Education Always

Level: JHS, Basic 7  |  Subject: Integrated Science  |  Strand: Forces and Energy  |  Topic: Heat Transfer

Curriculum reference: B7.4.1.2.1 (NaCCA Integrated Science).

1. What is Heat?

• Heat is a form of energy that flows from a hot object to a cold object.
• Heat is measured in joules. Temperature (how hot or cold) is measured with a thermometer in degrees Celsius (°C).
• Heat always flows from the hotter place to the cooler place until both are at the same temperature.

2. Three Ways Heat is Transferred

Method	How it works	Where it happens	Example
Conduction	Heat passes from particle to particle without the material moving	Solids, mainly metals	A metal spoon in hot soup becomes hot; a cooking pot handle gets hot
Convection	Heat is carried by the movement of the heated liquid or gas itself. Hot fluid rises, cold fluid sinks.	Liquids and gases	Boiling water in a pot; sea breeze; hot air rising from a fire
Radiation	Heat travels as waves, with no material needed	Can pass through empty space	Warmth from the Sun; heat from a charcoal fire felt at a distance

3. Conductors and Insulators

• Good conductors let heat pass easily: metals such as copper, iron and aluminium. Cooking pots are metal.
• Insulators (poor conductors) do not let heat pass easily: wood, plastic, cloth, air and rubber. Pot handles are wood or plastic.
• Gases and liquids are poor conductors, but they transfer heat well by convection.

4. Simple Activities

• Conduction: hold one end of a metal rod and heat the other end. Soon the end you hold becomes hot. A wooden stick does not do this.
• Convection: put a few crystals of potassium permanganate in water and heat it from below. The colour rises and circulates.
• Radiation: place your hand near (not touching) a hot iron or sit near a fire. You feel the warmth.

5. Uses and Applications

• Metal cooking pots conduct heat to the food.
• Wood or plastic handles stop heat from burning our hands.
• Houses have windows or vents near the roof so hot air can rise and leave (convection).
• Light-coloured clothes reflect radiation and keep us cooler in hot weather.
• A vacuum flask keeps drinks hot or cold by reducing conduction, convection and radiation.
• Shiny roofing sheets and white walls reflect heat from the Sun.

Remember: Conduction is in solids, convection is in liquids and gases, and radiation needs no material. Metals are good conductors; wood and plastic are insulators.

Education Always (education.inspiringalways.com). Original notes written to follow the NaCCA Basic 7 Integrated Science curriculum.