Chapter 2Matter & Change

Properties of Matter

– Bamboo has properties that make it a good choice for use in chopsticks. It has no noticeable odor or taste. It is hard, yet easy to split, and it is heat resistant. You will learn how properties can be used to classify and identify matter.

Describing Matter

– Properties used to describe matter can be classified as extensive or intensive.

Describing Matter

– Extensive Properties– The mass of an object is a measure of the amount of

matter the object contains.

– The volume of an object is a measure of the space occupied by the object.

– An extensive property is a property that depends on the amount of matter in a sample.

Describing Matter

– Intensive Properties• An intensive property is a

property that depends on the type of matter in a sample, not the amount of matter. The hardness of a bowling ball is an example of an intensive property.

Identifying Substances

• Identifying Substances– Why do all samples of a substance have the same

intensive properties?

Identifying Substances

• Matter that has a uniform and definite composition is called a substance. These kettles are mainly copper. Copper is an example of a substance.

Identifying Substances

•This sculpture of a falcon is made of gold. Gold is an example of a substance.

Identifying Substances

• Every sample of a given substance has identical intensive properties because every sample has the same composition.

Identifying Substances

• A physical property is a quality or condition of a substance that can be observed or measured without changing the substance’s composition.

• Hardness, color, conductivity, and malleability are examples of physical properties.

Identifying Substances

States of Matter• States of Matter

– What are three states of matter?– Three states of matter are solid, liquid, and gas.

States of Matter

– Solids• A solid is a form of

matter that has a definite shape and volume.

States of Matter

– Liquid• A liquid is a form of

matter that has an indefinite shape, flows, yet has a fixed volume.

States of Matter

– Gases• A gas is a form of matter

that takes both the shape and volume of its container.

 

The Three States of Matter

States of Matter

– Animation 1 – Relate the states of matter to the arrangements

of their particles.

States of Matter

• Vapor describes the gaseous state of a substance that is generally a liquid or solid at room temperature, as in water vapor.

Physical Changes

• Physical Changes– How can physical changes be classified?

Physical Changes

• During a physical change, some properties of a material change, but the composition of the material does not change.

• As gallium melts in a person’s hand, the shape of the sample changes, but the composition of the material does not change.

Physical Changes

•Physical changes can be classified as reversible or irreversible.

• 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.

– 1. Which of the following would be described as an extensive property of matter?

• temperature

• color

• mass

• hardness

Section Quiz.

Section Quiz.

– 2. Which properties can be observed without changing the composition of a substance?

• all properties of a substance

• intensive properties

• chemical properties

• physical properties

Section Quiz.

– 3. Match the states of matter with the following descriptions:

(1) takes the volume and shape of its container

(2) has a definite shape and volume

(3) has a definite volume but an indefinite shape

• (1) liquid, (2) solid and (3) gas

• (1) gas, (2) solid, and (3) liquid

• (1) gas, (2) liquid, and (3) solid

Mixtures

– Panning is one way to separate gold from a mixture of gold and materials such as sand or gravel. A pan containing the mixture is place underwater and shaken vigorously from left to right. You will learn how to classify and separate mixtures.

Classifying Mixtures

• Classifying Mixtures– How can mixtures be classified?

Classifying Mixtures•A mixture is a physical blend of two or more components.

•A salad bar provides a range of items. Customers choose how much of each item to use in their salads. Each salad has a different composition.

Classifying Mixtures

– Based on the distribution of their components, mixtures can be classified as heterogeneous mixtures or as homogeneous mixtures.

Classifying Mixtures

–Heterogeneous Mixtures•A mixture in which the composition is not uniform throughout is a heterogeneous mixture.

Classifying Mixtures–Homogeneous Mixtures

•A mixture in which the composition is uniform throughout is a homogeneous mixture.

•Another name for a homogeneous mixture is a solution.

Classifying Mixtures

• The term phase is used to describe any part of a sample with uniform composition and properties.

– A homogenous mixture consists of a single phase.

– A heterogeneous mixture consists of two or more phases.

Classifying Mixtures• When oil and vinegar are mixed they form layers, or phases.

The oil phase floats on the water phase.

Separating Mixtures

• Separating Mixtures– How can mixtures be separated?

Separating Mixtures

– Differences in physical properties can be used to separate mixtures.

Separating Mixtures– Filtration

• The process that separates a solid from the liquid in a heterogeneous mixture is called filtration.

• A colander is used to separate pasta from the water in which it was cooked. This process is a type of filtration.

Separating Mixtures– Distillation

• During a distillation, a liquid is boiled to produce a vapor that is then condensed into a liquid.

– 1. Which of the following phrases describes a mixture?• composition varies• composition may vary• components cannot be separated

– 2. Which of the following is a homogeneous mixture?• vinegar• iron filings in sand• chicken noodle soup• muddy water

– 3. Which technique is used to separate homogeneous mixtures?• filtration• distillation• magnetism• dissolving

Elements and Compounds

– Take two pounds of sugar, two cups of boiling water, and one quarter teaspoon of cream of tartar. Add food coloring and you have the sticky, sweet concoction known as cotton candy. You will learn how substances are classified as elements or compounds.

Distinguishing Elements and Compounds

• Distinguishing Elements and Compounds– How are elements and compounds

different?

Distinguishing Elements and Compounds

• An element is the simplest form of matter that has a unique set of properties.

• A compound is a substance that contains two or more elements chemically combined in a fixed proportion.

Distinguishing Elements and Compounds

– Compounds can be broken down into simpler substances by chemical means, but elements cannot.

Distinguishing Elements and Compounds

– Breaking Down Compounds

• A chemical change is a change that produces matter with a different composition than the original matter.

• When table sugar is heated, it goes through a series of chemical changes.

Distinguishing Elements and Compounds

• The final products of these chemical changes are solid carbon and water vapor. The following diagram summarizes the process.

•

Distinguishing Elements and Compounds

–Properties of Compounds–In general, the properties of compounds are quite different from those of their component elements.

–When the elements sodium and chlorine combine chemically to form sodium chloride, there is a change in composition and a change in properties.

Distinguishing Elements and Compounds

• Chlorine is used to kill harmful organisms in swimming pools.

Distinguishing Elements and Compounds

• Sodium is stored under oil to keep it from reacting with oxygen or water vapor in the air. Sodium vapor produces the light in some street lamps.

Distinguishing Elements and Compounds

• Sodium Chloride (commonly known as table salt) is used to season or preserve food.

Distinguishing Substances and Mixtures

• Distinguishing Substances and Mixtures– How can substances and mixtures be

distinguished?

Distinguishing Substances 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.

Classification of MatterMatter

Can it be separated?Yes No

Pure Substances

Mixtures

Is composition uniform?

Homogeneous Heterogeneous

Yes No Can it be decomposed by ordinary chemical means?Yes No

Compounds Elements

Blend of two or more kinds of matter, each of which retains its own identity and properties

Has a fixed composition; has exactly the same properties throughout; has exactly the same composition

Symbols and Formulas

• Symbols and Formulas– What do chemists use to represent

elements and compounds?

Symbols and Formulas– Chemists use chemical symbols to represent

elements, and chemical formulas to represent compounds.

– These chemical symbols were used in earlier centuries.

Symbols and Formulas

• Each element is represented by a one or two-letter chemical symbol.

– 1. Passing an electric current through a certain substance produces oxygen and sulfur. This substance cannot be a(n)

• compound.• mixture.• element.• solution.

– 2. Which of the following is a mixture?

• sodium chloride

• carbon dioxide

• sucrose

• air

– 3. The symbol for the element potassium is

• K.

• Po.

• P.

• Pt.

Chemical Reactions

– Iron is abundant, easy to shape when heated, and relatively strong, especially when mixed with carbon in steel. Over time, objects made of iron will rust if they are left exposed to air. You will learn to recognize chemical changes and to distinguish them from physical changes.

Chemical Changes

• Chemical Changes– What always happens during a chemical change?

Chemical Changes

• The ability of a substance to undergo a specific chemical change is called a chemical property.

• Chemical properties can be used to identify a substance. But chemical properties can be observed only when a substance undergoes a chemical change.

Chemical Changes

– During a chemical change, the composition of matter always changes.

– Recall that during a physical change, the composition of matter never changes.

Chemical Changes

• A magnet separates iron from sulfur. This is an example of a physical change.

Chemical Changes• A mixture of iron and sulfur is heated. The iron and

sulfur react and form iron sulfide. This is an example of a chemical change.

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.

–A substance present at the start of the reaction is a reactant.

–A substance produced in the reaction is a product.

Recognizing Chemical Changes

• Recognizing Chemical Changes– What are four possible clues that a chemical

change has taken place?

Recognizing Chemical Changes

– Possible clues to chemical change include:• a transfer of energy• a change in color• the production of a gas• the formation of a precipitate.

Chemical Changes

• A precipitate is a solid that forms and settles out of a liquid mixture.

• Clues to chemical changes have practical applications.

Conservation of Mass

• Conservation of Mass– How are the mass of the reactants and the mass of the

products of a chemical reaction related?

Conservation of Mass

– During any chemical reaction, the mass of the products is always equal to the mass of the reactants.

Conservation of Mass• The law of conservation of mass states that in any

physical change or chemical reaction, mass is conserved.

• The conservation of mass is easily observed when a change occurs in a closed container.

– 1. Which of the following is a chemical reaction?

• melting of lead

• dissolving sugar in water

• rusting of iron

• crushing of stone

– 2. Which of the following is NOT a possible clue that a chemical change is taking place?

• a change of state

• a change in color

• production of a gas

• formation of a precipitate

– 3. During any chemical change, the mass of the products is

• always equal to the mass of the reactants.

• always greater than the mass of the reactants.

• always less than the mass of the reactants.

• sometimes different than the mass of the reactants.

Pure Substances

and Mixtures

Pure Substances and Mixtures• If matter is not uniform throughout, then it is a

heterogeneous mixture.• If matter is uniform throughout, it is

homogeneous.• If homogeneous matter can be separated by

physical means, then the matter is a mixture.• If homogeneous matter cannot be separated by

physical means, then the matter is a pure substance.

• If a pure substance can be decomposed into something else, then the substance is a compound.

Periodic TableGroups

Periods

Metalloids

Noble Gases