1. Chapter 2 What Is Matter

2. When we study matter, we are studying chemistry
When we study matter, we are studying chemistry. It is the study of what things are made of, what their properties are, and how they change and interact.

3. Each object around you is matter. Matter is everything that is anything. Matter is defined as anything that has volume (takes up space) and mass.

4. Elements An element is a pure substance that cannot be separated into simpler substances by physical or chemical means. An element is considered a pure substance meaning that it is only made of one kind of particle. In fact, elements are made of only one type of atom.

5. In chemistry, elements are designated by a one or two letter symbol
In chemistry, elements are designated by a one or two letter symbol. Each of the more than 110 elements that we know has properties that are different than the rest.

6. Compounds A chemical compound is a pure substance that is made of two or more elements that are chemically combined. Because of this definition, we know that the substances that make up a compound change into a new identity and cannot be separated physically.

7. The components of a compound combine in a definite ration by mass
The components of a compound combine in a definite ration by mass. In this way, we can write a formula to describe it. H2O Each compound has a set of characteristic properties that identify it. These properties will be different from those of the substances that form it.

8. Compounds can be broken down chemically into the substances that formed it or into simpler compounds. 2H2O → 2H2 + O2

9. Atoms can combine chemically to form molecules
Atoms can combine chemically to form molecules. Each molecule has a formula which tells which elements and how many atoms they contain.

10. Elements and compounds are pure substances that have a fixed composition and definite properties.

11. Mixtures A pizza is a good example of a mixture
Mixtures A pizza is a good example of a mixture. A mixture is a combination of two or more substances that are not chemically combined. Because the substances are not chemically combined, each substance retains its identity and can be physically separated back out of the mixture. The components of a mixture may be mixed in any ratio and still be considered a mixture.

12. If a mixture contains large particles dispersed in a liquid or a gas that will settle out, it is classified as a suspension. If the particles of a suspension are not stirred constantly, they will settle out. Particles of a suspension can also be filtered out. The particles are large enough to be caught in filters. Other examples of suspensions would be dirty water, dust storms, and Italian dressing.

13. Suspensions are considered heterogeneous mixtures because different samples may contain different compositions.

14. Gelatin, egg whites, and blood plasma have such small particles suspended that they cannot be filtered and won’t settle out. They are called an colloid. Colloids exhibit the Tyndall effect.

15. Bubbles and foam are gases that are leaving a liquid but the coating of liquid around them holds them on the surface.

16. Smoke is an aerosol.

17. A solution is a mixture that appears to be a single substance but is actually two substances distributed in each other in a single phase. We often call a solution a homogeneous mixture. Saltwater is a common solution. Salt is very soluble in water. If a substance will not dissolve, it is considered insoluble. The salt is dissolved so it is considered the solute and the water does the dissolving so it is considered the solvent. If two liquids dissolve into one another, they are said to be miscible. If the liquids are like oil and water, they are considered immiscible

18. Actually, solutions do not have to be a solid dissolved in a liquid
Actually, solutions do not have to be a solid dissolved in a liquid. Since there are three common phases of matter, there are nine possible types of solutions. Such as: Air is a gas dissolved in a gas. Soft drinks are a gas dissolved in a liquid. Humid air is a liquid dissolved in a gas. Antifreeze is a liquid dissolved in a liquid. Saltwater is a solid dissolved in a liquid. And brass is a solid dissolved in a solid. Solid solutions are called alloys.

19. Properties of Matter

20. All matter has traits that can be used to identify it
All matter has traits that can be used to identify it. These traits are called properties.

21. Physical properties are traits that can be determined without changing the identity of the matter. We constantly rely on physical properties to tell us about the world around us. Physical properties include dimensions, thermal conductivity, state, malleability, ductility, expansion-contraction, solubility, color, and density.

22. Density is a very important physical property since it can be used to determine the identity of substances. Density is calculated by dividing the mass of an object by its volume. The units are then stated as grams per cubic centimeter.

23. The physical properties of matter often help determine its uses
The physical properties of matter often help determine its uses. Copper is useful for wires, antifreeze is useful in cars, and aluminum is useful for building airplanes.

24. Chemical Properties
Chemical properties are those properties that are based on the ability of a substance to change into a different substance. These might include flammability, reactivity to acids and bases, reactivity with water, and oxidation.

25. Indicators of Chemical Reactions Include:
Changes in temperature
Evolution of a gas
Formation of a precipitate
Emission of light
Generation of electric current
Sounds
Changes in color

26. Properties such as color, solubility and density which are useful in identifying matter are called characteristic properties. They may be chemical or physical in nature.

27. Changes in Matter

28. Physical changes are changes that affect one or more physical properties. These might include melting, evaporating, crushing, bending, mixing, and dissolving. One should remember that since a physical change only affects physical properties, it can be undone. One should remember that dissolving is a physical change.

29. A mixture is a combination of two or more substances that are not chemically combined. Because the substances are not chemically combined, each substance retains its identity and can be physically separated back out of the mixture.

30. A chemical change is one that occurs when a substance changes into an entirely new substance with new properties. These would include baking a cake, the souring of milk, the burning of fuel, rusting, and the fizzing away of an alkaseltzer.

31. There is a definite set of clues that a chemical change is taking place:
temperature change
evolution of a gas
formation of a precipitate (new solid)
production of light
production of electric current
production of sound
color change