Heat Flashcards
What is heat
A form of energy
What is temperature
The measure of how hot or cold an object is
SI unit of heat energy and Temperature
Heat: Joules (J)
Temperature: Kelvin (K)
What is the movement of heat
From a hotter region to a colder region
What is conduction
The transfer of heat without the physical movement of the medium
What is the order of conduction and why
- Solid — Liquid — Gas
- As the particles are closer packed in solids than gasses, the heat passes to each particle easier
What are the characterisitics of Expansion
- The temperature increases
- The object gains heat
- The particles move faster and further apart
What are the characterisics of Contraction
- The temperature decreases
- The object loses heat
- The particles move slower and closer together
Case of Expansion in solids
- In hit weather, a metal railway gains heat and expands
- If the track was made in 1 continuous strip it would buckle
- This can cause the train to derail
- Hence, expansion gaps are made for the track to safely expand
Case of Contraction in solids
- In cold weather, the power lines and network cables loose heat and contract
- if the lines are exactly straight, they might snap if the cable gets too tight
- Hence they are made loose to let it safely contract
What is a bimetalic strip
A strip of metal made of two different metals that expand at different rates
(brass on top steel below)
Which expands/contracts more in the bimetalic strip
Brass
What is the concept of a hot air balloon
Hot air rises and cold air sinks
(The flame heats the air allowing it to rise)
Why are metals better conductors of heat
The particles are much more closely packed and this allows the transfer of heat energy to occur quicker
What is Convection
The transfer of heat from one place to another by the movement of the medium
Describe the process of convection in a liquid
- The water at the bottom of the flask is heated up and it gains heat
- As the volume of water at the bottom increases, it decreases in density
- The change of density allows it to rise to the top of the flask
- Due to having a lower density, the water at the top sinks to the bottom
- This continues and convection currents are formed in the water allowing heat energy to be distributed evenly throughout the water.
Explain the convection process in gasses
- The air above the candle gains heat and expands
- The decrease in density allows it to rise up.
- The cooler air in the other chimney moves down to take the place of the risen air.
- This then forms a convection current
What is radiation
The transfer of heat without the need of a medium
What are the factors that affect conduction
- Particulate State of medium
- Material of solid
Factors that affect radiation
Temperature, Surface area, Color and texture of the surface
How does Temperature affect radiation
The hotter the object, the higher rate of radiation from it
How does Surface area affect radiation
The larger the surface area, the higher the rate of radiation
How does Texture of a surface affect radiation
The rougher the surface, the higher the rate of radiation
how does colour of a surface affect radiation
The duller the colour of the surface, the higher the rate of radiation
