Class 7 Science — Chapter 5: Changes Around Us: Physical and Chemical

What you'll learn

• ▸Physical Changes
• ▸Chemical Changes
• ▸Rusting of Iron
• ▸Combustion
• ▸Conditions for Combustion (The Fire Triangle)
• ▸Testing for Carbon Dioxide
• ▸Acid-Base Reaction Example (Vinegar and Baking Soda)
• ▸Bioluminescence

Chapter Summary

--- PAGE 1 --- 5 Changes Around Us: Physical and Chemical 0777CH05 I placed a cube of ice here half an hour ago. It has now become water! A bud that I saw yesterday on this rose plant has become a flower today. The bottle containing cold water is not cold anymore. Yesterday, I saw some brown spots on a banana, but today it has more brown spots and a strong smell. These students are describing some changes. What kinds of changes are they talking about? --- PAGE 2 --- Activity 5.1: Let us think and reflect You might have observed various changes happening around you. Some of them are listed in Table 5.1, you may notice that something is changing in each case. Take a moment to reflect on the changes in each case. Record your observations in Table 5.1. Table 5.1: Some changes observed around us S.No. Change Observation(s) 1. Melting ice cubes 2. Chopping vegetables 3. Boiling water 4. …

Practice Questions from this Chapter

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1. Differentiate physical versus chemical changes. Get Solution →
2. Give more examples of chemical reactions. Get Solution →
3. Explain why leaves change color. Get Solution →
4. What kind of change occurs when only the physical properties of a substance, like its shape, size, or state, are altered? Get Solution →
5. According to the text, what new substance is formed when a magnesium ribbon is burnt? Get Solution →
6. What is the name for the minimum temperature at which a substance catches fire? Get Solution →
7. What happens to lime water when carbon dioxide gas is passed through it? Get Solution →
8. A change in which one or more new substances are formed is called a: Get Solution →

Did you know?

• 💡 Some metals like gallium melt just from the heat of your hand.
• 💡 Toasting bread transforms its flavor through complex chemical reactions.
• 💡 Glow sticks light up by mixing chemicals that release energy.
• 💡 Sound is a physical change, causing air particles to vibrate.
• 💡 The Statue of Liberty is green because copper rusted over time.

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