Apologia Chemistry Module 04 Review

Front 1

What is the difference between elements and compounds?

Back 1

Elements result when atoms of the same type are collected together, and compounds result when molecules of the same type are collected together.

Front 2

Why is it important to classify the various types of matter?

Back 2

If we can properly classify the various types of matter we see, it will be easier for us to determine how that matter is changing.

Front 3

Give some common examples of pure substances.

Back 3

sulfur, iron, sugar, and table salt

Front 4

Give a simple example of how you would turn table salt from a pure substance into a mixture.

Back 4

Take table salt and dissolve it in pure water, the result would be a mixture. This mixture would have two compounds: H^2O and NaCl.

Front 5

True or false? While in a mixture, individual elements or compounds retain their individual properties.

Back 5

True.... think about adding salt to water. The taste of the water would be salty, but not as salty as only salt since the water dilutes the salt.

Front 6

What is the difference between iron and sulfur, and iron sulfide?

Back 6

Sulfur and iron: since this is a mixture, the sulfur retains its properties (its yellow color, for example), and the iron retains its properties (its black color, for example). These properties can be used to separate the two elements.

For iron sulfide, two elements (sulfur and iron) are heated together so that they form the compound iron sulfide. Although iron sulfide contains both sulfur and iron, it is not a mixture: it is a pure substance. Both the sulfur and the iron have “given up” their individual properties to become a compound. This, then, is a pure substance.

Front 7

How could you go about getting the iron and sulfur out of iron sulfide?

Back 7

You would have to DECOMPOSE the iron sulfide back into a mixture of iron and sulfur and then separate the two.

Front 8

Pure substances can be either elements or compounds. True? Or False?

Back 8

True!

Front 9

Explain how Italian salad dressing is a heterogeneous mixture.

Back 9

The dressing mixture has a different composition depending on where you observe the sample. When you take Italian dressing out of the refrigerator, there are seeds, herbs, and spices in the bottle, but they are mostly at the bottom.

Front 10

Why is Coca Cola a homogeneous mixture?

Back 10

Coke® is a mixture of several ingredients, but there is no difference in taste or composition from the top of the Coke® can to the bottom.

Front 11

Can you turn a heterogeneous mixture into a homogeneous mixture? If so, give an example. If not, why not?

Back 11

Yes, you can. Think: milk. When milk is taken from a cow, it is a heterogeneous mixture. The cream in the milk tends to rise to the top, while the water tends to fall to the bottom. Before you buy the milk, however, it is treated so that the cream stays evenly distributed throughout the milk. Thus, the formerly heterogeneous mixture is turned into a homogeneous mixture.

Front 12

Without humidity.... what is the percentage-wise breakdown of the gases in the air we breathe?

Back 12

78% nitrogen, 21% oxygen, 0.9 % argon, 0.03% carbon dioxide, and 0.07% other gases

Front 13

Too much oxygen in the atmosphere is a bad thing. It causes bodily damage and can even cause forest fires! In fact, that is why the air we breathe is only half oxygen and the rest are other gases. True or False?

Back 13

Everything in that statement is true except the fact that oxygen only makes up 1/4th of the air we breath! So the answer is false because it isn't all true....

Front 14

How does our body utilize nitrogen?

Back 14

We breathe in nitrogen with every breath, but then we breathe it right out again because it does not interact with our bodies. So our body doesn't use nitrogen....

Front 15

Classify the following as elements, compounds, homogeneous mixtures, or heterogeneous mixtures:

copper

Back 15

Copper is on the periodic chart, so it is an element.

Front 16

Classify the following as elements, compounds, homogeneous mixtures, or heterogeneous mixtures:

carbon dioxide

Back 16

Carbon dioxide is the name for the molecule CO^2, and molecules form a compound.

Front 17

Classify the following as elements, compounds, homogeneous mixtures, or heterogeneous mixtures:

cake icing

Back 17

Icing has sugar, butter, and flavorings in it, and they are mixed together so the composition is the same throughout. Thus, icing is a homogeneous mixture.

Front 18

Classify the following as elements, compounds, homogeneous mixtures, or heterogeneous mixtures:

tomato

Back 18

If you cut a tomato open, you can see that there is a skin on the outside and pulp and seeds on the inside. Since the composition is different inside and outside, a tomato is a heterogeneous mixture.

Front 19

Classify the following as elements, compounds, homogeneous mixtures, or heterogeneous mixtures:

sugar water

Back 19

Sugar water is sugar dissolved in water. The composition is the same throughout, so it is a homogeneous mixture.

Front 20

Classify the following as elements, compounds, homogeneous mixtures, or heterogeneous mixtures:

sodium

Back 20

Sodium is on the periodic table, so it is an element.

Front 21

Classify the following as elements, compounds, homogeneous mixtures, or heterogeneous mixtures:

fruitcake

Back 21

Fruitcake has several different things in it, and the composition varies throughout, so it is a heterogeneous mixture

Front 22

Classify the following as elements, compounds, homogeneous mixtures, or heterogeneous mixtures:

sodium fluoride

Back 22

Sodium fluoride is the name for the molecule NaF, so it is a compound.

Front 23

Classify the following as elements, compounds, homogeneous mixtures, or heterogeneous mixtures:

tap water

Back 23

Tap water, as was mentioned in the previous module, has more than just water in it. There is also sodium fluoride and chlorine in tap water if it comes from a city water supply. Since tap water has the same composition throughout, it is a homogeneous mixture.

Front 24

What is the most convenient way to distinguish between chemical and physical change?

Back 24

Whether or not a change is EASILY reversible. Emphasis on the "easily"... Because in principle, all chemical reactions are reversible.

If you look at the ease of reversing a reaction, however, physical changes can usually be reversed relatively easily.

Front 25

Classify the following change as physical or chemical:


Steam condenses into water.

Back 25

Steam is simply water vapor. Thus, when steam condenses back into liquid water, there is no change in the molecules. Also, this change can be easily reversed by simply boiling the water again. Either way you look at it, this is a physical change.

Front 26

Classify the following change as physical or chemical:

Gasoline burns in an automobile engine.

Back 26

When gasoline burns, it combines with oxygen to make carbon dioxide and water, just like when wood burns. Also, it is impossible to get the gasoline back once it's burned, so this change is irreversible. Either way you look at it, this is a chemical change

Front 27

Classify the following change as physical or chemical:

A barber cuts your hair.

Back 27

When a barber cuts your hair, he or she does not change the chemical makeup of the hair. He or she simply changes its length. This could also be reversed by gluing the hair back in place. It might look a little funny, but it still could be reversed. Either way you look at it, this is a physical change.

Front 28

Classify the following change as physical or chemical:

Milk sours.

Back 28

Milk has its distinctive taste because of the molecules that make it up. The change in taste that occurs in sour milk is because the molecules have changed. Also, you cannot “unsour” milk. Either way you look at it, this is a chemical change.

Front 29

Classify the following change as physical or chemical:

Sugar is dissolved in water.

Back 29

When sugar is dissolved in water, the water tastes slightly sweet. That is because the sugar is still there; it is just evenly distributed around the water. Also, this change can be reversed by just boiling off the water. Either way you look at it, this is a physical change

Front 30

Classify the following change as physical or chemical:

Milk is poured on cereal.

Back 30

When milk is poured on cereal, the only change is that the cereal gets soggy. No molecules have changed. Also, you can reverse this change by picking the cereal out of the milk and letting it dry. Either way you look at it, this is a physical change.

Front 31

Classify the following changes as physical or chemical:

An iron nail rusts

Back 31

When iron (Fe) rusts, the red color appears because the iron has reacted with the oxygen in the air to make Fe^2O^3, what we call rust. Also, there is no way to “unrust” a nail. You can scrape the rust away, but it will not turn back into iron. It will simply fall on the ground as a fine, red powder. Either way you look at it, this is a chemical change.

Front 32

What are the three phases of matter?

Back 32

solid, liquid, gas

Front 33

What is the main difference between phases of matter?

Back 33

the volume they occupy

Front 34

Rank the three phases of matter in terms of how much volume they take up.... with the least amount of volume first.

Back 34

All substances take up the least amount of volume in their (1.) solid phase, a little more volume in their (2.) liquid phase, and the largest amount of volume in their (3.) gas phase.

Front 35

The closer atoms or molecules get to one another, the less volume is occupied by the substance that they comprise. True or False?

Back 35

True.

Front 36

Why do the molecules get closer together or farther apart? If molecules are attracted to one another, why don't they all just get as close as possible to one another, always making a solid?

Back 36

Because of the kinetic theory of matter!

Front 37

Cubes of frozen alcohol are put into liquid alcohol. Will the cubes float or sink?

Back 37

Since all substances, except water, occupy less volume in the solid phase than in the liquid phase, frozen cubes of alcohol would be more dense than liquid alcohol. As a result, the frozen cubes of alcohol would sink in liquid alcohol.

Front 38

Natural gas companies store most of their natural gas in liquid form rather than in its gas phase, even though they must deliver it to their customers as a gas. Why do they do this?

Back 38

Since liquid natural gas occupies significantly less volume than natural gas in its gas phase, the gas company can store significantly larger amounts of natural gas when it is in its liquid form. The money natural gas companies save with the increased storage capacity makes up for the cost of cooling natural gas down to its liquid phase so that it can be stored.

Front 39

Explain the kinetic theory of matter.

Back 39

The molecules or atoms that make up all of the matter we observe are always in constant motion. Any matter that you can actually see is made up of billions and billions and billions of atoms or molecules. These atoms or molecules are in random motion.

Front 40

Explain why matter in a solid state does not appear to be moving.

Back 40

The reason that matter in the solid phase doesn't appear to be moving is that for every molecule (or atom) that is vibrating one way, there is another molecule (or atom) vibrating another way. Thus, on average, the solid matter cannot move anywhere, because all its molecules or atoms are moving in different directions.

Front 41

In the liquid phase, molecules and atoms do not just vibrate; they move around. Describe this movement in terms of a water molecule in a glass full of water.

Back 41

A molecule of water will travel throughout the entire volume of the glass, continually running into things, changing directions, and speeding off again.

Front 42

In the gas phase, things are just like the liquid phase, with something just a bit different in regards to the molecules. What is this difference?

Back 42

The molecules travel faster and they make fewer collisions with other molecules because they are farther apart from one another.

Front 43

The molecules in a substance must have energy in order to move around as they do. Where do they get this energy?

Back 43

They get it from the surroundings. The higher the temperature of the surroundings, the faster the molecules move. The faster the molecules move, the farther they get away from the other molecules in the substance. As the molecules (or atoms) get farther away from their neighbors, the substance eventually changes phase. This is why a substance changes from solid to liquid to gas as the temperature is increased.

Front 44

How is the temperature of a substance determined?

Back 44

The temperature of a substance is actually determined by the speed at which the molecules (or atoms) in the substance are moving. The faster the molecules (or atoms) move, the higher the temperature.

Front 45

If a substance is cooled down 10 degrees, will its molecules be moving faster or slower? Will the molecules be closer together or farther apart?

Back 45

When substances are cooled, the atoms or molecules which make them up begin to lose energy and thus move slower. As they move slower, they get closer together.

Front 46

Almost all natural substances occupy less volume in the solid phase than in the liquid phase. What is one common exception to this rule?

Back 46

Solid water (ice) actually occupies more volume than liquid water.

Front 47

Why are we very lucky that water is an exception to the phase change rule?

Back 47

* makes it possible for fresh-water organisms to survive (lake doesn't freeze from the bottom up ....)

* many biochemists believe that it also makes it possible for life as we know it to exist.

* keeps water a liquid at normal temperatures due to hydrogen bonding

Front 48

How do you know when a chemical change (reaction) has taken place?

Back 48

Chemical change occurs when the molecules within a substance change into different molecules.

Front 49

True or False? Nearly every rule in chemistry has its exceptions.

Back 49

TRUE. Very, very important that you should know this!

Front 50

Name the eight homonuclear diatomics.

Back 50

Nitrogen, oxygen, chlorine, fluorine, bromine, iodine, astatine, and hydrogen

Front 51

What is the chemical formula for nitrogen?

Back 51

N^2

Front 52

What is the chemical formula for:

oxygen

Back 52

O^2

Front 53

What is the chemical formula for:

chlorine

Back 53

Cl^2

Front 54

What is the chemical formula for:

fluorine

Back 54

F^2

Front 55

What is the chemical formula for:

bromine

Back 55

Br^2

Front 56

What is the chemical formula for:

iodine

Back 56

I^2

Front 57

What is the chemical formula for:

astatine

Back 57

At^2

Front 58

What is the chemical formula for:

hydrogen

Back 58

H^2

Front 59

The concept of a homonuclear diatomic applies not only to an element, but also to an atom within a molecule. True or False?

Back 59

FALSE. The concept of a homonuclear diatomic applies ONLY to an element, not to an atom within a molecule.

Front 60

The chemical formula for burning coal can be written:

Carbon plus oxygen yields carbon dioxide.

How would you write the chemical equation?

Back 60

C + O^2 ---> CO^2

Front 61

In a chemical equation, what does the arrow (------>) represent?

Back 61

It represents the word "yields"

Front 62

True or false? A chemical equation has the products on the left hand side of the arrow because those are the "products" that are combined.

Back 62

FALSE! The REACTANTS are on the left side, because those chemicals react when mixed. (Products on right side!)

Front 63

How does a chemical reaction proceed? (work)

Back 63

The molecules must disassemble into their constituent atoms, and then the atoms recombine to form the products.

Front 64

What does it mean when a small letter is enclosed in parentheses in a chemical equation? (s) is an example.

Back 64

Whenever you see a small letter enclosed with parentheses in a chemical equation, you know that it is a symbol telling you the phase of the substance. An “(s)” is used to denote solid, an “(l)” means liquid, a “(g)” stands for gas, and an “(aq)” represents a substance that has been dissolved in water.

Front 65

What does “aq” mean?

Back 65

The letters “aq” are an abbreviation for the Latin term aqueous , which means “in water.”

Front 66

Chemists always use phase symbols in their chemical reactions. True or False?

Back 66

False. Chemists do not always use phase symbols in their chemical reactions. Sometimes they are there; sometimes they are not. It is always preferable to include them, however, because they provide us with important information. Don't be confused if you do not see them, though.

Front 67

How would you write the following in a chemical equation?

Methane + oxygen yields carbon dioxide + water.

Back 67

CH^4 (g) + O^2 (g) + O^2 (g) ---> CO^2 (g) + H^2O (g) + H^2O (g)

REMEMBER: A chemical reaction must start with its reactants, end up with its products, and have no extra atoms left over. Which is why we doubled up on the CO^2 and H^2O in order to make sure that there are NO extra atoms left over in the end!!

Front 68

In chemical reactions, sometimes water will be a liquid, sometimes it will be a gas, and sometimes it will be a solid. How do you know what to label it as in a chemical equation?

Back 68

Well, only experience can help you make that distinction. (until then, the book will tell you!)

Front 69

"Clean" the following chemical equation up .

CH^4 (g) + O^2 (g) + O^2 (g) ----> CO^2 (g) + H^2O (g) + H^2O (g)

Back 69

CH^4 (g) +2O^2 (g) ---> CO^2 (g) + 2H^2O (g)

Front 70

What does the number two in front of the H mean in the following? (the first number two ~ also known as the coefficient)

2H^2O

Back 70

The big numbers to the left of each chemical formula tell you how MANY molecules of each substance are necessary in order for the reaction to work.

As usual, if there is no number to the left of a chemical formula, we must assume it is “1.”

Front 71

So what do the numbers in the subscripts tell you?

Back 71

The numbers in the subscripts are part of the molecule's chemical formula. They tell you what molecules you are dealing with.

Front 72

If a chemical equation has five H atoms on its reactants side, it must have five H atoms on its products side. True or False?

Back 72

True.

Front 73

What is the trick to counting the atoms in a chemical chemical reaction in order to make sure it is balanced?

Back 73

Remember that the number to the left of each molecule tells you how many molecules there are in the equation. The numbers in subscripts tell you how many of each atom are in the molecule. Thus, to count the number of atoms on each side of the equation, we must take the number to the left of the molecule and multiply it by the subscript number that follows each atom. This will tell us the total number of each atom on each side of the equation.

Front 74

Is the following equation balanced?

2HCl (aq) + CaBr^2 (s) ---> 2HBr (s) + 2 CaCl^2 (aq)

Back 74

Nope. The Cl's and Ca's are not balanced!!!

Front 75

Is this balanced?

6CO^2 + 6H^2O ----> C^6H^12O^6 + 6O^2

Back 75

Yes, it is balanced!

Front 76

Is the following equation balanced?

2C^2H^6 (g) + 7O^2(g) ----> 4CO^2 (g) + 6H^2O(g)

Back 76

Yes. It is balanced.

Front 77

Is the following equation balanced?

6NH^4Cl + Al^2S^3 ----> AlCl^3 + 3N^2H^8S

Back 77

This is not a balanced chemical equation because it is not balanced with respect to Cl or Al.

Front 78

What numbers in a chemical equation can be changed when you are attempting to balance it?

Back 78

You can alter the number of molecules involved by changing the numbers that appear to the left of each molecule. Those numbers can be changed in any way, as long as they are not made negative. You cannot, however, change any of the numbers that appear in the subscripts

Front 79

Balance the following equation:

N^2 (g) + H^2 (g) ----> NH^3 (g)

(Hint: in order to do so, you must change the coefficients)

Back 79

N^2 (g) + 3H^2 (g) -----> 2NH^3 (g)

Front 80

What is the general rule of thumb to follow when you are trying to balance atoms in a chemical equation to make it easier? (easier = GOOD!!!!) :o)

Back 80

Start with atoms that appear in only one molecule on each side of the equation.

Front 81

Using the general rule of thumb for making it easier to balance equations, write a balanced equation for the
following formula:

Propane (C^3H^8) reacts with oxygen to make carbon dioxide and water.

Back 81

C^3H^8 + 5O^2 ----> 3CO^2 + 4H^2O

Front 82

Hydrogen and oxygen can react together violently to make water. Write a balanced chemical equation for this reaction.

Back 82

2H^2 + O^2 -----> 2H^2O

Front 83

Solid calcium carbonate (CaCO3) is made when solid calcium reacts with gaseous oxygen and solid carbon. What is the balanced chemical equation for this reaction?

Back 83

2Ca(s) + 3O^2 (g) + 2C(s) ----> 2CaCO^3 (s)

Front 84

Balance the following equation:

C^5H^12 (l) + O^2 (g) ----> CO^2 (g) + H^2O (g)

Back 84

C^5H^12 (l) +8O^2 (g) ---> 5CO^2 (g) + 6H^2O (g)

Front 85

If a substance can be physically separated into its components, is it a pure substance or a mixture?

Back 85

Anything that can be separated into its components must be a mixture. Compounds must first be
decomposed before they can be separated into their component element

Front 86

If a substance can be given a single chemical name, e.g. calcium bromide, is it a pure substance or a mixture?

Back 86

Anything that has a single chemical name is made up of a single atom or molecule. As a result, it
must be a pure substance.

Front 87

What element makes up the majority of the air we inhale?

Back 87

Nitrogen makes up 78% of the air we breathe.

Front 88

What element makes up the majority of the air we exhale?

Back 88

Once again, the answer is Nitrogen. Since we don't use up the nitrogen we breathe in, it also makes up the vast majority of what we exhale. You may have learned in biology that we breathe in oxygen and breathe out carbon dioxide. This is true, but oxygen is only 21% of what we breathe in and carbon
dioxide is only 4% of what we breathe out!

Front 89

One type of phase change we did not discuss is sublimation. Sublimation occurs when a solid changes directly into a gas, without passing through a liquid phase. Does sublimation occur when something is heated or when something is cooled?

Back 89

Since molecules move faster and are farther apart in the gas phase compared to the solid phase, a
transition from solid to gas must occur when a substance is heated.

Front 90

If a liquid goes through a phase change and all you know is that the molecules slowed down and moved closer together, what phase did the liquid turn into?

Back 90

The only phase in which molecules move slower and are closer together than in the liquid phase is the solid phase.

Front 91

What makes water an exception to the phase change rule?

Back 91

Water expands when it freezes; thus, its molecules get farther apart. All other natural substances
contract when they freeze because their molecules get closer together.

Front 92

What is the difference between a chemical change and a physical change?

Back 92

A chemical change alters the identity of the substances involved in a change. A physical change does not.

Front 93

List the chemical formulas of the homonuclear diatomic elements.

Back 93

The homonuclear diatomics are N^2, O^2, Cl^2, F^2, Br^2, I^2, At^2, and H^2.

Front 94

What makes a chemical equation balanced?

Back 94

A chemical equation is balanced if each type of atom in the equation is present in the same number on both sides of the arrow.

Front 95

Classify the following as either a mixture or a pure substance:

a. An egg
b. A gold nugget
c. A bottle of HNO^3
d. Lemonade dissolved in water

Back 95

a. An egg is a mixture because it has a shell, yolk, and white, which are all different substances.

b. A gold nugget is pure gold, so it is a pure substance.

c. Since the bottle has only HNO^3 in it, it has only one substance and is therefore a pure substance.

d. Lemonade dissolved in water is a mixture, because the lemonade retains its properties, as does the water.

Front 96

Reclassify everything below as an element, compound, homogeneous mixture, or
heterogeneous mixture.

a. An egg
b. A gold nugget
c. A bottle of HNO^3
d. Lemonade dissolved in water

Back 96

a. An egg is a heterogeneous mixture because the shell, yolk, and white are all in separate places.

b. Gold (Au) is an element.

c. HNO^3 is a compound, because it is a molecule made up of more than one element.

d. Lemonade dissolved in water is a homogenous mixture because its composition is the same
throughout the sample.

Front 97

Classify the following as physical or chemical changes:

a. A precious vase is smashed to bits.

b. Eggs, flour, sugar, milk, and vanilla are baked, making a cake.

c. Dry ice turns into gas.

d. Charcoal is burned in a grill.

e. Kool-Aid is dissolved in water.

Back 97

a. This is a physical change because the vase.s molecules did not change. It is also easily
reversible: The vase could be put back together.

b. This is a chemical change. The molecules in the different ingredients actually react when they
are baked to form new molecules. The other way to look at this is you cannot unbake a cake.

c. This is a physical change, because the CO^2 is just changing phase.

d. This is a chemical change. Burning charcoal turns the carbon into CO^2. The other way to look at it is that you cannot unburn charcoal.

e. This is a physical change. Dissolving one substance into another never changes their molecules.
Alternatively, you could easily reverse this by boiling off the water to recover the Kool-Aid.

Front 98

What is the chemical formula of nitrogen gas?

Back 98

Nitrogen is a homonuclear diatomic, so its formula is N^2.

Front 99

Is the following equation balanced?
CaF^2 (aq) + 2NH^4Cl (aq) ----> CaCl^2 (aq) + NH^4F (aq)

Back 99

The equation is not balanced.