Unit 1: 1 - Energy Transfer by Heating Flashcards
What is the human organ that detects infrared radiation?
The skin.
What type of radiation do all objects emit?
Infrared radiation.
What emission is proportional to the temperature of an object?
Infrared (the hotter the object, the more infrared radiation is given off).
How can infrared radiation reach the Earth and keep it warm?
As it is part of the light (electromagnetic) spectrum, it can travel through a vacuum.
What types of surfaces are good absorbers of infrared radiation?
Dark, matt surfaces.
What type of surfaces are good emitters of infrared radiation?
Dark, matt surfaces.
What type of surfaces are good reflectors of infrared radiation?
Light, shiny surfaces.
What are the 3 (main) states of matter?
Solid, liquid and gas.
What state of matter does conduction mainly occur?
Solids (liquids and gases are poor conductors).
What are the best conductors and why?
Metals, as they contain free electrons that can carry energy. These gain energy and collide more into other particles and transfer.
How does a solid conduct heat?
The particles are heated at one end, so they gain kinetic energy and vibrate more. The particles then vibrate into each other and transfer this energy to adjacent particles - which transfers heat along the solid.
Poor conductors are called…
Insulators.
What materials does convection mainly occur in?
Fluids (liquids and gases).
How does convection conduct energy through materials?
When a fluid is heated it expands. The fluid then becomes less dense and rises. The warm fluid is replaced by a cooler, denser fluid. The resulting convection current transfers energy throughout the fluid.
Why doesn’t convection occur in solids?
Because the particles in solids are fixed in place so they cannot move around.
What is evaporation?
When a liquid turns into a gas.
Give 3 ways to increase the rate of evaporation.
- Increasing the surface area of a liquid;
- Increasing the temperature of a liquid;
- Creating a draught of air across the liquid’s surface.
What is condensation?
When a gas turns into a liquid.
Give 2 ways to increase the rate of condensation.
- Increasing the surface area;
- Reducing the surface temperature.
The greater the temperature difference between an object and its surroundings, ____.
The greater the rate in which energy is transferred.
Apart from the temperature differences, give 3 factors that affect the rate at which energy is transferred.
- The object’s surface area;
- The object’s shape;
- The materials the object is in contact with.
Give 3 ways in which to maximise the energy transfer.
- Use good conductors;
- Colour an object dull black;
- Have the air flow around the object maximised.
Give 3 ways in which to minimise energy transfer.
- Prevent convection currents (and conduction) by trapping air in small pockets in a solid;
- Use materials that are good insulators;
- Colour materials white and shiny.
How does a vacuum minimise heat transfer?
Because it contains no particles, so conduction and convection currents cannot occur.
