What Is Chemistry?

1. 1.1 What Is Chemistry? • Matter is anything that has mass and occupies space. • Chemistry is the study of the composition of matter and the changes that matter undergoes.

2. 1.1 What Is Chemistry? • Because living and nonliving things are made of matter, chemistry affects all aspects of life and most natural events.

3. 1.1 Areas of Study • Five traditional areas of study are • organic chemistry • inorganic chemistry • biochemistry • analytical chemistry • physical chemistry

4. 1.1 Pure and Applied Chemistry • Pure chemistry is the pursuit of chemical knowledge for its own sake. • Applied chemistry is research that is directed toward a practical goal or application.

5. 1.1 Pure and Applied Chemistry • Pure research can lead directly to an application, but an application can exist before research is done to explain how it works.

6. 1.1 Pure and Applied Chemistry • Aspirin • Long before researchers figured out how aspirin works, people used it to relieve pain, and doctors prescribed it for patients who were at risk for a heart attack. • In 1971, it was discovered that aspirin can block the production of a group of chemicals that cause pain and lead to the formation of blood clots. This is an example of pure research.

7. 1.1 Pure and Applied Chemistry • Technology • Technology is the means by which a society provides its members with those things needed and desired. • Technology allows humans to do some things more quickly or with less effort. • There are debates about the risks and benefits of technology.

8. 1.1 Why Study Chemistry? • Chemistry can be useful in explaining the natural world, preparing people for career opportunities, and producing informed citizens.

9. Classifying Mixtures • A mixture is a physical blend of two or more components. • A salad bar provides a range of items. Customers choose how much of each item to use in their salads. Each salad has a different composition.

10. Classifying Mixtures • Based on the distribution of their components, mixtures can be classified as heterogeneous mixtures or as homogeneous mixtures.

11. Classifying Mixtures • Heterogeneous Mixtures • A mixture in which the composition is not uniform throughout is a heterogeneous mixture.

12. Classifying Mixtures • Homogeneous Mixtures • A mixture in which the composition is uniform throughout is a homogeneous mixture. • Another name for a homogeneous mixture is a solution.

13. Classifying Mixtures • The term phase is used to describe any part of a sample with uniform composition and properties. • A homogenous mixture consists of a single phase. • A heterogeneous mixture consists of two or more phases.

14. Classifying Mixtures • When oil and vinegar are mixed they form layers, or phases. The oil phase floats on the water phase.

18. Separating Mixtures • Separating Mixtures • How can mixtures be separated?

19. Separating Mixtures • Differences in physical properties can be used to separate mixtures.

20. Physical Changes • Is a change that affects one or more physical properties of a substance withoutchanging its identity. • Break a piece of chalk • Changes its size and shape, but still chalk • Dissolving sugar, cutting hair, melting ice, sanding wood, crushing a soda can, mixing oil & vinegar.

21. Physical Changes continued • During a physical change, energy can be absorbed or released. • After the physical change, substance may look different, but the atoms that make up the substance are the same. • Pounding a gold nugget into a ring • Crushing quartz crystals into sand (still SiO2) • Changing states of matter are physical changes • Melting, freezing, evaporating • Physical changes are often easily reversed

22. Physical Changes continued • Dissolving is a physical change • Sugar dissolves into water, but the sugar molecules have not changed, the particles just spread out in the water. • Mixtures can be separated • Each component still has the same chemical makeup it had before they were mixed • Separate mushrooms from a pizza • Separate salt from water by heating – evaporates water, salt remains • Use a magnet to separate iron containing nails from the ones that do not contain iron

24. Separating Mixtures • Filtration • The process that separates a solid from the liquid in a heterogeneous mixture is called filtration. • A colander is used to separate pasta from the water in which it was cooked. This process is a type of filtration.

25. Separating Mixtures • Distillation • During a distillation, a liquid is boiled to produce a vapor that is then condensed into a liquid.

26. Section Quiz. • 1. Which of the following phrases describes a mixture? • composition varies • composition may vary • components cannot be separated

27. Section Quiz. • 2. Which of the following is a homogeneous mixture? • vinegar • iron filings in sand • chicken noodle soup • muddy water

28. Elements and Compounds • Take two pounds of sugar, two cups of boiling water, and one quarter teaspoon of cream of tartar. Add food coloring and you have the sticky, sweet concoction known as cotton candy. You will learn how substances are classified as elements or compounds.

29. Distinguishing Elements and Compounds • Distinguishing Elements and Compounds • How are elements and compounds different?

30. 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.

31. 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.

32. Distinguishing Elements and Compounds • Compounds can be broken down into simpler substances by chemical means, but elements cannot.

33. 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 heated, it goes through a series of chemical changes.

34. Chemical changes CANNOT be reversed by physical changes • Once you have formed the new substances, you can’t reverse them by using physical changes • Can’t unbake a cake • Once milk is sour, its done • Once something is rusted, can’t go back • Some chemical changes can be reversed by other chemical changes

36. Distinguishing Substances and Mixtures Distinguishing Substances and Mixtures How can substances and mixtures be distinguished?

37. Distinguishing Substances and Mixtures 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.

38. Distinguishing Substances and Mixtures This flowchart summarizes the process for classifying matter.

42. Symbols and Formulas • Symbols and Formulas • What do chemists use to represent elements and compounds?

43. Symbols and Formulas • Chemists use chemical symbols to represent elements, and chemical formulas to represent compounds. • These chemical symbols were used in earlier centuries.

44. Symbols and Formulas • Each element is represented by a one or two-letter chemical symbol.

46. Vertical columns – groups or families • know the names • Horizontal rows – periods • 3 main classes – metals, nonmetals, metalloids (semi-conductors)

47. Section Quiz • 1. Passing an electric current through a certain substance produces oxygen and sulfur. This substance cannot be a(n) • compound. • mixture. • element. • solution.

48. Section Quiz • 2. Which of the following is a mixture? • sodium chloride • carbon dioxide • sucrose • air