1. Heat Energy can move by Radiation 

• No atoms are needed

• It moves in electromagnetic waves

• Infra-red Radiation

• E.g from the Sun to the Earth, heat energy moves as waves of infrared radiation

• Black objects absorb radiant heat better, they also emit it better than white objects

  • This is why a chilly bin is white inside

Radiation is the transfer of heat through electromagnetic waves, primarily in the infrared part of the spectrum. Unlike conduction and convection, radiation does not require atoms to travel through. 

This is how the Sun’s heat travels through the vacuum of space to reach Earth. Any object with a temperature above absolute zero emits thermal radiation. 

Absorption and Emission: The color and texture of a surface influence how well it absorbs and emits radiant heat. 

Dark, matte surfaces (like black paint) are excellent absorbers and emitters of thermal radiation. 

Light, shiny surfaces (such as those found inside a chilly bin or an emergency blanket) are poor at absorbing and emitting heat, making them effective reflectors. This is why a chilly bin is often white or has a shiny interior—to reflect heat away and keep the contents cold.

What colour shirt is best to wear in the middle of summer, and which is the worst?

2. Heat Energy can move by Convection

• Convection currents: heat rises, cold sinks

• Liquids and gases: it involves flowing

• fluid movement

• How heat moves with an oil heater in your lounge, heat rises up to the ceiling, pushing down the cold air, which then gets hot. This takes time (so your heat pump is faster as it is pumping)

• Also, the reason your kettle has its heating element on the bottom of the bottle, not the top

When a fluid is heated, it expands and becomes less dense, causing it to rise rapidly. As this happens, cooler, denser fluid sinks to take its place, resulting in a continuous and efficient convection current.

Consider how a room heater operates: warm air rises and effectively pushes cooler air down to be heated. 

In a kettle, the heating element is strategically placed at the bottom, ensuring that the water heats efficiently as the warm water rises and the cooler water sinks. This process guarantees optimal heating throughout the entire kettle.

3. Heat Energy can move by Conduction.

• Solids: it involves touching

• Conduction = Direct Contact

• eg. wooden vs metal spoons in soup

  • The metal spoon will get hot, the wooden one will not

    • This is because the atoms in a metal are close together and can bump into each other, transferring the heat along the spoon. 

    • The wooden spoon has a more random arrangement of atoms, so they are less efficient bumpers

Conduction is how heat energy is transferred through direct contact in solids, where particles are closely packed. 

When one end of a solid is heated, its particles gain kinetic energy and vibrate more, passing these vibrations to neighboring particles, similar to a domino effect. This is why a metal spoon becomes hot when placed in hot soup.

Materials are classified as conductors or insulators based on heat transfer efficiency. Conductors, like metals, transfer heat well due to their mobile electrons. Insulators, such as wood or plastic, transfer heat poorly because their particles are less effective at passing vibrations.