How much do we really understand the difference between heat and temperature and how it is conducted?
If we think of a cup of hot tea, when we hold onto the cup it feels warm to the touch. Heat moves from the cup to my hand, showing us that warm things will heat cold things by the transfer of heat or heat energy.
So to explain, the cup of tea was hot in comparison to my hand. When I held the cup the molecules in my hand moved faster as heat energy flowed from the mug to my hand. As a result the mug had then less heat energy as this had been transferred to the colder item (my hand) and the molecules within the cup begins to move slower and will continue to decrease in temperature until the mug reaches the temperature of the room.
Two cold items can actually heat one another if you were to rub the two together. Heat is not a calorific object but a form of energy created by the movement of molecules in any object.
How do we measure the amount of heat energy that an object has?
Temperature is the measure of how much heat energy an object has.
These 3 statements are all correct
- The mug of tea has a higher temperature than my hand
- The molecules in the mug of tea are moving faster than the molecules in my hand
- Heat energy will flow in the direction from the tea to my hand (not vice versa)
Heat can be transferred in one of 3 forms:
Heat conduction or thermal conduction is the process where heat is transferred within a body due to the collision of neighbouring particles. For example:
A child that has been out in the snow all day, comes into the house and cuddles up to his mother to keep warm. This is because the heat is transferred from the mothers’ body to his body using conduction.
Heat convection occurs when heat is transferred through a liquid or gas by the hotter material moving into a cooler area
Boiling water is a great example of everyday convection. Heat passes from the burner into the pot, heating the water from the bottom. The hot water then rises and the cooler water moves down to replace it causing a circular motion.
The term radiation refers to energy that travels through space or matter in the form of energetic waves or particles (called infrared light). When radiation occurs, waves move out in all directions from the producer of the energy.
For example when you park your car when you arrive at work on a sunny day with no shade, the car will heat up throughout the day as the energy from the sun is transferred to the car which is held by the vehicle and released throughout the day, making the car extremelywarm when you enter it.
We can use all of these forms of heat transfer to warm us, when we are cold. In a work environment you conduction would not really be used as a good form would be to use a hot water bottle.
Convection is often used in warehouse heating and factory heating in the form of industrial warm air heaters. Warm air heating works by pulling the cold air within the building and pushing it over the heat exchanger where the cold air is heated and then pushed out via a fan into the building, where the air is distributed around the building until the room reaches the required temperature.
Radiation is often used when considering garden centre heating using infrared radiant heaters. These work by heating the objects in the room, rather than the air and releasing the heat energy during the day, helping to maintain a comfortable temperature for the employees, customers and a perfect environment for plant growth.