CIE iGCSE Co-ordinated Sciences-P2.3.4 Consequences of thermal energy transfer- Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-P2.3.4 Consequences of thermal energy transfer – Study Notes
CIE iGCSE Co-ordinated Sciences-P2.3.4 Consequences of thermal energy transfer – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
Core
- Identify and explain some of the basic everyday applications and consequences of conduction, convection and radiation
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
Everyday Applications and Consequences of Conduction, Convection and Radiation
1. Conduction
Applications:
- Cooking utensils (saucepans, frying pans) use metals such as copper and aluminium because they are good conductors.
- Saucepan handles are made of wood or plastic (insulators) to prevent burns.
Consequences:
- Accidental burns from touching hot metal objects.
- Poor insulation in houses → heat lost through walls and windows.
Explanation: Metals conduct heat quickly because of lattice vibrations and free electrons. Insulators conduct poorly, so they protect from burns or reduce heat loss.
2. Convection
Applications:
- Heating water in a pan: hot water rises, cold water sinks, forming convection currents that spread heat evenly.
- Room heating: warm air from a radiator rises, cooler air sinks → circulation.
- Hot air balloons: heated air inside becomes less dense, balloon rises.
Consequences:
- Uneven heating in poorly designed rooms → cold spots.
- Sea breezes caused by differential heating of land and water.
Explanation: Convection transfers heat in fluids due to density changes (hot fluid rises, cooler fluid sinks).
3. Radiation
Applications:
- Solar panels absorb radiation from the Sun to produce electricity or heat water.
- Thermos flasks: shiny silvered surfaces reduce heat loss by reflecting radiation.
- Radiators and fires: transfer heat by infrared radiation across a room.
Consequences:
- Wearing black clothes in hot sun feels hotter because black absorbs more radiation.
- Shiny, light-coloured surfaces reduce heating effects of radiation.
Explanation: Radiation is transfer of heat by infrared waves, requiring no medium, and is affected by surface colour and texture.
Comparison Table
| Method | How It Works | Everyday Applications | Consequences |
|---|---|---|---|
| Conduction | Energy transfer by particle vibrations and free electrons (in metals) | Cooking pans (good conductors), pan handles (insulators) | Burns from hot metals; heat loss through poorly insulated walls |
| Convection | Bulk movement of fluids due to density differences (hot rises, cool sinks) | Water heating in pans; radiators; hot air balloons | Uneven heating in rooms; sea breezes |
| Radiation | Transfer of energy by infrared waves; no medium needed | Solar panels; thermos flasks; fires/radiators | Black clothes feel hotter in sunlight; reflective surfaces stay cooler |
Example :
Why is the inside of a thermos flask silvered?
▶️ Answer/Explanation
Step 1: Heat inside the flask can be lost by radiation.
Step 2: Shiny, silvered surfaces are poor absorbers and poor emitters of radiation, but good reflectors.
Final Answer: The silvered surface reduces heat loss by reflecting thermal radiation back inside the flask.
Example :
On a cold winter evening, you are sitting near a fireplace. Explain how you feel warm in terms of conduction, convection, and radiation.
▶️ Answer/Explanation
Step 1 (Radiation): The fire emits thermal energy mainly as infrared radiation, which travels through the air and warms your skin directly.
Step 2 (Convection): Hot air near the fire becomes less dense and rises, while cooler air from the room moves in to take its place. This convection current carries warm air towards you.
Step 3 (Conduction): If you touch the fireplace or a heated metal object near it, heat is transferred directly to your hand by conduction.
Final Answer: You feel warm near the fire due to radiation directly from the flames, convection currents carrying warm air, and conduction when touching heated objects.