CHEMISTRY
Unit 2 Review Guide
1. Define the following terms:
a) Element
substance that cannot be broken down any further
b) Compound
substance that can be broken into simpler substances, like elements
c) Mixture
mixture of elements, or compounds/elements, or compounds physically combined
d) Homogeneous mixture (solution)
a mixture that you CANNOT see the parts (like alcohol & water)
e) Heterogeneous mixture
a mixture that you CAN see the parts (like oil and water)
f) Substance
either an element or compound, uniform & unchanging composition
g) Mass
a measure of how matter is in an object
h) Qualitative Data
describing the qualities of data (like color, shape, etc.) NO NUMBERS
i) Quantitative Data
describing data in terms of numbers (the mass of an object)
2. Provide an example of a heterogeneous and homogeneous mixture.
Heterogenous: M&M's, Homogenous: soda
3. Provide an example of a quantitative and qualitative data.
Quantitative: the apple weighed 10 grams, Qualitative: the apple is red
4. Describe characteristics of a chemical and physical change. Provide an example for
physical and chemical change. physical: observed without changing the chemical composition (crushing)
chemical: cannot be observed without changing the chemical composition (rusting, cooking, burning)
5. What is the Law of conservation of matter?
matter/mass is neither created nor destroyed
6. Describe each of the separation techniques
a. Filtration
for heterogenous mixtures (i.e. sand/water)
b. Crystallization/Evaporation
for homogenous mixtures that have had a solid dissolved in it (salt/water)
c. Chromatography
for separating ink
d. Distillation
uses differences in boiling points to separate homogenous mixtures of 2 liquids
7. What is the Law of definite proportions?
% by mass = mass of ELEMENT / mass of COMPOUND x100
B
A
8. A 15 g sample of Iron combines with oxygen to form 35.40 g of Iron and Oxygen called Iron C
II oxide. How many grams of oxygen are used in the reaction?
(Hint: Law of conservation of mass)
Make your chemical
A + B → C; B is Oxygen
reactions simple by
15g + B → 35.40g
substituting
compounds &
B = 35.40-15 = 20.4 = 20g
elements with simple
letters like A, B, etc.
9. If 5.5 g of A reacts with 15.5 g of B to produce AB, what is the % by mass of A in the
compound? What is the % by mass of B in the compound?
A + B → AB
Use the law of conservation of
5.5g + 15.5g → AB; AB = 21.0 g
mass to first find the mass of AB
produced. Then set up % by
%A = 5.5/21.0 * 100 = 26%
mass problems for each element
in that compound.
%B = 15.5/21.0 * 100 = 74%
10. When mercury oxide is heated, it decomposes into mercury and oxygen. If 38.5 g of mercury
oxide decomposes, producing 5.0 g of oxygen, what is the % by mass of oxygen in mercury
oxide?
Decomposes = breaks apart
Trick question. You don't need to
%O: = 5.0/38.5 * 100 = 13%
find the mass of mercury b/c they
give you mass of Oxygen and
only ask for %O.
11. The chemical formula for Potassium Nitrate is KNO3. A 101 g sample contains 39 g of
Potassium (K), 48 g of oxygen (O) and 14 g of Nitrogen (N). What is the mass percentage of
each element in Potassium Nitrate?
Check:
%K = 39/101 * 100 = 39%
39+48+14 = 101% b/c of rounding
%O = 48/101 * 100 = 48%
%N = 14/101 * 100 = 14%
C
B
A
12. 20 grams of MgCO3 on heating produces 5 g CO2 and Xg MgO. What is the mass
of MgO produced in this reaction?
A→B+C
20g → 5g + Xg
X = 15g because 20-5 is 15.
13. Given:
1. Sodium chloride and water
2. Ethanol and water
a. Name the technique that you would use to separate and identify the components of the
solution.
b. Provide specific details of the method used.
c. State the advantage of the method you choose.
1. NaCl and H2O
a. Crystallization
b. Evaporating the water would result in the salt re-crystallizing
c. A fairly simple process in that it involves little effort.
2. Ethanol and water
a. Distillation
b. By using the differences in their boiling points, alcohol would boil first, leaving water
behind.
c. Fairly easy to do, and very accurate at separating a homogenous mixture.
Chemistry I Worksheet
Classification of Matter and Changes
NAME
INSTRUCTIONS: Write E in the blank if the material is heterogeneous or O if it is homogeneous.
1. Wood
E
6. Dirt
2. Freshly-brewed black coffee
O
7. Sausage-and-mushroom pizza
E
3. Water
O
8. Air
O
4. Lucky Charms®
E
9. Milk
E (microscope)
5. Salt
10. Gold
Compound
E
Element
INSTRUCTIONS: Classify each of the following as an element [E], a compound [C], or a mixture [M].
11. Gold
E
16. Air
M
12. Water
C
17. Carbon dioxide
C
13. Seawater
M
18. Silver
E
14. Sugar
C
19. Ice
C
15. A chocolate sundae
M
20. A Big Mac®
M
INSTRUCTIONS: Classify each of the following properties of matter as physical [P] or chemical [C].
21. Color
P
26. Reacts violently with chlorine
C
22. Density
P
27. Good conductor of heat
P
23. Burns easily (flammable)
C
28. Dissolves readily in water
P
24. Not affected by acids
C
29. Melts at 145 C
P
25. Boils at 450 C
P
30. Malleable
P
INSTRUCTIONS: Classify each of the following changes in matter as physical [P] or chemical [C].
31. Grinding chalk into powder
P
36. Burning gasoline
C
32. Dissolving salt in water
P
37. Hammering gold into foil
P
33. Dissolving zinc in acid
C
38. Melting ice
P
34. Tearing a piece of paper
P
39. Digesting food
C
35. Stretching copper into wire
P
40. Making hydrogen from water
C
INSTRUCTIONS: Classify each of the following as an intensive property [I] or an extensive property [E].
41. Mass
E
46. Color
I
42. Density
I
47. Volume
E
43. Melting point
I
48. Length
E