Changes Around Us: Physical and Chemical — Quiz

Q1. Ravi folds a few sheets of paper into birds and boats and then unfolds them again. The chapter classifies this change as

• A. A chemical change because new shapes are formed
• B. Combustion
• C. An irreversible change because creases remain
• D. A physical change because no new substance is formed

Q2. Priya crushes a small piece of chalk into fine powder. The chapter treats this change as

• A. Chemical, because the chalk piece cannot be put back together
• B. Chemical, because a new substance is formed
• C. Physical, because only the size changes and no new substance forms
• D. Combustion

Q3. Burning of wood, as discussed in the chapter, is best classified as

• A. A physical change only
• B. A chemical change involving combustion
• C. Erosion
• D. A reversible change

Q4. A school in Rampur dries wet clothes in the sun. Going by the chapter's definitions, drying of wet clothes is

• A. A chemical change, as water becomes a new substance
• B. A physical change, as only water evaporates and no new substance is formed
• C. Erosion of the cloth
• D. Combustion of moisture

Q5. In Activity 5.3, two glass tumblers A and B contain tap water and lime water respectively. When air is blown through a straw into both, what is observed?

• A. Both turn milky
• B. A turns milky, B shows only bubbles
• C. Both show only bubbles
• D. B turns milky, A shows only bubbles

Q6. In Activity 5.4 the gas formed from vinegar and baking soda is passed through fresh lime water. The lime water turning milky shows that the gas is

• A. Oxygen
• B. Hydrogen
• C. Carbon dioxide
• D. Water vapour

Q7. The chapter classifies rusting of iron as a chemical change because

• A. The iron piece only changes its colour
• B. A new brown substance, iron oxide, is formed
• C. Rust can be reversed easily
• D. Rust is the same substance as iron

Q8. Which of the following is given in the chapter as an example of a combustible substance?

• A. Iron nail
• B. Stone
• C. Kerosene
• D. Common salt

Q9. In Activity 5.5 one of the two burning candles is covered with an inverted glass tumbler. After some time the covered candle is extinguished because

• A. The wax used up completely
• B. The supply of oxygen is cut off
• C. The candle melted away
• D. Nitrogen from air smothered it

Q10. Of the chapter, the burning of a candle involves

• A. Only a physical change
• B. Only a chemical change
• C. Both physical and chemical changes
• D. Neither physical nor chemical change

Q11. Which of the following changes from Activity 5.8 can be reversed back to its original form?

• A. Chopping vegetables
• B. Making popcorn from corn
• C. Melting of ice
• D. Burning of wood

Q12. The chapter says that when water evaporates, the water vapour can be turned back into liquid water by

• A. Combustion
• B. Condensation
• C. Erosion
• D. Rusting

Q13. Which of these is given as an example of a desirable change?

• A. Rusting of iron
• B. Decay of food in storage
• C. Changing of milk into curd
• D. Air pollution from paint drying

Q14. Which of the following helps break up large rocks into smaller pieces by physical weathering?

• A. Reaction of water with rock minerals
• B. Iron in basalt forming iron oxide
• C. Temperature changes, growing roots of trees and freezing of water in cracks
• D. Burning of magnesium ribbon

Q15. From the chapter's Let Us Enhance Our Learning exercise, which combination of statements correctly describes a physical change? (i) The state of the substance may or may not change. (ii) A substance with different properties is formed. (iii) No new substance is formed. (iv) The substance undergoes a chemical reaction.

• A. (i) and (ii)
• B. (ii) and (iii)
• C. (i) and (iii)
• D. (iii) and (iv)