible. Who is correct, and why?

• Mel is correct because butter cannot be changed. If the butter is turned into a liquid it cannot be reversed and turned back to a solid.
• Mel is incorrect because butter cannot be changed. If the butter is turned into a liquid it cannot be reversed and turned back to a solid.
• Becca is correct because the changes to butter can be reversed. Becca could melt the butter and then use the refrigerator to cool it down and make it solid again.
• Becca is incorrect because the changes to butter can be reversed. Becca could melt the butter and then use the refrigerator to cool it down and make it solid again.
• Neither of the girls are correct.

Lily is making cookies. She uses eggs, flour, sugar, chocolate chips, butter, and vanilla. During what part of this process does making cookies cause an irreversible change?

• adding the chocolate chips
• putting the ingredients in a bowl
• baking the cookies in the oven
• eating the cookies

When does a physical change occur?

• When molecules combine to form a new substance.
• When a new element is created.
• When the size, shape or state of matter changes.
• When elements combine to form a new molecule.

On Saturday morning, John cooked scrambled eggs for his family. Would the eggs have gone through a reversible or irreversible change and why?

• The eggs have gone through a reversible change, because they are still eggs.
• The eggs have gone through an irreversible change, because they are scrambled.
• Since the eggs have been heated and cooked, they cannot reverse back to being raw.
• The eggs have been heated, but when they cool they will go back to being raw.

Which two changes can be reversed?

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• 
• 
• 
• 

Which of the following is a clue that a chemical change has taken place?

• Ashes form when the change takes place.
• The substance is smaller than it was before the change took place.
• The substance is smaller than it was before.
• The substance looks the same as it did before the change.

What is the difference between a physical change and a chemical change?

• A physical change can only occur in liquids, and a chemical change can occur in a solid, liquid or a gas.
• A physical change is when the size, shape or state of matter changes, and a chemical change is when the molecules of matter change to from a new substance.
• A physical change can occur in a solid, liquid or a gas, and a chemical change can only occur in liquids.
• A physical change is when the molecules of matter change to from a new substance, and a chemical change is when the size, shape or state of matter changes.

The chart shows four changes made by heating. Which change cannot be reversed by cooling?

• Change 1 cannot be reversed by cooling.
• Change 2 cannot be reversed by cooling.
• Change 3 cannot be reversed by cooling.
• Change 4 cannot be reversed by cooling.