Fall Semester Final Exam - Chemistry Review Answers
1.
What is an element? Substance made of only one type of atom, which cannot be broken down into
any simpler substances by chemical or physical means.
2.
What is an atom? Smallest particle of an element that still has the properties of that element.
3.
What is a compound? A substance made of two or more elements. Compounds have different
properties from the elements from which they are made.
4.
What is a molecule? A particle with two or more atoms. Molecules can be made of atoms from the
same element or from different elements.
5.
6.
7.
Label each of the following diagrams, as one of the following: nucleus, atom, element, or molecule.
_______________
_______________
Element
Compound
Atom
Nucleus
Describe the 3 types of sub-atomic particles, including their charge, location and mass.
Name
Charge
Location
Mass (in amu’s)
Proton
Positive
Nucleus
1 AMU
Neutron
Zero (Neutral)
Nucleus
1 AMU
Electron
Negative
Cloud
0.005 AMU
Label the three sub-atomic particles in the
diagram to the right, and label the nucleus
Electron
Cloud
and electron cloud.
Proton
Neutron
Nucleus
Electron
8.
What is an atomic number? What does it tell about an element? The atomic number is the number of
protons in an atom. All atoms of the same element have the same number of protons.
9.
Define “atomic mass” as used and listed on the periodic table. What does it tell about an element?
The average number of protons plus neutrons in the nucleus of an atom. For any one element, the
number of protons does not change, but the number of neutrons can change with different isotopes.
10.
Describe the properties of metals. Shiny, conducts heat and electricity well, not brittle (malleable
and ductile).
11.
Describe the properties of non-metals. Brittle, not conductive, not shiny.
12.
Describe the properties of metalloids. Blend of properties of metals and non-metals: brittle but shiny,
with some electrical conductivity.
13.
Define “malleable.” Ability to be compressed or beat into a thinner shape.
14.
Define “ductile.” Ability to be stretched into a wire.
15.
Which of the above properties allows aluminum to be squeezed into thin foil? Malleable.
16.
In the simplified periodic table to the right,
identify each numbered area as containing
metals, non-metals or metalloids. (p.62-63)
17.
1. Metals
2. Metals
3. Metalloids
4. Non-metals
What is a group or family on the periodic table? (p.61) An up-down vertical column. What does the
group or family number indicate about the atomic structure of an atom for any element within that
group? The number of valence electrons, and thus the chemical properties.
18.
What is true about the properties of all elements within a group or family? They all have similar
chemical properties.
19.
Give an example of three elements that all have the same chemical properties. Sodium, Potassium and
Lithium, all in group 1.
20.
What is a period on the periodic table? A left to right horizontal row.
What does the period number indicate about the atomic structure of an atom for any element with
that period? The number of energy levels or electron orbits.
21.
How can the number of protons (and electrons) be determined for a particular element, using the
periodic table? From the atomic number, for a neutrally charged atom.
22.
What are valence electrons? The electrons in the outer most energy level or orbit of an atom.
23.
How can the number of valence electrons for elements in groups 1-2 & 13-18 be determined?
From the one’s digit of the group number. For example, elements in group 1 have one valence
electron, and elements in group 13 have three valance electrons. The only exception is helium,
which only has two valence electrons, even though it is in group 18.
24.
How can the number of electrons shells (also called energy levels or orbitals) for an element be
determined? From the period number.
25.
What groups or families have the most reactive elements? Why? Groups 1 and 17, because they only
need to lose or gain one valence electron to react.
26.
The elements in group 17, including fluorine, bromine, chlorine and iodine, are called the halogens.
Describe the reactivity of the halogens, and why they have this reactivity. The halogens are very
reactive, because they each have seven valence electrons, and only need to gain one valence
electron to react.
27.
Which of the following elements is most reactive: carbon, sodium, magnesium, boron? Most reactive
is sodium, followed by magnesium, boron and then carbon. Why? Sodium only has one valence
electron to lose in order to react. Magnesium has two valance electrons, boron has three, and
carbon has four. The fewer the valance electrons that have to be either gained or lost to reach a
complete valance electron orbit, the more reactive the element.
28.
What group or family has the least reactive elements? Why? Group 18, because all of their valance
electron orbits are full, and they have no need to react to become more stable.
29.
Which group contains the “noble gases”? Group 18. Why are they called noble gases? Because they
do not react with any other elements or each other.
30.
What is a physical change? Give three examples. A physical change does not change the chemical
formula for a substance; it only changes the form, size or shape, such as cutting paper or wood, or
boiling water.
31.
What is a chemical change? Give three examples. A chemical change or chemical reaction occurs
when a new substance is made from the combination of other substances. Examples include burning
wood, cooking food and rusting metal.
32.
Give five different kinds of evidence that would suggest that a chemical change (reaction) has taken
place. Creation of new substance, temperature change, color change, creation of solid precipitate
from two clear solutions, creation of a gas, creation of light.
33.
Describe two physical changes and two chemical changes that occur in the human digestive system.
Physical: Chewing food in the mouth, and mixing food in the stomach.
Chemical: Mixing saliva in the mouth, and other enzymes in the stomach and intestines.
34.
Describe the direction of energy flow in a food web or energy pyramid. Energy flows up from the
plants (producers) to the first level consumers to second-level consumers to third-level consumers.
35.
For each of the following elements, list the symbol (S), atomic number (A.N.), atomic mass (A.M.),
number of protons (P), neutrons (N) and electrons (E), number of electron shells (E.S.) and number of
valence electrons (V.E.).(7G: p.62)
36.
Element
S
A.N.
A.M.
P
N
E
E.S.
V.E.
Sodium
Na
11
23 (22.99)
11
12
11
3
1
Hydrogen
H
1
1 (1.008)
1
0
1
1
1
Oxygen
O
8
16 (15.99)
8
8
8
2
6
Carbon
C
6
12 (12.01)
6
6
6
2
4
How many atoms are in one molecule of C6H12O6? 24
How many atoms are there for each element? C:6 H: 12 O: 6
37.
What is the law of conservation of mass? In a chemical reaction, matter is neither created nor
destroyed.
38.
In a balanced chemical reaction, the mass of the reactants equals the mass of the products. In other
words, there are the same number and kind of atoms on both sides of the chemical equation.
39.
In the chemical equation 6H2O + 6CO2 C6H12O6 + 6O2, what are the reactants? Water (H2O) and
carbon dioxide (CO2). What are the products? Sugar (C6H12O6) and oxygen (O2). How many total
atoms are involved in this reaction? 36 (Hint: Only count one side of the equation)
40.
Is each of the following chemical equations balanced? (Hint: An equation must be balanced because of
the law of conservation of mass.)
2H2O 2H2 + O2
Balanced
6HCl + 2Al 2AlCl3 + 3H2 Balanced
41.
Al + CuCl2 AlCl3 + Cu
Unbalanced
4Fe + 3O2 2Fe2O3
Balanced
2HCl + NaOH 4NaCl + H2O Unbalanced
What is the formula for density? Density = Mass / Volume
If a rock has a mass of 90 g and a volume of 30 cm3, what is the density of the rock, in g/cm3?
3.0 g / cm3
127 possible
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