1. 2.1 Classifying Matter Each piece of your clothing has a label that recommends cleaning methods. A 100%-cotton shirt may need to be ironed after washing. A cotton and polyester blend fabric may come out of the dryer wrinkle free. There is no cleaning process that works for all materials.

2. 2.1 Classifying Matter A pure substance is matter that always has exactly the same composition. Table salt and table sugar are two examples of pure substances. Substances can be classified into two categories—elements and compounds. Pure Substances

3. 2.1 Classifying Matter How do mixtures differ from pure substances? An element is a substance that cannot be broken down into simpler substances. Elements An element has a fixed composition because it contains only one type of atom. No two elements contain the same type of atom.

4. 2.1 Classifying Matter Examples of Elements Some elements are solids at room temperature. Most soft drink cans are made from aluminum. Carbon is the main element in the marks you make with a pencil. The elements oxygen and nitrogen are the main gases in the air you breathe. Two elements are liquids at room temperature–bromine and mercury. Elements

5. 2.1 Classifying Matter Symbols for Elements Chemists use symbols of one or two letters to represent elements. The first letter is always capitalized. If there is a second letter, it is not capitalized. C represents carbon. Al represents aluminum. Au represents gold. (The Latin name for gold is aurum.) Elements

6. 2.1 Classifying Matter Symbols for Elements Symbols allow scientists who speak different languages to communicate without confusion. For example, nitrogen is azote in France, stickstoff in Germany, and nitrógeno in Mexico. But all scientists use N as the symbol for the element nitrogen. Elements

7. 2.1 Classifying Matter Aluminum, carbon, and gold are elements that you can see in common objects, such as cans, pencils, and rings. Mixtures containing iodine are used to prevent and treat infections. Elements AluminumCarbonGoldIodine

8. 2.1 Classifying Matter A compound always contains two or more elements joined in a fixed proportion. Compounds A compound is a substance that is made from two or more simpler substances and can be broken down into those simpler substances.

9. 2.1 Classifying Matter The properties of a compound differ from those of the substances from which it is made. Water is composed of the elements hydrogen and oxygen. Oxygen and hydrogen are gases at room temperature, but water is a liquid. Hydrogen can fuel a fire, and oxygen can keep a fire burning, but water does not burn or help other substances to burn. Compounds

10. 2.1 Classifying Matter Silicon dioxide is a compound found in most light- colored grains of sand and in crystals of quartz. It is a colorless, transparent solid. Yet, silicon dioxide is made from a colorless gas (oxygen) and a gray solid (silicon). In silicon dioxide, there are always two oxygen atoms for each silicon atom. Compounds Silicon Oxygen Silicon dioxide

11. 2.1 Classifying Matter If you make salsa, a recipe can guide you. You can use exactly the amounts in the recipe, or you can adjust the ingredients to your own taste. Salsa is a mixture. Each batch may be slightly different. Mixtures

12. 2.1 Classifying Matter The properties of a mixture can vary because the composition of a mixture is not fixed. Mixtures can retain some of the properties of their individual substances. The properties of a mixture are less constant than the properties of a substance. Mixtures

13. 2.1 Classifying Matter Mixtures can be classified by how well the parts of the mixture are distributed throughout the mixture. Heterogeneous Mixtures In a heterogeneous mixture, the parts of the mixture are noticeably different from one another. Homogeneous Mixtures In a homogeneous mixture, the substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from another. Mixtures

14. 2.1 Classifying Matter The sand is a heterogeneous mixture of different kinds of grains. The spoon is stainless steel, a homogeneous mixture of iron, chromium, and nickel. Mixtures

15. 2.1 Classifying Matter Do the Contents of Two Cans of Mixed Nuts Meet FDA Regulations? According to Food and Drug Administration (FDA) regulations, a can labeled mixed nuts must contain at least four types of shelled nuts other than peanuts. The mass of each type of nut must be not less than 2 percent of the total mass and not more than 80 percent of the total mass. Mixtures

16. 2.1 Classifying Matter 1. Comparing and Contrasting How are the two brands of mixed nuts alike? How are they different? Answer: Mixtures

17. 2.1 Classifying Matter 1. Comparing and Contrasting How are the two brands of mixed nuts alike? How are they different? Answer: Both brands contain the same types of nuts but the amount of each type differs. Mixtures

18. 2.1 Classifying Matter 2. Calculating What is the percent by mass of each type of nut in each can? Answer: Mixtures

19. 2.1 Classifying Matter 2. Calculating What is the percent by mass of each type of nut in each can? Answer: Brand A: 44.2% peanuts, 13.64% almonds, 16.79% Brazil nuts, 13.4% cashews, 5.77% hazelnuts, and 6.21% pecans Brand B: 54.8% peanuts, 8.90% almonds, 5.59% Brazil nuts, 21.06% cashews, 4.82% hazelnuts, and 4.82% pecans Mixtures

20. 2.1 Classifying Matter 3. Drawing Conclusions Do the contents of each can meet the FDA regulations? Explain. Answer: Mixtures

21. 2.1 Classifying Matter 3. Drawing Conclusions Do the contents of each can meet the FDA regulations? Explain. Answer: Yes. Both brands contain more than four types of nuts other than peanuts. The masses are within the 2% to 80% range. Mixtures

22. 2.1 Classifying Matter 4. Inferring On the Brand A label, the nuts are listed in this order: peanuts, Brazil nuts, almonds, cashews, pecans, and hazelnuts. What do you think determines the order? Answer: Mixtures

23. 2.1 Classifying Matter 4. Inferring On the Brand A label, the nuts are listed in this order: peanuts, Brazil nuts, almonds, cashews, pecans, and hazelnuts. What do you think determines the order? Answer: The ingredients are listed in order by total mass. The ingredient with the largest mass is listed first. Mixtures

24. 2.1 Classifying Matter What is the main difference among solutions, suspensions, and colloids? Solutions, Suspensions, and Colloids The size of the particles in a mixture has an effect on the properties of the mixture. Based on the size of its largest particles, a mixture can be classified as a solution, a suspension, or a colloid.

25. 2.1 Classifying Matter Solutions When substances dissolve and form a homogeneous mixture, the mixture that forms is called a solution. Suspensions A suspension is a heterogeneous mixture that separates into layers over time. Solutions, Suspensions, and Colloids

26. 2.1 Classifying Matter Colloids A colloid contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension. Like solutions, colloids do not separate into layers. You cannot use a filter to separate the parts of a colloid. Solutions, Suspensions, and Colloids

27. 2.1 Classifying Matter These liquids represent three categories of mixtures. Windshield wiper fluid is a solution. Muddy water collected from a swamp is a suspension. Milk is a colloid. Solutions, Suspensions, and Colloids

28. 2.1 Classifying Matter Assessment Questions 1.Which of these substances is a compound? a.copper b.water c.oxygen d.carbon

29. 2.1 Classifying Matter Assessment Questions 1.Which of these substances is a compound? a.copper b.water c.oxygen d.carbon ANS:B

30. 2.1 Classifying Matter Assessment Questions 2.Which of these groups of letters could be used as a symbol for an element? a.HF b.Cm c.Car d.fe

31. 2.1 Classifying Matter Assessment Questions 2.Which of these groups of letters could be used as a symbol for an element? a.HF b.Cm c.Car d.fe ANS:B

32. 2.1 Classifying Matter Assessment Questions 3.Which of the following statements does not apply to a compound? a.It is made of two or more elements. b.It has components that are joined in fixed proportions. c.It can be separated into components by physical methods. d.It can be broken down into elements or other compounds.

33. 2.1 Classifying Matter Assessment Questions 3.Which of the following statements does not apply to a compound? a.It is made of two or more elements. b.It has components that are joined in fixed proportions. c.It can be separated into components by physical methods. d.It can be broken down into elements or other compounds. ANS:C

34. 2.1 Classifying Matter Assessment Questions 4.How does a compound differ from a mixture? a.A compound cannot be broken down into simpler substances. b.Compounds can be separated by physical processes and mixtures cannot. c.The composition of a mixture cannot vary. d.A compound is made of two or more elements in fixed proportion.

35. 2.1 Classifying Matter Assessment Questions 4.How does a compound differ from a mixture? a.A compound cannot be broken down into simpler substances. b.Compounds can be separated by physical processes and mixtures cannot. c.The composition of a mixture cannot vary. d.A compound is made of two or more elements in fixed proportion. ANS:D

36. 2.1 Classifying Matter Assessment Questions 5.Which of these materials is a heterogeneous mixture? a.air b.seawater c.sand d.steel

37. 2.1 Classifying Matter Assessment Questions 5.Which of these materials is a heterogeneous mixture? a.air b.seawater c.sand d.steel ANS:C

38. 2.1 Classifying Matter Assessment Questions 6.Which of the following can be separated with a filter? a.colloids b.compounds c.solutions d.suspensions

39. 2.1 Classifying Matter Assessment Questions 6.Which of the following can be separated with a filter? a.colloids b.compounds c.solutions d.suspensions ANS:D

40. 2.2 Physical Properties There are pitchers of ice water and lemonade on a picnic table. How do you know which liquid is in each pitcher? It’s easy! Lemonade is yellow and has a tart taste that is hard to miss. A yellow color and a tart taste are two properties of lemonade.

41. 2.2 Physical Properties What are some examples of physical properties? A physical property is any characteristic of a material that can be observed or measured without changing the composition of the substances in the material. Examples of Physical Properties Viscosity, conductivity, malleability, hardness, melting point, boiling point, and density are examples of physical properties.

42. 2.2 Physical Properties Viscosity The tendency of a liquid to keep from flowing is called its viscosity. Thick liquids, such as corn syrup and honey, have a high viscosity. Thin liquids, such as vinegar and water, have a low viscosity. Examples of Physical Properties

43. 2.2 Physical Properties Conductivity A material’s ability to allow heat to flow is called conductivity. Materials that have a high conductivity, such as metals, are called conductors. Good conductors of heat are usually also good conductors of electricity. Examples of Physical Properties

44. 2.2 Physical Properties Malleability The ability of a solid to be hammered without shattering is malleability. Most metals, such as gold, are malleable. An ice cube or piece of glass breaks into small pieces when struck with a hammer. Solids that shatter when struck are brittle, not malleable. Examples of Physical Properties

45. 2.2 Physical Properties Hardness One material can scratch another material if it is harder than the other material. A kitchen knife can scratch a copper sheet because stainless steel is harder than copper. The material used to sharpen the knife blade must be harder than stainless steel. Diamond is the hardest known material. Examples of Physical Properties

46. 2.2 Physical Properties This Tlingit carver is using an adze to carve a canoe from Western red cedar. Red cedar is a relatively soft wood. The adze is hard. Examples of Physical Properties

47. 2.2 Physical Properties Melting and Boiling Points The temperature at which a material changes state is a physical property. The temperature at which a substance changes from solid to liquid (melts) is its melting point. The temperature at which a substance changes from liquid to gas (boils) is its boiling point. Examples of Physical Properties

48. 2.2 Physical Properties Melting and Boiling Points Which of these substances are liquids at room temperature (20  C, or 68  F)? Answer: Examples of Physical Properties

49. 2.2 Physical Properties Melting and Boiling Points Which of these substances are liquids at room temperature (20  C, or 68  F)? Answer: octane, water, and acetic acid Examples of Physical Properties

50. 2.2 Physical Properties Density The ratio of the mass of a substance to its volume is its density. Density can be used to test the purity of a substance. Silver has a density of 10.5 g/cm 3. A coin with a density of 9.9 g/cm 3 is not made from silver, or it contains substances in addition to silver. Examples of Physical Properties

51. 2.2 Physical Properties How can knowing the physical properties of matter be useful? Physical properties are used to identify a material, to choose a material for a specific purpose, or to separate the substances in a mixture. Using Physical Properties

52. 2.2 Physical Properties Using Properties to Identify Materials A material can be identified by its properties. Decide which properties to test. Do tests on a sample of the unknown material. Compare the results with the data reported for known materials. Using Physical Properties

53. 2.2 Physical Properties Using Properties to Choose Materials Properties determine which materials are chosen for which uses. For example, shoelaces must be flexible, that is they must be able to bend without breaking. They must also be durable, that is, they must be able to withstand repeated use. Using Physical Properties

54. 2.2 Physical Properties Laces in hiking boots are usually made of nylon or leather, not from wood. Using Physical Properties

55. 2.2 Physical Properties What processes are used to separate mixtures? Filtration and distillation are two common separation methods. Using Properties to Separate Mixtures

56. 2.2 Physical Properties Filtration You can separate hot tea from loose tea leaves by pouring the mixture through a strainer. Filtration is a process that separates materials based on the size of their particles. Using Properties to Separate Mixtures

57. 2.2 Physical Properties These students filter (sift) dirt through a wire screen to locate small objects. Particles of dirt are small enough to pass through the holes, but objects such as broken bits of pottery are too large. Using Properties to Separate Mixtures

58. 2.2 Physical Properties Distillation Sometimes all the particles in a solution are small enough to pass through a filter. Distillation is a process that separates the substances in a solution based on their boiling points. Using Properties to Separate Mixtures

59. 2.2 Physical Properties The change of water from a liquid to a gas during boiling is a physical change. A physical change occurs when some of the properties of a material change, but the substances in the material remain the same. Recognizing Physical Changes

60. 2.2 Physical Properties During a physical change, the size and shape of a material can change but not the composition. Some examples include melting butter in a pan crumpling a piece of paper slicing a tomato Recognizing Physical Changes

61. 2.2 Physical Properties Some but not all physical changes can be reversed. Braiding hair is a reversible change. Cutting hair cannot be reversed. Recognizing Physical Changes

62. 2.2 Physical Properties Assessment Questions 1.Which of the following is not a physical property? a.density b.boiling point c.flammability d.conductivity

63. 2.2 Physical Properties Assessment Questions 1.Which of the following is not a physical property? a.density b.boiling point c.flammability d.conductivity ANS:C

64. 2.2 Physical Properties Assessment Questions 2.Which of these materials is not malleable? a.copper b.aluminum c.glass d.gold

65. 2.2 Physical Properties Assessment Questions 2.Which of these materials is not malleable? a.copper b.aluminum c.glass d.gold ANS:C

66. 2.2 Physical Properties Assessment Questions 3.In choosing a material for use as a wire to carry electric current, which physical property would be most important? a.conductivity b.malleability c.hardness d.boiling point

67. 2.2 Physical Properties Assessment Questions 3.In choosing a material for use as a wire to carry electric current, which physical property would be most important? a.conductivity b.malleability c.hardness d.boiling point ANS:A

68. 2.2 Physical Properties Assessment Questions 4.Which of these statements best describes a physical change in a pure substance? a.The substance changes into one or more new substances. b.Some of the properties of the substance change, but the material remains the same. c.The properties of the material do not change, and the material remains the same. d.The substance is separated into two or more simpler substances.

69. 2.2 Physical Properties Assessment Questions 4.Which of these statements best describes a physical change in a pure substance? a.The substance changes into one or more new substances. b.Some of the properties of the substance change, but the material remains the same. c.The properties of the material do not change, and the material remains the same. d.The substance is separated into two or more simpler substances. ANS:B

70. 2.2 Physical Properties Assessment Questions 1.The process of filtration uses the difference in boiling points of substances to separate a mixture. True False

71. 2.2 Physical Properties Assessment Questions 1.The process of filtration uses the difference in boiling points of substances to separate a mixture. True False ANS:F, distillation

72. 2.3 Chemical Properties How would you describe these candles? Color, hardness, and density are physical properties that you can use in the description. You can also say that the candles are burning. The ability to burn is not a physical property. As a candle burns, new substances form.

73. 2.3 Chemical Properties When can chemical properties be observed? Observing Chemical Properties

74. 2.3 Chemical Properties As a candle burns, its compounds combine with oxygen in the air to form water and carbon dioxide. A chemical property is any ability to produce a change in the composition of matter. Flammability and reactivity are two examples of chemical properties. Observing Chemical Properties

75. 2.3 Chemical Properties Chemical properties can be observed only when the substances in a sample of matter are changing into different substances. Observing Chemical Properties

76. 2.3 Chemical Properties Flammability Materials that burn can be used as fuel. Flammability is a material’s ability to burn in the presence of oxygen. Reactivity The property that describes how readily a substance combines chemically with other substances is reactivity. Observing Chemical Properties

77. 2.3 Chemical Properties Rust forms when oxygen reacts with iron and water. Rust is a brittle, reddish-brown compound. Because iron is highly reactive, you would not choose iron to make jewelry or coins. Observing Chemical Properties

78. 2.3 Chemical Properties Nitrogen has many uses that depend on its low reactivity. Researchers in Japan pump nitrogen gas into the steel tanks that hold seawater in ships. The nitrogen displaces the oxygen dissolved in the water and prevents rusting. Observing Chemical Properties

79. 2.3 Chemical Properties What observations might indicate that a chemical change has occurred? Three common types of evidence for a chemical change are a change in color, the production of a gas, and the formation of a precipitate. Recognizing Chemical Changes

80. 2.3 Chemical Properties The color change in a banana peel is caused by chemical changes that are taking place in the cells of the banana. A chemical change occurs when a substance reacts and forms one or more new substances. Recognizing Chemical Changes

81. 2.3 Chemical Properties A Change in Color A change in color is a clue that a chemical change has produced at least one new substance. A shiny silver bracelet that is exposed to air will darken. As a match burns, it shrivels up and turns black. A new copper roof and an old copper roof have different colors. Recognizing Chemical Changes

82. 2.3 Chemical Properties A new copper roof has a reddish color. The green patina on an old copper roof is a mixture of copper compounds. Recognizing Chemical Changes

83. 2.3 Chemical Properties Production of a Gas When you mix vinegar with baking soda, bubbles of carbon dioxide form immediately. A similar chemical change happens when you use baking powder as an ingredient in a cake recipe. Bubble of carbon dioxide expand and cause the cake to rise. Recognizing Chemical Changes

84. 2.3 Chemical Properties Formation of a Precipitate Any solid that forms and separates from a liquid mixture is called a precipitate. When an acid is added to milk, proteins in the milk undergo a chemical change that causes them to stick together in clumps and form a precipitate–cottage cheese. Recognizing Chemical Changes

85. 2.3 Chemical Properties What is the difference between chemical and physical changes? Is a Change Chemical or Physical?

86. 2.3 Chemical Properties When matter undergoes a chemical change, the composition of the matter changes. When matter undergoes a physical change, the composition of the matter remains the same. Is a Change Chemical or Physical? Are different substances present after a change takes place? If not, then the change is physical, not chemical.

87. 2.3 Chemical Properties Even if you observe a color change, a gas, or a precipitate, you cannot be sure that a chemical change has taken place. When an iron horseshoe is heated, its color changes from gray to red, but the iron is still iron. That means the change is physical, not chemical. Is a Change Chemical or Physical?

88. 2.3 Chemical Properties Assessment Questions 1.Which of these properties is a chemical property of sulfur? a.yellow b.flammable c.brittle d.soft

89. 2.3 Chemical Properties Assessment Questions 1.Which of these properties is a chemical property of sulfur? a.yellow b.flammable c.brittle d.soft ANS:B

90. 2.3 Chemical Properties Assessment Questions 2.Which of the following is not a common type of evidence for a chemical change? a.a change of state b.a color change c.a gas produced d.a precipitate formed

91. 2.3 Chemical Properties Assessment Questions 2.Which of the following is not a common type of evidence for a chemical change? a.a change of state b.a color change c.a gas produced d.a precipitate formed ANS:A

92. 2.3 Chemical Properties Assessment Questions 3.You can be certain that a chemical change has occurred when a.there is a visible change. b.the change is irreversible. c.the temperature changes. d.a new substance is formed.

93. 2.3 Chemical Properties Assessment Questions 3.You can be certain that a chemical change has occurred when a.there is a visible change. b.the change is irreversible. c.the temperature changes. d.a new substance is formed. ANS:D