Let's go through each part of the task carefully and solve it step by step.
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Q.4: True or False
1) A change in size or shape is physical change.
✔ True
- Explanation: Changing the size or shape of a substance (like cutting paper, crushing a can, or melting ice) does not create a new substance. The chemical composition remains the same. This is a
physical change.
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2) A chemical substance means new substance with new properties was formed.
✔ True
- Explanation: A
chemical change occurs when one or more new substances are formed with different chemical properties than the original substances. For example, rusting iron forms iron oxide — a new substance with different properties.
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3) Chemical change is when water freezes.
✘ False
- Explanation: When water freezes, it changes from liquid to solid (ice), but it's still
H₂O. No new substance is formed. This is a
physical change, not a chemical one.
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4) When milk turns sour, it is physical change as change in odour do not indicate chemical change.
✘ False
- Explanation: When milk turns sour, bacteria produce lactic acid, changing the chemical composition of the milk. This results in a sour smell and taste — these are signs of a
chemical change. Changes in odor often
do indicate a chemical change.
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✔ Summary for Q.4:
1) True
2) True
3) False
4) False
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Q.5: Give examples of:
####
1. Chemical Change
a)
Rusting of iron
- Iron reacts with oxygen and moisture to form iron oxide (rust). New substance formed → chemical change.
b)
Burning wood
- Wood burns and produces ash, smoke, and gases like carbon dioxide. New substances are formed → chemical change.
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####
2. Physical Change
a)
Melting ice
- Ice turns into water. Still H₂O, just changed state. No new substance → physical change.
b)
Boiling water
- Water turns into steam. It’s still water in gas form. No chemical change → physical change.
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✔ Final Answers:
Q.4:
1) True
2) True
3) False
4) False
Q.5:
1. Chemical:
a) Rusting of iron
b) Burning wood
2. Physical:
a) Melting ice
b) Boiling water
Let me know if you'd like this explained further!
Parent Tip: Review the logic above to help your child master the concept of physical properties of matter worksheet.
