1. Heterogeneous Mixtures
Matter:
Classification, Properties, and The Law of Conservation of Mass
Matter
Pure Substances
Elements
Compounds
Mixtures
Homogeneous Mixtures
Heterogeneous Mixtures

2. What is Matter? Matter: Anything that takes up space and has mass
Can exist in different phases

3. Classification of Matter
All matter falls into 2 categories:
Pure Substances OR
Mixtures

4. Pure Substances
CANNOT be broken down into simpler components by simple physical methods
2 Subtypes:
Elements
Compounds

5. Mixtures
CAN be separated into simpler components by simple physical methods
2 Subtypes:
Homogeneous Mixtures
Heterogeneous Mixtures

7. Elements vs. Compounds Elements - the simplest form of matter
cannot be separated into simpler substances by chemical or physical means
the building blocks for all other substances.
Compounds - substances that can be separated into simpler substances by chemical means

8. Elements vs. Compounds
atoms of an element (only one type of atom) molecules of a compound (more than one type of atom)

9. Elements vs. Compounds molecules of an element (only one type of atom)
mixture of 2 different elements and a compound

10. Mixtures vs. Compounds
Mixtures are formed by physically combining 2 or more pure substances. The properties of the starting materials are unchanged.
Compounds are formed chemically, and involve bonds. The properties of the compound are different from those of the starting materials.

11. Mixtures vs. Compounds

12. Composition of matter Pure substances have chemical formulas
The composition of a pure substance is fixed. It does not vary.
Pure substances have chemical formulas
The composition of a mixture varies. It is NOT fixed.
Mixtures do NOT have chemical formulas

13. Chemical Formulas
Indicate how many atoms of each type are in a molecule
For an element it is the element symbol: Hg C O2
For a compound each element must be listed, and a subscript is used to tell how many atoms of that element
NH3 CO2 H2O2

14. Learning Check CCl4 C2H4O2 FeClO4
How many elements are in each of the following chemical formulas?
CCl4 C2H4O2 FeClO4
NI3 NiSO4 C2H6SO2
How many atoms are in each of the chemical formulas above?

15. Solutions Homogeneous mixtures typically APPEAR to be pure substances.
They exist in a single phase that is uniform.
Homogeneous mixtures are sometimes called solutions.

16. Common Solutions
These substances appear to be pure substances, but are actually mixtures.

17. Heterogeneous vs. homogeneous mixtures

18. Learning Check Limestone (CaCO3) Air Bronze Copper Sugar + water
Material
Pure Substance or Mixture
Element, Compound, Homogeneous, Heterogeneous
Limestone (CaCO3)
Air
Bronze
Copper
Sugar + water
Concrete
Pure Water
Caffeine (C8H10N4O2)

19. Properties of Matter Matter has properties:
color, odor, density, phase, hardness, reactivity…
These properties distinguish one substance from another
Properties of Matter fall into 2 subcategories:
Physical Properties
Chemical Properties

20. Physical Properties
Characteristics that can be observed (or measured) without changing the sample’s composition
Examples: boiling point, melting point, color, odor, malleability, density, phase, luster, length, mass
Can depend on the amount of substance present – extensive properties
Can be independent of the amount present – intensive properties

21. Chemical Properties
The ability of a substance to combine with or change into a different substance
Examples: reactivity with O2, reactivity with H2O, reactivity with light, flammability, toxicity, chemical stability
To observe a chemical property, the substance must be changed

22. Learning Check
Identify the following as physical or chemical properties: ability of wood to burn hardness of diamond shape of a leaf mass of a beaker ability of fireworks to explode

23. Changes in Matter Matter often undergoes changes
There are 2 types of changes:
Physical Changes
Chemical Changes

24. Physical Changes
Changes that alter the physical properties of a substance without altering the composition of the substance
NO new substances are formed
Examples: cutting hair, crumpling paper, freezing water, bend a wire, melt gold, mixing raisins with nuts, dissolving salt in water

25. Chemical Changes
Changes that alter the composition of a substance and result in the formation of new substances
Examples: burning paper, cooking an egg, a banana rotting, a nail rusting, fireworks exploding

26. Chemical Changes
Evidence of chemical changes: color change *** (can be misleading) change in odor change in temperature formation of gas bubbles (NOT boiling) formation of a precipitate (solid) light or sound produced difficult/impossible to reverse (return cake ingredients to initial state)

27. Learning Check
Identify the following as chemical or physical changes: crush a can break a glass digest food light a match dissolve alka selzer in water add food coloring to water add lemon juice to milk

28. Separation of Mixtures
Mixtures are formed by a physical process, and can be separated by a physical process

29. Separation methods There are many methods of separating mixtures
Different methods use different properties of the components in the mixture
Some common methods are:
crystallization, filtration, distillation, centrifugation, chromatography, hand separation, magnetic separation

30. Separation Methods Some properties used to separate mixtures are:
Size of components
Phase of components
Use of magnetism
Miscibility of components
Boiling point of components
Adsorption of components

31. Filtration
Solids are removed from liquids via filtration

32. Crystallization
Crystals are produced from a solution of a solvent and a substance in liquid form. The crystals can then be separated by filtration.

33. Distillation
A solid dissolved in a liquid or 2 soluble liquids are separated by distillation

34. Fractional Distillation
Separates miscible liquids by boiling point

35. Centrifugation
Particles in a suspension sediment (settle out) at different rates based on their density and size. Larger and denser particles sediment faster.

36. Chromatography
Mixtures are separated based on how the components interact with the mobile and stationary phases.

37. Using miscibility
Liquids that are not miscible (do not completely mix) can be separated using a separating funnel.

38. Separation using magnetism
Allows separation of magnetic metals from nonmagnetic materials. Example: iron filings and sand

39. Learning Check How would you separate the following mixtures:
water and salt
water and chopped nuts
iron filings and sand
sand and rice

40. Learning Check How would you separate the following mixtures:
water and salt distillation or evaporation
water and chopped nuts filtration
iron filings and sand magnetism
sand and rice hand pick or sieve

41. Learning Check Some mixtures are more complicated
Multiple steps are required
How would you separate a mixture of salt, sand, water, and iron filings?

42. Learning Check
How would you separate a mixture of salt, sand, water, and iron filings?
Filter the mixture to remove sand and iron filings from salt and water
Use a magnet to remove iron filings from sand
Use distillation (or evaporation) to remove salt from water

43. Law of Conservation of Mass
Matter is neither created nor destroyed during a chemical reaction.
chemical changes occur, but the total mass is unchanged
the form of the matter changes, not the mass
Significance:
total mass reactants = total mass products

44. Law of Conservation of Mass
50 grams of sodium (Na) reacts with chlorine (Cl2) to form 126 grams of salt (NaCl). How many grams of chlorine (Cl2) reacted? total mass of reactants = 50 g + ? g Cl2 total mass of products = 126 g mass of reactants = mass of products 50 g + mass of Cl2 = 126 g mass of reacted Cl2 = 76 g

45. Learning Check
178.8 g of water (H2O) is separated into hydrogen gas (H2) and oxygen gas (O2). The hydrogen gas has a mass of 20.0 g. What is the mass of the oxygen gas produced?

46. Learning Check
178.8 g of water (H2O) is separated into hydrogen gas (H2) and oxygen gas (O2). The hydrogen gas has a mass of 20.0 g. What is the mass of the oxygen gas produced? mass of reactants = mass of products g = 20.0 g + mass of O g – 20.0 g = mass of O2 mass of O2 = g

47. Law of Conservation of Mass
No atoms are gained or lost in a chemical reaction This can be expressed visually:

48. Law of definite proportions
A compound is always composed of the same elements in the same proportion by mass.
Uniform composition - allows us to write a chemical formula for a compound
CH4 = methane C2H6 = ethane
one C atom and 4 H atoms in every molecule of CH4
two C atoms and 6 H atoms in every molecule of C2H6

49. Law of definite proportions
A compound is always composed of the same elements in the same proportion by mass.
CH4 = methane
every compound has a molecular mass (the sum of the masses of all its atoms)
C = amu H = amu x 4
CH4 = = amu amu
(since 4 H atoms)

50. Law of definite proportions
A compound is always composed of the SAME elements in the SAME proportion by mass.
the proportions of the different elements in a compound are expressed by % by mass
every atom of a compound has the same % by mass (the same mass proportions of each element)

51. Percent by mass
Every compound has a fixed composition which is expressed by a chemical formula.
The relative amounts of each element in the compound can be expressed as a percent by mass of the total mass of the compound.

52. Percent by mass
Compound: CH4 mass of CH4 sample = g mass of C in sample = g % by mass C = x 100 = 74.9%

53. Learning Check
Compound: NH3 mass of NH3 sample = 20.4 g mass of N in sample = g mass of H in sample = ? % by mass of H in sample = ?

54. Learning Check Compound: NH3 mass of NH3 sample = 20.4 g
mass of N in sample = g
mass of H in sample = 3.63 g g (20.4 g g)
% by mass of H in sample = x 100
= 17.8%

55. Law of multiple proportions
Many compounds are formed from the same set of elements, but in different ratios. CO CO2 H2O H2O2 NO2 N2O N2O4

56. Law of multiple proportions
If two elements can combine to form more than one compound, the ratios of the masses of one element that combines with a fixed mass of the other element will be small whole numbers. CO CO2 1 C : 1 O 1 C : 2 O

57. Law of multiple proportions
The mass of a C atom is constant
The mass of an O atom is constant
C = g/mol O = g/mol
12 parts C:16 parts O for CO
12 parts C:32 parts O for CO2

58. Law of multiple proportions
If two elements can combine to form more than one compound, the ratios of the masses of one element that combines with a fixed mass of the other element will be small whole numbers. Since both compounds have one C atom, consider the mass of C to be fixed. 12 parts C:16 parts O for CO 12 parts C:32 parts O for CO2

59. Law of multiple proportions
If two elements can combine to form more than one compound, the ratios of the masses of one element that combines with a fixed mass of the other element will be small whole numbers. CO CO2 mass of C is g (approximate as 12) mass of O is g (approximate as 16) For CO the ratio is 12:16 For CO2 the ratio is 12:32 The ratio of O in CO to O in CO2 equals to 16:32, or 1:2.

60. Law of multiple proportions
Significance: All chemical formulas for compounds formed by combining the same elements in different proportions will involve whole numbers. NO2 N2O N2O4 Never N1.5O2.1