Chemistry Physical & Chemical Changes Part 9 (Questions) Class 7 VII

TL;DR

This video explains the differences between physical and chemical changes, and how they relate to burning wood, cutting it into small pieces, painting an iron gate, and rusting of iron objects in coastal areas.

Transcript

hello friends this video on physical and chemical changes part 9 is brought to you by exam for your calm no more fear from exam number 7 explain why burning of wood and cutting it into small pieces are considered as two different types of changes that's quite obvious because now when we talk about burning of wood what happens here heat is released ... Read More

Key Insights

• 🙂 Burning wood is a chemical change due to the release of heat, light, and the formation of new substances.
• 💱 Cutting wood into small pieces is a physical change as it only involves changes in shape and size.
• ♻️ Painting an iron gate prevents rusting by creating a protective barrier between the iron and moisture.
• 💨 Rusting of iron objects is faster in coastal areas due to the higher levels of moisture in the air.
• 👱 Moist air increases the chances of rusting, while dry air reduces the possibility.
• 🫢 Liquefied petroleum gas (LPG) exists as a liquid in the cylinder and becomes a gas when burned, undergoing a physical change.
• 🙂 Burning LPG is a chemical change as it involves the release of heat, light, and the formation of new substances.

Questions & Answers

Q: Why is burning wood considered a chemical change?

Burning wood involves the release of heat, light, and the formation of new substances like carbon dioxide and ashes. These changes signify chemical reactions and a change in chemical composition.

Q: What are the changes involved in cutting wood into small pieces?

Cutting wood into small pieces only involves changes in shape and size. There is no change in the chemical composition of the wood.

Q: How does painting prevent an iron gate from rusting?

Painting creates a protective layer between the iron and moisture in the air, preventing contact and oxidation. It acts as a barrier, preventing the rusting process.

Q: Why is rusting of iron objects faster in coastal areas compared to deserts?

Coastal areas have higher levels of moisture in the air due to the presence of water bodies, increasing the chances of rusting. In deserts, the air is drier, reducing the possibility of rust formation.

Summary & Key Takeaways

• Burning wood is a chemical change as it involves the release of heat and light, the formation of new substances, and a change in chemical composition. Cutting wood into small pieces is a physical change as it only involves changes in shape and size.

• Painting an iron gate prevents rusting by creating a protective layer between the iron and moisture in the air, preventing contact and oxidation.

• Rusting of iron objects is faster in coastal areas due to the presence of moist air, which increases the chances of oxidation and rust formation.