Elements, Compounds, and Mixtures

1. Elements, Compounds, and Mixtures Chapter K3 Table of Contents Section 1 Elements Section 2 Compounds Section 3 Mixtures

2. Section1 Elements Chapter K3 Elements, the Simplest Substances • An element is a pure substance that cannot be separated into simpler substances by physical or chemical means. Water (H2O) is comprised of 2 elements, hydrogen and oxygen.

3. Section1 Elements Chapter K3 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.

4. Section1 Elements Chapter K3 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.

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6. Section2 Compounds Chapter K3 Compounds The word compound refers to something that consists of two or more parts. Think Compound word: Homework = Home + Work Compound leaves: Two Questions: How might you make a compound using elements? What are some compounds that you know?

7. Section2 Compounds Chapter K3 Compounds: How might you make a compound using elements? Sodium Chloride (salt) is formed when the unstable metal sodium reacts with chlorine gas. Interesting fact: salt is the only family of rocks regularly eaten by humans.

8. Section2 Compounds Chapter K3 Compounds: How might you make a compound using elements? We used two compounds: --Vinegar --Baking Soda To make a new compound: --Carbon Dioxide gas

9. Section2 Compounds Chapter K3 Compounds: Made of Elements • A compound is 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.

10. Section2 Compounds Chapter K3 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.

11. Section2 Compounds Chapter K3 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.

12. Section3 Mixtures Chapter K3 Properties of Mixtures • Amixtureis a combination of two or more substances that are not chemically combined. • For Example: Pizza

13. Section3 Mixtures Chapter K3 Properties of Mixtures • 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.

14. Section3 Mixtures Chapter K3 Again!!! No Chemical Changes take place in a Mixture!!! So, each substance has the same chemical makeup it had before the mixture was formed.

15. Section3 Mixtures Chapter K3 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.

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17. Section3 Mixtures Chapter K3 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—this differs from a compound! • 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.

18. Section3 Mixtures Chapter K3 Solutions • Asolutionis 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, thesoluteis the substance that is dissolved. Thesolventis the substance in which the solute is dissolved.

19. Section3 Mixtures Chapter K3 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. Brass is an alloy of copper and zinc. The proportions of the metals can vary.

20. Section3 Mixtures Chapter K3 Solutes, Solvents, and Solutions Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept

21. Section3 Mixtures Chapter K3 Solutions, continued • Particles in SolutionsThe 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.

22. Section3 Mixtures Chapter K3 Concentrations of Solutions • A measure of the amount of solute dissolved in a solvent isconcentration. • 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.

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24. Section3 Mixtures Chapter K3 Concentrations of Solutions, continued • Solubilityis 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.

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26. Section3 Mixtures Chapter K3 Concentrations of Solutions, continued • Dissolving Gases in LiquidsGases 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.

27. Section3 Mixtures Chapter K3 Suspensions • A suspensionis 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.

28. Section3 Mixtures Chapter K3 Colloids • A colloidis a mixture in which the particles are dispersed throughout but are not heavy enough to settle out. • A colloid cannot be separated by passing it through a filter.