1. Chapter 3 Matter – Properties and Changes

2. I. Substances A substance is matter that has a uniform and unchanging composition - table salt is a substance, it is always 100% sodium chloride (NaCl) - water is a substance, it is always composed of hydrogen and oxygen (H2O) - salt water, or seawater, is not a substance; different samples from multiple locations may not have the same levels of water, salts, and other dissolved particles

3. II. Physical Properties of Matter A physical property is a characteristic that can be observed or measured without changing the sample’s composition i.e. density, color, odor, taste, hardness, melting point, boiling point, conductivity

4. A. Extensive properties Extensive properties are dependent upon the amount of substance present i.e. mass, length, volume, height

5. B. Intensive properties Intensive properties are independent of the amount of substance present i.e. density, appearance Some unknown substances can be identified by their unique intensive properties ex. Real gold and “fools” gold have the same appearance but real gold has its own unique density that is different from “fools” gold

6. III. Chemical Properties of Matter A chemical property is the ability of a substance to combine with or change into one or more other substances as a result of its contact with other substances or the application of thermal or electrical energy The inability of a substance to change into another substance is also a chemical property

7. IV. Observing Properties of Matter Observations of properties may vary depending on the conditions of the immediate environment It is important to state the specific conditions in which observations are made because both chemical and physical properties depend on temperature and pressure

8. V. States of Matter A. Solids A form of matter that has its own definite shape and volume Particles of matter are very tightly packed Expands only slightly when heated Because its shape is definite, a solid may not conform to the shape of the container in which it is placed

9. B. Liquids A form of matter that flows, has constant volume, and takes the shape of its container Particles are not rigidly held in place and are less closely packed than are the particles in a solid Tend to expand when heated

10. C. Gases A form of matter that flows to conform to the shape of its container and fills the entire volume of its container Particles are very far apart Easily compressed The word gas refers to a substance that is naturally in the gaseous state at room temperature

11. -The word vapor refers to the gaseous state of a substance that is a solid or a liquid at room temperature; is should not be confused with gas ex. Water is a liquid at room temperature; steam, its gaseous state, is a vapor

12. VI. Physical Changes A physical change alters a substance without changing its composition Temperature and pressure alter a substances state of matter which is also a physical change that does not change its composition - these properties are listed as the melting point and boiling points of a substance and can help identify unknown substances (p.914-916)

13. VII. Chemical Changes A chemical change, or chemical reaction, involves one or more substances changing into new substances The new substances formed in the reaction have different compositions and different properties from the substances present before the reaction occurred

14. In chemical reactions, the starting substances are called reactants and the new substances that are formed are called products Terms referring to chemical changes include explode, rust, oxidize, corrode, tarnish, ferment, burn, or rot

15. VIII. Conversion of Mass The law of conservation of mass states that mass is neither created nor destroyed during a chemical reaction – it is conserved mass reactants = mass products

16. IX. Mixtures A mixture is a combination of two or more pure substances in which each pure substance retains its individual chemical properties A. Heterogeneous Mixtures A mixture that does not blend smoothly throughout and in which the individual substances remain distinct

17. B. Homogeneous Mixtures A mixture that has constant composition throughout Homogeneous mixtures are also referred to as solutions - solutions can contain solids, liquids, or gases - solid-solid solutions are called alloys

18. X. Separating Mixtures Because the substances in a mixture are physically combined, the processes used to separate a mixture are physical processes that are based on the difference in physical properties of the substances

19. A. Filtration Heterogeneous mixtures composed of solids and liquids are separated by filtration Filtration is a technique that used a porous barrier to separate a solid from a liquid

20. B. Distillation Homogeneous mixtures composed of two liquids can be separated by distillation Distillation is a technique that is based on differences in boiling points of the substances involved - a mixture is heated until the substance with the lowest boiling point boils to a vapor that can be condensed into a liquid and collected

21. C. Crystallization Homogeneous mixtures composed of a solid dissolved in a liquid can be separated by crystallization When a solution contains as much dissolved substance as it can possible hold, the addition of a tiny amount more often causes the dissolved substance to come out of solution and collect as crystals on some available surface

22. D. Chromatography Chromatography is a technique that separates the components of a mixture (called the mobile phase) on the basis of the tendency of each to travel or be drawn across the surface of another material (called the stationary phase) http://www.youtube.com/watch?v=gpFb635N2wo&feature=related

23. XI. Elements An element is a pure substance that cannot be separated into simpler substances by physical or chemical means Each element has a unique chemical name and symbol that are universally accepted

24. A. A first look at the periodic table As many new elements were being discovered in the early nineteenth century, schemes for organizing the elements on the basis of patterns of similarities in chemical and physical properties were being proposed Dmitri Mendeleev devised the first accepted chart by organizing the elements in rows and columns based on their similarities and masses

25. Mendeleev was able to predict the properties of elements that were yet to be discovered and where they belonged on the table Mendeleev’s table was further developed into the periodic table of elements

26. - elements are organized into horizontal rows called periods and vertical columns called groups or families

27. XII. Compounds A compound is a combination of two or more different elements that are combined chemically i.e. water, table salt, aspirin Compounds can be broken down into simpler substances by chemical means - often requires external energy such as heat or electricity The properties of a compound are different from those of its individual parts

28. XIII. Law of Definite Proportions The law of definite proportions states that a compound is always composed of the same ratio of the mass of each element that compose it, or percent by mass Percent by mass (%) = mass of element/mass of compound X 100 H H O

29. The law of definite proportions also suggests that the mass of the compound is equal to the sum of the masses of the elements that made up the compound Compounds with different mass proportions must be different compounds H H O H H O O

30. XIV. Law of Multiple Proportions The law of multiple proportions states that when different compounds are formed by a combination of the same elements, different masses of one element combine with the same relative mass of the other element in a ratio of small whole numbers