UNIT 4: Matter, Energy, and Changes

Transcription

1 UNIT 4: Matter, Energy, and Changes ì Mrs. Howland Chemistry 10 Gra7on High School Some slides modified from: Pearson EducaBon, Inc., or its affiliates. All Rights Reserved

2 UNIT OBJECTIVES: ì SKILLS: Students will be able to ì Classify various examples of maoer using observabons and measurable data. ì Describe a laboratory procedure used to separate various types of mixtures (wrioen or drawn). ì IdenBfy properbes as physical or chemical. ì IdenBfy properbes as intensive or extensive. ì Compare and contrast physical and chemical properbes adn changes. ì Create a model of the three states of maoer (solid, liquid, gas) and the effect of temperature on phase change. ì Measure volume and mass for various examples of maoer and calculate density. ì Use density to idenbfy various substances. ì Explain law of conservabon of mass. ì Calculate percent yield. TEXTBOOK RESOURCE: Chapter 2, Ma6er and Change, pg

3 What we already KNOW MATTER is anything that HAS MASS and OCCUPIES SPACE

4 OBSERVATIONS: Describing Matter ì What you observe when you look at a parbcular sample of maoer is its properdes. ì Is a solid shiny or dull? ì Does a liquid flow quickly or slowly? ì Is a gas odorless, or does it have a smell? ì WATCH: Physical and Chemical Changes hops://goo.gl/p093o7

5 Intensive and Extensive Properties ì ProperBes used to describe maoer can be classified as extensive or intensive properbes. ì An extensive property is a property that depends on the amount of maoer in a sample. ì An intensive property is a property that depends on the type of maoer in a sample, not the amount of maoer.

6 Extensive Properties ì Recall that maoer is anything that has mass and takes up space. ì The mass of an object is a measure of the amount of maoer the object contains. ì The mass of a basketball is greater than the mass of a golf ball.

7 Extensive Properties ì The volume of an object is a measure of the space occupied by the object. ì The volume of a basketball is greater than the volume of a golf ball. ì Mass and volume are both examples of extensive properdes.

8 Intensive Properties ì There are properbes to consider when selecbng a basketball besides mass and volume. ì The outer covering may be made of leather, rubber, or a synthebc composite. Each of these materials has different properbes that make the basketballs suitable for different playing situabons. ì For example, leather balls are suitable for indoor play but not outdoor play. ì Leather balls absorb water and dirt more than rubber balls do.

9 Intensive Property ì Absorbency is an example of an intensive property. ì An intensive property is a property that depends on the type of maoer in a sample, not the amount of maoer.

10 EXAMPLES:

11 VOCABULARY: Intensive Properties ì COLOR ì ODOR ì LUSTER: How light is reflected from the surface ì MELTING POINT: Temperature at which ì BOILING POINT: Temperature at which ì SPECIFIC HEAT CAPACITY: The amount of heat energy required to raise the temperature of a substance per a unit of mass

12 VOCABULARY: Intensive Properties ì MALLEABILITY: Capable of being shaped without breaking ì DUCTILITY: Ability of solid material to deform under tensile stress (elongabon) ì CONDUCTIVITY: Ability to conduct heat or electricity ì DENSITY: How compact or concentrated a substance is; amount of mass per volume ì PRESSURE: Force exerted on a surface per unit area

13 VOCABULARY Malleability DucDlity Luster

14 Identifying SUBSTANCES ì MaOer that has a uniform and definite composibon is called a substance. ì Aluminum and copper are examples of substances, which are also referred to as pure substances ì Every sample of a given substance has idendcal intensive properdes because every sample has the same composibon.

15 Properties of Some Substances Physical Properties of Some Substances Substance State Color Melting point ( C) Boiling point ( C) Neon Gas Colorless Oxygen Gas Colorless Chlorine Gas Greenish-yellow Ethanol Liquid Colorless Mercury Liquid Silvery-white Bromine Liquid Reddish-brown 7 59 Water Liquid Colorless Sulfur Solid Yellow Sodium chloride Solid White Gold Solid Yellow Copper Solid Reddish-yellow

16 Three States of Matter ì Depending on the circumstances, you use three different words to refer to water water, ice, and steam. ì Water, which is a common substance, exists in three different physical states. So can most other substances.

17 Three States of Matter Three states of maoer are solid, liquid, and gas.

18 SOLIDS ì A solid is a form of maoer that has a definite shape and volume. ì The shape of a solid doesn t depend on the shape of its container. ì The parbcles in a solid are packed Bghtly together, o7en in an orderly arrangement. ì Mostly incompressible ì Expand only slightly when heated

19 LIQUIDS ì A liquid is a form of maoer that has an indefinite shape, flows, and yet has a fixed volume. ì ParBcles in a liquid are in close contact with one another, but the arrangement of parbcles in a liquid is not rigid or orderly. ì Takes the shape of the container in which it is placed ì Almost incompressible ì Expands slightly when heated

20 GASES ì A gas is a form of maoer that takes both the shape and volume of its container. ì Takes both the shape and volume of its container. ì ParBcles in a gas are usually much farther apart than the parbcles in a liquid. ì Easily compressible.

21 Compressibility

22 GAS vs. VAPOR ì The words vapor and gas are somebmes used interchangeably. But there is a difference. ì The term gas is used for substances, like oxygen, that exist in the gaseous state at room temperature. ì Vapor describes the gaseous state of a substance that is generally a liquid or solid at room temperature, as in water vapor.

23 Phase Changes Temperature = Measure of intensity of heat; movement of parbcles

24 Phase Changes THINK: How does the temperature (and energy) change between phases?

25 Phase Change Diagram

26 Physical Changes ì MelBng, freezing, and boiling are all PHYSICAL CHANGES. ì During a physical change, some properbes of a material change, but the composibon of the material does not change. Words such as boil, freeze, melt, and condense are used to describe physical changes. So are words such as break, split, grind, cut, and crush.

27 Reversible and Irreversible PHYSICAL CHANGES ì Reversible = Can be changed back to original state ì EXAMPLE: MelBng a popsicle ì Irreversible = Cannot be changed back to original state ì EXAMPLE: Ripping paper

28 Types of Physical Changes ì Physical changes can be classified as reversible or irreversible. ì All physical changes that involve a change from one state to another are reversible. ì MelBng is an example of a reversible physical change. ì Cukng hair, filing nails, and cracking an egg are examples of irreversible physical changes.

29 Chemical Change ì Words such as burn, rot, rust, decompose, ferment, explode, and corrode usually signify a chemical change. ì The ability of a substance to undergo a specific chemical change is called a chemical property. ì Chemical properbes can be used to idenbfy a substance. ì But chemical properbes can be observed only when a substance undergoes a chemical change.

30 Chemical Property and Change ì Iron is able to combine with oxygen to form RUST. ì The ability to rust is a chemical property of iron.

31 Physical Change vs. Chemical Change ì When charcoal is broken into smaller pieces, the change is a physical change. ì The substances present before the change are the same substances present a7er the change. ì During a physical change, the composidon of the ma6er never changes.

32 Physical Change vs. Chemical Change ì During a chemical change, the composibon of maoer always changes. ì When the charcoal is heated and burned, a chemical change occurs. ì The substances in charcoal react with oxygen in the air to form other substances.

33 Chemical Change ì How are compounds broken down ( separated )? ì A chemical change is a change that produces maoer with a different composibon than the original maoer. ì When the elements sodium and chlorine combine chemically to form sodium chloride, there is a change in composibon and a change in properbes.

34 Chemical Change ì Chlorine (Cl) is a pale yellow poisonous gas. ì Sodium (Na) is a so7 grey solid. ì Sodium chloride (commonly known as table salt) is a white solid.

35 Chemical REACTIONS ì A chemical change is also called a chemical reacdon. ì One or more substances change into one or more new substances during a chemical reacdon. A substance present at the start of the reacbon is a reactant. A substance produced in the reacbon is a product.

36 Elements vs. Compounds ì Substances can be classified as elements or compounds. ì An element is the simplest form of maoer that has a unique set of properbes. ì ì A compound is a substance that contains two or more elements chemically combined in a fixed proporbon. Compounds CAN be broken down into simpler substances by chemical means, but elements CANNOT.

37 Elements vs. Compounds

38 What do you THINK? Can elements be broken down by chemical changes? Can compounds?

39 CLASSIFICATION ì Science is an ORGANIZED process ì Therefore, scienbsts are always classifying things

40 CLASSIFICATION OF MATTER ì ClassificaBon by COMPOSITION and PROPERTIES à Why not classify by phases? Remember that water (H2O) can exist in more than one phase (liquid, gas, and solid) MaOer changes phases with change in heat energy

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42 How do we classify matter? All maoer can be classified by composidon as: 1) Elements 2) Compounds 3) Mixtures

43 FLOW CHART ~ Matter

44 How to classify ì We classify maoer by asking a series of quesbons: ì Is the maoer UNIFORM throughout? ì Can it be separated by physical means? ì Can it be separated by chemical means?

45 VOCABULARY ì MIXTURE: TWO (2) or more substances not chemically combined. Can be physically separated by physical means. Substances retain their individual properbes. ì SOLUTION ~ One substance dissolves in another ì ELEMENT: Simplest form of pure substance. Can not be broken down further by chemical or physical means. ì MOLECULE: Pure substance. TWO (2) or more atoms chemically bonded together. Can be separated by chemical means. ì COMPOUND: Pure substance. TWO (2) or more different atoms chemically bonded together. Can be separated by chemical means.

46 Mixtures ì Most samples of maoer are mixtures. ì Based on the distribubon of their components, mixtures can be classified as heterogeneous mixtures or homogeneous mixtures. ì A mixture in which the composibon is not uniform throughout is a heterogeneous mixture. ì A homogeneous mixture is a mixture in which the composibon is uniform throughout.

47 Heterogeneous Mixtures ì In chicken noodle soup, the ingredients in the soup are not evenly distributed throughout the mixture. ì HETEROGENEOUS: Likely to have different amounts of chicken and noodles in each spoonful! ì A mixture in which the composibon is not uniform throughout is a heterogeneous mixture. Components are in two or more phases.

48 Homogeneous Mixtures ì The substances in the olive oil are evenly distributed throughout the mixture. ì A homogeneous mixture is a mixture in which the composibon is uniform throughout. Components are in a single phase. ì Another name for a homogeneous mixture is a soludon.

49 THINK ABOUT IT: ì At the beach, you realize that both ocean water and sand are mixtures. ì ì Which is a homogeneous mixture (or soludon)? Which is a heterogeneous mixture?

50 HOMOGENOUS MIXTURES ì COLLOIDS ì SOLUTION ì ALLOY

51 COLLOIDS ì ParBcles are mixed together, but not dissolved ì ParBcles are relabvely large and permanently suspended

52 SOLUTION ì One substance dissolved in another ì Solute ~ what is dissolved ì Solvent ~ what does the dissolving

53 ì SoluBon of metal elements ALLOY

54 How do we classify matter? All maoer can be classified by properbes as: 1) Physical 2) Chemical

55 1. PHYSICAL PROPERTIES ì Can usually be SEEN ì DO NOT change the substance s composibon ì Reversible ì TYPES: ì COLOR/TASTE ì MELTING POINT ì BOILING POINT ì FREEZING POINT ì CONDUCTIVITY = ability to conduct electricity ì VISCOSITY = thickness of maoer, usually liquid

56 PHYSICAL PROPERTIES

57 How do you separate a MIXTURE? ì ì Differences in physical properbes can be used to separate mixtures. METHODS: Magnet Filter Centrifuge Chromatography EvaporaBon DisBllaBon CrystallizaBon DecanBng

58 How do you separate a COMPOUND? ì Via a chemical reacbon:

59 2. CHEMICAL PROPERTIES ì CharacterisBcs that are exhibited as one substance is chemically transformed into another ì DO change the substance s composibon ì NOT Reversible ì CharacterisBcs that describe the behavior of maoer. Examples: Flammability, rusbng of steel, digesbon of food

60 Which has greater mass? 100 kg of lead or 100 kg of feathers?

61 Lead and Feathers ì Although 100 kg of feathers may take up much more room than 100 kg of lead, they both sbll weigh 100 kg! ì The steel has greater mass for its size because it is more DENSE ì Thus, a material such as feathers takes up much more room (volume) than a denser material such as steel, for the same mass or weight

62 Equal Size CUBES If you take the same volume of different substances, then they will have different MASSES Q) Which has the greatest mass and therefore the most dense? What IS density? Density is the Mass per unit Volume

63 What is DENSITY? ì Density is a PHYSICAL PROPERTY ì Density = mass per given volume of a material ì Steel has a greater density ~ 7.8 grams of mass per cubic cenbmeter ì Aluminum has a lower density ~ 2.7 grams/ cm 3 It s not just about solids! Liquids & gases are mafer & have density, too

64 Density of Common Materials ì DENSITY IS AN INTENSIVE PROPERTY ì EXAMPLE: A steel nail and a steel cube have different masses, so they have different amounts of ma6er ì Their VOLUMES are also different! ì BUT if you calculate density (density = mass volume) the DENSITY is the same for both the nail and the cube, despite how much you have!

65 Which one is MORE dense? ì If each box has the same volume, and each ball has the same mass, which box would weigh more? Why?

66 Density as a PROPERTY of Matter ì Solids that are strong, such as steel, typically have high density. ì HIGH density means there are many atoms per cubic cenbmeter (EXAMPLES: mercury, lead) ì Soe materials typically have lower density ì Solids with low density are not as strong ì LOW density means there are relabvely large spaces between atoms this is why ICE is more dense than liquid water! (EXAMPLES: gasoline, cork)

67 Using DENSITY to IDENTIFY SUBSTANCES ì Density is an ID Tag for common substances

68 Why does density vary? ì The density of a material depends on two things: 1. The individual mass of each atom or molecule 2. How Dghtly the atoms are packed

69 Calculating DENSITY ì To calculate density, you need to know: MASS and VOLUME

70 Finding MASS ì We will measure mass using a digital balance

71 Finding VOLUME: Cubes & Rectangular Prisms ì Use a metric ruler ì Measure all 3 sides: length, width, height à UNITS: mm, cm, m, km (base unit is meters!) ì Volume = L x W x h

72 Finding VOLUME: Cylinders ì Use a metric ruler ì Measure the height & diameter ì Divide the diameter in half to find the radius à UNITS: mm, cm, m, km (base unit is meters!)

73 Water Displacement method ì Fill a graduated cylinder with water à Read inibal volume ì Drop the object in (without splashing water!) à Calculate the change in volume! ì UNITS: ml, L Finding VOLUME: Irregular Objects

74 Calculating Density: You try it! Find the density of a cube measuring 5.7cm on a side, with a mass of 630 g.

75 Calculations Using Density Formula: Cover up what you are solving for! Divide up and down and mulbply across. Here we are solving for VOLUME. VOLUME = Mass / Density

76 Calculations Using Density Formula: You try it! A student determines the density of manganese to be 5.54 g/cm 3. If a sample had a mass of 3.43g what was the volume? The density of benzene is 0.88 g/ml. Calculate the mass of 250 ml of benzene.

77 VOLUME ~ Why can we use both cm 3 AND ml? ì Volume is derived from length ì This cube has volume of 1 m 3 There are 10 decimeters in a meter, so the volume is : (10 dm) 3 = 1000 dm 3 ì A cubic decimeter (1 dm 3 ) is also called a liter (L) 1 decimeter = 10 cm, so 1 liter can be divided into 1000 cubes that each have a volume of 1 cm 3