Physical Science 8:Matter

WILLMAR PUBLIC SCHOOL 2013-2014 EDITION

HIGH SCHOOL SCIENCE

CHAPTER 8

MatterIn this chapter you will:1. Describe physical and chemical properties of matter.2. Describe evidence that indicates a physical change and/

or a chemical change are taking place. Distinguish chemical changes from physical changes.

3. Classify pure substances as elements or compounds. Classify mixtures as heterogeneous or homogeneous. Classify mixtures as solutions, suspensions, or colloids.

4. Distinguish pure substances from mixtures.5. Describe the characteristics of an element & compounds

and the symbols used to identify elements.6. Describe and classify the three main states of matter

then explain the behaviors of gases, liquids, and solids using kinetic theory.

7. Describe phase change and the six phase changes then identify phase changes as endothermic or exothermic.

8. Explain what happens to the motion, arrangement, and average kinetic energy during phase changes. Explain how temperature can be used to recognize a phase change.

OBJECTIVE:

1. Describe physical and chemical properties of matter.

2. Describe evidence that indicates a physical change and/or a chemical change are taking place. Distinguish chemical changes from physical changes.

Vocabulary:

matter physical property

physical change chemical property

chemical change reactivity

flammability change in color

production of gas production of a precipitate

SECTION 8.1

What is Matter?Both you and the speck of dust consist of atoms of matter. So does the ground beneath your feet. In fact, everything you can see and touch is made of matter. The only things that aren’t matter are forms of energy, such as light and sound. Although forms of energy are not matter, the air and other substances they travel through are. So what is matter? Matter is defined as anything that has mass and volume. Mass is the amount of matter in a substance. Volume is the amount of space matter takes up.

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Matter has both physical and chemical properties. Physical properties can be measured or observed without matter changing to a different substance. Chemical properties of matter can be measured or observed only when matter undergoes a change to become an entirely different substance.

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. Physical properties are typically things you can detect with your senses. For example, they may be things that you can see, hear, smell, or feel. Physical properties include the state of matter and its color and odor. For example, oxygen is a colorless, odorless gas. Chlorine is a greenish gas with a strong, sharp odor. Other physical properties include hardness, freezing and boiling points, the ability to dissolve in other substances, and the ability to conduct heat or electricity. Physical properties can be used to identify materials since each material has a unique combination of physical properties.

A physical change occurs when some of the properties of a material change, but the substances in the material remain the same. Crumpling a paper or slicing tomatoes are actions that change the size and shape of the material, but not its composition. When matter undergoes physical change, it doesn’t become a different substance. Therefore, physical changes are often easy to reverse. For example, when liquid water freezes to form ice, it can be changed back to liquid water by heating and melting the ice.

A chemical property is any ability to produce a change in the composition of matter. Chemical properties are properties that can be measured or observed only when matter undergoes a change to become an entirely different kind of matter. For example, the ability of iron to rust can only be observed when iron actually rusts. When it does, it combines with oxygen to become a different substance called iron oxide. Iron is very hard and silver in color, whereas iron oxide is flakey and reddish brown. Besides the ability to rust, other chemical properties include reactivity and flammability. Reactivity is the ability of matter to combine chemically with other substances. Some kinds of matter are extremely reactive; others are extremely unreactive. For example, the metal magnesium is very reactive, even with water. When a pea-sized piece of magnesium is added to a small amount of water, it reacts explosively. Flammability is the ability of matter to burn. When matter burns, it combines with oxygen and changes to different substances. Wood is an example of flammable matter. When wood burns, it changes to ashes, carbon dioxide, water vapor, and other gases.

A chemical change occurs when a substance reacts and forms one or more new substances. There are three types of evidence used to identify a chemical change: change in color, production of a gas, and/or formation of a precipitate.

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A change in color is a clue that a chemical change has produced at least one new substance. Over time, a new shiny penny will change color.

A production of a gas is when bubbles form, and a clue that a chemical change has occurred. These bubbles are a new substance that is in the form of a gas. When you mix vinegar with baking soda, bubbles of carbon dioxide form immediately.

A formation of a precipitate, or a solid that forms or separates from a liquid, is another clue that a chemical change has occurred. If you add lemon juice to milk, small bits of a white solid will separate from the liquid.

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When matter undergoes a chemical change, the composition of matter changes. When matter undergoes a physical change, the composition of the matter does not change.

The properties of matter, both physical and chemical, depend on the substances that matter is made of. Matter can exist either as a pure substance or as a mixture.

Section Review:

1. What are some physical properties?

2. Explain how a physical change can be reversed.

3. What are some chemical properties?

4. When can you observe a chemical change?

5. Give an example of a change of color.

6. Give an example of a production of gas.

7. Give an example of a formation of a precipitate.

8. How are physical changes and chemical changes different?

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OBJECTIVE:

1. Classify pure substances as elements or compounds.

2. Describe the characteristics of an element & compounds and the symbols used to identify elements.

3. Distinguish pure substances from mixtures.

Vocabulary:

pure substance

element

atom

compound

crystal

molecule

SECTION 8.2

Pure SubstancesThe properties of matter, both physical and chemical, depend on the substances that matter is made of. Matter can exist either as a pure substance or as a mixture.

Matter that always has exactly the same composition is classified as a pure substance, or simply a substance. An element is a pure substance because it cannot be separated into any other substances. Currently, 92 different elements are known to exist in nature, although additional elements have been formed in labs. All matter consists of one or more of these elements. Some elements are very common; others are relatively rare. The most common element in the universe is hydrogen, which is part of Earth’s atmosphere and a component of water. The most common element in Earth’s atmosphere is nitrogen, and the most common element in Earth’s crust is oxygen. Table salt and table sugar are two examples of pure substances. Every sample of a given substance has the same properties because a substance has a fixed, uniform composition.

Substances can be classified into two categories—elements and compounds. An element is a substance that cannot be broken down into simpler substances. A compound is a

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substance that is made from two or more simpler substances and can be broken down into those simpler substances.

An element is a substance that cannot be broken down into simpler substances. For about 2000 years, people accepted Aristotle’s idea that all matter is made up of just four elements: earth, air, water, and fire. Starting about 500 years ago, scientists began discovering all of the elements that are known today. An atom is the smallest particle of an element.  All the atoms of an element are like one another, and are different from the atoms of all other elements. An element has a fixed composition because it contains only one type of atom.

Each element has a unique set of properties that make it different from all other elements. As a result, elements can be identified by their properties. For example, the elements iron and nickel are both metals that are good conductors of heat and electricity. However, iron is attracted by a magnet, whereas nickel is not. How could you use this property to separate iron objects from nickel objects?

Chemists use symbols to represent elements. The symbols allow scientists who speak different languages to communicate without confusion. Each symbol has either one or two letters. The first letter is always capitalized. If there is a second letter, it is not capitalized.

A compound is a substance that is made from two or more simpler substances and can be broken down into those simpler substances. The simpler substances are either elements or other compounds. A compound always contains two or more elements joined in a fixed proportion.

Two things are true of all compounds:

1. A compound always has the same elements in the same proportions. For example, carbon dioxide always has two atoms of oxygen for each atom of carbon, and water always has two atoms of hydrogen for each atom of oxygen.

2. A compound always has the same composition throughout. For example, all the carbon dioxide in the atmosphere and all the water in the ocean have these same proportions of elements.

The properties of a compound differ from those of the substances from which it is made. For example, water is composed or is made up of the elements hydrogen and oxygen. Water is classified as a compound. Oxygen and hydrogen are gases at room temperature, but water is a liquid.

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Hydrogen can fuel a fire, and oxygen can keep a fire burning, but water does not burn or help other substances to burn. In fact, water is one of the substances commonly used to put out fires.

Some compounds form rigid frameworks called crystals. Other compounds form individual molecules. A molecule is the smallest particle of a compound that still has the compound’s properties.

Section Review:

1. Why does every sample of a given substance have the same properties?

2. What are the two categories that substances can be classified?

3. Why do chemists use symbols to represent the elements?

4. How many symbols are used for each element?

5. If there is a second letter, is it capitalized?

6. What does a compound always contain?

7. Properties of a compound are the (same or different).

8. How is water different that the Hydrogen and Oxygen that make up water?

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OBJECTIVES:

1. Classify mixtures as heterogeneous or homogeneous.

2. Classify mixtures as solutions, suspensions, or colloids.

3. Distinguish pure substances from mixtures.

Vocabulary:

mixture

heterogeneous

homogeneous

solution

suspension

colloid

SECTION 8.3

MixturesThe properties of matter, both physical and chemical, depend on the substances that matter is made of. Matter can exist either as a pure substance or as a mixture.

A mixture is made up of two or more different substances which are mixed but not combined chemically. Mixtures tend to retain some of the properties of their individual substances. But the properties of a mixture are less constant than the properties of a substance.  The properties of a mixture can vary because the composition of a mixture is not fixed. Mixtures can be classified by how well the parts of the mixture are distributed throughout the mixture.

Heterogeneous comes from the Greek words hetero and genus, meaning “different” and “kind.” In a heterogeneous mixture, the parts of the mixture are noticeably different from one another.

Homogeneous comes from the Greek word homo and genus, meaning “same” and “kind”. In a homogeneous mixture, the substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from another. A homogeneous mixture appears to contain only one substance.

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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 colloid, or a suspension.

When substances dissolve and form a homogeneous mixture, the mixture that forms is called a solution. Liquid solutions are easy to recognize. They do not separate into distinct layers over time. If you pour a liquid solution through a filter, none of the substances in the solution are trapped in the filter. The particles in a solution are too small to settle out of the solution, be trapped by a filter, or scatter light. A solution is a homogeneous mixture with tiny particles. An example is salt water. The particles of a solution are too small to reflect light. As a result, you cannot see them. That’s why salt water looks the same as pure water. The particles of solutions are also too small to settle or be filtered out of the mixture.

A colloid is a homogeneous mixture in which very small particles of one substance are distributed evenly throughout another substance. A colloid contains some particles that are intermediate in size. Colloids do not separate into layers, plus you cannot use a filter to separate the parts. The scattering of light is a property that can be used to distinguish colloids from solutions. A colloid is a homogeneous mixture with medium-sized particles. Examples include homogenized milk and gelatin. The particles of a colloid are large enough to reflect light, so you can see them. But they are too small to settle or filter out of the mixture.

A suspension is a heterogeneous mixture that separates into layers over time. You could use a filter to separate the substances. Suspended particles settle out of a mixture or are trapped by filter because they are larger than the particles in a solution. Because larger particles can scatter light in all directions, suspensions are cloudy. A suspension is a heterogeneous mixture with large particles. An example is muddy water. The particles of a suspension are big enough to reflect light, so you can see them. They are also big enough to settle or be filtered out. Anything that you have to shake before using, such as salad dressing, is usually a suspension.

The components of a mixture keep their own identity when they combine, so they retain their physical properties. Examples of physical properties include boiling point, ability to dissolve, and particle size. When components of mixtures vary in physical properties such as these, processes such as boiling, dissolving, or filtering can be used to separate them. Two processes that are used to separate mixtures are filtration and distillation. Filtration uses a filter, a material with tiny holes, to separate out solid particles that are contained in a liquid or gas. Distillation is a method of separating a mixture in a solution from its solvent based on their boiling points.

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Section Review:

1. What are the properties of a mixture like?

2. How are heterogeneous and homogeneous mixtures different?

3. What determines if a mixture is a solution, suspension or colloid?

4. Homogenized milk is a colloid. It has been treated to prevent its different components from separating when it stands. When non-homogenized milk stands, the cream rises to the top because it is less dense than the rest of the milk. Which type of mixture is non-homogenized milk? Explain your answer.

5. How could you use water and a coffee filter to separate a mixture of salt and sand?

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OBJECTIVES:

1. Describe and classify the three main states of matter then explain the behaviors of gases, liquids, and solids using kinetic theory.

2. Describe phase change and the six phase changes then identify phase changes as endothermic or exothermic.

3. Explain what happens to the motion, arrangement, and average kinetic energy during phase changes. Explain how temperature can be used to recognize a phase change.

Vocabulary:

solid liquid gas

phase change freezing melting

vaporization condensation sublimation

deposition endothermic change

exothermic change

SECTION 8.4

States of MatterMatter can be classified in four different states: solid, liquid, gas and plasma. Matter can be classified on the states based on whether their shapes and volumes are definite or variable. Definite means does not change when you change the container. Definite does not mean that the shape or volume can never change. Variable mean it changes as you change the container. A given kind of matter has the same chemical makeup and the same chemical properties regardless of its state. That’s because state of matter is a physical property. As a result, when matter changes state, it doesn’t become a different kind of substance. For example, water is still water whether it exists as ice, liquid water, or water vapor.

Kinetic theory of matter states that all particles of matter are in constant motion. There are forces of attraction among the particles in all matter.

Solid is the state of matter in which materials have definite shape and definite volume. Almost all solids have some type of orderly arrangement of particles at the atomic level. If particles do not have enough kinetic energy to overcome the force of attraction between them, matter exists as a solid. The particles are packed closely together and held rigidly in place. All they can do is vibrate. This explains why solids have a fixed volume and a fixed shape. Solids have a definite shape and volume because particles in a solid vibrate around fixed locations like students during class.

Liquid is the state of matter in which a material has definite volume but variable shape. A liquid always has the same

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shape as its container and can be poured from one container to another. If particles have enough kinetic energy to partly overcome the force of attraction between them, matter exists as a liquid. The particles can slide past one another but not pull apart completely. This explains why liquids can change shape but have a fixed volume. A liquid takes the shape of its container because particles in a liquid move to new locations like students during passing time. The volume of a liquid is constant because forces of attraction keep particles close together.

Gas is a state of matter in which materials have variable shape and volume. A gas takes the shape and volume of its container. If particles have enough kinetic energy to completely overcome the force of attraction between them, matter exists as a gas. The particles can pull apart and spread out. This explains why gases have neither a fixed volume nor a fixed shape. The constant motion of particles in a gas allows a gas to fill a container of any shape or size, like students leaving at the end of the school day.

When at least two states of the same substance are present, scientists describe each different state as a phase. A phase change is the reversible physical change that occurs when a substance changes from one state of matter to another.

Melting, freezing, vaporization, condensation, sublimation, and deposition are the six common phase changes. Phase changes are grouped in pairs. If you were to measure the temperature of a substance before, during, then after a phase change, you would notice that before and after the phase change the temperatures would change; however, during the phase change the temperature of the substance does not change.

Melting and freezing are opposite phase changes. These phase changes occur between solids and liquids. Melting is the phase change from solid to liquid. Freezing is the phase change from liquid to solid.

Vaporization and condensation are opposite phase changes. These phase changes occur between liquid and gas. Vaporization is the phase change from liquid to gas. Boiling

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is the phase change vaporization. Condensation is the phase change from gas to liquid.

Sublimation and deposition are opposite phase changes. These phase changes occur between gas and solid. Sublimation is the phase change from solid straight to gas. Deposition is the phase change from gas straight to solid.

Deionization and ionization are phase changes between gas and plasma. These two phase changes are not as common.

During a phase change, energy is transferred between a substance and its surroundings. The direction of the transfer depends on the type of phase change. Energy is either absorbed or released during a phase change.

During an endothermic change, the system absorbs energy from its surroundings. Endothermic phase changes are melting, vaporization, sublimation, and ionization.

During an exothermic change, the system releases energy to its surroundings. Exothermic phase changes are deionization, deposition, condensation, and freezing.

Section Review:

1. What happens to the temperature during a phase change?

2. What is the opposite phase change to condensation?

3. What phases or states does sublimation change between?

4. Why does a liquid keep its volume but can change shape?

5. What phase changes are endothermic?

6. What phase changes are exothermic?

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