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Date
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General Chemistry – Unit 4 Review
Important:
To prepare adequately for the Unit 4 Test, you should not only do this review, but you
should read and fill in notes on the Unit 4 Objectives and you should review all materials
from class including notes, worksheets, labs and quizzes. Thorough preparation also
includes redoing problems, especially those with which you initially struggled.
Fill in the blanks in the table with the words from the following list: heterogeneous, liquid,
matter, element, mixture, homogeneous, solid, compound, gas and pure substance.
______
Particles are independent,
widely separated, with no
attractive forces between them.
They fill the volume of the
container.
Particles constantly make and
break temporary attractions
between each other. Particles
can slip past one another easily.
They take the shape of the
container.
These have fixed compositions, one set of
intrinsic physical properties (density, mp,
bp). and can be separated only by chemical
means
These cannot be broken down into
simpler substances by physical or
chemical means. The smallest
particle of this is called an atom.
These have variable composition. Their
physical properties vary depending on the
composition. They can be separated by
physical means.
These are made of elements in fixed
mass ratios. They can be broken
down into simper substances by
chemical means.
Exists in one phase only and has
uniform properties throughout the
sample.
Modeling Chemistry
Strong attractions between
particles lock them into a
fixed arrangement.
1
May exist in more than one phase
and have variable properties in
different parts of the sample
U4 gen rev
For each of the diagrams below, describe the contents of each cell using the terms atoms,
molecules, elements, compound, mixture, solid, liquid and gas
1.
2.
3.
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U4 gen rev
4.
6. Identify the separation techniques pictured below. Which technique would be useful to
separate a mixture of sand and salt? Of salt and water?
7. Below left is a 2-D array that represents an ionic lattice. At right is a 2-D array that
represents a molecular solid. In what ways are they similar? In what ways are they
different?
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U4 gen rev
8. Recall your representations of the atoms in the Sticky Tape activity. Below is a pair of
tapes before they have been pulled apart. Explain why they would not exert a force
(either attractive or repulsive) on one another.
9. Below are groups of the inner cores of the atoms of the tapes after they have been
pulled apart. Sketch in the mobile negative charges to show how the top tape becomes
(+) and the bottom becomes (-).
10. Below is a group of the inner cores of a piece of metal foil. Sketch in where you would
expect to find the mobile negative charges if a top (+) tape were brought to the left of
the foil. Explain your diagram.
Modeling Chemistry
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U4 gen rev
11. Explain why ionic compounds can conduct electric current as liquids but molecular
compounds cannot. Use complete sentences. You may use particle diagrams to aid your
explanation.
12. Describe in terms of physical properties how molecular compounds differ from ionic
compounds. List 4 properties/characteristics for each.
13. List some physical properties and chemical properties of hydrogen gas based on the
electrolysis of water demo.
14. Is electrolysis of water a physical or chemical change? Explain why or why not.
Include particle diagrams to aide your explanation.
15. Identify the following compounds as ionic or molecular.
a. CO2 _________________________
b. NaCl ________________________
c. C2H4 ________________________
d. HCl _________________________
16. Identify the bond type in each of the compounds a-d in #15 above.
a. ______________________________
b. ______________________________
c. ______________________________
d. ______________________________
17. Identify the following as physical or chemical changes:
a. cutting paper - _____________________
b. boiling water - _____________________
c. burning propane - __________________
d. iron rusting - ______________________
e. burning steel wool- _________________
f. dissolving salt in water- ____________
Modeling Chemistry
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U4 gen rev