Chemistry Unit Test 2015 Sci 7 practice test
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
1. When trying to identify 3 unknown clear liquids, Joe found that they all
smelled alike and had boiling points that were very similar. What should he
conclude?
A. All substances have the same boiling point.
B They are all the same substance.
C. All substances have different boiling points.
D. There is not enough information to make a conclusion.
Answer is D you need a number of physical properties to
identify a substance.
2. Sugar water is an example of
A. a set of atoms.
B. an element.
C. a mixture.
D. a compound.
Answer is C a mixture it is actually a solution ( an extremely
well mixed mixture (homogenous). Each sample of a
solution is going to give the same amount of solute and
solvent. Other mixtures will not.
3. A chemical bond is formed when
A. there is a change in density.
B. gravity increases.
C. protons are shared between atoms.
D. electrons are shared between atoms.
The answer is D which describes a covalent bond. However
bonding is always associated with the valence electrons
(electrons in the outer shell).
4.
Particles of a gas
A. are tightly packed together and vibrate.
B. take volume and the shape of the container.
C. have definite shape.
D. are free to flow throughout a container but remain in close
contact with one another. The answer is B, A describes a
solid, C also a solid and D a liquid.
5. What is condensation?
A. a gas becoming a liquid
B. a liquid becoming a solid
C. a gas becoming a solid
D. a liquid becoming a gas
The answer is A.
6. What information does an element’s location in the periodic table tell you?
A. its properties.
B. its chemical name.
C. its chemical symbol.
D. when it was discovered.
The answer is A. Stress that this is the #1 question in
chemistry.
7. What determines how an atom interacts with another atom?
A. number of protons.
B. number of neutrons.
C. atomic mass.
D. number of valence electrons.
The answer is D
8. Where are transition metals located on the periodic table?
A. to the left of the zigzag line
B. to the right of the zigzag line
C. in Groups 3-12
D. in Groups 1 and 2
The answer is C
9. The elements that are highly reactive are
A. the carbon family.
B. the metals.
C. the halogens.
D. the noble gases.
The answer is C halogens, although alkali metals and
alkaline Earth metals are highly reactive not all the metals
are very reactive. Halogens(group 17) are the most reactive
nonmetals.
10. In chemical reactions, what does the principle of conservation of mass
mean?
A. The total mass of the reactants is greater than the total mass of
the products.
B. The same number of atoms of each element are in the reactants
as are in the products.
C. The total mass of the reactants is less than the total mass of the
products.
D. Matter is not changed.
The answer is B. What goes in must come out. In a
chemical reaction matter is always changed so D is
incorrect. However it is never created or destroyed.
11. Which of the following is a balanced chemical equation?
A. H2O2 --> H2O + O2
C. 2SO2 + O2 + 2H2O --> 2H2SO4
B. Fe2O3 + 3 C --> 4 Fe + 3 CO2
D. 2 Mg + HCl --> MgCl2 + H2
Have a student count the atoms on the chalk board for their fellow
students. The answer is C.
12. In an equation, numbers often appear in front of a chemical formula
(coefficient: 6 H2O). These numbers tell you the
A. number of atoms in a molecule.
B. number of elements in a reaction.
C. number of molecules.
D. number of reactants in an equation.
The answer is C
13. When an atom gains an electron, it becomes a
A. positive ion.
B. negative ion.
C. neutral ion.
D. neutral atom.
The ion will then have 1 more negative charge than positive
charge so it will be a negative ion.B
14. An ionic bond is formed when
A. one atom gains protons and the other loses them.
B. one atom gains neutrons and the other loses them.
C. one atom gains electrons and the other loses them.
D. both atoms lose electrons.
In a chemical reaction protons and neutrons are never lost
or gained only electrons C
15. Nonmetals react to each other by sharing electrons. This bond is called
A. an ionic bond.
B. a covalent bond.
C. a physical bond.
D. a crystal bond.
The answer is B
16. How many electrons would you draw for a Lewis model of Beryllium (Be)?
A. 2
C. 6
B. 8
D. 16
Beryllium is a Alkaline Earth metal and has 2 valence electrons. The Lewis
model is the element symbol and the valence electrons.
Short Answer
Use the diagram to answer each question.
Densities of Common Substances
Substance
g/mL
Gasoline
0.7
Water
1.0
Lead
11.3
Silver
10.5
17. If silver is placed carefully into liquid water, will it sink or float? Explain why
using data from the table.
The answer is Silver will sink because it has higher density than water.
Stresstothe students they should use the vocabulary in the question
in the answer and not use mass but density.
~~~~~~~~~~~~~~~~~~~~~~~
Use the diagram to answer each question.
18. Which diagram represents a gas? State A. B or C.
A
answer is C lower density more energy. B is liquid atoms in contact
with each other but free to move around. A is solid tightly packed and
lower movement shown by smaller action lines.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Use the diagram to answer each question.
19. What is the atomic mass of aluminum? 27 the sum of protons and
neutrons
20. How many neutrons are in an atom of phosphorus? The answer is 16,
the atomic number subtracted from the atomic mass. You don’t need
a periodic table to answer these questions. All the information you
need is availale in the table above.
~~~~~~~~~~~~~~~~~~~~~~~~~~
21. When the marshmallow was heated, the outside of the marshmallow
became a light brown and a sweet odor was detected.
Does this observation refer to a physical change or a chemical change?
Explain.
The answer is a chemical change because new substances are
formed. The brown is carbonize sugar and the sweet odor is a byproduct of the combustion. Remind student to review the
physical/chemical change activity sheet I gave them (the sheet with
the candle and the marshmallows.
22. The products formed from a reaction include LiCl and Cu2O.
a) What elements were in the reactants?
Caution student to answer the question and list elements. They are
Li (Lithium), Cl (Chlorine), Cu( copper) and O (oxygen)
b) How do you know? Because of the law of conservation of mass or
matter.
23. Identify the reactant(s) and product(s) of the following reaction.
Zn
+
2 HCl
--->
ZnCl2
+
H2
Zinc + Hydrochloric Acid ---> zinc chloride and hydrogen
Reactants Zn, HCl products ZnCl2 and H2
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Short Answer
24. a. How did the following ion form?
Cu +3
This ion was formed by giving up or donating 3 electrons to another element.
25. What would the chemical formula of a compound be if Calcium (Ca)
reacted with Chlorine(Cl)?
CaCl2 Calcium is an alkaline Earth metal and has 2 valence electrons.
Chlorine is a halogen and has 7 valence electrons. A calcium atom will donate
its 2 valence electrons (one to each of 2 chlorine atoms) and fill like it has a full
shell of 8 like Argon (Ar). Each Chlorine will now have 8 valence electrons and
feel like it has a full shell like Argon (Ar).