AnswersLA-Physical Science AUnit Test

Unit Test — Cumulative exam Answers

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Formaldehyde is an organic compound. Each molecule includes two hydrogen (H) atoms, one oxygen (O) atom, and one carbon (C) atom. Below are the dot structures for each of these elements.Which diagram shows how the covalent bonds most likely form in a formaldehyde molecule?

Question illustration
A
Option
B
Option
C
Option
D
Option
2
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How do the nuclei of covalently bonded atoms help keep the bond together?

A
Neutral particles in the nucleus provide enough mass that the force of gravity holds the atoms together.
B
Neutral particles in the nucleus can become positive or negative in order to balance the charges.
C
Positive particles in the nucleus change into negative particles that enter electron shells.
D
Positive particles in the nucleus are attracted to shared electrons, so the atoms stay close together.
3

Which important change in electronic devices, such as televisions and computers, is a result of the use of metalloids as semiconductors?

A
Electronic devices have become smaller.
B
Electronic devices are now more brittle.
C
Electronic devices now use more energy.
D
Electronic devices have become more expensive.
4

What kind of acceleration occurs when an object speeds up?

A
positive
B
negative
C
neutral
D
zero
5

What is conserved in physical changes?

A
shape
B
energy
C
mass
D
density
6

During which changes of state do atoms that cannot move past one another become free to move?

A
vaporization and sublimation
B
boiling and deposition
C
sublimation and melting
D
condensation and melting
7

Which is the only element in group 1 on the periodic table that forms covalent bonds?

A
hydrogen
B
lithium
C
potassium
D
sodium
8

This is how manganese appears in the periodic table.

Question illustration
A
period symbol of manganese
B
isotope symbol of manganese
C
group symbol of manganese
D
chemical symbol of manganese
9

The element sulfur (S) is most likely to form covalent bonds with the element

A
helium (He).
B
magnesium (Mg).
C
zinc (Zn).
D
oxygen (O).
10

Which tools would Sara use to find an irregularly shaped object’s mass and volume?

A
a meter stick, a ruler, and water
B
a meter stick, a balance, and water
C
a balance, water, and a ruler
D
a balance, water, and a beaker
11

Which represents an endothermic reaction?

A
wood burning in a fire
B
splitting a gas molecule
C
using a heat pack on an injury
D
TNT exploding
12

A student combined equal amounts of two solutions. One solution had a pH of 2 and the other had a pH of 12. Which would most likely be the resulting pH?

A
1
B
3
C
6
D
11
13

The atomic number of beryllium (Be) is 4, and the atomic number of barium (Ba) is 56. Which comparison is best supported by this information?

A
They are in the same group because they have similar atomic masses, but they are in different periods because they have different chemical properties.
B
They are in the same group because they have similar chemical properties, but they are in different periods because they have very different atomic numbers.
C
They are in the same group because their atomic numbers are each multiples of four, but they are in different periods because they have different chemical properties.
D
They are in the same group because they have similar atomic masses, but they are in different periods because they have very different atomic numbers.
14

What are the coefficients for the reaction _Cl2O5 + _H2O → _HClO3 once it is balanced?

A
1, 1, 1
B
1, 1, 2
C
1, 2, 2
D
2, 1, 1
15

Chanel has some cotton candy that came in a cloudy shape. She wants to make it more dense. Which describes the candy before and after Chanel manipulated it?

A
The candy before was a cube, and the candy after was a ball.
B
The candy before was compacted, and the candy after was fluffy.
C
The candy before was fluffy, and the candy after was compacted.
D
The candy before was a ball, and the candy after was a cube.
16

The pH of a solution is 7. Which best describes the solution?

A
The solution has more hydrogen ions than hydroxide ions.
B
The solution has fewer hydrogen ions than hand soap.
C
The solution has the same number of hydrogen ions as apple juice.
D
The solution has the same number of hydrogen ions and hydroxide ions.
17

Rutherford used positively charged particles to investigate the structure of the atom. The results surprised him, and he developed the atomic model shown below.

Question illustration
A
A few positive particles bounced back because they bounced off of the net formed by the ovals.
B
A few positive particles bounced back because they were pushed away from the positive center.
C
Most positive particles passed through because of the empty space between the outer edge and the center.
D
Most positive particles passed through because they were attracted by the small particles moving around the center.
18

Ella makes this table to organize her notes on whether atoms gain or lose energy during the changes of state.

Question illustration
A
freezing, boiling, and melting
B
melting, vaporization, and sublimation
C
sublimation, deposition, and condensation
D
freezing, deposition, and condensation
19

Where are alkaline earth metals found on the periodic table?

A
Group 1
B
Group 2
C
Groups 3–12
D
Group 17
20

While looking at bromine (Br) on the periodic table, a student needs to find another element with very similar chemical properties but with a different atomic mass. Which best describes the student’s options?

A
There are two possible elements, and they are directly to the left and right of bromine.
B
There are two possible elements, and they are directly above and below bromine.
C
There are many possible elements, and they are all in the same vertical column as bromine.
D
There are many possible elements, and they are all in the same horizontal row as bromine.

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