Model Answers for Worksheets of Grade 8
Directed Reading A for CHAPTER 2 SECTION 1, 2 AND 3 SECTION 1: WHAT IS MATTER?
1. They are all made of matter.
2. Matter is anything that has mass and takes up space.
3. B
4. D
5. Volume is the amount of space taken up by an object.
6. volume
7. meniscus
8. cubic
9. length, width, and height
10. Answers may vary. Sample answer: The volume could be measured by
placing the object in a graduated cylinder with water. The volume of water displaced is the volume of the object.
11. because 1 milliliter of water is equal to 1 cubic centimeter
12. D
13. C
14. A
15. D
16. The only way to change the mass is to change the amount of matter it contains.
17. mass
18. weight
19. weight
20. mass
21. weight
22. weight
23. mass
24. C
25. Something must act on an object to change the motion of the object.
26. The more mass an object has, the greater its inertia.
27. Answers may vary. Sample answer: A full cart has more mass than an empty one. More mass means the cart has more inertia. Because it has more inertia, a full cart is harder to put into motion.
SECTION 2: PHYSICAL PROPERTIES
1. B
2. C
3. D
4. A
5. F
6. C
7. B
8. E
9. G
10. physical property
11. density
12. density
13. The densest layer will settle on the bottom.
14. The least dense layer will be found on top.
15. because 1 kg of lead would take up less space than 1 kg of feathers
16. The object will sink.
17. Answers may vary. Sample answer: If you know the density of the
substance, you could compare it with the density of water. If the density of the object is less than the density of water it will float.
18. D _ m/V
19. density; volume; mass
20. volume
21. Answers may vary. Sample answer: because a substance’s density is always the same at a given temperature and pressure and because most substances have different densities
22. physical change
23. changes in state
24. PC
25. X
26. PC
27. PC
28. PC
29. PC
30. identity
31. Answers may vary. Sample answer: When matter undergoes a physical
change, one or more physical properties are changed. For example, if a lump of copper is drawn out into a thin wire, only its shape is changed, not its identity.
SECTION 3: CHEMICAL PROPERTIES
1. C
2. A
3. B
4. D
5. B
6. Answers will vary. Sample answer: The burning changes wood to smoke and ashes.
7. chemical
8. characteristic
9. B
10. C
11. Answers may vary. Sample answer: Baking a cake involves chemical
changes because the cake has completely different properties than
its original ingredients. It is impossible to reverse the results of those changes.
12. Answers may vary. Sample answer: The creation of new substances with
new properties shows that a change is chemical. Other signs include fizzing
or foaming, a change in color or odor, the production of heat, sounds, or
light being given off.
13. chemical changes
14. Answers may vary. Sample answer: Some chemical changes can be reversed with more chemical changes. For example: The water formed in a
space shuttle’s rockets can later be split back into hydrogen and oxygen
using an electric current.
15. B
16. A
17. physical changes
18. CC
19. PC
20. CC
21. PC
22. CC
23. CC
24. PC
25. PC
Ch2 Section1: Vocabulary worksheet
SECTION: WHAT IS MATTER?
1. Matter: anything that has mass and takes up space
2. Volume: a measure of the size of a body or region in three-dimensional space
3. Meniscus: the curve at a liquid’s surface by which one measures the volume of the liquid
4. Mass: a measure of the amount of matter in an object
5. Weight: a measure of the gravitational force exerted on an object; its value can change with the location of the object in the universe
6. Inertia: the tendency of an object to resist being moved or, if the object is moving, to resist a change in speed or direction until an outside force acts on the object.
Ch 2 Section 2: Reinforcement worksheet
A MATTER OF DENSITY
1. Green liquid: 0.75 kg/L; Blue liquid: 0.9 kg/L; Red liquid: 1.2 kg/L; Black liquid: 0.8 kg/L
2. First (bottom): red; Second: blue; Third: black; Fourth (top): green
3. B
4. The layers of the diagram should be shaded/labeled in the following order from the top: green, black, blue, red.
5. Accept all reasonable answers. Sample answer: I could open the spigot at the bottom of the tank and let the red liquid out.
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CHAPTER 3
CH3: SECTION 1
SECTION: THREE STATES OF MATTER
1. B 7. C
2. A 8. C
3. C 9. B
4. B 10. A
5. A 11. D
6. D 12. A
Vocabulary and Section
Summary
SECTION: THREE STATES OF MATTER
1. States of matter: the physical forms ofmatter, which include solid, liquid, and gas
2. Solid: the state of matter in which the volume and shape of a substance are fixed
3. Liquid: the state of matter that has a definite volume but not a definite shape
4. Surface tension: the force that acts on the surface of a liquid and that tends to minimize the area of the surface
5. Viscosity: the resistance of a gas or liquid to flow
6. Gas: a form of matter that does not have a definite volume or shape
Chapter 3 States of Matter
SECTION 1 THREE STATES OF MATTER
Section Review Worksheet
1. Solid: brick, penny, ice cube
Liquid: water, milk, soda, oil
Gas: air, oxygen, water vapor
2. They are always moving.
3. The particles of a liquid can move past one another, but the particles of a solid stay in fixed positions.
4. The particles of a gas can move far away from one another, but the particles of a liquid stay close to one another.
5. Surface tension
6.
State of matter | Definite shape | Definite volume |
Solid | yes | yes |
Liquid | no | yes |
Gas | no | no |
CH3 Section 2: Behavior of Gases
SECTION: BEHAVIOR OF GASES
1. C
2. temperature
3. The particles of gas in the balloon will have less energy, and the particles of gas will not push as hard on the walls of the balloon.
4. volume
5. container
6. pressure
7. The pressure is greater in the basketball because it contains more particles of gas in the same volume. More particles of gas hit the inside of the basketball. This makes the force on the inside surface increase, which produces greater pressure.
8. B
9. C
10. Boyle’s law
11. As the balloon rises, the pressure of the gas decreases as the volume increases. The balloon would pop if it were completely filled before being released.
12. Charles’s law
13. Charles’s law
Reinforcement
MAKE A STATE-MENT
Liquid: has surface tension; has viscosity; changes shape when placed in a different container; does not change in volume; Particles are close together.
Gas: Particles break away completely from one another; changes shape when placed in a different container; has viscosity; changes volume to fill its container; obeys Boyle’s law; amount of empty space can change
Solid: Particles are close together; Particles vibrate in place; Particles are held tightly in place by other particles; does not change in volume; has definite shape.
Vocabulary
SECTION: BEHAVIOR OF GASES
1. Temperature: a measure of how hot (or cold) something is; specifically, a measure of the movement of particles
2. Volume: a measure of the size of a body or region in three-dimensional space
3. Pressure: the amount of force exerted per unit area of a surface
4. Boyle’s law: the law that states that the volume of a gas is inversely proportional to the pressure of a gas when temperature is constant
5. Charles’s law: the law that states that the volume of a gas is directly proportional to the temperature of a gas when pressure is constant.
CH3: Section3
SECTION: CHANGES OF STATE
Direct Reading B
1. freezing
2. melting
3. evaporation
4. condensation
5. melting
6. endothermic
7. freezing
8. exothermic
9. evaporation
10. change of state
11. C
12. D
13. sublimation
14. endothermic
15. B
Section Review worksheet
1. The particles of a solid only vibrate. The particles of a liquid can move past one another. The particles of a gas are free to move anywhere.
2. Energy is added or removed during a change of state. A change of state does not make a new substance, so changes of state are physical changes.
3. Melting requires energy. Freezing is the removal of energy. Both happen at the same temperature.
4. Both processes change a liquid to a gas. Evaporation is a slower process than boiling. In an open container, you need to heat a liquid in order to boil it.
5. Sublimation requires energy and changes a solid directly to a gas. Condensation gives off energy and changes a gas to a liquid.
