AnswersCrowley Credit Recovery Physics ASafety in Science

Safety in Science — Unit test Answers

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Which metal is most likely to form more than one kind of positively charged ion?

A
sodium (Na)
B
barium (Ba)
C
nickel (Ni)
D
magnesium (Mg)
2
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Atoms of arsenic (As) are often added to silicon (Si) in a process called doping to change the conductivity of the silicon. How does the addition of arsenic change the conductivity of silicon?

A
An atom of arsenic has one fewer valence electron and more electron shells than an atom of silicon, so the conductivity decreases because the arsenic atom gains an electron.
B
An atom of arsenic has one more valence electron and more electron shells than an atom of silicon, so the conductivity decreases because the arsenic atom loses the electron.
C
An atom of arsenic has one fewer valence electron and fewer electron shells than an atom of silicon, so the conductivity increases because the arsenic atom gains an electron.
D
An atom of arsenic has one more valence electron and more electron shells than an atom of silicon, so the conductivity increases because the arsenic atom loses the electron.
3

Sonya is studying a nonmetal element. She learns that the element is like other elements in its group because it can bond to form a salt or an acid. She also learns that the element is the most reactive element in its group. Which element is Sonya most likely studying?

A
sulfur (S)
B
neon (Ne)
C
fluorine (F)
D
iodine (I)
4

What best describes the states of nonmetals when they are at room temperature?

A
Most nonmetals are gaseous, but some are liquid or solid.
B
All nonmetals are gaseous unless they bond with a metal.
C
Most nonmetals are solids, but some are gaseous or liquid.
D
All nonmetals are solid unless they bond with a metal.
5

Which of the following observations would indicate that a material is a pure substance?

A
It does not dissolve in water.
B
It changes color after heating.
C
It cannot be physically broken down into different types of atoms.
D
It can be physically broken down into different types of molecules.
6

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.
7

A piece of sodium metal can be described as

A
a pure substance and a compound.
B
an impure substance that is reactive.
C
an impure substance that is unreactive.
D
a pure substance and an element.
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

Which element is most likely to carry electric current easily?

A
tin (Sn)
B
sulfur (S)
C
antimony (Sb)
D
selenium (Se)
10

Isra is analyzing the properties of several samples of elements to find out which sample is a metalloid. Which set of properties most likely belongs only to a metalloid?

A
forms basic compounds and is a solid
B
has a high luster and is very brittle
C
is a gas and has low electrical conductivity
D
is brittle and forms acidic compounds
11

These models show the electron structures of two different nonmetal elements.

Question illustration
A
Element 1 is more reactive because it has fewer electron shells and is toward the top of its group on the periodic table.
B
Element 1 is more reactive because it has more electrons in its valence shell and is farther to the right on the periodic table.
C
Element 2 is more reactive because it does not have a valence shell close to the nucleus, so it will attract electrons.
D
Element 2 is more reactive because it does not have a full valence shell, so it will attract electrons.
12

Which statement describes heterogeneous mixtures?

A
They are made up of two or more pure substances that are not chemically bonded together and appear non-uniform.
B
The substances they are composed of can only be separated chemically.
C
The substances they are composed of have fixed ratios between their components.
D
They are made up of two or more pure substances that are chemically bonded together and appear uniform.
13

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.
14

Which physical method can separate a mixture of steel ball bearings and marbles?

A
boiling
B
evaporation
C
filtration
D
sorting
15

Who was the first chemist to organize elements by atomic number?

A
Johann Wolfgang Döbereiner
B
Antoine Lavoisier
C
Henry Moseley
D
John Newlands

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