2.1 Notes I. Matter

1. 2.1 Notes I. Matter Matter—all material you can hold or touch; anything that has mass and takes up space --Every sample of matter is either an element, a compound, or a mixture. Atoms: smallest particle that has properties of an element

2. Element: • -cannot be broken down into similar substances • -each element is made of only one kind of atom • -each element has a symbol (Al, B) • -elements combine chemically to make compounds

3. 4. Compounds are different from the elements that make them

4. 4. Compounds are different from the elements that make them -NaCl, sodium chloride

5. 4. Compounds are different from the elements that make them -NaCl, sodium chloride - sodium is highly combustible

6. 4. Compounds are different from the elements that make them -NaCl, sodium chloride - sodium is highly combustible - chlorine is deadly

7. 4. Compounds are different from the elements that make them -NaCl, sodium chloride - sodium is highly combustible - chlorine is deadly -when the two combine chemically, they form a substance that we eat every day -Each molecule of a compound contains two or more elements that are chemically combined.

8. 5. Molecule: smallest unit of a substance that exhibits properties of the substance -made of atoms -act as a unit -may be made of the same element F2, Br2, O2, N2 , S8

9. 6. Chemical formulas represent compounds. -Subscript tells how many atoms of each element are in the compound -Numbers in front show # of molecules

10. H2O 1 molecule of water 2 atoms of hydrogen 1 atom of oxygen

11. 3C12H22O11 3 molecules of sugar 12 carbon atoms 22 hydrogen atoms 11 oxygen atoms

12. II. Pure Substance / Mixture Pure substance: matter that has a fixed composition and definite properties ex:

13. II. Pure Substance / Mixture Pure substance: matter that has a fixed composition and definite properties ex: pure grape juice Mixture: combination of pure substances that are not chemically combined. ex: *Elements and compounds are pure substances, but mixtures are not.

14. Mixtures 1. Heterogeneous: not uniformly mixed ex

15. Mixtures 1. Heterogeneous: not uniformly mixed ex 2. Homogeneous: uniformly mixed ex

16. 3. Miscible: liquids that dissolve into each other ex

17. 3. Miscible: liquids that dissolve into each other ex 4. Immiscible: liquids that do not dissolve into each other ex

18. 5. Gases can mix with liquids -carbonated drinks are homogeneous mixtures of liquid and carbon dioxide, CO2

19. Make a graphic organizer with these words: Compound Element Heterogeneous Homogeneous Matter Mixture Pure Substance

20. compound, element, heterogeneous, homogeneous, matter, mixture, pure substance

21. Ch. 2 Section 2 Notes • Properties of Matter • Pg. 51-58

22. Physical Properties • Physical properties are characteristics that can be observed without changing the identity of the substance. • Ex. Shape and mass • Ex. Color, volume, texture

23. Physical properties help identify substances. • At room temperature and under atmospheric pressure, all samples of pure water are colorless and liquid.

24. Physical properties can be observed or measured. • Use senses to observe some basic physical properties. • You can observe the state of a substance, the physical form of a substance. • Solid, liquid, and gas

25. The temperature at which a substance changes from a solid to a liquid is the melting point. • The temperature at which a liquid changes to a gas is the boiling point. • A characteristic of any pure substance is that its boiling point and its melting point are constant if the pressure remains the same. • At constant pressure, pure water always has the same boiling point and the same melting point.

26. Other physical properties that can be measured are: • Strength • Hardness • magnetism • Conducts heat • Conducts Electricity

27. Physical properties help determine uses. • Clean or dirty • If something will fit into another thing or not • Clothing matches • Etc.

28. Density is a physical property • Density is a measurement of how much matter is contained in a certain volume of a substance. • Density = mass/volume • D = m/v • Density of a solid is expressed in g/cubic cm • Density of a liquid: g/mL

29. Find the density of an object that has a mass of 10.0 grams and a volume of 2.5 cubic centimeters. D= m/v

30. Density is different from weight. • Read pg. 55

31. Chemical Properties • A chemical property describes how a substance changes into a new substance, either by combining with other elements or by breaking apart into new substances. • Chemical properties are generally not as easy to observe as physical properties.

32. Flammability is a chemical property. • Flammability is the ability to burn. • A chemical property of wood is flammability A substance always has its chemical properties, even when you cannot observe them. A substance that does not burn has a chemical property of nonflammability.

33. Reactivity is a chemical property. Another chemical property is the reactivity of elements or compounds with oxygen, water, or other substances. Reactivity is the capacity of a substance to combine with another substance. Ex. When iron is exposed to oxygen, it rusts.

34. Physical and chemical properties are different. • You can observe physical properties without changing the identity of the substance. • You can observe chemical properties only in situations in which the identity of the substance changes. • Many substances have either chemical or physical properties in common. • Usually NOT both!

35. CH. 2 Section 3 Notes • Changes of Matter • Pg. 59-64

36. Physical Changes • A physical change affects one or more physical properties of a substance without changing the identity of the substance. • Ex. Breaking chalk, dissolving sugar in water, sanding a piece of wood, mixing oil and vinegar, cutting, crushing, melting, etc.

37. Physical changes do not change a substance’s identity. • During a physical change, energy is absorbed or released. • After a physical change, a substance may look different, but the arrangement of atoms that make up the substance is not changed.

38. Dissolving is a physical change. • When you stir sugar into water, the sugar dissolves and seems to disappear. • Look at Figure 3 on page 60. • When sugar dissolves, the sugar molecules become spread out between the water molecules. • The molecules of the sugar do not change. • Therefore, dissolving is a physical change.

39. Chemical Changes • Some materials are useful because of their ability to change and combine to form new substances. • The burning of the compounds is a chemical change. • A chemical change happens when one or more substances are changed into entirely new substances that have different properties. • The chemical properties of a substance describe which chemical changes can happen.

40. Chemical changes happen everywhere. • Look on pg. 61 at Figure 4 • When a battery dies, the chemicals inside the battery have changed. • The oxygen you breathe is undergoing a series of chemical changes and reactions. • Leaves changing colors. • Etc.

41. Chemical changes form new substances. • When you mix ingredients together when baking, the interaction of the ingredients together is much different than it would be if each of the ingredients were by themselves.

42. Chemical changes can be detected. • A change in odor or color is often a clue that a chemical change has occurred. • Chemical changes often cause color changes, fizzing or foaming, or the production of sound, heat, light, or odor.

43. Chemical changes cannot be reversed by physical changes. • Because new substances are formed in a chemical change, a chemical change cannot be reversed by physical changes. • Most are impossible to reverse. • Under the right conditions, some chemical changes can be reversed by other chemical changes.

44. Breaking Down Mixtures and Compounds. • A mixture is a combination of substances that are not chemically combined. • A compound is made up of atoms that are chemically combined. • As a result of this difference, mixtures and compounds must be separated in different ways. • Mixtures can be separated by physical changes, but compounds must be broken down by chemical changes.

45. Mixtures can be physically separated. • Because mixtures are not chemically combined, each part of a mixture has the same chemical makeup that it had before the mixture was formed. • Each substance keeps its identity. • Therefore, mixtures can be separated by physical means.

46. If components of a mixture have different boiling points, you can heat the mixture in a distillation device. • Another technique for separating mixtures is to use a centrifuge.

47. Some compounds can be broken down through chemical changes. • Some compounds can be broken down into elements through chemical changes. • Electric currents can be used to separate some compounds. • Other compounds undergo chemical changes to form simpler compounds.