1. Chapter 2 Matter and Change 2.1 Properties of Matter 2.2 Mixtures
2.3 Elements and Compounds
2.4 Chemical Reactions
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2. Identifying a Substance
Describing Matter
Identifying a Substance
Each object in this figure has a different chemical
makeup, or
composition.
The soda can is mainly aluminum.
The watering can is mainly copper.
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3. Identifying a Substance
Describing Matter
Identifying a Substance
Matter that has a uniform and definite composition is called a Pure substance.
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4. Identifying a Substance
Describing Matter
Identifying a Substance
Aluminum and copper have some properties in common, but there are differences besides their distinctive colors.
Aluminum is highly reflective and is often used in silver paint.
Pure copper can scratch the surface of aluminum because copper is harder than aluminum.
Copper is a conductor of heat or electric current.
Copper and aluminum are both malleable, which means they can be hammered into sheets without breaking.
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5. Identifying a Substance
Describing Matter
Identifying a Substance
Hardness, color, conductivity, and malleability are examples of physical properties.
A physical property is a quality or condition of a substance that can be observed or measured without changing the substance’s composition.
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6. Physical Properties of Some Substances
Interpret Data
This table lists physical properties for some substances.
Physical Properties of Some Substances
Substance
State
Color
Melting point (°C)
Boiling point (°C)
Neon
Gas
Colorless
–249
–246
Oxygen
–218
–183
Chlorine
Greenish-yellow
–101
–34
Ethanol
Liquid
–117 78
Mercury
Silvery-white
–39
357
Bromine
Reddish-brown –7 59
Water
100
Sulfur
Solid
Yellow
115
445
Sodium chloride
White
801
1413
Gold
1064
2856
Copper
Reddish-yellow
1084
2562
The states of the substances are given at room temperature.
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7. Identifying a Substance
Describing Matter
Identifying a Substance
Physical properties can help chemists identify substances.
For example, a colorless substance that was found to boil at 100˚C and melt at 0˚C would likely be water.
A colorless substance that boiled at 78˚C and melted at –117˚C would definitely not be water. It would likely be ethanol.
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8. Physical Changes
Physical Changes
The shape of the sample changes during melting as the liquid begins to flow, but the composition of the sample does not change.
Melting is a physical change.
During a physical change, some properties of a material change, but the composition of the material does not change.
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9. So are words such as break, split, grind, cut, and crush.
Physical Changes
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.
There is a difference between these two sets of words. Each set describes a different type of physical change.
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10. Physical changes can be classified as reversible or irreversible.
Melting is an example of a reversible physical change.
If a sample of liquid gallium cools below its melting point, the liquid will become solid.
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11. Physical Changes
All physical changes that involve a change from one state to another are reversible.
Cutting hair, filing nails, and cracking an egg are examples of irreversible physical changes.
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12. Water boils and becomes water vapor
Water boils and becomes water vapor. Is this a reversible or irreversible physical change?
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13. Water boils and becomes water vapor
Water boils and becomes water vapor. Is this a reversible or irreversible physical change?
It is a reversible physical change because it involves a change from one state to another.
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14. Chemical Changes
A chemical change is a change that produces matter with a different composition than the original matter.
Words such as burn, rot, rust, decompose, ferment, explode, and corrode usually signify a chemical change.
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15. A chemical change is also called a chemical reaction.
Chemical Changes
A chemical change is also called a chemical reaction.
One or more substances change into one or more new substances during a chemical reaction.
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16. Chemical Changes
Heating is one of the processes used to break down compounds into simpler substances.
The layer of sugar is heated until it breaks down into solid carbon and water vapor.
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17. CHEMISTRY & YOU
What happens to the compounds in bread when it is overcooked that causes the change in the taste of the bread?

18. CHEMISTRY & YOU
What happens to the compounds in bread when it is overcooked that causes the change in the taste of the bread?
The compounds undergo a chemical change that changes the taste of the bread. They are broken down into solid carbon. 18

19. Breaking Down Compounds
Distinguishing Elements and Compounds
Breaking Down Compounds
Can the substances that are produced when sugar is broken down when heated also be broken down?
There is no chemical process that will break down carbon into simpler substances because carbon is an element.

20. Breaking Down Compounds
Distinguishing Elements and Compounds
Breaking Down Compounds
When an electrical current passes through water, it is broken down into oxygen and hydrogen.

21. Recognizing Chemical Changes
What are four possible clues that a chemical change has taken place?
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22. Possible clues to chemical change include:
Recognizing Chemical Changes
Possible clues to chemical change include:
a transfer of energy (Endo vs Exo)
a change in color
the production of a gas
or the formation of a precipitate .
A precipitate is a solid that forms and settles out of a liquid mixture.
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23. Recognizing Chemical Changes
If you observe a clue to chemical change, you cannot be certain that a chemical change has taken place.
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24. Recognizing Chemical Changes
If you observe a clue to chemical change, you cannot be certain that a chemical change has taken place.
The clue may be the result of a physical change.
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25. Recognizing Chemical Changes
If you observe a clue to chemical change, you cannot be certain that a chemical change has taken place.
The clue may be the result of a physical change.
For example, energy is always transferred when matter changes from one state to another.
Bubbles form when you boil water or open a carbonated drink.
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26. Recognizing Chemical Changes
The only way to be sure that a chemical change has occurred is to test the composition of a sample before and after the change.
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27. Clues to chemical change often have practical applications.
Recognizing Chemical Changes
Clues to chemical change often have practical applications.
Production of a Gas
Bubbles of carbon dioxide form when two antacid tablets are dropped into a glass of water.
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28. Clues to chemical change often have practical applications.
Recognizing Chemical Changes
Clues to chemical change often have practical applications.
Color Change
When a test strip is dipped in a solution, the color change is used to determine the pH of the solution.
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29. Clues to chemical change often have practical applications.
Recognizing Chemical Changes
Clues to chemical change often have practical applications.
Formation of a Precipitate
One step in the production of cheese is a reaction that causes milk to separate into solid curds and liquid whey.
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30. Iron is able to combine with oxygen to form rust.
Chemical Property
The ability of a substance to undergo a specific chemical change is called a chemical property.
Iron is able to combine with oxygen to form rust.
The ability to rust is a chemical property of iron.
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31. Chemical properties can be used to identify a substance.
Chemical Changes
Chemical properties can be used to identify a substance.
But chemical properties can be observed only when a substance undergoes a chemical change.
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32. Chapter 2 Matter and Change . 2.2 Mixtures 2.1 Properties of Matter
2.3 Elements and Compounds
2.4 Chemical Reactions
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33. Describing Matter
Based on the distribution of their components, mixtures can be classified as heterogeneous mixtures or homogeneous mixtures.
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34. Heterogeneous Mixtures
Describing Matter
Heterogeneous Mixtures
In chicken noodle soup, the ingredients in the soup are not evenly distributed throughout the mixture.
There is likely to be different amounts of chicken and noodles in each spoonful.
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35. Heterogeneous Mixtures
Describing Matter
Heterogeneous Mixtures
A mixture in which the composition is not uniform throughout is a heterogeneous mixture.
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36. Describing Matter
Homogeneous Mixtures
The substances in the olive oil are evenly distributed throughout the mixture.
So, olive oil doesn’t look like a mixture.
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37. The same is true for vinegar.
Describing Matter
Homogeneous Mixtures
The same is true for vinegar.
Vinegar is a mixture of water and acetic acid, which dissolves in the water.
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38. Olive oil and vinegar are homogeneous mixtures.
Describing Matter
Homogeneous Mixtures
Olive oil and vinegar are homogeneous mixtures.
A homogeneous mixture is a mixture in which the composition is uniform throughout.
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39. Olive oil and vinegar are homogeneous mixtures.
Describing Matter
Homogeneous Mixtures
Olive oil and vinegar are homogeneous mixtures.
A homogeneous mixture is a mixture in which the composition is uniform throughout.
Another name for a homogeneous mixture is a solution.
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40. Many solutions are liquids.
Describing Matter
Homogeneous Mixtures
Many solutions are liquids.
But some are gases, like air.
And some are solids, like stainless steel, which is a mixture of iron, chromium, and nickel.
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41. How can mixtures be separated?
Separating Mixtures
Separating Mixtures
How can mixtures be separated?
Differences in physical properties can be used to separate mixtures.
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42. Separating Mixtures
Filtration
The coffee filter at right can separate ground coffee beans from brewed coffee.
The liquid brewed coffee passes through the paper filter, but the solid coffee grounds cannot pass through the filter.
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43. Filter paper used in a laboratory is similar to coffee filters.
Separating Mixtures
Filtration
Filter paper used in a laboratory is similar to coffee filters.
Filter paper is often placed in a funnel.
Then the mixture is poured into the funnel.
Solid particles that cannot pass through the filter remain in the funnel.
The rest of the particles pass through.
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44. Separating Mixtures
Filtration
The process that separates a solid from a liquid in a heterogeneous mixture is called filtration.
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45. Separating Mixtures
Distillation
Tap water is a homogeneous mixture of water and substances that are dissolved in the water.
One way to separate water from the other components in tap water is through a process called distillation.
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46. Separating Mixtures
Distillation
During a distillation, a liquid is boiled to produce a vapor that is then condensed into a liquid.
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47. Distillation Separating Mixtures
The figure below shows an apparatus used to perform a small-scale distillation.
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48. Separating a Heterogeneous Mixture
Sample Problem 2.1
Separating a Heterogeneous Mixture
How could a mixture of aluminum nails and iron nails be separated?
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49. Which physical property does filtration rely on to separate mixtures
Which physical property does filtration rely on to separate mixtures? Which does distillation rely on?
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50. Which physical property does filtration rely on to separate mixtures
Which physical property does filtration rely on to separate mixtures? Which does distillation rely on?
Filtration relies on the size of a particle, or molecule, of a substance.
Distillation relies on the boiling point of the substance.
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51. Separation of a Mixture
Filtration
Decant/Pour off
Distillation
Chromatography
Centrifugation
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52. Chapter 2 Matter and Change 2.3 Elements and Compounds
2.1 Properties of Matter
2.2 Mixtures
2.3 Elements and Compounds
2.4 Chemical Reactions

53. Distinguishing Elements and Compounds
How are elements and compounds different?

54. Substances can be classified as elements or compounds.
Distinguishing Elements and Compounds
Substances can be classified as elements or compounds.
An element is the simplest form of matter that has a unique set of properties.
Oxygen and hydrogen are two of the more than 100 known elements.

55. Substances can be classified as elements or compounds.
Distinguishing Elements and Compounds
Substances can be classified as elements or compounds.
A compound is a substance that contains two or more elements chemically combined in a fixed proportion.

56. Distinguishing Elements and Compounds
Carbon, oxygen, and hydrogen are chemically combined in the compound sucrose.
In every sample of sucrose, there are twice as many hydrogen particles as oxygen particles.
The proportion of hydrogen particles in sucrose is fixed.

57. There is a key difference between elements and compounds.
Distinguishing Elements and Compounds
There is a key difference between elements and compounds.
Compounds can be broken down into simpler substances by chemical means, but elements cannot.

58. Breaking Down Compounds
Distinguishing Elements and Compounds
Breaking Down Compounds
Physical methods that are used to separate mixtures cannot be used to break a compound into simpler substances.
Boil liquid water and you get water vapor, not the oxygen and hydrogen that water contains.

59. Breaking Down Compounds
Distinguishing Elements and Compounds
Breaking Down Compounds
Physical methods that are used to separate mixtures cannot be used to break a compound into simpler substances.
Dissolve a sugar cube in water and you still have sucrose, not oxygen, carbon, and hydrogen.
This does not mean that sucrose or water cannot be broken down into simpler substances.
But methods must involve a chemical change.

60. Breaking Down Compounds
Distinguishing Elements and Compounds
Breaking Down Compounds
A chemical change is a change that produces matter with a different composition than the original matter.

61. Properties of Compounds
Distinguishing Elements and Compounds
Properties of Compounds
In general, the properties of compounds are quite different from those of their component elements.
Sugar is a sweet-tasting white solid, but carbon is a tasteless black solid.

62. Properties of Compounds
Distinguishing Elements and Compounds
Properties of Compounds
In general, the properties of compounds are quite different from those of their component elements.
Hydrogen is a gas that burns in the presence of oxygen—a colorless gas that supports burning.
The product of this chemical change is water, a liquid that can stop materials from burning.

63. Properties of Compounds
Distinguishing Elements and Compounds
Properties of Compounds
When the elements sodium and chlorine combine chemically to form sodium chloride, there is a change in composition and a change in properties.
Sodium is a soft gray metal.

64. Properties of Compounds
Distinguishing Elements and Compounds
Properties of Compounds
When the elements sodium and chlorine combine chemically to form sodium chloride, there is a change in composition and a change in properties.
Chlorine is a pale yellow poisonous gas.

65. Properties of Compounds
Distinguishing Elements and Compounds
Properties of Compounds
When the elements sodium and chlorine combine chemically to form sodium chloride, there is a change in composition and a change in properties.
Sodium chloride (commonly known as table salt) is a white solid.

66. Can elements be broken down by chemical changes? Can compounds?

67. Can elements be broken down by chemical changes? Can compounds?
There are no chemical processes that can break down an element into simpler substances.
Compounds can be broken down by chemical changes.

68. Distinguishing Substances and Mixtures
How can substances and mixtures be distinguished?

69. Distinguishing Sub-stances and Mixtures
If the composition of a material is fixed, the material is a substance. If the composition of a material may vary, the material is a mixture.

70. Distinguishing Sub-stances and Mixtures

71. Conservation of Mass
Conservation of Mass
How are the mass of the reactants and the mass of the products of a chemical reaction related?
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72. Conservation of Mass
During any chemical reaction, the mass of the products is always equal to the mass of the reactants.
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73. Mass also holds constant during physical changes.
Conservation of Mass
Mass also holds constant during physical changes.
When 10 grams of ice melt, 10 grams of liquid water are produced.
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74. Conservation of Mass
The scientific law that reflects these observations is the law of conservation of mass.
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75. Conservation of Mass
The scientific law that reflects these observations is the law of conservation of mass.
The law of conservation of mass states that in any physical change or chemical reaction, mass is conserved.
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76. Conservation of Mass
The scientific law that reflects these observations is the law of conservation of mass.
The law of conservation of mass states that in any physical change or chemical reaction, mass is conserved.
Mass is neither created nor destroyed.
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77. Conservation of Mass
The law of conservation of mass is more easily observed when a change occurs in a closed container.
When the liquids in the figure at left are mixed, they react. None of the products are gases.
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