CBSE Class 7 > Class 7 Notes > Science (Curiosity) - New NCERT > Mnemonics : Changes Around Us: Physical and Chemical
Mnemonics : Changes Around Us: Physical and Chemical
Physical & Chemical Changes
1. Physical Change
A physical change changes only the form of a substance, not its nature.Mnemonic: Friends Never Lie.
- Friends= Form changes
- Never= No new substance
- Lie= Looks different
2. Chemical Change
A chemical change forms one or more new substances.Mnemonic: NEW
- N = New substance
- E = Energy change
- W = Won't reverse
Reversible & Irreversible Changes
1. Reversible Change Examples
A reversible change can be undone.Mnemonic: WE Bake Muffins
- W = Water boiling
- E = Evaporation
- Bake= Balloon inflating
- Muffins= Melting ice
2. Irreversible Change Examples
An irreversible change cannot be undone.Mnemonic: Bhai Chup Raho Please!
- Bhai= Burning paper
- C hup= Cutting vegetables
- Raho= Rusting iron
- Please= Popcorn
Prevention of Rusting
Rusting can be prevented by blocking air or moisture.
Mnemonic: POG(O)
- P = Painting
- O = Oiling
- G = Galvanising
Lime Water Reaction
Lime water reacts with carbon dioxide to form calcium carbonate.
What students need to learn: When carbon dioxide is bubbled through clear lime water (Calcium hydroxide), it reacts to form a white, insoluble solid called Calcium carbonate. This solid is suspended in the water, giving it a characteristic milky or cloudy appearance.
Mnemonic: 3Cs
- C = Carbon dioxide
- C = Calcium hydroxide
- C = Calcium carbonate
Natural Processes & Special Changes
1. Erosion
Erosion moves weathered particles by wind or water.Mnemonic: WWE
- W = Wind
- W = Water
- E = Erosion
2. Bioluminescence
Bioluminescence is light produced by living organisms.Mnemonic: BIO-LIGHT
- B = Biological
- L = Light
- I = Insects
- G = Glow
- H = Heat absent
- T = Transformation
The document Mnemonics : Changes Around Us: Physical and Chemical is a part of the Class 7 Course Science (Curiosity) Class 7 - New NCERT.
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FAQs on Mnemonics : Changes Around Us: Physical and Chemical
| 1. What are physical changes and how do they differ from chemical changes? |  |
Ans. Physical changes are alterations that do not affect the chemical composition of a substance. Examples include changes in state, like melting or freezing, where the substance remains the same chemically. In contrast, chemical changes involve the formation of new substances with different properties, such as rusting iron or burning wood.
| 2. Can you explain reversible and irreversible changes? | |
Ans. Reversible changes are those that can be undone, allowing the original substance to return to its initial state, such as water freezing into ice and then melting back to water. Irreversible changes, however, cannot be reversed easily, and the original substance cannot be recovered, like when food is cooked or when iron rusts.
| 3. What are some examples of chemical reactions that involve fire? | |
Ans. Examples of chemical reactions involving fire include combustion, where a substance reacts with oxygen to produce heat and light, such as burning wood or gasoline. These reactions typically result in new products, such as carbon dioxide and water, signifying a chemical change.
| 4. How does rusting occur and why is it considered a chemical change? | |
Ans. Rusting occurs when iron reacts with oxygen and moisture in the environment, forming iron oxide. This process is considered a chemical change because it results in a new substance, rust, which has different properties from the original iron.
| 5. What are natural processes and special changes in the context of physical and chemical changes? | |
Ans. Natural processes refer to changes that occur in nature without human intervention, such as the weathering of rocks or the growth of plants. Special changes are specific alterations that may be induced intentionally, like the cooking of food or the manufacturing of materials, which often involve either physical or chemical changes.
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Apr 19, 2026 Last updated
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