7.1: Warmth and Coldness (Pg. 182 – 184):
TB: Check Your Learning: Read Pages 182-184. Answer the following questions:
1.
Describe how home heating and cooling has changed over time, and how it has remained the same.
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.
2.
Why do buildings have chimneys?
Buildings have chimneys because burning fuel for heat releases toxic gases. The chimney is a vent that carries the waste gas to the outside of the house.
3.
List two costs, or drawbacks, of using an electric air conditioner, and two benefits. a) One cost of air conditioner is the actual cost to buy it and to run it. Air conditioners use a lot of electricity, which can be costly. The electricity often comes from the burning of fuels, which creates air pollution. Pollution is another cost of air conditioners. Air conditioners are beneficial because they keep a building at a comfortable temperature. When it is extremely hot out they can also help people avoid heat stroke and other health hazards.
4.
Why should we try to use less oil, natural gas, and electricity?
Oil and natural gas are found in limited supplies. If we continue to use them at the current rate, they may run out. Since electricity is often generated from burning oil and natural gas, using electricity also consumes them.
PB: Check Your Understanding: Pages 133
1. Tell how two different animals stay cool.
Dogs pant; honeybees flap their wings…
2. Why do buildings have chimneys?
Burning wood or oil produces toxic fumes that can harm people. The toxic fumes need to be pushed outside. Chimneys are vents that release the fumes outside.
3. Describe two good (advantages) and two bad (disadvantages) things about using electric air conditioners.
Good: They cool down people’s homes. They do not create toxic gases; they use electricity.
Bad: The use a great deal of electricity (expensive). They are also harmful to the environment.
4. Key Question: How do you keep yourself warm or cool? Provide examples from your own personal experience.
Some people warm their homes using oil. Some people have large windows to let in sunlight for warmth.
Some people cool their homes with a fan. We close the window shades to block sunlight so the house can stay cool.

7.2: Explaining Hot and Cold (Pg. 185-186)
TB: Check Your Learning: Read Pages 185-186. Answer the following questions:
1.
a) Describe a key idea about heat that you understood from this section (Define heat).
Heat is the transfer of warmer objects to cooler objects. b) Write an explanation of heat.
Heat is the movement of energy from warmer objects to cooler objects.
2.
Summarize the key ideas of the particle theory in your own words or with labelled diagrams (Define the particle theory).
Matter is made up of tiny particles. There are empty spaces between particles. Particles move continuously in random direction. Heating particles increases their speed and the distance between them.
Since particles attract each other (by the force of attraction), they tend to stay together.
3.
How does the particle theory help to explain the difference between a drop of cold water and a drop of hot water?
According toe the particle theory of matter, the molecules in the hot water must be moving faster than molecules in a drop of cold water.
4.
Explain what is wrong with the statement: “A mug of hot chocolate contains more heat than a glass of cold water.”
Heat is not something that can be contained since it is not a tangible thing. Heat is a process. A better sentence would read “The particles in the mug of hot chocolate have more energy than the particles in the cold glass of water.”
PB: Check Your Understanding: Pages 137
1. The particles theory says that everything is made up of particles we cannot see. The particles have spaces between them, and they are always moving. The particles attract one another. When you add energy to the particles, they move faster.
2. We often use heat to talk about anything that is warm. In science, heat is the transfer of energy from hotter to colder substances. You can’t just say an object has heat.
3. I know that an object is warm because its particles are moving faster than when the object is cold.
PB: Check Your Understanding: Pages 138
1. Particles in a cold object are not moving. a warm object.
False; They are moving but more slowly than in
2. The particles that make up matter are invisible. True
3. Energy moves from a colder object to a warmer object. False; Particles move from a warmer object to a colder object.
4. When you add heat to an object, its particles move faster . its particles move faster.
False; when you add energy to an object,


TB: Check Your Learning: Read Pages 187-189. Answer the following questions:
1.
Name and briefly describe the two kinds of energy that all particles possess. a) Kinetic Energy: Is the energy of motion. b) Thermal Energy: Is the kinetic energy plus the energy of attraction between particles.
2.
Describe the relationship between temperature and energy.
Temperature is a measurement of the kinetic energy of all the particles in an object or all the particles in an area such as the air in a room.
3.
4.
List the three states of matter in order of decreasing kinetic energy. a) Which state of matter is most easily compressed to take up a smaller volume? b) Write a sentence explaining this observation.
Gas, liquid, and solid.
Gases are most easily compressed.
There is a lot of space between gas particles, but not a lot of space between particles in liquids or solids, so it is easier to compress gasses than liquids or solids.
5.
When a substance is cooled, what happens to its particles? How does cooling affect the volume of the substance?
When a substance is cooled, the particles within the substance slow down. Slower particles travel shorter distances, so the volume of a substance decreases as it contracts.
6.
Define the followings:
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.
PB: Check Your Understanding: Pages 133
7.5: Living with Thermal Expansion and Contraction (Pg. 192 – 194)
Check Your Learning: Read Pages 192-194. Answer the following questions:
1.
Carefully read the following statements and decide if they are true or false. If the statement is false, then rewrite the statement to make it true. (DO not simply restate the statement in the negative.) (T/F) a) The particles of a material get bigger when heated. F. The particles in a material move faster when heated.
b) The particles of a material move faster when heated. T c) Of the three states of matter, gases expand the least. F. Gases expand the most of the three states of matter.
d) The particles of a solid vibrate. T
2.
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.
During the summer, hot weather causes the door to expand because the particles in the metal are moving faster. During winter, the weather cools, the particles in the metal slow down, and the door contracts. The door frame expands inward and outwards, so this can cause doors to stick during warmer weather when they open easily during cooler weather.
3.
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. a) The steel rods inside the reinforced concrete used in buildings need to expand at the same rate as the concrete itself. If the steel rods expand faster than the concrete, the concrete can crack and make the building unstable. B) Dental fillings must expand at the same rate as the teeth that they get put into, otherwise the tooth could crack. C) Bridge segments are separated by expansion joints; otherwise when the segments expanded in hot weather the bridge would buckle. D) Sidewalks also come in segments and use a similar design so the segments do not crack when they expand.
4.
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.

Name: __________________________
2. Briefly summarize the particle theory in your own words.
Date: ________________________
The particle theory says that all matter is made of tiny particles (too small to be seen) that are moving around. Particles have spaces between them and are attracted to each other. Particles move faster as they absorb more energy.
3. Complete the following table.
Table 1: Descriptions of Three States on Matter.
Solid Liquid Gas
Volume constant
Shape definite
Type of Particle Motion vibrating
Spaces between Particles small
Fairly constant
Takes shape of container
Vibrate, rotate, move past each other
Small, but greater than in a solid
Changing
Takes shape of container
Vibrate, rotate, move past each other large
4. Use the particle theory to explain why gases expand more than liquids or solids when they are heated.
Gas particles move so fast, bonds cannot form easily between individual particles. Fast-moving particles move greater distances, so when gases are heated their particles move even faster and the gas expands.
5. Write a definition of “heat,” using your own words.
Heat is the transfer of thermal energy from warmer objects to cooler objects.
6. From what you have seen or read, list two examples of: a) b)
Thermal Expansion in Solids: The metal in a bridge expands in the heat. So does the wood in a desk drawer.
Thermal Expansion in Liquids: Mercury in a thermometer expands when the temperature increases. As Earth’s temperature increases, the oceans expand. c) Thermal Expansion in Gases: Over-inflated car tires can burst when they expand. A balloon expands when the gas inside is heated.
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.