Matter and Its Properties. Unit 2

Transcription

1 Matter and Its Properties Unit 2

2 Lesson 1: Physical & Chemical Properties & Changes Unit 2: Matter and Its Properties

3 Section 1: Physical Properties & Change Lesson 1: Physical & Chemical Properties & Changes

4 I Spy Choose an object in the room. Without naming the object, describe it until your partner can guess the object.

5 Physical Properties What words did you use to play I Spy? The characteristics of a substance that can be observed without changing the identity of the substance are called physical properties. Observation includes both measuring and handling a substance. You can use your five senses to detect physical properties.

6 Color Shape Size Texture Volume Mass Many more Physical Properties Examples

7 Determining Physical Properties In order to determine a physical property, think about whether observing the property involves changing the substance to a different substance. If it does not change the substance, it is a physical property. For example, you can stretch a rubber band. Does stretching it change what it is made of? Even though it may look different, it is still a rubber band.

8 Determining Physical Properties Mass and volume are both examples of physical properties. Measuring these two properties does not change the identity of the substance. If you have a lump of clay that has a mass of 200 g, and you break it in half, you have only 100 g of clay. Although you changed some properties (size, shape, mass, volume) it is still clay.

9 Physical Properties of Substances Some physical properties are specific to a substance. In this case, it makes no difference how much of the substance you have; the property does not change. Example: Density 200 g piece of clay with a volume of 100 cm 3 = density of 2 g/cm 3 Break into two pieces 100 g piece of clay wiht volume of 50 cm 3 = density of 2 g/cm Example: Color

10 Physical Changes A physical change is a change in any physical property of a substance, not in the substance itself. Examples: Breaking the piece of clay Stretching the rubber band What about when water changes from a liquid into water vapor?

11 Physical Changes Remember, a substance can go through many physical changes and still remain the same substance. Wool: 1. Wool is sheared from the sheep, cleaned, and placed into machine that separates the wool fibers from each other. (PC: shape, volume, texture) 2. The wool fibers are spun into yarn, and the fibers are twisted so that they are intertwined. (PC: shape, volume) 3. The yarn is dyed. (Note: The dye changes the color of the wool, but it does not change the wool into another substance so this particular example of color change is a PC) 4. The yarn is knitted into a sweater. (The wool is still wool.)

12 Determining Physical Changes It can be difficult to determine if a specific change is a physical change or not. Some changes, such as in color, also can occur when new substances are formed during the change. When deciding whether a change is a physical change or not, ask yourself whether you have the same substance you started with. If the substance is the same, then the changes it underwent were all physical changes.

13 Checkpoint: Physical Properties & Changes 1. What affect does observing a substance s physical properties have on the substance? 2. Why does the density of a substance remain the same for different amounts of the substance?

14 Checkpoint: Physical Properties & Changes 1. What affect does observing a substance s physical properties have on the substance? The identity of the substance does not change.

15 Checkpoint: Physical Properties & Changes 2. Why does the density of a substance remain the same for different amounts of the substance? As mass increases or decreases, so does volume. Therefore, the relationship between mass and volume remains the same.

16 Section 2: Chemical Properties & Change Lesson 1: Physical & Chemical Properties & Changes

17 Other Properties How do you keep a fire burning? You add wood because you know that wood burns. You wouldn t add iron because iron doesn t burn. The ability to burn cannot be a physical property because it changes the substance into something else.

18 Chemical Properties Chemical properties describe how substance can form new substances. Example: Combustibility (how well an object can burn) Other examples: Rusting (iron) Tarnishing (copper)

19 Chemical Changes Chemical properties can be identified by the changes they produce. The change of one substance into another substance is called a chemical change. A chemical change affects the substances involved in the change. The combinations of atoms are rearranged to make new substances. Examples: A piece of wood burning, an iron fencing rusting, a silver spoon tarnishing

20 Chemical Changes Not all chemical changes are as destructive as burning, rusting, or tarnishing. Chemical changes are involved in cooking. Example: boiling an egg Example: Digesting food

21 Indication of a Chemical Change The only indication of a chemical change is that a new substance has been formed. Use observations of the change and your previous experience to judge which type of change has occurred.

22 Signs of a Chemical Change If you observe two or more of these signs during a change, you most likely are observing a chemical change: Production of an odor Change in temperature Change in color Formation of bubbles Formation of a solid (precipitate)

23 Checkpoint: Chemical Changes 1. What is the difference between a physical and a chemical change? 2. What are some signs that a chemical change may have occurred?

24 Checkpoint: Chemical Changes 1. What is the difference between a physical and a chemical change? A physical change does not change the substance into a new substance. A chemical change does change the substance into a new substance.

25 Checkpoint: Chemical Changes 2. What are some signs that a chemical change may have occurred? Production of an odor Change in temperature Change in color Formation of bubbles Formation of a solid (precipitate)

26 Lesson 2: States of Matter Unit 2: Matter and Its Properties

27 Section 1: States of Matter Lesson 2: States of Matter

28 States of Water Ice, water, and water vapor are different states of water. It doesn t matter what state it is in it is still 2 parts hydrogen and 1 part oxygen. When the substance changes from one to another, the molecules do not change into something new. When the substance changes from one to another, the arrangement of the molecules do change, which is why each state of matter has its own characteristics.

29 States of Matter States of matter are the different forms in which matter can exist. Three main states: Solid Liquid Gas

30 Solid A solid is a substance that has a fixed volume and a fixed shape. The molecules are close together and may form a regular pattern. Molecules are locked in place, but they vibrate. Because they are attached to others, individual molecules cannot move from one location to another. A solid does not easily change its shape or volume.

31 Liquid A liquid has a fixed volume but does not have a fixed shape. They take on the shape of the container they are in. The molecules are attracted to one another and are close together. Molecules are not fixed in place; they move freely enough to collide and move past one another. Molecules in liquids can move independently, which is why they can flow.

32 Gas A gas has no fixed volume or shape. A gas can take on both the shape and the volume of the container. The molecules are not close to one another, and can move easily in any direction. The molecules frequently collide. There is much more space between particles that space can increase or decrease with changes in temperature and pressure.

33 Comparing Particles

34 States of Matter Analogy Solid Gas Liquid

35 Comparing Particles The particles in a solid are usually closer together than the particles in a liquid. Particles in solid steel are closer together than the particles in molten steel. However, water is an exception to this rule. The molecules in ice actually have more space between them than the molecules in liquid water do.

36 Important for Life The fact that the molecules in ice are farther apart than the molecules in liquid water has important consequences for life on Earth. Because there is more space between its molecules, ice floats on liquid water. Ice remains on the surface of rivers and lakes when they freeze. The ice layer helps insulate the water and slow does the freezing process. Animals living in the rives and lakes can survive in the liquid water layer below the ice layer.

37 Plasma There are other states of matter. Plasma is actually the most common state of matter in the universe (99% of the universe is considered to be in the plasma state). Plasma are gases who particles have so much energy that they become electrically charged. The charges in plasmas give them special properties. Lightning Fluorescent light Pixels (TV, computer, etc.)

38 Checkpoint: States of Matter 1. What is the difference between a solid, liquid, and gas?

39 Section 2: Changes of State Lesson 2: States of Matter

40 Changing from One State to Another Matter can change from one state to another. When it does, the substance does not change into something new. Therefore, changes in state are physical changes.

41 Melting Melting is the process by which a solid becomes a liquid. Different solids melt at different temperatures. The lowest temperature at which a substance begins to melt is called its melting point. As the solid heats up, the particles gain kinetic energy and vibrate faster. If the vibrations are fast enough, the particles break loose and slide past one another (aka: melts). Some substance have a well-defined melting point. Example: the melting point of ice is 0 C

42 Freezing Freezing is the process by which a liquid becomes a solid. As the temperature of a liquid is lowered, its particles lose energy. As a result, they move more slowly. Eventually, the particles move slowly enough that the attractions among them cause the liquid to become a solid. The temperature at which a specific liquid becomes a solid is called the freezing point.

43 Freezing Vs. Melting Point The freezing point of a substance is the same as the substance s melting point. At this particular temperature, the substance can exist as either a solid or a liquid. At temperatures below the freezing / melting point, the substance is a solid. At temperatures above the freezing / melting point, the substance is a liquid.

44 Evaporation Evaporation is a process by which a liquid becomes a gas. Although all particles in a liquid move, they do not all move at the same speed. Some particles move faster than others. The fastest moving particles at the surface of the liquid can break away from the liquid and escape to become gas particles. As temperature increases, the kinetic energy in the liquid increases. More particles can escape from the surface. As a result, the liquid evaporates more quickly.

45 Sublimation Sublimation is the process by which a solid changes directly into a gas. Certain conditions when solids lose particles through a process similar to evaporation. Example: dry ice Frozen carbon dioxide that sublimates in normal atmospheric conditions

46 Boiling Boiling is a process by which a liquid becomes a gas through the production of bubbles. The bubbles contain energetic water molecules that have escaped from the liquid water to form a gas. Boiling can occur only when the liquid reaches the boiling point the temperature at which the liquid can change to a gas. Different liquids have different boiling points. Water has a boiling point of 100 C.

47 Condensation Condensation is the process by which a gas changes into a liquid. When the temperature of a gas cools, it loses kinetic energy. As the particles move more slowly, the attractions among them cause droplets of liquid to form. Condensed water often forms when warm air comes into contact with a cold surface, such as a glass of ice.

48 Checkpoint: Changing States 1. Describe a way in which matter can change from one state to another.

49 melting boiling or evaporating freezing condensing

50 Lesson 3: Particle Movement Unit 2: Matter and Its Properties

51 Kinetic Energy All matter is made of moving particles. All matter is made of atoms, and atoms are always in motion. Atoms are in motion even if the objects themselves do not change their positions. The motion of these tiny particles gives the object energy.

52 Kinetic Theory of Matter Kinetic energy energy of motion The states of matter are the result of how particles of matter behave.

53 Kinetic Theory of Matter Solid particles are not free to move around very much. They vibrate back and forth in the same position and are held tightly together by forces of attraction.

54 Kinetic Theory of Matter Liquid particles move much more freely than particles in a solid. They are constantly sliding around and tumbling over each other as they move.

55 Kinetic Theory of Matter Gas particles are far apart and move around at high speeds. Particles might collide with one another, but otherwise they do not interact much.

56 Temperature and Kinetic Energy Particles of matter move at different speeds and have different kinetic energies. It is impossible to know the kinetic energy of each particle in an object. However, the average can be determined. Temperature is a measure of the average kinetic energy of all the particles in an object.

57 Temperature and Kinetic Energy A substance that has a high temperature has particles that move very fast and has a high average kinetic energy. The substance feels hot. A substance that has a low temperature has particles that move very slow and has a low average kinetic energy. The substance feels cold.

58 Measuring Temperature Fahrenheit scale: Freezing point of water = 32 F; Boiling point of water= 212 F Celsius scale: Freezing point of water = 0 C; Boiling point of water= 100 C

59 Temperature Conversions Fahrenheit to Celsius: C = 5 / 9 ( F 32) Celsius to Fahrenheit: F = ( 9 / 5 ) C + 32

60 Temperature Conversion What temperature is 100 C in F? 9/5 = * 100 = = 212 F

61 Temperature Conversion What temperature is 32 F in C? (32-32) = 0 5 / 9 = * 0 = 0 C

62 Lesson 4: Density Unit 2: Matter and Its Properties

63 Mass All objects are made up of matter. Matter can be defined as anything that has mass and takes up space. Mass is the measure of the amount of matter an object contains. Different objects contain different amounts of matter. For example, an elephant has more mass than a mouse. For example, a metal fork has more mass than a plastic fork.

64 Measuring Mass We use a triple-beam balance to measure the mass of an object. The standard unit of measurement for mass is the kilogram (kg).

65 Volume Matter also has volume. Volume is the measure of the amount of space an object takes up. For example, an elephant has a greater volume than a mouse because the elephant takes up more space. For example, a metal fork and a plastic fork might take up the same amount of space. Therefore, the two objects have the same volume, even though they have different masses. Often, the volume of an object includes other substances inside the object. For example, the volume of a basketball is the volume the whole sphere takes up. Most of the volume is taken up by air.

66 Calculating Volume of Liquids We use a graduated cylinder (or a beaker) to measure the volume of a liquid. The standard unit of measurement for volume of liquids is the milliliter (ml).

67 The formula for the volume of a rectangular prism is: Length x Width x Height The standard unit of measurement for volume of solids is cubic centimeters (cm 3 ). C D 5 x 9 x 3 = 5 x 4 x 6 = 135 cm cm 3

68 Calculating Volume of Irregular Objects When an object is irregular shaped, there is no formula to calculate the volume. Water Displacement: 1. Add water to a graduated cylinder. Record the volume. 2. Submerge the object in water. The water level will go up. 3. Subtract the volume of the water before the object was added from the volume of the water and the object together. The object displaces a volume of water equal to the volume of the object.

69 Density Density is a measure of the amount of mass present in a given volume of a substance. Density describes how closely packed matter is. For example, a bowling ball and a basketball are about the same size. But the bowling ball has a much greater mass. Therefore, the bowling ball is much denser than the basketball. Density depends on both the mass and the volume of the object.

70 Density Simulation Demo 1: Same Mass, Decreasing Volume 1. Spread out as far apart from each other as possible, staying within your section. 2. Calculate the density per section by dividing the number of students by the number of sections. 3. Now move into ½ of the room. 4. Determine the density. Demo 2: Same Volume, Increasing Mass 1. Start with 4 students in one section. Calculate the density of the block. 2. Double the number of students (8) in the block and calculate the density. 3. Continue.

71 Density Simulation How does changing the volume (or area) change the density? How does changing the mass (number of students) change the density?

72 Which one is more dense? Which square is more dense?

73 Which one is more dense? Now which one is more dense?

74 Density Formula Density = mass (mass volume) volume Units for density: g OR g cm 3 ml ALWAYS REMEMBER UNITS! Why are these the units for density?

75 Density Formula Triangle

76 Density Practice Problems What is the density of a pebble with a mass of 25 grams and a volume of 5 ml? Mass= Volume= 25g 5 ml Mass/Volume= Answer = 5 g/ ml 25g/ 5 ml

77 Density Practice Problems What is the density of a rectangular piece of wood with a mass of 80 grams and measures 2 cm by 5 cm by 4 cm? Mass= Volume= 80g 2 x 5 x 4 = 40 cm 3 Mass/Volume= Answer = 2 g/ cm 3 80g/ 40 cm 3

78 Density Practice Problems I threw a plastic ball in the pool for my dog to fetch. The mass of the ball was 125 grams. What must the volume of the pool be to have a density of 5g/mL? Mass= Density= 125g 5g/ ml Mass/Density= 125g / 5 g/ml Answer = 25 ml

79 Comparing Densities

80 Buoyant Force Buoyant force is the upward force a fluid exerts on any object in the fluid. Also referred to as buoyancy. All objects in a fluid, whether they float or sink, experience a buoyant force. However, an object that is actually floating is called a buoyant object.

81 Buoyant Force Buoyant force exists because of the difference in pressure in fluids. Pressure is the measure of how much force is acting on a certain area. In any fluid, the pressure varies with depth. The greater the depth, the greater the pressure the fluid exerts. The force due to water pressure acts on the surface of the object. As the depth increases, a greater force acts on the surface of the object.

82 Floating Vs. Sinking In order to determine if an object will float or sink, you must compare the buoyant force pushing the object upward with the downward force of gravity (aka the weight of the object). If the two are equal, the object will neither rise nor sink. If the weight is greater, the object will sink. If the buoyant force is greater, the object will rise to the surface and float. An object floating on the surface of a liquid has no net force on it. No net force Net force

83 Buoyancy and Density The buoyant force depends on the volume of a object, and the weight depends on the mass of the object. Whether or not an object will float or sink depends on the relative densities of the object and the fluid. If the object is denser than the fluid it is in, it will sink. For, example, a glass marble will sink in a beaker of water. The buoyant force, which is equal to the weight of the water the marble displaces, is smaller than the weight of the marble. As a result, there is a net downward force on the marble, making the marble sink.

84 Density Practice Problems Frank has a paper clip. It has a mass of 9g and a volume of 3cm 3. What is its density? Frank also has an eraser. It has a mass of 3g, and a volume of 1cm 3. What is its density?

85 Density Practice Problems Jack has a rock. The rock has a mass of 6g and a volume of 3cm 3. What is the density of the rock? Jill has a gel pen. The gel pen has a mass of 8g and a volume of 2cm 3. What is the density of the rock?

86 Density Practice Problems Al Licia has a watch. It has a mass of 4g and a volume of 2cm 3. What is the density of the watch? Mia has a wallet. It has a mass of 15g and a volume of 5cm 3. What is the density of the wallet?