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Edexcel iGCSE Physics (4PH1) 5.3 Change of State Exam Style Question Paper 1B - New Syllabus

Edexcel iGCSE Physics (4PH1) Paper 1B - All Chapters

Questions 

In some countries, snow can fall and collect on the ground. Diagram 1 shows that after the snow has fallen, the sky can be clear, leaving the snow directly exposed to the Sun.

(a) Explain why the white snow will take a long time to melt, even though directly exposed to the Sun. (2)

(b) Diagram 2 shows a different piece of ground that has a metal drain cover. If the snow lands on metal, the snow takes a shorter time to melt.

Explain why the snow melts in a shorter time on the metal drain cover. (3)

(c) Explain how a convection current above the snow increases the time taken for the snow to melt. (3)

Syllabus Topic Codes (Edexcel International GCSE Physics 4PH1):

• 4.8: Radiation, Absorption, and Emission — part (a)
• 4.6–4.7: Thermal Energy Transfer and Convection in Everyday Phenomena — parts (b) and (c)
▶️ Answer/Explanation

(a) White snow and thermal radiation [2 marks]

  • White snow is a poor absorber and good reflector of infrared radiation.
  • Therefore, it absorbs less thermal energy from the Sun, so it takes longer to melt.

(b) Metal drain cover [3 marks]

  • The ground or metal drain cover is warmer than the snow.
  • Metal is a good thermal conductor.
  • Thermal energy is therefore transferred efficiently from the drain cover to the snow, causing it to melt faster.

The key point is that conduction through the metal provides a relatively rapid transfer of thermal energy to the snow.

(c) Convection current above the snow [3 marks]

  • Warmer air above the snow rises.
  • Colder air remains closer to the snow.
  • The colder air transfers less thermal energy to the snow, so the rate of energy transfer to the snow decreases and the snow takes longer to melt.

In a convection current, warmer, less dense air rises and is replaced by cooler, denser air. In this situation, the cooler air near the snow reduces the rate at which thermal energy is transferred to it.

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