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Elements, Compounds, and Mixtures

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Section 1 Elements

Section 2 Compounds

Section 3 Mixtures

Chapter 4

Concept Mapping

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Section 1 Elements

Bellringer

Refer to Figure 4 in your book for help answering the following questions:

What do gold, iron, and aluminum have in common?

What do oxygen, neon, and sulfur have in common?

How is silicon different from aluminum or oxygen?

Chapter 4

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Copyright © by Holt, Rinehart and Winston. All rights reserved.

Section 1 Elements

Objectives

• Describe pure substances.

• Describe the characteristics of elements, and give examples.

• Explain how elements can be identified.

• Classify elements according to their properties.

Chapter 4

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Section 1 Elements

Elements, the Simplest Substances

• An element is a pure substance that cannot be separated into simpler substances by physical or chemical means.

• Only One Type of Particle A substance in which there is only one type of particle is a pure substance. Elements are made of particles called atoms.

Chapter 4

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Section 1 Elements

Properties of Elements

• Each element can be identified by its unique set of properties. An element may share a property with another element, but other properties can help you tell the elements apart.

• Identifying Elements by Their Properties Elements can be identified by using their physical properties and their chemical properties.

Chapter 4

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Section 1 Elements

Classifying Elements by Their Properties

• Categories of Elements Three major categories are:

• Metals are shiny, and they conduct heat energy and electric current.

• Nonmetals conduct heat and electricity poorly.

• Metalloids have properties of both metals and nonmetals.

Chapter 4

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Section 1 Elements

Classifying Elements by Their Properties, continued

• Categories Are Similar By knowing the category to which an unfamiliar element belongs, you can predict some of its properties.

• The next slide show examples and properties of metals, nonmetals, and metalloids.

Chapter 4

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Section 1 ElementsChapter 4

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Section 2 Compounds

Bellringer

The word compound refers to something that consists of two or more parts. How might you make a compound using elements? What are some compounds that you know?

Write your answer in your science journal.

Chapter 4

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Section 2 Compounds

Objectives

• Explain how elements make up compounds.

• Describe the properties of compounds.

• Explain how a compound can be broken down into its elements.

• Give examples of common compounds.

Chapter 4

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Section 2 Compounds

Compounds: Made of Elements

• A compound is a pure substance composed of two or more elements that are chemically combined. Elements combine by reacting with one another.

• A particle of a compound is a called a molecule. Molecules of compounds are formed when atoms of two or more elements join together.

Chapter 4

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Section 2 Compounds

Compounds: Made of Elements

• The Ratio of Elements in a Compound Elements join in a specific ratio according to their masses to form a compound.

• For example, every sample of water has a 1:8 mass ratio of hydrogen and oxygen.

Chapter 4

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Section 2 Compounds

Properties of Compounds

• Each compound can be identified by its physical and chemical properties.

• Properties: Compounds Versus Elements A compound has properties that differ from those of the elements that form it.

Chapter 4

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Section 2 Compounds

Breaking Down Compounds

• Compounds can be broken down into their elements or into simpler compounds by chemical changes.

• Methods of Breaking Down Compounds Sometimes, energy is needed for a chemical change to happen. Two ways to add energy are to apply heat and to apply an electric current.

Chapter 4

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Section 2 Compounds

Compounds in Your World

• Compounds in Nature Some compounds found in nature are proteins, carbon dioxide, and carbohydrates.

• Compounds in Industry Some compounds must be broken down for use in industry. Other compounds, are made in industry for use as medicines, food preservatives, and synthetic fabrics.

Chapter 4

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Section 3 Mixtures

Bellringer

When you add sugar to coffee, tea, iced tea, or lemonade, the sugar disappears. What do you think happens to the sugar?

Write your answer in your science journal.

Chapter 4

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Section 3 Mixtures

Objectives

• Describe three properties of mixtures.

• Describe four methods of separating the parts of a mixture.

• Analyze a solution in terms of its solute and solvent.

Chapter 4

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Section 3 Mixtures

Objectives, continued

• Explain how concentration affects a solution.

• Describe the particles in a suspension.

• Explain how a colloid differs from a solution and a suspension.

Chapter 4

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Section 3 Mixtures

Properties of Mixtures

• A mixture is a combination of two or more substances that are not chemically combined.

• No Chemical Changes in a Mixture No chemical changes happen when a mixture is made. So, each substance has the same chemical makeup it had before the mixture was formed.

Chapter 4

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Section 3 Mixtures

Properties of Mixtures, continued

• Separating Mixtures Through Physical Methods Mixtures can be separated by using physical changes. Physical changes do not change the identities of the substances.

• The next slide shows some common ways to separate mixtures by using physical changes.

Chapter 4

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Section 3 MixturesChapter 4

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Section 3 Mixtures

Properties of Mixtures, continued

• The Ratio of Components in a Mixture The components of a mixture do not need to be mixed in a definite ratio.

• For example, granite is a mixture of three minerals. Different ratios of the minerals give granite different colors, but the mixture is always called granite.

Chapter 4

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Section 3 Mixtures

Solutions

• A solution is a mixture that appears to be a single substance. The process in which particles of substances separate and spread evenly throughout a mixture is known as dissolving.

• In a solution, the solute is the substance that is dissolved. The solvent is the substance in which the solute is dissolved.

Chapter 4

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Section 3 Mixtures

Solutions, continued

• Examples of Solutions Liquid solutions include soft drinks, gasoline, and tap water. Solutions may also be gases, such as air.

• Solutions may also be solids, such as steel. Alloys are solid solutions of metals or nonmetals dissolved in metals.

Chapter 4

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Section 3 Mixtures

Solutes, Solvents, and Solutions

Chapter 4

Click below to watch the Visual Concept.

Visual Concept

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Section 3 Mixtures

Solutions, continued

• Particles in Solutions The particles in solutions are so small that they never settle out. They also cannot be removed by filtering.

• The particles in solutions are so small that they don’t even scatter light.

Chapter 4

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Section 3 Mixtures

Concentrations of Solutions

• A measure of the amount of solute dissolved in a solvent is concentration. • Concentrated or Dilute? Solutions can be described as being concentrated or dilute. But these two terms do not tell you the amount of solute that is dissolved.

• The next slide shows how to calculate concentration.

Chapter 4

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Section 3 MixturesChapter 4

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Section 3 Mixtures

Concentrations of Solutions, continued

• Solubility is the ability of a solute to dissolve in a solvent at a certain temperature.

• The solubility of most solids in water increases with temperature. The graph on the next slide shows this relationship.

Chapter 4

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Section 3 MixturesChapter 4

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Section 3 Mixtures

Concentrations of Solutions, continued

• Dissolving Gases in Liquids Gases become less soluble in liquids as the temperature is raised.

• Dissolving Solids Faster in Liquids Three ways to make a solute dissolve faster are mixing the solution, heating the solution, and crushing the solute into smaller particles.

Chapter 4

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Section 3 Mixtures

Suspensions

• A suspension is a mixture in which particles of a material are dispersed throughout a liquid or a gas but are large enough that they settle out.

• The particles in a suspension are large enough to scatter or block light. A suspension can be separated by passing it through a filter.

Chapter 4

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Section 3 Mixtures

Colloids

• A colloid is a mixture in which the particles are dispersed throughout but are not heavy enough to settle out.

• Particles in a colloid are large enough to scatter light. A colloid cannot be separated by passing it through a filter.

Chapter 4

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Elements, Compounds, and Mixtures

Use the terms below to complete the Concept Mapping on the next slide.

Chapter 4

Concept Mapping

mixture

colloid

filter

element

suspension

solution

compound

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Elements, Compounds, and MixturesChapter 4

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Elements, Compounds, and MixturesChapter 4