States, changes, latent heat, evaporation, factorsPractice Questions & MCQs
Practice States, changes, latent heat, evaporation, factors questions from Matter in Our Surroundings (Class 9 Science) - important MCQs with answers and step-by-step solutions. Solve the sample questions below, then practice the full set free on the RankByte app.
States, changes, latent heat, evaporation, factorsQuiz - Solve & Score
Q1. Which of the following correctly compares the densities of the three states of a typical substance?
- A.Solid > Liquid >> Gas, with the gas being thousands of times less dense
- B.Gas > Liquid > Solid
- C.Liquid > Solid > Gas
- D.Solid = Liquid > Gas
Answer: A. Solid > Liquid >> Gas, with the gas being thousands of times less dense
To see why, recall that Particles in a solid are most tightly packed and in a gas are very far apart, so solid > liquid >> gas in density for most substances. Water is an exception only because ice (a special solid) is less dense than liquid water. Hence the answer is A) Solid > Liquid >> Gas, with the gas being thousands of times less dense.
Q2. Which of these phenomena is best explained by the diffusion of gases?
- A.The smell of perfume opened in one corner of a closed room spreads throughout
- B.Water rises in a thin capillary tube
- C.Iron rusts in moist air
- D.Sugar dissolves in water on stirring
Answer: A. The smell of perfume opened in one corner of a closed room spreads throughout
That leaves only option A). Confirm with the chapter rule: Diffusion is the spontaneous mixing of substances due to particle motion. Perfume vapour molecules spread through air because both gases have rapidly moving, weakly-attracted particles that mix without external stirring (chemistry, chapter 'Matter in Our Surroundings'). Answer: A) The smell of perfume opened in one corner of a closed room spreads throughout.
Q3. Why is the latent heat of fusion of ice (334 J g^-1) much smaller than that of vaporisation (2260 J g^-1)?
- A.Melting only loosens the lattice while vaporisation must completely separate molecules against all attractions
- B.Ice molecules are smaller than water molecules
- C.Melting and vaporisation occur at very different molecular weights
- D.Fusion is exothermic and vaporisation is endothermic
Answer: A. Melting only loosens the lattice while vaporisation must completely separate molecules against all attractions
Quick parse - a typical chemistry numerical. The data on the table: 334 J, 2260 J. We are after the quantity the stem asks for. Pick the chapter relation that contains every given quantity and the unknown; rearrange for the unknown. Common-sense check: Fusion only disrupts the regular crystalline arrangement. Lock in option A) Melting only loosens the lattice while vaporisation must completely separate molecules against all attractions.
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