Preview Section 1 Elements Section 2 Compounds Section 3 Mixtures Elements, Compounds, and Mixtures Preview Section 1 Elements Section 2 Compounds Section 3 Mixtures Concept Mapping

Objectives Describe pure substances. Section 1 Elements Objectives Describe pure substances. Describe the characteristics of elements; give examples. Explain how elements can be identified. Classify elements according to their properties.

Elements, the Simplest Substances Section 1 Elements Elements, the Simplest Substances Element: pure substance that cannot be separated into simpler substances by physical or chemical means.

pure substance: substance in which there is only one type of atom

Properties of Elements Section 1 Elements Properties of Elements Each element can be identified by its unique set of properties. An element may share property w/ another element, but other properties help distinguish elements from each other. Elements can be identified by using physical properties and chemical properties.

Identification of Elements Physical Properties Chemical Properties Melting point Boiling point Density Colour Hardness Texture Solubility in water Magnetic Flammability Reactivity with oxygen Reactivity with acid

Classifying Elements by Their Properties, ctd Section 1 Elements Classifying Elements by Their Properties, ctd Categories Are Similar By knowing category to which unfamiliar element belongs  can predict some of its properties. The next slide show examples and properties of metals, nonmetals, and metalloids.

Classifying Elements by Their Properties Section 1 Elements Classifying Elements by Their Properties Three Major Categories of Elements: METALS NONMETALS METALLOIDS shiny good conductor of heat and electricity malleable ductile dull (not shiny) poor conductor brittle solids nonmalleable semiconductors (somewhat conduct heat, electricity) some shiny; some dull somewhat malleable somewhat ductile

Section 1 Elements

Bellringer The word compound refers to something that 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? How many compounds can you think of that you use every day. Record your answers in your science journal.

Objectives Explain how elements make up compounds. 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.

Compounds: Made of Elements Section 2 Compounds Compounds: Made of Elements Compound: pure substance composed of two or more elements that are chemically combined. [Elements combine by reacting with one another.] Molecule: particle of a compound, formed when atoms of two or more elements join together.

Compounds: Made of Elements 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. EX: every sample of water has a 1:8 mass ratio of hydrogen and oxygen.

Properties of Compounds 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. EX: sodium chloride sodium (soft, silvery metal, reacts violently w/water + chlorine (poisonous greenish gas) = sodium chloride (white, crystalline solid, safe to eat)

Breaking Down Compounds 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. 2 ways to add energy: apply heat apply electric current

Compounds in Your World Section 2 Compounds Compounds in Your World Cpds in Nature EX: proteins, carbon dioxide, carbohydrates. Compounds in Industry Some cpds must be broken down for industrial use. Other cpds made in industry for use as medicines, food preservatives, synthetic fabrics.

Bellringer When you add sugar to coffee, tea, iced tea, or 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? Does the same thing happen to salt when you add it to soup? Does temperature, acidity, or color matter? Why or why not? Record your answers in your science journal.

Objectives Describe three properties of mixtures. Section 3 Mixtures Objectives Describe three properties of mixtures. Describe four methods of separating parts of a mixture. Analyze a solution in terms of its solute and solvent. Explain how concentration affects a solution. Describe the particles in a suspension. Explain how a colloid differs from a solution and a suspension.

Properties of Mixtures Section 3 Mixtures Properties of Mixtures mixture: 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. Each substance has the same chemical makeup it had before the mixture was formed.

Properties of Mixtures, ctd Section 3 Mixtures Properties of Mixtures, ctd 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.

Section 3 Mixtures

Properties of Mixtures, ctd Section 3 Mixtures Properties of Mixtures, ctd The Ratio of Components in a Mixture The components of a mixture do NOT need to be mixed in a definite ratio. EX: granite is mixture of three minerals. Different ratios of the minerals give granite different colors, but the mixture is always called granite.

Solutions solution: a mixture that appears to be a single substance. Section 3 Mixtures Solutions solution: a mixture that appears to be a single substance. dissolving: process in which particles of substances separate and spread evenly throughout a mixture solute: the substance that is dissolved. solvent: the substance in which the solute is dissolved.

Solutions, ctd Examples of Solutions Section 3 Mixtures Solutions, ctd Examples of Solutions Liquid solutions: soft drinks, gasoline, and tap water. Gaseous solutions: air. Solid solutions: steel, metal alloys such as brass Alloys: solid solutions of metals or nonmetals dissolved in metals.

Section 3 Mixtures Solutions, ctd 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 they don’t even scatter light.

Concentrations of Solutions Section 3 Mixtures Concentrations of Solutions concentration: measure of the amount of solute dissolved in a solvent Concentrated or Dilute? Solutions can be described as being concentrated or dilute. But these two terms DO NOT tell the amount of solute that is dissolved. The next slide shows how to calculate concentration.

Concentrations of Solutions, ctd Section 3 Mixtures Concentrations of Solutions, ctd Solubility: ability of a solute to dissolve in a solvent at a certain temperature. The solubility of most solids in water increases with temperature.

Concentrations of Solutions, ctd Section 3 Mixtures Concentrations of Solutions, ctd Dissolving Gases in Liquids Gases become LESS soluble in liquids as temperature increases. Dissolving Solids Faster in Liquids Three ways to make a solute dissolve faster: mixing the solution heating the solution crushing the solute into smaller particles (increase surface area).

Section 3 Mixtures Suspensions suspension: 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.

Section 3 Mixtures Colloids colloid: 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.