Chemistry is the study of matter and the changes it undergoes, with the atom being its basic functional unit. 


Concept: Understanding Matter

Video Transcript

Hey guys! Welcome to Clutch. My name is Jules Bruno, and I'll be your Chemistry 1 tutor this semester. Growing up, we’re taught about Math, English and some of the other social sciences early on in life. But for very few of us, we might get exposed to chemistry when we’re in high school. But even then, we’re only shown a small glimpse of the possibilities behind chemistry. For the vast majority of us, we don't see chemistry until we get to college. At that point, we're talking about empirical formula and moles, ionic bonds and covalent bonds. It might seem a little bit confusing. It's my goal this semester to help to demystify chemistry and break it down into a much simpler aspect so that you can better understand more complex ideas.
Our teachers sometimes talk to us as though we’re chemists, but the thing is we’re not chemists. We’re students. It's my goal this semester whether you’re majoring in chemistry or majoring in some other subject to help you guys better understand the advanced topics we’re going to cover this semester so that you can succeed in this course.
What we're going to do now is we're going to head to our first topic. Now, if we take a look, we're going to see that our first topic is basically what is chemistry. Chemistry is just the study of matter and the changes that it undergoes. Matter is basically anything that has mass to it and takes up space. Your book, your book bag, your computer. Everything around us is made up of matter, even ourselves. Everything that has some mass to it and takes up any amount of space is considered matter.
We're going to say the changes matter undergoes are two types. Matter can undergo physical changes in which it just changes the state it’s in. For example, we have an ice cube water solid melting in the sun. It going’s from water as a solid to water as a liquid. A physical change does not change the compound itself. It stays the same compound. The second type of change we're talking about is chemical change. Chemical change basically changes the composition, the makeup, of that compound. Let's say I superheat the water and it basically gets vaporized into hydrogen gas and oxygen gas. It started off as water, but now it’s something completely different, two new products. This is an example of a chemical change.
We're going to say that the basic functional unit in chemistry is defined as the atom. We're going to say when two or more these atoms chemically bond together, they're going to form an independent structure which we call a molecule. When I say atom, I really mean element. Let's say we have an element A. It could combine with itself, a second amount of itself, to give us a molecule A2 or that element A or atom A could combine with something totally different, an atom B to create a molecule AB. Basically when I say atom, really meaning elements, individual elements. They can either combined with themselves to create molecules or they could combine with something entirely different from themselves to still make a molecule.

Matter is anything that takes up space and has mass

Concept: Classifications of Matter

Video Transcript

Now we’re going to have to say we have to classify the different types, the different states of matter. Now we’re going to say that under appropriate conditions of temperature and pressure matter can exist in 3 different states. We know what these are, they’re solids, liquids and gases. And here on the bottom I basically give us 3 illustrations to help us see the different types of matter, the different states of matter. So we’re going to say in the first blank, we’re going to say these have a fixed shape and volume. Meaning that if I put them in a container they hold on to their properties, their physical features. So if we take a look at this first container we can see that we have some type of solid in there. Maybe a lump of clay, a lump of dirt. That’s going to be our solid. Solids don’t take on the shape of the container or fill up the volume. For the next one we say that these guys take up the shape and volume of the container. Now some of you might say this is a liquid, but that’s not always true. The better answer is, are gases. Gases will take up the shape and volume of the container. Now if we take a look at this third image right here you can see that inside the container it looks a little bit pink. That pink color is basically gas molecules spreading themselves out as far as possible to take up every single inch inside of that container. We’re going to say that when gases do that they’re behaving ideally. We won’t get to see this yet, we’ll see this later on in the semester when we’re focusing predominately on gases. But just remember, this is a normal behavior of gases. If you give them any amount of room, they’re going to take all of that room up. So that leaves us that last one. We’re going to say that liquids will conform to the shape of the container, but not necessarily the volume. They don’t always take up the volume, so for example we take a look at this picture. We can see that we have a red liquid at the bottom of the container, but there’s not enough liquid to take up the entire volume of the container. We can say that we might have 10 milliliters of the liquid, but the container itself can hold up to about 30 milliliters. As a result, we don’t have enough liquid to take up the entire volume. So, just remember chemistry is just the study of matter, matter has 3 different states. Each one have certain properties that they hold true to themselves, and remember we’re going to talk more later on about physical and chemical changes that matter can undergo. Understand these basic principles so that we can branch away from them to more complex and more chemical based equations, and ideas and concepts.

Under appropriate conditions of pressure and temperature, most substances can exist in 3 states of matter.

Concept: Volume, compressibility and viscosity of phases of matter 

Video Transcript

From this, we can take a microscopic explanation to see what each of these different states of matter have in common and what they have different from one another. We're going to say that for the gases, the gases—remember they assume the shape and volume of their containers.
We can see that in the third container, it's kind of like a pink haze inside of the container. That's because if you give a gas a chance, it will take up every single inch of space that's available. It will take on the full shape and fill up the entire volume of any container it's in.
For the liquid, the liquid, we're going to say it assumes the shape of the portion of its container it occupies. In the middle container, we can see that liquid becomes a cylinder, just like the container it's in. It takes on the same shape of it, but if there's not enough liquid, it can't take up the volume. Liquid usually just take up the shape but not necessarily the volume. If there's not enough liquid to fill up the entire container then it won't take up the volume.
Solid, solids we're going to say maintain a fixed shape and volume.
For the next category, we're talking about compressibility. All these means is 'Am I able to squeeze the atoms to make them more tightly packed, to bring them closer to one another?' Remember, compressibility just means, 'Am I able to squeeze the atom within each of these states of matter?'
Here the gases, the molecules are very far apart. The atoms, they are super far apart, they're bouncing everywhere. Because they're far apart, I'm able to squeeze them and caused them to become closer together. We're going to say that gases are very compressible. I'm able to use pressure, increase the pressure and squeeze them closer together.
In liquids, the liquids are not as tightly packed as solids, but they really are next to each other. They're sliding against each other, sliding around each other. We're going to say that liquids are not easily compressible. We can barely do anything to put them closer together.
Solids, we already said in the beginning that solids form a rigid structure. The atoms are tightly packed. They're as close as we can make them. We're going to say that solids are not compressible at all.
Finally the last concept viscosity! Viscosity, just think of it as resistance to flow. We're going to say that viscosity is the resistance to flow. What does this mean? That just means that something that is viscous does not want to move. Let's think of two different examples.
Let's say we have two buckets. We have a bucket of water and a bucket of honey. Let's say, right in front of us is maybe someone we don't quite like, maybe a childhood bully, maybe a classmate, maybe even a professor.
If I took that container, that bucket of water and tipped it over on top of the head of the person, the water would fall on to them very quickly. Water moves very easily, because water has a low viscosity. It doesn't have a big resistance to flow. It will flow easily. So, we say if you flow easily, you have a low viscosity.
If we took that bucket of honey though and we tipped it over, we would say that honey is more viscous. Honey moves very slowly. It wouldn't be able to dump all of the content on to the person's head. It would move very slowly. If you move very slowly, you're viscous.
We're going to say that gases, gases have a low viscosity. They move very easily. They're bouncing off the walls, bouncing everywhere. Gases have a low viscosity. Liquids will also have a low viscosity. The water we talked about, water flows easily, so we'd say that water has a low viscosity. Solids are kind of slow. So we're going to say solids have a high viscosity. They don't move very easily.
Now, for solids, how could we make them less viscous, make them move faster? You can apply heat. We're going to say, if you increase the temperature of a substance, then you excite that molecules in that substance and then you decrease viscosity. Just remember that, increasing temperature lowers viscosity. Increasing temperature makes you move faster. If you move faster, you're less viscous.
What we're going to do now, and we've seen all the different types of explanations for the three states of matter and we're going to pay very close attention to our gases. We're going to say that the gas is distinct from the liquids and the solids. Because it's so much more compressible, because it's more greatly affected by temperature and pressure than the other two, that's where we're going to pay so much attention to the gases.
We're going to pay attention to the gases and help us formed the ideal gas law. That's what these sets of videos are going to be focused on. Just the ideal gas law, the different types of matter that exists especially gas.
Guys, just remember, when it comes to gases, they're very distinct from the other two and because of that we're going to pay very close attention to them and the effects that happen to them when we messed around with the pressure, messed around with the temperature and play around with the volume. 

The closeness of molecules within the three phases of matter affects how they respond to changes in volume, pressure and temperature. 

Mixtures Additional Practice Problems

Describe how properties of seawater illustrate the two characteristics that define mixtures.

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Which of the following is a homogeneous mixture? 

a. gasoline 

b. vegetable oil and water 

c. sugar dissolved in water 

d. a and c 

e. a, b, and c

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Is brass an element, compound, or mixture?

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Which of the following is a homogeneous mixture?

(a) copper

(b) salt water

(c) carbon dioxide

(d) salad

(e) neon

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Is Air an element, a compound, or a mixture?

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Which of the following is NOT an example of a solution?

(A) bronze

(B) the atmosphere

(C) sterling silver

(D) Gatorade

(E) all of these are examples of solutions

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Consider the following substance
I. saline IV solution
II. salt (NaCl)
III. aluminum foil
IV. salad dressing

Which of the following is true?
A) I and III are pure substances, IV is a homogeneous mixture.
B) I and II are homogeneous mixtures
C) Both II and III are pure substances, I is a homogeneous mixture
D) None of the above is true

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The figure shows all but which of the following:

A)  two elements and a compound.

B)  a chemical reaction.

C)  one mixture and one pure substance.

D)  three compounds.

E)  five molecules.

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When a purple liquid was distilled, a blue liquid separated from a red solid.  What is the most likely identity of the purple liquid?

a) an element

b) some unknown entity

c) a solution

d) a compound

e) a pure substance

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Which of the following is a homogeneous mixture?

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Sea water is an example of

a. a compound

b. an element

c. a heterogeneous mixture

d. a homogenous mixture

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You have two beakers, one filled to the 100-mL mark with sugar (the sugar has a mass of 180.0 g) and the other filled to the 100-mL mark with water (the water has a mass of 100.0 g). You pour all the sugar and all the water together in a bigger beaker and stir until the sugar is completely dissolved. 

b. Which of the following is true about the volume of the solution? Explain.
i. It is much greater than 200.0 mL.
ii. It is somewhat greater than 200.0 mL.
iii. It is exactly 200.0 mL.
iv. It is somewhat less than 200.0 mL.
v. It is much less than 200.0 mL.

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The diagram represents solid carbon dioxide, also known as dry ice. Which of the diagrams below best represents the dry ice after it has sublimed into a gas? 

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Explain the difference between a homogeneous and a heterogeneous mixture.

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Explain the difference between a pure substance and a mixture. 

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What should your response be if you enter an unfamiliar laboratory workspace and see this sign?

(A) You should immediately evacuate the premises and then call for OSHA.

(B) You should put on full protective clothing, including goggles, respirator, and body suit.

(C) You should be aware that chemical waste is being processed in the immediate area.

(D) You should pay careful attention to your surroundings for potential hazards.

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A student combined 1 mL of 1.0 M solutions of nitrate salts of barium, calcium, magnesium, and strontium with several different testing reagents. The observations are recorded in this table .
Note: ppt = precipitate, rxn = reaction

An unknown solution contains two of these four ions: barium, calcium, magnesium, and stronium. The unknown solution forms a white precipitate with H2SO4 and it does not react with K2CrO4. What conclusion about the two ions in the unknown can be drawn from this evidence?

(A) It contains only strontium and barium ions.

(B) It contains only barium and calcium ions

(C) It contains barium ion and either magnesium or calcium ions.

(D) It contains strontium ion and either magnesium or calcium ions.

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In which case could the given gas be identified by the reaction given?

     Gas                                           Reaction

(A) Chlorine                                will turn starch blue

(B) ammonia                               will turn moist red litmus paper blue

(C) nitrogen                                will support combustion

(D) hydrogen chloride                will etch glass 


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The percentage of water in an unknown hydrated salt is to be determined by weighing a sample of the salt, heating it to drive off the water, cooling to room temperature, and re-weighing. Which procedural mistake would result in determining a percentage of water that is too low?

(A) I only

(B) II only

(C) both I and II

(D) neither I nor II

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Two or more substances in variable proportions, where the composition is variable throughout are considered

A) a solution.

B) a homogeneous mixture.

C) a compound.

D) an amorphous solid..

E) a heterogeneous mixture.

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Two or more substances in variable proportions, where the composition is constant throughout are considered

A) a compound.

B) an element.

C) a heterogeneous mixture.

D) a homogeneous mixture.

E) a crystalline solid.

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A substance composed of 2 or more elements in a fixed, definite proportion is considered

A) a homogeneous mixture.

B) a heterogeneous mixture.

C) a compound.

D) a solution.

E) an alloy.

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Choose the homogeneous mixture from the list below.

A) soda (pop)

B) air

C) concrete

D) trail mix

E) blood

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Choose the homogeneous mixture from the list below.

A. Ice water

B. Wet sand

C. Trail mix

D. Plain black coffee

E. Chocolate chip cookie

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Classify the following as a pure substance or mixture (what kind).

A) Smoke

B) A bar of gold

C) Air

D) Salt

E) Baking soda

F) Honey

G) Fruit Salad 

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Answer each of the following questions based on the images provided below. 

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Consider the following substances:

I. Gatorade

II. Crystalline sugar

III. Copper wire

IV. Salsa

Which of the following is true?

A. I and III are pure substances, IV is a homogeneous mixture.

B. I and II are homogeneous mixtures.

C. Both II and III are pure substances, I is a homogeneous mixture.

D. None of the above is true.

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Which of the following is a heterogeneous mixture?

a. A bottle of brine (slightly salty water).

b. A dish of steamed vegetables, fresh from the microwave oven.

c. The contents of a balloon containing helium, nitrogen, and oxygen gases.

d. A beaker containing a well-stirred mixture of ethanol (drinking alcohol) and water

e. All of the above.

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Suppose a container holds 1 gram of each of these gases: carbon dioxide, oxygen, water vapor, and dinitrogen pentoxide, along with 50 g of water. What is true?

A. The contents are a homogenous mixture.

B. Every molecule is also a compound.

C. Both metals and non-metals are in the container.

D. There are 4 pure substances. 

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A homogeneous mixture of two or more substances is called:

a) a compound.

b) an electrolyte.

c) a solution.

d) a solvent.

e) a mess.

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