Which of the following explanations of an effect of heating a material is incorr

Question

Which of the following explanations of an effect of heating a material is incorrect?

    a) When heated, a material which expands does so because the molecules push each other away.

    b) Heat conduction is carried out by colliding molecules transferring kinetic energy.

    c) While a material is boiling, the heat added increases the kinetic energy of the molecules.

  d) While melting, a well mixed sample of ice and water does not change temperature.

    e) When water evaporates from a room-temperature glass of water, it cools the water slightly.

[9] Which of the following is NOT a characteristic of a diffusion process?

            (a) Flow involves collisions of particles.   

            (b) Flow is from high concentration to low concentration.

            (c) Entropy increase drives the process.

            (d) Such processes can be recast as resistance-current models.

            (e) None of these (that is, all of the above are characteristics of diffusion processes).

[10] Which of the following would decrease the specific heat of a material?

            a) more attractive interactions between molecules.    

            b) the molecules have more motions to put energy into.

            c) a low molecular weight.(grams per mole).

            d) large size molecules (length, radius, etc.)

            e) none of these.

[11] A diffusion process has reached equilibrium. When this happens,

            a) q stops flowing.                 b) the concentration gradient changes sign.

            c) the flow of q becomes a constant rate.     d) the flow of q is equal in both directions.

Explanation / Answer

The correct option is - when heated, a material which expands does so because the molecules push each other away.

Explanation - When heat is added to a substance, the molecules gain kinetic energy and hence tend to move faster and away from each other. There is nothing like pushing away.

Heat conduction is carried out by colliding molecules transferring kinetic energy is fine as heat is always conducted through collision of molecules.

While a material is boiling, the heat added increases the kinetic energy of the molecules and that is also fine as during boiling or say phase transformation temperature does not change.

While melting, a well mixed sample of ice and water does not change temperature as already mentioned in phase transformation temprature does not change.

When water evaporates from a room-temperature glass of water, it cools the water slightly and this is fine as well because the most energetic of the liquid particles evaporate out and hence average energy of the liquid come down.

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