DESCRIBE PHYSICAL & CHEMICAL CHANGES IN TERMS OF ENDOTHERMIC & EXOTHERMIC PROCESSES

1. DESCRIBE PHYSICAL & CHEMICAL CHANGES IN TERMS OF ENDOTHERMIC & EXOTHERMIC PROCESSES COS 5.0

2. WHAT YOU’LL LEARN • Explain the relationship between, matter atoms & elements • Categorize materials as pure substances or mixtures • Identify elements & compounds • Perform calculations involving density • Compare & Contrast physical & chemical properties • Determine how the law of conservation of mass applies to chemical changes • Compare & Contrast physical & chemical changes • Describe how to detect whether a chemical change has taken place. • Describe the four common states of matter. • List the different changes of state & describe how particles behave in each state • Describe differences between endothermic & exothermic reactions

3. MATTER

4. COMPOSITION MATTER • anything that has mass and takes up space (volume) ATOMS • smallest particle of an element that has same properties of element MOLECULES • smallest unit of a substance that keeps all of physical and chemical properties of that substance. • Two or more atoms that are chemically bonded

5. CLASSIFICATION

6. PURE SUBSTANCE • sample of matter, either a single element or a single compound, that has definite chemical and physical properties

7. ELEMENTS • substance that cannot be separated or broken down into simpler substances by chemical means • Can be found as solids, liquids, or gases • Found on periodic table • Made of identical atoms • Pure substances • Represented by abbreviations/symbols consisting of one or two letters • Examples: H, N, S, O, P, Au, Hg, Na

8. COMPOUNDS • substance made of atoms of two or more different elements that are chemically combined • they always combine in same proportions. • Can be broken down through chemical means • Pure substances • Every compound is different from the elements it contains.

9. CHEMICAL FORMULAS • combo of chemical symbols and numbers to represent a substance. • Subscript • represents number of atoms • located lower right of chemical symbol • Examples: NO2, NH3, NaCl, C6H6O6

10. MIXTURES • two or more substances that are NOT chemically combined. • Variable composition • Each components retains their characteristic properties • May be separated into pure substances by physical methods • classified by how thoroughly the substances mix. • Two types

11. HOMOGENEOUS • may be pure substances or solutions • Pure substances may be compounds or elements • substances are evenly distributed “well mixed” • Look/have the same composition throughout • Particles are small and not easily recognized • can be separated by physical means (dissolution, centrifuge, gravimetric filtering, etc.). • Examples: milk, yogurt

12. HETEROGENEOUS • made of more than one kind of substance. • substances aren’t mixed uniformly “least mixed” • different particles in mixtures are large enough to be seen • easily separated by physical means (ie. density, polarity, metallic properties).

13. MIXTURE PURE SUBSTANCE yes no yes no Is the composition uniform? Can it be decomposed by chemical means? Matter Flowchart MATTER yes no Can it be separated by physical means? Homogeneous Mixture (solution) Heterogeneous Mixture Compound Element

14. PROPERTIES OF MATTER

15. PHYSICAL PROPERTIES • characteristic of matter that can be directly observed without changing identity of substance • you can see, such as color, shape, hardness, and texture • easily measured

16. MASS • amount of matter in an object • SI Unit: G r a m s (g)

17. WEIGHT • measure of pull of gravity on an object • SI Unit: N e w t o n s (N) • Formula: W = m g

18. VOLUME • amount of space taken up by an object . • SI Unit: L i t e r s (L).

19. DENSITY • mass per unit of volume • Formula: Density = mass/volume

20. M V M D = D V

21. M D V Density 1. An object has a volume of 825 cm3 and a density of 13.6 g/cm3. Find its mass. GIVEN: V = 825 cm3 D = 13.6 g/cm3 M = ? WORK: M = DV M = (13.6 g/cm3)(825cm3) M = 11,220 g

22. WORK: V = M D V = 25 g 0.87 g/mL M D V Density 2. A liquid has a density of 0.87 g/mL. What volume is occupied by 25 g of the liquid? GIVEN: D = 0.87 g/mL V = ? M = 25 g V = 28.7 mL

23. WORK: D = M V D = 620 g 753 cm3 M D V Density 3. You have a sample with a mass of 620 g & a volume of 753 cm3. Find density. GIVEN: M = 620 g V = 753 cm3 D = ? D = 0.82 g/cm3

24. Let’s Try Some More Density Problems

25. WORK: D = M V D = 500 g 25 cm3 M D V Density 1. If the mass of a rock is 500 g and its volume is 25 cm3, what is its density? GIVEN: M = 500 g V = 25 cm3 D = ? D = 20 g/cm3

26. M D V Density 2. If the density of a liquid is 1.2 g/ml and its volume is 10 ml, what is its mass? GIVEN: V = 10 ml D = 1.2 g/ml M = ? WORK: M = DV M = (1.2 g/ml)(10 ml) M = 12 g

27. WORK: V = M D V = 80 kg 1.6 kg/l M D V Density 3. If Bob’s mass is 80 kg and his density is 1.6 kg/l, what is his volume? GIVEN: D = 1.6 kg/l V = ? M = 80 kg V = 50 mL

28. BOILING POINT • temperature and pressure at which a liquid becomes a gas • liquid is still the same substance

29. MELTING POINT • temperature and pressure at which a solid becomes a liquid

30. VISCOSITY • resistance (difficulty) of a liquid to flow easily • How “thick” or “thin” a liquid is • high viscosity: Honey, motor oil, corn syrup • low viscosity: water, milk, soda

31. CONDUCTIVITY • ability to conduct heat or an electric current • High conductivity: metals (copper, aluminum…) • Low conductivity: wood, rubber, plastic

32. MALLEABILE • Ability to be hammered into a thin sheet.

33. DUCTILE • Ability to be drawn into a thin wire

34. CHEMICAL PROPERTIES • describes how a substance can change or react to form new substances.

35. FLAMMABILITY • ability of a substance to react in presence of oxygen and burn when exposed to a flame

36. REACTIVITY • how easily a chemical reacts with other substances.

37. CHANGES OF MATTER

38. LAW OF CONSERVATION OF MATTER • matter cannot be created nor destroyed. • It is just converted from one form to another

39. STATES OF MATTER

40. SOLIDS • Have a definite shape • Have a definite volume • Least amount of movement of particles. • Particles arranged in a regular pattern and tightly packed.

41. LIQUIDS • Have an indefinite shape • Have a definite volume • will assume the shape of its container. • Particles are close together but move about freely.

42. GASES • Have an indefinite shape • Have an indefinite volume • Can fill any container

43. PLASMA • most common form of matter. • makes up over 99% of the visible universe • dangerous, very high energy (found in stars)

44. ENDOTHERMIC/EXOTHERMIC REACTIONS • Endothermic = heat energy is absorbed, cools surroundings • Exothermic = heat energy is released, warms surroundings

45. PHYSICAL CHANGES • substance changes state but does not change its chemical composition. • Type of matter remains the same • example: water freezing into ice, cutting a piece of wood into smaller pieces

46. DISSOLVING • to disintegrate, break up, or disperse • When a substance dissolves, the molecules of the substance do not change. Ways of Dissolving: • solid in a liquid, • gas in a liquid • liquid in a liquid

47. MELTING • to become altered from a solid to a liquid state usually by heat • endothermic • ice cubes melting

48. BOILING • Change of a substance from a liquid to a gas. • endothermic two types: • Boiling: • rapid • gas bubbles are produced throughout • Evaporation • slow • occurs at the surface • is a cooling process • ocean water evaporates to form clouds & rain droplets

49. CONDENSATION • Change of a gas to a liquid. • exothermic • water vapor turns into dew

50. SUBLIMATION • Changing directly from solid to gas or gas to solid skipping the liquid state. • endothermic • formation of frost/snow & dry ice