1. Solids, Liquids, and Gases And Classification of Matter

2. How is Lithium similar to Carbon? Different?
All matter is composed of small particles. The particles that compose one substance have characteristics in common with the particles that compose another substance, but there are differences between the particles as well.

3. Energy and State of Matter
The amount of energy that particles contain has a major impact on the properties of the substance containing those particles, such as state of matter.

4. Kinetic Theory
The kinetic theory is an explanation of how particles in matter behave.

5. Kinetic Theory
The three assumptions of the kinetic theory are as follows:
All matter is composed of small particles (atoms, molecules, and ions).
These particles are in constant, random motion.
These particles are colliding with each other and the walls of their container.

6. Solids
Atoms in solids are held tightly in place by the attraction between the particles.
This attraction between the particles gives solids a definite shape and volume. However, the kinetic energy in the particles causes them to vibrate in place.

7. Where do particles get kinetic energy?
Thermal energy is the total energy of a material’s particles within and between the particles—including kinetic—from vibrations and movement, and potential—resulting from forces that act within or between particles.

8. Average Kinetic Energy
In science, temperature means the average kinetic energy of particles in the substance, or how fast the particles are moving.
On average, molecules of frozen water at 0°C will move slower than molecules of water at 100°C.

9. Average Kinetic Energy
Therefore, water molecules at 0°C have lower average kinetic energy than the molecules at 100°C.
Molecules will have kinetic energy at all temperatures, including absolute zero.

10. Transfer of Energy During Collisions
At the same temperature, particles transfer a small amount of energy during collisions with other particles but the amount of energy transferred is very small and can be neglected in most cases because it is most likely being gained back when other particles transfer their energy through similar collisions.

11. As Energy is added, what happens
to temperature?

12. Solid State
The particles of a solid are closely packed together. There is very little space between the particles.
Most solid materials have a specific type of geometric arrangement in which they form when cooled.

13. Solid State
The type of geometric arrangement formed by a solid is important because chemical and physical properties of solids often can be attributed to the type of geometric arrangement that the solid forms.

14. What happens to a solid when thermal energy (heat) is added to it?
The particles on the surface of the solid vibrate faster.
These particles collide with and transfer energy to other particles.
Soon the particles have enough kinetic energy to overcome attractive forces to neighboring particles.

15. Changing States in Solids
The particles gain enough kinetic energy to slip out of their ordered arrangement and the solid melts.
This is known as the melting point, or the temperature at which a solid begins to liquefy.
Energy is required for the particles to slip out of the ordered arrangement.

16. Energy and State Change
Heat of fusion is the amount of energy required to change a substance from the solid phase to the liquid phase at its melting point.

17. Solid to Liquid
Because energy must be added to change a solid to a liquid, the Heat of Fusion value will be a positive number, signifying energy (heat) is being added. Ex> +480 Joules

18. Liquid to Solid
Heat of Fusion is also the amount of energy needed to convert a liquid to a solid.
To convert liquid back to the solid state, an equal amount of energy must be removed from the liquid, making the Heat of Fusion value a negative number, signifying the removal of energy.
Ex> -480 Joules

19. Liquid Flow
Particles in a liquid have more kinetic energy than particles in a solid.

20. Liquid Flow
This extra kinetic energy allows particles to partially overcome the attractions to other particles.

21. Liquid Flow
Thus, the particles can slide past each other, allowing liquids to flow and take the shape of their container.

22. Liquid Flow
However, the particles in a liquid have not completely overcome the attractive forces between them
This causes the particles to cling together, giving liquids a definite volume and no definite shape.

23. Gas State
Gas particles have enough kinetic energy to overcome the attractions between them.
Gases do not have a fixed volume or shape.
Therefore, they can spread far apart or contract to fill the container that they are in.

24. How does a liquid become a gas?
The particles in a liquid are constantly moving.
Some particles are moving faster and have more kinetic energy than others. The particles that are moving fast enough can escape the attractive forces of other particles and enter the gas state.

25. Gas State This process is called vaporization.
Vaporization can occur in two ways—evaporation and boiling.
Evaporation is vaporization that occurs at the surface of a liquid and can occur at temperatures below the liquid’s boiling point.

26. Gas State
Evaporation does not occur at a specific temperature, but higher temperatures correlate to faster evaporation. To evaporate, particles must have enough kinetic energy to escape the attractive forces of the liquid. They must be at the liquid’s surface and traveling away from the liquid.

27. Gas State
Unlike evaporation, boiling occurs throughout a liquid at a specific temperature depending on the pressure on the surface of the liquid.
The boiling point of a liquid is the temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on the surface of the liquid.

28. Gas State The temperature at which water boils
can change depending on varying atmospheric
pressure in different locations.

29. Gas State
Heat of vaporization is the amount of energy required for the liquid at its boiling point to become a gas.

30. What happens to the attractive forces between particles in a gas?
The gas particles are moving so quickly and are so far apart that they have overcome the attractive forces between them.
Diffusion is the spreading of particles throughout a given volume until they are uniformly distributed.

31. Gas State

32. Heating Curve of a Liquid
This type of graph is called a heating curve because it shows the temperature change of water as thermal energy, or heat, is added.
Notice the two areas on the graph where the temperature does not change.
At 0°C, ice begins melting.

33. Heating Curve of a Liquid
The temperature remains constant during melting.
After the attractive forces are overcome, particles move more freely and their average kinetic energy, or temperature, increases.

34. Heating Curve of a Liquid
At 100°C, water is boiling or vaporizing and the temperature remains constant again.
Temperature remains constant in state changes such as melting or boiling.

35. Plasma State
Scientists estimate that much of the matter in the universe is plasma.
Plasma is matter consisting of positively and negatively charged particles.
Although this matter contains positive and negative particles, its overall charge is neutral because equal numbers of both charges are present.

36. Thermal Expansion
The kinetic theory also explains other characteristics of matter in the world around you.
Have you noticed the seams in a concrete driveway or sidewalk?
These separation lines are called expansion joints.

37. Thermal Expansion
When concrete absorbs heat, it expands. Then when it cools, it contracts.
If expansion joints are not used, the concrete will crack when the temperature changes.

38. Expansion of Matter
Particles move faster and separate as the temperature rises. This separation of particles results in an expansion of the entire object, known as thermal expansion.
Thermal expansion is an increase in the size of a substance when the temperature is increased.

39. Expansion of Matter
The kinetic theory can be used to explain the contraction in objects, too.
When the temperature of an object is lowered, particles slow down.
Contraction is when the attraction between the particles increases and the particles move closer together. The movements of the particles closer together result in an overall shrinking of the object

40. Expansion in Liquids
A common example of expansion in liquids occurs in thermometers.
The addition of energy causes the particles of the liquid in the thermometer to move faster.

41. Expansion in Liquids
The particles in the liquid in the narrow thermometer tube start to move farther apart as their motion increases.

42. Expansion in Liquids
The liquid in a thermometer has to expand only slightly to show a large change on the temperature scale.

43. Expansion in Gases
Hot-air balloons are able to rise due to thermal expansion of air.
The air in the balloon is heated, causing the distance between the particles in the air to increase.

44. Expansion in Gases
As the hot-air balloon expands, the number of particles per cubic centimeter decreases.

45. Expansion in Gases
This expansion results in a decreased density of the hot air. Because the density of the air in the hot-air balloon is lower than the density of the cooler air outside, the balloon will rise.

46. The Strange Behavior of Water
Water molecules are unusual in that they have slightly positive and slightly negative areas.
These charged regions affect the behavior of water.
As temperature of water drops, the particles move closer together.

47. The Strange Behavior of Water
The unlike charges will be attracted to each other and line up so that only positive and negative regions are near each other.
Because the water molecules orient themselves according to charge, empty spaces occur in the structure.
These empty spaces are larger in ice than in liquid water, so water expands when going from a liquid to a solid state.

48. The Strange Behavior of Water

49. Pure Substances
Materials are made of a pure substance or a mixture of substances.
A pure substance, or simply a substance, is a type of matter with a fixed composition.
A substance can be either an element or a compound.

50. Elements
All substances are built from atoms. If all the atoms in a substance have the same identity, that substance is an element.
The graphite in your pencil point and the copper coating of most pennies are examples of elements.

51. Elements About 90 elements are found on Earth.
More than 20 others have been made in laboratories, but most of these are unstable and exist only for short periods of time.

52. Properties of Matter
15.1

53. Properties of Matter
15.1

54. Compounds
Can you imagine yourself putting something made from a silvery metal and a greenish-yellow, poisonous gas on your food?
A compound is a substance in which atoms of two or more elements are combined in a fixed proportion.

55. Compounds
Table salt is a chemical compound that fits this description. Even though it looks like white crystals and adds flavor to food, its components—sodium and chlorine—are neither white nor salty.

56. Mixtures
A mixture, such as the pizza or soft drink shown, is a material made up of two or more substances that can be easily separated by physical means.

57. ex> seawater, air

58. Heterogeneous Mixtures
Unlike compounds, mixtures do not always contain the same proportions of the substances that make them up.
A mixture in which different materials can be distinguished easily is called a heterogeneous mixture.

59. Heterogeneous Mixtures
Most of the substances you come in contact with every day are heterogeneous mixtures. Some components are easy to see, like the ingredients in pizza, but others are not.
For example, the cheese in pizza is also a mixture, but you cannot see the individual components.

60. ex>chocolate chip cookies, granite

61. Homogeneous Mixtures
A homogeneous mixture contains two or more gaseous, liquid, or solid substances blended evenly throughout.

62. Homogeneous Mixtures
Soft drinks contain water, sugar, flavoring, coloring, and carbon dioxide gas.
Soft drinks in sealed bottles are examples of homogeneous mixtures.

63. Homogeneous Mixtures
Another name for homogeneous mixtures like a cold soft drink is solution.
A solution is a homogeneous mixture of particles so small that they cannot be seen with a microscope and will never settle to the bottom of their container.

64. Homogeneous Mixtures
Solutions remain constantly and uniformly mixed.

65. Colloids
Milk is an example of a specific kind of mixture called a colloid.
A colloid is a type of mixture with particles that are larger than those in solutions but not heavy enough to settle out.

66. Detecting Colloids
One way to distinguish a colloid from a solution is by its appearance.
Fog appears white because its particles are large enough to scatter light.
Sometimes it is not so obvious that a liquid is a colloid.
You can tell for certain if a liquid is a colloid by passing a beam of light through it.

67. Detecting Colloids
A light beam is invisible as it passes through a solution, but can be seen readily as it passes through a colloid. This occurs because the particles in the colloid are large enough to scatter light, but those in the solution are not.
This scattering of light by colloidal particles is called the Tyndall effect.

68. Suspensions
Some mixtures are neither solutions nor colloids. One example is muddy pond water.
Pond water is a suspension, which is a heterogeneous mixture containing a liquid in which visible particles settle.

69. Suspensions
The table summarizes the properties of different types of mixtures.

70. Physical Properties
Any characteristic of a material that you can observe without changing the identity of the substances that make up the material is a physical property.
Examples of physical properties are color, shape, size, density, melting point, and boiling point.

71. Physical Properties

72. Appearance
How would you describe a tennis ball? You could begin by describing its shape, color, and state of matter.
You can measure some physical properties, too. For instance, you could measure the diameter of the ball.

73. Behavior
Some physical properties describe the behavior of a material or a substance.
Attraction to a magnet is a physical property of the substance iron.
Every substance has a specific combination of physical properties that make it useful for certain tasks.

74. Using Physical Properties to Separate
The best way to separate substances depends on their physical properties.
Size is one physical property often used to separate substances.

75. Using Physical Properties to Separate
Look at the mixture of iron filings and sand shown.
You probably won’t be able to sift out the iron filings because they are similar in size to the sand particles. What you can do is pass a magnet through the mixture.

76. Using Physical Properties to Separate
The magnet attracts only the iron filings and pulls them from the sand. This is an example of how a physical property, such as magnetic attraction, can be used to separate substances in a mixture.

77. The Identity Remains the Same
Physical Change
The Identity Remains the Same
A change in size, shape, or state of matter is called a physical change.
These changes might involve energy changes, but the kind of substance—the identity of the element or compound—does not change.

78. Physical Changes

79. The Identity Remains the Same
Iron is a substance that can change states if it absorbs or releases enough energy—at high temperatures, it melts.
Color changes can accompany a physical change, too.

80. The Identity Remains the Same
For example, when iron is heated it first glows red. Then, if it is heated to a higher temperature, it turns white.

81. Techniques

82. Using Physical Change to Separate
Many such areas that lie close to the sea obtain drinking water by using physical properties of water to separate it from the salt.
One of these methods, which uses the property of boiling point, is a type of distillation.

83. Distillation
The process for separating substances in a mixture by evaporating a liquid and recondensing its vapor is distillation.
It usually is done in the laboratory using an apparatus similar to that shown.

84. Distillation
Two liquids having different boiling points can be separated in a similar way.
The mixture is heated slowly until it begins to boil.
Vapors of the liquid with the lowest boiling point form first and are condensed and collected. Then, the temperature is increased until the second liquid boils, condenses, and is collected.

85. Chemical Properties and Changes
The tendency of a substance to burn, or its flammability, is an example of a chemical property because burning produces new substances during a chemical change.
A chemical property is a characteristic of a substance that indicates whether it can undergo a certain chemical change.

86. Chemical Properties

87. The Identity Changes
A change of one substance to another is a chemical change.
The foaming of an antacid tablet in a glass of water and the smell in the air after a thunderstorm are other signs of new substances being produced.
Click image to view movie

88. Chemical Changes

89. The Identity Changes
Clues such as heat being released or the formation of bubbles or solids in a liquid are helpful indicators that a reaction is taking place.
However, the only sure proof is that a new substance is produced.
The only clue that iron has changed into a new substance is the presence of rust.
Burning and rusting are chemical changes because new substances form.

90. Using Chemical Change to Separate
One case where you might separate substances using a chemical change is in cleaning tarnished silver.
Tarnish is a chemical reaction between silver metal and sulfur compounds in the air which results in silver sulfide.
It can be changed back into silver using a chemical reaction.

91. Using Chemical Change to Separate
You don’t usually separate substances using chemical changes in the home.
In industry and chemical laboratories, however, this kind of separation is common. For example, many metals are separated from their ores and then purified using chemical changes.

92. Weathering—Chemical or Physical Change?
The forces of nature continuously shape Earth’s surface. Rocks split, deep canyons are carved out, sand dunes shift, and curious limestone formations decorate caves.
Do you think these changes, often referred to as weathering, are physical or chemical? The answer is both.

93. Physical
Large rocks can split when water seeps into small cracks, freezes, and expands.
However, the smaller pieces of newly exposed rock still have the same properties as the original sample.
This is a physical change.

94. Chemical
Solid calcium carbonate, a compound found in limestone, does not dissolve easily in water.
However, when the water is even slightly acidic, as it is when it contains some dissolved carbon dioxide, calcium carbonate reacts.
It changes into a new substance, calcium hydrogen carbonate, which does dissolve in water.

95. Chemical
A similar chemical change produces caves and the icicle shaped rock formations that often are found in them.

96. The Conservation of Mass
Suppose you burn a large log until nothing is left but a small pile of ashes.
At first, you might think that matter was lost during this change because the pile of ashes looks much smaller than the log did.

97. The Conservation of Mass
In fact, the mass of the ashes is less than that of the log.

98. The Conservation of Mass
However, suppose that you could collect all the oxygen in the air that was combined with the log during the burning and all the smoke and gases that escaped from the burning log and measure their masses, too.
Then you would find that no mass was lost after all.

99. The Conservation of Mass
Not only is no mass lost during burning, mass is not gained or lost during any chemical change.
According to the law of conservation of mass, the mass of all substances that are present before a chemical change equals the mass of all the substances that remain after the change.