Here is the solution to the worksheet, with an explanation for each answer.
The key difference between a
physical change (P) and a
chemical change (C) is:
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Physical Change (P): A change in the form or state of matter *without* creating new substances. The chemical composition remains the same. These changes are usually reversible.
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Chemical Change (C): A change where one or more substances are transformed into *new* substances with different chemical compositions and properties. This often involves breaking and forming chemical bonds and is usually irreversible.
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1. Ice melting to water
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Answer: P
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Explanation: Ice (solid H₂O) turning into liquid water (liquid H₂O) is a change of state. The substance is still water (H₂O) before and after. No new chemical substances are formed. You can freeze the water back into ice, making it reversible.
2. Chocolate ice cream melting to liquid cream
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Answer: P
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Explanation: The solid ice cream is changing into a liquid state due to heat. While it might look messy, the chocolate, milk, sugar, etc., are not undergoing a chemical reaction to become new substances; they are simply mixing together as the solid structure melts. The fundamental chemical components remain unchanged.
3. Paper is shredded
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Answer: P
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Explanation: Shredding paper cuts it into smaller pieces. The material is still paper (cellulose fibers). Its chemical identity hasn't changed. You could theoretically tape the pieces back together (though impractical), showing it's a physical alteration of shape and size.
4. White bread is toasted in the toaster
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Answer: C
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Explanation: Toasting involves heating the bread, which causes chemical reactions (like the Maillard reaction and caramelization) between sugars and proteins. This creates new flavor compounds and turns the bread brown. The texture and taste change permanently – you cannot "un-toast" bread. New substances are formed.
5. Vegetables are chopped up and made into a salad
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Answer: P
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Explanation: Chopping vegetables changes their size and shape. Mixing them into a salad combines them physically without altering their chemical makeup. A tomato is still a tomato, a carrot is still a carrot. No new chemical substances are created by cutting or mixing.
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Final Answers:
1.
P
2.
P
3.
P
4.
C
5.
P
Parent Tip: Review the logic above to help your child master the concept of chemical and physical changes worksheet.
