Matter and Change. Chapter 1

Transcription

1 Matter and Change Chapter 1

2 What is Chemistry? Chemistry is the study of the composition, structure, and properties of matter and the changes it undergoes.

3 What does Chemistry do? Chemistry deals with questions such as: What is that material made of? What is its makeup and internal arrangement? How does it behave and change when heated, cooled, or mixed with other materials and why does this behavior occur?

4 Branches of Chemistry Organic chemistrythe study of most carbon-containing compounds Inorganic chemistry- all substances not classified as organic, mainly those not containing carbon

5 Physical chemistry- the study of the properties and changes of matter and their relation to energy Analytical chemistry- the identification of the components and composition of materials

6 Biochemistry- the study of substances and processes occurring in living things Theoretical chemistry- the use of math and computers to understand the principles behind observed chemical behavior and to design and predict properties of new compounds

7 In all areas of chemistry, scientists work with chemicals any substance that has definite composition

8 Matter and its Properties Explaining what matter is involves finding properties that all matter has in common All matter has volume- the amount of 3-D space an object occupies All matter has mass- a measure of the amount of matter

9 Matter officially defined - anything that has mass and takes up space

10 Basic Building Blocks of Matter

11 The fundamental building blocks of matter are atoms and molecules. These particles make up elements and compounds.

12 An atom is the smallest unit of an element that maintains the properties of that element. A molecule- a neutral group of atoms that are held together by covalent bonds

13 An element is a pure substance made of only one kind of atom. A compound is a substance that is made from the atoms of two or more elements that are chemically bonded.

14 Properties of Matter

15 Every substance, whether it is an element or a compound, has characteristic properties.

16 Extensive properties depend on the amount of matter that is present. Volume, mass, and the amount of energy in a substance EXTENSIVE = AMOUNT

17 Intensive properties do not depend on the amount of matter present. Melting point, boiling point, density, and the ability to conduct electricity and heat

18 Physical Properties and Physical Changes

19 A physical property is a characteristic that can be observed or measured without changing the identity of the substance. Melting and boiling point

20 A change in a substance that does not involve a change in the identity of the substance is a physical change. Cutting, grinding, melting, and boiling

21 Changes of State

22 A change of state is a physical change of a substance from one state to another.

23 Matter in the solid state has definite volume and definite shape. Matter in the liquid state has definite volume but an indefinite shape

24 Matter in the gas state has neither definite volume nor definite shape Plasma is a high temperature physical state of matter in which atoms lose their electrons.

25 Chemical Properties and Chemical Changes

26 A chemical property relates to a substance s ability to undergo changes that transform it into different substances. Burning, rusting, tarnishing

27 A change in which one or more substances are converted into different substances is called a chemical change (chemical reaction).

28 The substances that react in a chemical change are called the reactants. The substances that are formed by the chemical change are the products

29 Carbon + oxygen carbon dioxide Chemical changes DO NOT affect the total amount of matter present before and after a reaction. Called the Law of Conservation of Matter

30 How do you know if a chemical change has occurred? 1. Color change 2. Temperature change 3. Production of a gas (bubbles) 4. Precipitate forms

31 What is a precipitate? A precipitate forms when two clear solutions are combined and a solid substance settles out, the solid is insoluble and is called the precipitate. Sometimes the solution will just look cloudy.

32 Energy and Changes in Matter When physical or chemical changes occur, energy is always involved. Energy can be absorbed (endothermic the environment gets colder) or released (exothermic the environment gets hotter), but is not created or destroyed.

33 Mixtures

34 A mixture is a blend of two or more kinds of matter. It can usually be separated by physical means.

35 Homogeneous mixtures are uniform in composition, stays the same throughout. (A.K.A. solutions.) Air, sugar water, brass

36 Heterogeneous mixtures are not uniform in composition. Dirt, salad, granite, wood, an apple

37 Pure Substances

38 A pure substance has a fixed composition and differs from a mixture in the following ways: Every sample of a given pure substance has exactly the same characteristic properties and exactly the same composition.

39 Pure substances are either compounds or elements. A compound can be decomposed, or broken down into two or more simpler compounds or elements by a chemical change.

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41 Elements

42 Elements are pure substances that cannot be decomposed by chemical change.

43 They are organized into groups based on similar chemical properties. This organization of elements is the periodic table.

44 The vertical columns of the periodic table are called groups, or families. Each group contains elements with similar chemical properties.

45 The horizontal rows of elements in the periodic table are called periods. Elements that are close to each other in the same period tend to be more similar than elements that are far apart.

46 Periodic Table

47 Types of Elements Metals Nonmetal Metalloids Nobel Gases

48 Metals A metal is an element that is a good conductor of heat and electricity. Gold Copper Aluminum

49 Most are solids at room temperature and tend to be shiny. Malleable can be hammered or rolled into thin sheets

50 Ductile can be drawn into a fine wire Have high tensile strength ability to resist breaking when pulled.

51 Nonmetals A nonmetal is an element that is a poor conductor of heat and electricity. a) Carbon b) Sulfur c) Phosphorous d) Iodine

52 Many are gases at room temperature, but some are solids. Only one is a liquid. Nonmetal solids tend to be brittle.

53 Metalloids A stair-step line separates the metals from the nonmetals (see periodic table). A metalloid is an element that has some characteristics of metals and some characteristics of nonmetals.

54 All are solid at room temperature. Tend to be less malleable than metals, but not as brittle as nonmetals. Some have a metallic luster.

55 Noble Gases Group 18 Generally unreactive Gases at room temperature Neon, argon, krypton, and xenon are used in lighting. Helium is used in party balloons and weather balloons because it is less dense than air.