Heat transfer by conduction — KCSE Physics

KCSE Physics · 114 practice questions · 8 syllabus objectives

37 easy39 medium38 hard

What You'll Learn

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

Explain why water is a poor conductor and why thick glass cracks when hot liquid is poured in

Explain heat conduction in solids in terms of lattice vibration and free electron transfer

Compare thermal conductivity of different materials and classify them as good conductors or insulators

Describe applications of thermal conduction (cooking pans, building insulation, double glazing)

Explain the mechanism of heat conduction in solids at molecular level and distinguish conductors from insulators

Describe experiments to compare thermal conductivity of different materials and state the variables to control

Explain applications of conduction: cooking utensils, vacuum flask, lagging, heat sinks, and double walls

Heat transfer by conduction

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easySHORT ANSWER2 marks

Identify two reasons why vacuum flasks are effective in reducing heat transfer by conduction. (2 marks)

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Part (a) — 2 marks

The vacuum between the inner and outer walls prevents conduction as there are no particles to transfer heat (1 mk)

The outer wall is usually made of insulating materials that have low thermal conductivity (1 mk)

easySHORT ANSWER3 marks

State how the arrangement of molecules in a solid affects its ability to conduct heat. (3 marks)

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Part (a) — 3 marks

Molecules in solids are closely packed, allowing efficient vibration transfer between them (1 mk)

The strong intermolecular forces in solids facilitate quick energy transfer compared to gases or liquids (1 mk)

Tightly arranged molecules permit better conduction as they can quickly pass kinetic energy during collisions (1 mk)

easySHORT ANSWER2 marks

Name two ways in which double glazing enhances thermal insulation in buildings. (2 marks)

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Part (a) — 2 marks

The air gap between the two panes reduces heat transfer by conduction (1 mk)

The reflective coatings on the glass help to minimise heat loss by radiation (1 mk)

List three ways in which free electrons contribute to heat conduction in metals. (3 marks)

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