Slide 1 of 25 Chemistry 2.3

Slide 2 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds 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. 2.3

© Copyright Pearson Prentice Hall Slide 3 of 25 Elements and Compounds > Distinguishing Elements and Compounds Compounds can be broken down into simpler substances by chemical means, but elements cannot. 2.3

Slide 4 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds 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 dehydrated, it goes through a series of chemical changes. 2.3

Slide 5 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds Distinguishing Elements and Compounds The final products of these chemical changes are solid carbon and water vapor. The following diagram summarizes the process. 2.3

Slide 6 of 25 © Copyright Pearson Prentice Hall Elements and Compounds > 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. 2.3

Slide 7 of 25 © Copyright Pearson Prentice Hall Elements and Compounds > Calcium Calcium metal is used as a reducing agent in preparing other metals such as thorium and uranium, and as an alloying agent for aluminium, beryllium, copper, lead and magnesium alloys.

Slide 8 of 25 © Copyright Pearson Prentice Hall Elements and Compounds > Carbon There are a number of pure forms of this element including graphite, diamond, fullerenes and graphene. Diamond is a colorless transparent crystalline solid, the hardest known material. Graphite is black and shiny but soft, and the nano-forms, fullerenes and graphene appear, in bulk, as black or dark brown soot-like powders

Slide 9 of 25 © Copyright Pearson Prentice Hall Elements and Compounds > Oxygen Industrially, oxygen is produced on a large scale from liquid air by liquefaction and fractional distillation. In the laboratory it can be prepared by the electrolysis of water or by adding manganese(IV) oxide as a catalyst to aqueous hydrogen peroxide. Oxygen is very reactive combines with most other elements. a component of many organic compounds is essential for the aerobic necessary for combustion used in steel industry. used in the manufacture of nitric acid, hydrogen peroxide chloroethene (precursor to PVC) used in oxy-acetylene welding and cutting of metals. used in the treatment of sewage and of effluent from industry.

Slide 10 of 25 © Copyright Pearson Prentice Hall Elements and Compounds > Oxygen

Slide 11 of 25 © Copyright Pearson Prentice Hall Elements and Compounds > Calcium Carbonate Calcium carbonate, or CaCO 3, comprises more than 4% of the earth’s crust and is found throughout the world. Its most common natural forms are; Chalk Limestone Marble Calcium carbonate is one of the most useful and versatile materials known to man. Many of us encounter calcium carbonate for the first time in the school classroom, where we use blackboard chalk. As limestone, calcium carbonate is a biogenic rock, and is more compacted than chalk. As marble, calcium carbonate is a coarse- crystalline, metamorphic rock, which is formed when chalk or limestone is recrystallised under conditions of high temperature and pressure.

© Copyright Pearson Prentice Hall Slide 12 of 25 Elements and Compounds > Distinguishing Substances and Mixtures 2.3 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.

© Copyright Pearson Prentice Hall Slide 13 of 25 Elements and Compounds > Distinguishing Substances and Mixtures This flowchart summarizes the process for classifying matter. 2.3

© Copyright Pearson Prentice Hall Slide 14 of 25

© Copyright Pearson Prentice Hall Slide 15 of 25 Practice Problems for Conceptual Problem 2.2 Problem Solving 2.19 Solve Problem 19 with the help of an interactive guided tutorial

© Copyright Pearson Prentice Hall Slide 16 of 25 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. 2.3

Slide 17 of 25 © Copyright Pearson Prentice Hall > Elements and Compounds Symbols and Formulas Each element is represented by a one or two- letter chemical symbol. 2.3

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