AnswersDAEP-Science 7 A20 Day TermUnit Test

Unit Test — Unit test Answers

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1
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When an atom that has no charge loses two electrons, it becomes a

A
positive ion.
B
negative ion.
C
positive isotope.
D
negative isotope.
2
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"Na2SO3” represents sodium sulfite.What does the 4 mean in the formula 4Na2SO3?

A
There are four atoms of sodium.
B
There are four atoms of sodium sulfite.
C
There are four formula units of sodium sulfite.
D
There are four elements in sodium sulfite.
3

Which would increase the rate of dissolving salt into water?

A
low temperature
B
little to no agitation
C
more surface area
D
darker colors
4

How many atoms of each element are in the chemical formula Ca(OH)2?

A
1 calcium, 1 oxygen, and 1 hydrogen
B
1 calcium, 2 oxygen, and 2 hydrogen
C
2 calcium, 1 oxygen, and 2 hydrogen
D
2 calcium, 2 oxygen, and 2 hydrogen
5

Which lists mixtures, in order, from the smallest particles to the largest particles?

A
solution, colloid, suspension
B
solution, suspension, colloid
C
suspension, colloid, solution
D
suspension, solution, colloid
6

The descriptions below explain two ways that water is used by plants on a sunny day.I. In a process called transpiration, some liquid water in leaves changes to water vapor. The water vapor is released into the air through tiny pores in the leaves. This allows more liquid water from the soil to be pulled up the roots and stem to replace water lost from the leaves.II. Plants use some of this water in leaves in a process called photosynthesis. During photosynthesis, water and carbon dioxide break apart and recombine to form two new substances, oxygen and glucose.

A
In transpiration, because some of its properties change, water undergoes a physical change but keeps its identity. In photosynthesis, because its identity changes, water undergoes a chemical change.
B
In transpiration, because some of its properties change, water undergoes a chemical change but keeps its identity. In photosynthesis, because its identity changes, water undergoes a physical change.
C
In transpiration, because its physical properties change, water undergoes a physical change and loses its identity. In photosynthesis, because it keeps its identity, water undergoes a chemical change.
D
In transpiration, because its chemical properties change, water undergoes a chemical change and loses its identity. In photosynthesis, because it keeps its identity, water undergoes a physical change.
7

Which best describes solubility?

A
the speed at which a substance dissolves
B
the ability of one substance to dissolve in another
C
the amount of surface area per a given mass
D
the temperature at which subtances become a mixture
8

Which best describes a mixture?

A
It has a single composition, and it has a set of characteristics that does not change.
B
It can have different compositions, but it has a set of characteristics that does not change.
C
It has a single composition, but it has a set of characteristics that does change.
D
It can have different compositions, and it has a set of characteristics that does change.
9

Scientists in a lab are working with two different samples of the element mercury. They know that the different samples are different isotopes.

A
the atomic number
B
the electric charge
C
the element name
D
the mass number
10

Which procedure would best allow a scientist to observe a chemical property of hydrochloric acid (HCl) solution?

A
cooling the HCl solution until it becomes solid, and measuring this temperature
B
adding zinc to the HCl solution and observing whether or not bubbles are produced
C
placing a conductivity probe into a beaker of HCl solution to determine if it conducts electricity
D
measuring the mass of and volume of a sample of HCl solution to find its density
11

In which reaction would the activation energy result in an endothermic reaction?

A
water freezing
B
an egg cooking
C
a candle burning
D
iron rusting
12

The activation energy of a reaction going on its own is 20 kJ. If the reaction was treated with a catalyst, which would most likely represent the amount of energy needed to start a reaction?

A
15 kJ
B
20 kJ
C
25 kJ
D
30 kJ
13

Which property describes a mixture?

A
It cannot be separated by physical methods.
B
It has a single chemical composition.
C
It cannot have more than one state of matter.
D
It cannot be described by a chemical symbol or formula.
14

Atom A and Atom B have the same number of protons, but they do not have the same number of neutrons.Which statement describes these atoms?

A
Atom A and Atom B are isotopes of the same element.
B
Atom A and Atom B are different elements.
C
Atom A and Atom B have different atomic numbers.
D
Atom A and Atom B have the same mass number.
15

Calcium carbonate (CaCO3) is a white solid with no odor. When CaCO3 is heated, the resulting substances are calcium oxide (CaO) and carbon dioxide (CO2). CaO is a white to gray solid with no odor, and CO2 is a gas with no odor and color.Which statement describes CaCO3?

A
It is a diatomic molecule that can’t be broken down by physical means.
B
It is a diatomic molecule that can’t be broken down by chemical means.
C
It is a compound that can be broken down by physical means.
D
It is a compound that can be broken down by chemical means.
16

The release of a gas from a chemical reaction is very quick. A scientist wants to measure what is released, but in small increments. What would allow the scientist to change the rate of the reaction so the results could be measured?

A
an enzyme
B
an inhibitor
C
a depressant
D
an accelerator
17

An atom of the element zinc has an atomic number of 30 and a mass number of 65. How many protons does an uncharged zinc atom have?

A
30
B
35
C
65
D
95
18

Which statement best describes the diagram below?

Question illustration
A
The pressure is greater at the bottom of the container.
B
The pressure is greater at the top of the container.
C
The temperature is greater at the top of the container.
D
The temperature is greater at the bottom of the container.
19

Carla is making two drinks. She is making one hot chocolate and one chocolate milk. Which best describes the agitation needed to make sure the cocoa powder is mixed in well?

A
Chocolate milk would require more agitation than hot chocolate does.
B
Hot chocolate would require more agitation than chocolate milk does.
C
They would both require the same agitation.
D
Neither would require any agitation.
20

Which describes a homogeneous mixture?

A
A solvent dissolves in a solute to make a solution.
B
A solute dissolves in a solvent to make a solution.
C
A solution dissolves in a solute to make a solvent.
D
A solution dissolves in a solvent to make a solute.

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