2Y: Heat, energy and energy transfer Flashcards
What is Heat?
Heat is a form of energy.
What is Heat measured in?
It is measured in joules (J).
Adding heat energy to a material can have three main effects. What are they?
- It can cause the temperature of a substance to increase.
- It can cause the material to expand.
- It can change the state of a substance from solid to liquid or from a liquid to a gas.
How does heat energy move from place to place?
There are three principal methods of heat transfer.
These are
- Conduction,
- Convection
- and Radiation
Describe the movement of heat energy?
Heat energy moves naturally from a warm place to a colder place. A hot cup of tea will lose heat energy to its cooler surroundings until the tea and the surroundings reach the same temperature.
Similarly a cold bottle of water will gain heat energy from its warmer surroundings until it reaches the same temperature as the surroundings.
What is conduction?
- Conduction is the movement of heat energy through a substance without any overall movement of the substance itself
When a piece of metal is heated, the particles of the metal vibrate more. These vibrating particles cause nearby particles to vibrate also. Heat energy is passed on from particle to particle moving from a hot area to a colder one. Even though the particles within the metal are vibrating, the metal itself is not moving. In general, conduction is the main method by which heat is transferred through a solid object (e.g. saucepan).
What do you call a poor conductor of heat energy?
Some substances are very poor conductors of heat energy. Another name for a bad conductor is an insulator. Substances such as polystyrene, wool, fleece and foam are good insulators. This can be a good thing as it stops the heat energy escaping from our homes and bodies.
What is convection?
- Convection is the movement of heat energy through liquids and gases due to the motion of the substance itself.
When the particles of liquids and gases are heated, they tend to rise. Cooler particles then fall to take their place. The upwards motion of warm particles and the downwards motion of cool particles is called a convection current (e.g. boiling a kettle).
When heating the liquid in a kettle, the heating element is placed at the bottom of the kettle. As the water around the heating element gets warm, it rises. This causes the entire contents of the kettle to be heated and not just the water around the heating element. The upwards motion of warmer liquid and the downward motion of cooler fluid is known as a convection current.
What is radiation?
- Radiation is the transfer of heat energy via radiation waves that can travel through a vacuum.
The energy of the Sun travels an enormous distance through space to get to Earth. Since there are no particles in space to pass on the heat energy by conduction or convection, how does the energy of the Sun get to us? The answer is by radiation. The Sun supplies many types of radiation (known as electromagnetic energy) to the Earth where it is converted into
heat energy.
What is temperature and what is it measured in?
Temperature is a measure of how hot an object is.
It is measured in degrees Celsius using a thermometer.
