# Gr.7 heat and environment test 2015-2016

Name the 5 main points in the particle theory. 1.All matter is made up of tiny particles. 2.Particles have space between them. 3.Particles are moving all the time. 4.Particles move faster when heated. 5.Particles attract each other.
What is heat? It is the transfer of energy from the particles of a warmer object to particles of a cooler object.
What is Kinetic energy? It is the energy that all moving object possess. A particle has more kinetic energy when moving faster and less when moving slower.
What is a temperature? a measure of average kinetic energy of particles of substance.
What is thermal energy? the total kinetic energy and energy attraction of all the particles of a material. Total kinetic energy+Energy of attraction=Thermal energy
Thermal energy transfer is? Thermal energy naturally moves from a substance with higher temperature to a substance with a lower temperature.
What is conduction? Conduction is the transfer of thermal energy through a substance or between substances in contact. Conduction is caused by the collision of particles.
What is Convection? Convection is a transfer energy from one part of a fluid to another by a circulating current of faster-moving and slower-moving particles.
What is radiation? Radiation energy is energy that travels in the form of electromagnetic waves though empty spaces. Examples of these waves are visible light, ultraviolet light, and infrared rays. Radiation is the transfer of radiant energy though electromagnetic waves.
Why is it important to consider the transfer of energy when building a house? The occupants of houses are more comfortable because warm spaces stay warm and some with coldness. People build to design house with least amount of energy as possible. Inslators prevent it.
Explain why the walls and doors of refrigerators and freezers contain thick slabs of polystyrene foam. This foam prevents the energy from passing from the warmer environment of the housing of the cold inside the fridge. This makes the fridge more energy efficient.
How does this help conserve energy? As little energy as possible is wasted because a "Thermal" envelope is created that separates the house from the outside environment. It prevents energy transfer by conduction and radiation.
What problem may this create? Moisture in the home is trapped. It may help mould to grow and wood to rot. Sealing all the cracks in a home may trap unhealthy gases that are produced by certain types of furniture and carpeting.
How does an air-to-air heat exchanger overcome this problem and still help conserve energy.Part 1 This device allows some of the thermal energy in the outgoing warm air to be transferred to the incoming fresh cold air. The air duct carrying the stale indoor air.
How does an air-to-air heat exchanger overcome this problem and still help conserve energy.Part 2 This allows a transfer of thermal energy from outgoing warm air to the incoming cool air. By the time the old indoor air-leaves the heat exchanger,mucle it's thermal energy has been transferred to the incoming air.
How does an air-to-air heat exchanger overcome this problem and still help conserve energy.Part 3 As a result the fresh air entering the home is already warm.
Thermal expantion When a substance is heated, its particles move faster, and have more kinetic energy. Due to having more kinetic energy, the substance expands. This is because when the particles move faster, they move farther apart.
Thermal Contraction When a substance is cooled, its particles move slower, and have less kinetic energy. The substance's volume decreases, because of the decrease in kinetic energy. This happens because when particles move slower, they don't move as far apart.

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