Transfer of Heat Energy and its Effects Flashcards
What are the effects of heat energy?
1) Change in Physical State.
2) Expansion and Contraction
3) Combination of 2 or more substances which forms a new substance.
4) Combustion
5) Thermal Decomposition
What is Expansion?
Expansion occurs when an object gains heat.
What is Contraction?
Contraction occurs an object loses heat.
Which state of matter, all out of all 3 states of matter, expands the fastest?
Gases
Which state of matter, all out of all 3 states of matter, expands the slowest?
Solids
When the volume of a substance increase, what else is also effected?
The density of the substance decreases. The mass remains constant at all times.
What are the 3 types of processes of Transmission of Heat?
Convection, Radiation and Conduction
What is Convection ?
The transfer of heat energy through a fluid (liquid only) by the movement of the substance itself.
What is Radiation?
It the transfer of heat energy through the form of electromagnetic waves, without needing any medium.
What is Conduction?
It is the transfer of heat energy through a substance from the hotter to the cooler parts of it without the substance itself moving.
How does Conduction work?
When an object is heated, the particles inside it spread further apart. Thus, the object expands.
What are the requirements of Radiation?
- Only can occur through a vaccuum.
- Rate of radiation depends on the temperature and nature of the surface of the hot body.
What are convection currents?
When the volume of the subsance increases, the density decreases. Then the hotter, less dense substance rises, displacing the cooler, denser the substance.
What are absorbers of radiation?
Objects that absorb radiation.
What qualities make objects better absorbers of radiation?
- Higher temperature
- Dark-coloured
- Dull
- Rough
What are conducters of heat?
Objects that can conduct heat.
What objects are good condutors of heat?
Metal are good conductors of heat.
What are poor conductors of heat called?
They are called insulators.
What objects are insulators of heat?
Non-metals
How is Conduction displayed in a frying pan?
The metal base of a frying pan is a good conductor of heat. It allows heat energy to be transferred quickly from the heat source to the food. The wooden handle is a poor conductor of heat. Our hands do not get burned because the heat energy is not conducted easily through handle to our hands.
How is Conduction displayed in Woollen clothing?
Air is a poor conductor of heat and is therefore a good insulator of heat. Porous materials, such as wool, trap pockets of air, making them excellent heat insulators. This is why clothes that are made from wool keep us warm beause heat from our body is not conducted readily through the air that is trapped by the wool.
How is conduction displayed through Double-glazed window?
Double-glazed windows are used to redce heat loss through the windows. A layer of air trapped between the glass panels forms an insulating layer.
How is Convection displayed through Air Conditioner?
Warm air, which is less dense, rises and collects under the ceiling.
