# Matter and Change Chapter 2.

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Matter and Change Chapter 2

2.1 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 Describing Matter
How are properties used to describe matter classified?

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. This bowling ball and candlepin are used in a game played mainly in New England

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. The copper kettles are about 150 years old.

Identifying Substances
This sculpture of a falcon is made of gold. Gold is an example of a substance. This gold falcon standard from Egypt is about 3000 years old. Analyzing Data Which of the properties listed in Table 2.1 could not be used to distinguish copper from gold?

Identifying Substances
Every sample of a given substance has identical intensive properties because every sample has the same composition. This gold falcon standard from Egypt is about 3000 years old. Analyzing Data Which of the properties listed in Table 2.1 could not be used to distinguish copper from gold?

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, boiling point, density and malleability are examples of physical properties. See reference table S

Identifying Substances

States of Matter States of Matter What are three states of matter?

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. The arrangement of particles is different in solids, liquids, and gases. In a solid, the particles are packed closely together in a rigid arrangement.

States of Matter Liquid
A liquid is a form of matter that has an indefinite shape, flows, yet has a fixed volume. The arrangement of particles is different in solids, liquids, and gases. In a liquid, the particles are close together, but they are free to flow past one another.

States of Matter Gases A gas is a form of matter that takes both the shape and volume of its container. The arrangement of particles is different in solids, liquids, and gases. In a gas, the particles are relatively far apart and can move freely. Relating Cause and Effect Use the arrangements of their particles to explain the general shape and volume of solids and gases.

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. The silvery substance in the photograph is gallium, which has a melting point of 30°C. Inferring What can you infer about the temperature of the hand holding the gallium?

2.2 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. You can choose the amount of each item you select from a salad bar. So your salad is unlikely to have the same composition as other salads containing the same items.

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

2.2 Classifying Mixtures A mixture in which the composition is not uniform throughout is a heterogeneous mixture. Sand, soil, granite, salsa, cereal, concrete, cookies, wood

2.2 Classifying Mixtures A mixture in which the composition is uniform throughout is a homogeneous mixture. Another name for a homogeneous mixture is a solution. Air, saltwater, brass, steel, soda, blood plasma, vinegar, gasoline

2.2 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.

2.2 Classifying Mixtures When oil and vinegar are mixed they form layers, or phases. The oil phase floats on the water phase. Olive oil and vinegar are homogeneous mixtures. The substances in these mixtures are evenly distributed. When olive oil is mixed with vinegar, they form a heterogeneous mixture with two distinct phases.

Separating Mixtures 2.2 Separating Mixtures
How can mixtures be separated?

Separating Mixtures Differences in physical properties can be used to separate mixtures. Density, magnetism, particle size, color, solubility, evaporation, distillation

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. 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. A distillation can be used to remove impurities from water. As liquid water changes into water vapor, substances dissolved in the water are left behind in the distillation flask. Inferring What can you infer about the boiling points of substances dissolved in the impure water?

2.3 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
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. When table sugar is heated, it goes through a series of chemical changes. The final products of these changes are solid carbon and water vapor.

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
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. Compounds and the elements from which they form have different properties. Observing Based on the photographs, describe two physical properties of sodium and two of chlorine.

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. Compounds and the elements from which they form have different properties. Observing Based on the photographs, describe two physical properties of sodium and two of chlorine.

Distinguishing Elements and Compounds
Sodium Chloride (commonly known as table salt) is used to season or preserve food. Compounds and the elements from which they form have different properties. Observing Based on the photographs, describe two physical properties of sodium and two of chlorine.

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 (pure). If the composition of a material may vary, the material is a mixture. *Substances have a chemical formula, mixtures do not.

Distinguishing Substances and Mixtures
This flowchart summarizes the process for classifying matter. The flow chart summarizes the process for classifying matter. Any sample of matter is either an element, a compound, or a mixture. Interpreting Diagrams What is the key difference between a substance and a solution?

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. The symbols used to represent elements have changed over time. Alchemists and the English chemist John Dalton (1766–1844) both used drawings to represent chemical elements. Today, elements are represented by one- or two-letter symbols.

Symbols and Formulas Each element is represented by a one or two-letter chemical symbol.

2.4 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. A mixture of iron filings and sulfur can be changed. a) A magnet separates the iron from the sulfur. b) Heat combines iron and sulfur in a compound. Classifying Which change is a chemical change? Explain.

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. A mixture of iron filings and sulfur can be changed. a) A magnet separates the iron from the sulfur. b) Heat combines iron and sulfur in a compound. Classifying Which change is a chemical change? Explain.

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
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. Clues to chemical change often have practical applications. a) Bubbles of carbon dioxide gas form when a geologist puts acid on a rock that contains compounds called carbonates. b) When a test strip is dipped in urine, the color change is used to estimate the level of the sugar glucose in urine. c) One step in the production of cheese is a reaction that causes milk to separate into solid curds and liquid whey.

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 total mass doesn’t change.) The conservation of mass is easily observed when a change occurs in a closed container. When the liquids in photograph A are mixed, they react. None of the products are gases. Analyzing Data How do you know that a reaction took place and that mass was conserved during the reaction?