Quantity of heat — KCSE Physics

KCSE Physics · 116 practice questions · 6 syllabus objectives

36 easy41 medium39 hard

What You'll Learn

Key learning outcomes for this topic, aligned to the KNEC KCSE syllabus.

Define heat capacity and specific heat capacity and determine them experimentally

Define specific latent heat of fusion and vaporisation and determine them experimentally

State factors affecting melting and boiling points and solve problems involving Q = mcΔT and Q = mL

Explain the functioning of a pressure cooker and a refrigerator

Interpret heating and cooling curves; explain temperature plateaus during phase changes

Solve numerical problems involving heat exchange, method of mixtures, and calorimetry

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easySHORT ANSWER2 marks

State the formula used to calculate the heat absorbed by a substance when its temperature changes. (2 marks)

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Part (a) — 2 marks

Q = mcΔT (1 mk)

Where Q is the heat absorbed, m is the mass, c is the specific heat capacity, and ΔT is the change in temperature (1 mk)

easySHORT ANSWER3 marks

List three reasons for the temperature plateau observed during the melting of ice. (3 marks)

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Part (a) — 3 marks

Heat energy is absorbed to break the bonds between ice molecules (1 mk)

Temperature remains constant as the phase change occurs (1 mk)

All added heat is used for melting rather than increasing temperature (1 mk)

easySHORT ANSWER2 marks

Identify two ways in which a pressure cooker increases the temperature of the boiling water. (2 marks)

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Part (a) — 2 marks

It increases the pressure inside the cooker, raising the boiling point of water above 100°C (1 mk)

It traps steam, which also increases temperature due to the increased pressure (1 mk)

State the difference between specific heat capacity and heat capacity. (4 marks)

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