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7 Cards in this Set
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Particle Theory: 1. all matter is made of particles 2.even though we cannot see the particles they are always in motion 3.have spaces between them 4.FOA 5.Move faster as they absorb energy |
Heat: The transfer of thermal energy from warmer to cooler objects. Lossing heat makes objects colder Gaining heat makes objects warmer. in a hot object is higher than the average kinetic energy in a colder object |
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Examples of thermal energy:
Solid- Metal in bridge that expands Liquid-Mercury Gas-over inflated car tires |
We have chimneys to release toxic gases that orginate from burning heat. They carry waste gases out.
Air conditioners cost alot of money to buy and run it. They use various amounts of costly electricty and pollution occurs.
Oil and gas are limited supply. If we keep using them at the current rate they may run out therefore we should use electricity which is often generated. |
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Thermal Contraction: 1. Mass does not change 2.# of particles do not change 3.Volume changes V increases (more spaces) V decreases (less spaces) |
Expansion joints allow steel and concrete to expand without cracking.
The helium gas in a balloon explands when you move a balloon from the cold outdoors into a warmer room inside. |
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Heat is not something that can be contained since it is not a tainable thing. Heat is a process. Solid, Liquid, Gas Particle Motion: Slowest, Slower, Particle Shaping:Very close together, Close together, Farthest apart
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(T) all matter is made of particles (T) the particles in matter are in motion (F) heating speeds up the motion of the particles (T) In a gas particles all move in the same direction (T) as matter is cooled the particles shrink. |
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Heating is still done largely by burning fuels, like it has been in the past, although people now have central heating to circulate the warm air throughout the house. Some people also use electric heaters. People used to use cool water to cool their houses. Now people use electric air conditioners.
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1. Kinetic Energy: Is the energy of motion.
2. Thermal Energy: Is the kinetic energy plus the energy of attraction between particles. |
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Kinetic energy: Energy that all moving objects posses; a particle has more KE when moving faster and less KE when moving slower. Temperature: A measure of the average KE if the particles of a substance. Thermal energy: The total KE and energy of attraction of all the particles of a material. Thermal expansion: An increase in the volume of a substance caused by heating. Thermal contraction: A decrease in the volume of a substance caused by cooling.
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1. A metal entrance door swings freely in the winter, but when the weather turns warm, the door sticks and seems too big for the doorframe. Using your knowledge of particle theory, explain what is happening.
2. When building a device of structure, engineers must carefully consider how the materials they choose will change when heated and cooled. List four situations where thermal expansion and contraction could be a problem. 3. You want to inflate an air mattress to use in a swimming pool on a hot summer day. Should you fill the mattress with as much air as possible? Why or why not? The air mattress will deflate somewhat when you put it in the pool, since the colder water will cause the fast-moving air particles to slow down. So you should pump as much air into the mattress as possible.
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8. Solids expand slightly when heated. For this reason, bridges and railway tracks are built with expansion joints. Use the particle theory to explain what might happen on a hot day if expansion joints were not used. On a hot day, the extra thermal energy causes the particles in a solid to vibrate more quickly and expand. If there were no expansion joints then the heat would cause the swelling bridge to buckle and possibly break.
10. Perspiration (sweat) helps a person cool down. What change of state is involved in sweating? Explain. Sweating involves a change from liquid to gas – the sweat evaporated from your body.
11. You are boiling vegetables on the stove and notice the lid of the pot moving up and down. Use the particle theory to explain what is happening. The heat from the stove causes water particles in the pot to absorb energy and turn into water vapour, or gas. As the gas gets hotter it expands and pushes the lid up, letting some of the water vapour escape.
14. a) Some people hang wet clothing out to dry on warm, sunny day. Why does wet clothing dry in this weather? Wet clothing dries because the water molecules in the clothing absorb the Sun’s energy. Eventually those water molecules absorb enough energy to heat yup and evaporate as a gas.
b) Some people have wet clothing out to dry even on freezing cold days. Will wet clothes dry in this weather? Explain. Yes, eventually the clothes will dry, although it could take a long time. As long as it is sunny, the water molecules will absorb the Sun’s energy and eventually turn from liquid to gas.
c) What would happen to juicy vegetables left on a plate in a freezer for long time? How can this be prevented? Juicy vegetables will eventually become dried out because the water in them will be drawn to the surface and from ice crystals. The ice crystals will get bigger as water particles from inside the freezer attach themselves to the vegetables. The best way to prevent this is to put the vegetables in a plastic bag, which blocks the ice crystals from the surrounding air.
15. A bimetallic strip is made of one type of metal on one side and a different metal on the other side (Fig. 2 on page 199). The strip bends one way when heated. Explain why the strip bends when heated. The strip bends when it is heated because one side expands more than the other side.
18. Briefly answer the key question on page 180: How does heat affect matter? Matter consists of particles moving or vibrating at different speeds. When a substance is heated, its particles absorb energy. This energy causes the particles to vibrate or move more quickly, increasing the volume of the substance. Enough heat can cause the particles in a solid to vibrate so quickly they break their bonds; the solid then melts, or changes to a liquid. Likewise, enough heat can cause the particles in a liquid to spread so far apart that the liquid evaporates, or changes to a gas.
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gas solid liquid |
