Heat transfer Flashcards
(17 cards)
What are the three different ways heat can be transferred?
- Conduction
- Convection
- Radiation
What is conduction ?
The transfer of heat energy through the vibration of particles
How does conduction happen in solids ?
The particles are held tightly together. When one particle vibrates, it bumps into other particles nearby and quickly passes vibrations on
How does conduction happen in cooking ?
When a pan is placed on a hob, heat energy from the hob caused the particles in the pan to vibrate a
more and gain heat energy
How do vibrating particles in the pan cause the pan it heat up ?
When particles collide with nearby particles they pass some of their extra heat energy on to them
When does the process of conduction stop ?
This process continues throughout the ona until the heat has passed all the way through
How does the conduction of the vibration of particles in the pan cook food placed in the pan ?
When food is placed into a hot pan, heat energy is transferred from the particles in the pan to the particles in the food in a similar way until the food is cooked through
What is convection ?
Is the transfer of heat energy through gases of liquids
How does convection work ?
- When you heat up a liquid, the liquid near the heat source warms up faster
- Warm air rises, colder liquid takes it place
- This colder liquid is heated and when it starts to rise, colder liquid takes its place
As convection continues what do you end up with ?
A circulation of fluid - after a while, thru circulation of heat results in the whole fluid being heated
Where else does convection take place apart from boiling water on a hob ?
An oven - hot air rises and cooler air falls in the same way
What is radiation ?
The transfer of heat energy through waves of radiation- like how radiation from the sun heats up the earth
Why is radiation different from convection and conduction ?
There is no direct contact between the heat source and the food
What cookers use radiation ?
Grills and toasters
How do cookers like grills and toasters use radiation ?
They emit waves of radiation - when these waves reach the food, they are absorbed and heat the food up
What do microwaves use radiation to heat up ?
Fat, sugar and water molecules in our food
