What is Matter? How can matter be classified? Every sample of matter is either an element, a compound, or a mixture.

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1 Matter Section 1 What is Matter? How can matter be classified? Every sample of matter is either an element, a compound, or a mixture. matter: anything that has mass and takes up space

2 Matter Section 1 Elements Why are carbon and copper classified as elements? Each element is made of one kind of atom. element: a substance that cannot be separated or broken down into simpler substances by chemical means atom: the smallest unit of an element that maintains the properties of that element

3 Matter Section 1 Elements in the Human Body

4 Matter Section 1 Elements, continued Elements are represented by symbols. Atoms that make up a molecule act as a unit. molecule: a group of atoms that are held together by chemical forces; a molecule is the smallest unit of matter that can exist by itself and retain all of a substance s chemical properties

5 Matter Section 1 Compounds How are elements related to compounds? Each molecule of a compound contains two or more elements that are chemically combined. Elements combine chemically to form a compound. compound: a substance made up of atoms of two or more different elements joined by chemical bonds

6 Matter Section 1 Compounds, continued Compounds have unique properties. Chemical formulas represent compounds. The following chemical formula represents the compound for indigo:

7 Matter Section 1 Pure Substances and Mixtures What is the difference between a pure substance and a mixture? Elements and compounds are pure substances, but mixtures are not. pure substance: a sample of matter, either a single element or a single compound, that has definite chemical and physical properties mixture: a combination of two or more substances that are not chemically combined

8 Matter Section 1 Pure Substances and Mixtures, continued Mixtures are classified by how thoroughly the substances mix. heterogeneous mixture: substances aren t mixed uniformly and are not evenly distributed homogeneous mixture: substances are evenly distributed, and the mixture is the same throughout miscible: substances that can be mixed immiscible: substances that cannot be mixed Gases can mix with liquids.

9 Matter Section 1 Types of Mixtures

10 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers Democritus and Leucippus proposed that matter is made of tiny particles called atoms. Atoms were an idea that few believed. The first evidence was called Brownian motion for Robert Brown, who first noticed the jerky motion of tiny particles.

11 10.1 Elements An element is a pure substance that cannot be broken down into other substance by chemical or physical means. All of the matter you are ever likely to experience is made from one or more elements in nature.

12 10.1 Elements For example, water can be broken down into its elements, hydrogen and oxygen, when energy is added.

13 10.1 Atoms A single atom is the smallest particle that retains the chemical identity of the element.

14 10.1 Compounds and elements Compounds are two or more different elements chemically bonded together.

15 10.1 Examples of compounds Compounds contain more than one type of atom joined together.

16 10.1 Molecules A molecule is a group of two or more atoms joined together chemically.

17 10.1 Mixtures How How many many atoms molecules are in are this in mixture? this mixture? Many substances you encounter are a mixture of different elements and compounds.

18 10.1 Elements, compounds, and mixtures Can you distinguish between atoms and molecules in these images?

19 Matter Section 2 Physical Properties Why are color, volume, and density classified as physical properties? Physical properties are characteristics that can be observed without changing the identity of the substance.

20 Matter Section 2 Physical Properties, continued Physical properties can help identify substances. Physical properties can be observed or measured. Examples: shape, color, odor, texture, state, melting point, boiling point, strength, hardness, magnetism, the ability to conduct electricity or heat melting point: the temperature and pressure at which a solid becomes a liquid boiling point: the temperature and pressure at which a liquid becomes a gas Physical properties help determine uses.

21 Matter Section 2 Physical Properties, continued Density is a physical property. density: the ratio of the mass of a substance to the volume of the substance mass density, volume or m D V common unit of density is g/cm 3 Density is different from weight.

22 Matter Section 2 Math Skills Density If 10.0 cm 3 of ice has a mass of 9.17 g, what is the density of ice? 1. List the given and unknown values. Given: mass, m = 9.17 g volume, V = 10.0 cm 3 Unknown: density, D =? g/cm 3

23 Matter Section 2 Math Skills, continued 2. Write the equation for density. density = mass/volume, or D = m/v 3. Insert the known values into the equation, and solve. D m V 9.17 g 10.0 cm D 3 D = g/cm 3

24 Matter Section 2 Chemical Properties Why are flammability and reactivity classified as chemical properties? A chemical property describes how a substance changes into a new substance, either by combining with other elements or by breaking apart into new substances.

25 Matter Section 2 Chemical Properties, continued Flammability is a chemical property. flammability: the ability to burn Reactivity is a chemical property. reactivity: the capacity of a substance to combine chemically with another substance

26 Matter Section 2 Chemical Properties, continued Physical and chemical properties are different. Physical properties can be observed without changing the identity of a substance. Chemical properties can be observed only in situations in which the identity of the substance changes.

27 12.1 Properties of Solids Different kinds of matter have different characteristics. Characteristics that can you observe directly are called physical properties. Physical properties include color, texture, density, brittleness, and state (solid, liquid, or gas). Ex. Iron is solid at room temp.

28 12.1 Properties of Solids A physical change is any change in the size, shape, or phase of matter in which the identity of a substance does not change. For example, when water is frozen, it changes from a liquid to a solid.

29 12.1 Properties of Solids Properties that can only be observed when one substance changes into a different substance are called chemical properties. Any change that transforms one substance into a different substance is called a chemical change. Ex. If you leave a nail outside, it rusts.

30 12.1 Properties of Solids The density of a solid material depends on two things: 1. the individual mass of each atom or molecule, Carbon atoms in diamond are packed very tightly. 2. how closely the atoms or molecules are packed together.

31 12.1 Properties of Solids Paraffin wax is also mostly carbon, but its density is only 0.87 g/cm 3. Paraffin s carbon atoms are mixed with hydrogen atoms in long molecules that take up more space. The density of paraffin is low compared to diamond.

32 12.1 Properties of Solids The atoms or molecules in a solid are arranged in two ways. 1. If the particles are arranged in an orderly, repeating pattern, the solid is crystalline. 2. If the particles are arranged in a random way, the solid is amorphous.

33 12.1 Properties of Solids Metals don t look like crystals because solid metal is made from very tiny crystals fused together in a jumble of different orientations.

34 12.1 Mechanical properties Strength describes the ability of a solid object to maintain its shape even when force is applied.

35 12.1 Mechanical properties Tensile strength is a measure of how much stress a material can withstand before breaking.

36 12.1 Mechanical properties Hardness measures a solid s resistance to scratching. How might you compare the hardness of these two metals?

37 12.1 Mechanical properties Elasticity describes a solid s ability to be stretched and then return to its original size. Brittleness is defined as the tendency of a solid to crack or break before stretching very much.

38 12.1 Mechanical properties A ductile material can be bent a relatively large amount without breaking. The ductility of many metals, like copper, allow then to be drawn into wire.

39 12.1 Mechanical properties Malleability measures a solid s ability to be pounded into thin sheets. Aluminum is a highly malleable metal.

40 Matter Section 3 Physical Changes Why is getting a haircut an example of a physical change? A physical change affects one or more properties of a substance without changing the identity of the substance. physical change: a change of matter from one form to another without a change in chemical properties

41 Matter Section 3 Physical Changes, continued Physical changes do not change a substance s identity. Examples of physical changes: cutting, crushing, reshaping, changing state Dissolving is a physical change.

42 Matter Section 3 Chemical Changes Why is baking bread an example of a chemical change? A chemical change happens when one or more substances are changed into entirely new substances that have different properties. chemical change: a change that occurs when one or more substances change into entirely new substances with different properties

43 Matter Section 3 Chemical Changes

44 Matter Section 3 Chemical Changes, continued Chemical changes happen everywhere. Examples of chemical changes: burning, rusting, digesting, decomposing Chemical changes form new substances. Chemical changes can be detected. Signs include: change of color, change of smell, fizzing, production of heat, production of sound, production of light Chemical changes cannot be reversed by physical changes.

45 Matter Section 3 Breaking Down Mixtures and Compounds How can mixtures and compounds be broken down? Mixtures can be separated by physical changes, but compounds must be broken down by chemical changes.

46 Matter Section 3 Breaking Down Mixtures and Compounds, continued Mixtures can be physically separated. Examples of separating a mixture: Separating saltwater into its parts by heating it: When the water evaporates, the salt remains. Using a distillation device to heat a mixture whose components have different boiling points: The component that boils and evaporates first separates from the mixture. Using a centrifuge: The mixture spins rapidly until the components separate.

47 Matter Section 3 Breaking Down Mixtures and Compounds, continued Some compounds can be broken down through chemical changes. Examples of separating a compound: When mercury(ii) oxide is heated, it breaks down into the elements mercury and oxygen. When a current is passed through melted table salt, the elements sodium and chlorine are produced. When you open a bottle of soda, carbonic acid in the soda breaks down into carbon dioxide and water.

48 10.3 Phases of Matter On Earth, pure substances are usually found as solids, liquids, or gases. These are called phases of matter.

49 10.3 The phases of matter A solid holds its shape and does not flow. The molecules in a solid vibrate in place, but on average, don t move far from their places.

50 10.3 The phases of matter A liquid holds its volume, but does not hold its shape it flows. Liquids flow because the molecules can move around.

51 10.3 The phases of matter A gas flows like a liquid, but can also expand or contract to fill a container. A gas does not hold its volume. The molecules in a gas have enough energy to completely break away from each other.

52 10.3 The phases of matter When they are close together, molecules are attracted through intermolecular forces.

53 10.3 The phases of matter The forces in chemical bonds are stronger than intermolecular forces.

54 10.3 Intermolecular forces Within all matter, there is a constant competition between temperature and intermolecular forces. When temperature wins the competition, molecules fly apart and you have a gas. When intermolecular forces win the competition, molecules clump tightly together and you have a solid.

55 10.3 Melting and boiling The melting point is the temperature at which a substance changes from a solid to a liquid.

56 10.3 Melting and boiling The temperature at which a liquid becomes a gas is called the boiling point.

57 Notice temperature is constant while ice melts!

58 10.3 Melting and boiling points of common substances Materials have a wide range of melting and boiling points.

59 10.3 Sublimation Sometimes a solid can change directly to a gas when heat energy is added. This process is called sublimation.