Physics: Concepts and Connections

Art Hobson

Chapter 2

Atoms: The Nature of Things - all with Video Answers

Educators

Chapter Questions

Problem 1

Is the atomic theory known, for certain, to be true?

Donald Albin

Donald Albin

Numerade Educator

Problem 2

Carbon atoms are about $25 \%$ lighter than oxygen atoms (the ratio of their weights is 3 to 4 ). What is the weight ratio of the carbon and oxygen that go into the formation of carbon monoxide? Answer the same question for carbon dioxide.

Donald Albin

Numerade Educator

Problem 3

A carbon atom is 12 times heavier than a hydrogen atom. If methane $\left(\mathrm{CH}_{4}\right)$ is chemically decomposed, what will be the ratio of the weights of the resulting carbon and hydrogen?

Donald Albin

Numerade Educator

Problem 4

A carbon atom is 12 times heavier than a hydrogen atom, and an oxygen atom is 16 times heavier than a hydrogen atom. If glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$ is chemically decomposed, what will be the ratio of the weights of the resulting elements?

Anand Jangid

Numerade Educator

Problem 5

How many atoms are in a molecule of $\mathrm{H}_{2} \mathrm{SO}_{4}$ (sulfuric acid)?

Sri Datta Vikas Buchemmavari

Sri Datta Vikas Buchemmavari

Numerade Educator

Problem 6

How many atoms are in the alcohol molecule $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH} ?$

Donald Albin

Numerade Educator

Problem 7

Which of these is a pure compound, which is an element, and which is neither: helium gas, carbon dioxide, polluted water, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6},$ gold, steam?

Donald Albin

Numerade Educator

Problem 8

Which of these is a pure compound, which is an element, and which is neither: pure water, oxygen gas, liquid mercury, $\mathrm{H}_{2} \mathrm{SO}_{4}, \mathrm{U},$ air?

Donald Albin

Numerade Educator

Problem 9

Suppose you obtained the smallest single particle of each of the following substances. In which cases would this particle be a molecule made of more than one atom, and in which cases would it be a single unattached atom: pure water, oxygen gas in the form found in Earth's atmosphere, $\mathrm{H}_{2} \mathrm{SO}_{4}, \mathrm{U},$ He, carbon dioxide, $\mathrm{H}_{2}, \mathrm{H} ?$

Donald Albin

Numerade Educator

Problem 10

Helium is an inert gas, meaning that it does not readily enter into chemical reactions with other substances. List five other substances that you would expect to also be inert gases.

Donald Albin

Numerade Educator

Problem 11

Chlorine has a strong tendency to combine with a single hydrogen atom to form HCl. Look in the periodic table and list at least three other elements that you would expect to combine with hydrogen the way that chlorine does.

Donald Albin

Numerade Educator

Problem 12

Consider a pure chemical substance A. Suppose that it can be chemically decomposed into two other pure substances $\mathrm{B}$ and C. Can we then conclude that $\mathrm{B}$ and $\mathrm{C}$ must be elements? That $\mathrm{B}$ and $\mathrm{C}$ must be chemical compounds? That $\mathrm{A}$ must be a chemical compound?

Donald Albin

Numerade Educator

Problem 13

What is the chemical formula for methane (carbon and four hydrogens)?

Donald Albin

Numerade Educator

Problem 14

What is the chemical formula for sulfur dioxide?

Donald Albin

Numerade Educator

Problem 15

What is the chemical formula for carbon tetrachloride ( tetra a means "four")?

Donald Albin

Numerade Educator

Problem 16

On the simplifying approximation that oxygen and carbon atoms have the same weight, how many tons of carbon dioxide gas are formed when 1 ton of coal burns (coal is nearly pure carbon)?

Donald Albin

Numerade Educator

Problem 17

In a typical large coal-fed electrical generating plant, a ton of coal is burned every 10 seconds. About how many tons of carbon dioxide enter the atmosphere every hour from such a plant?

Donald Albin

Numerade Educator

Problem 18

Why can't you observe Brownian motion in easily visible objects such bits of paper floating in water?

Donald Albin

Numerade Educator

Problem 19

What is the chemical formula for the odor of violets (see Figure 6$) ?$

Donald Albin

Numerade Educator

Problem 20

A dog follows an escaped convict's trail by putting its nose to the ground. Explain this from a microscopic point of view.

Donald Albin

Numerade Educator

Problem 21

If air is put into a sealed container that is then compressed (reduced in volume), what do you predict will happen to the air pressure on the container walls? Explain this from a microscopic point of view.

Donald Albin

Numerade Educator

Problem 22

If air is put into a sealed container and warmed, what do you predict will happen to the air pressure on the container walls? Explain this from a microscopic point of view.

Donald Albin

Numerade Educator

Problem 23

If a balloon is partially filled with air (so that it isn't fully expanded), sealed, and then warmed, what do you predict will happen to the balloon? Explain this from a microscopic point of view. What if the balloon is cooled instead?

Donald Albin

Numerade Educator

Problem 24

Why is it so difficult to remove the lid from a vacuum-sealed jar?

Donald Albin

Numerade Educator

Problem 25

Suppose that you observe the Brownian motion of tiny pollen grains floating in still air enclosed in a glass bottle. What would happen if you increased the amount of air? What would happen if you warmed the air?

Donald Albin

Numerade Educator

Problem 26

Why does the air pressure in a tire increase as you add air? Why does the air pressure in a tire increase as you warm the tire?

Donald Albin

Numerade Educator

Problem 27

Suggest an experiment that would show that air has weight.

Donald Albin

Numerade Educator

Problem 28

What if, in addition to its random molecular motion, all the air molecules in some volume of air had an overall collective motion, all of them moving, say, eastward. Could this collective motion be observed macroscopically? What would we call it?

Donald Albin

Numerade Educator

Problem 29

Write as ordinary numbers: $109 ; 1026 ; 3.6 \times 10^{13}$ $5.9 \times 10^{-8}$

Donald Albin

Numerade Educator

Problem 30

Write in powers of 10 notation: 3 trillion; five-thousandths; 730,000,000,000,$000 ; 0.0000000000082$

Donald Albin

Numerade Educator

Problem 31

The distance to the moon is $384,000 \mathrm{km} .$ Express this using powers of $10 .$ How far is this in meters? In millimeters?

Donald Albin

Numerade Educator

Problem 32

Our Milky Way galaxy contains perhaps 400 billion stars. Suppose that $0.05 \%$ (i.e., 0.0005 ) of these stars have planetary systems containing at least one Earthlike planet (one that could conceivably support Earthlike life). Express these two numbers using powers of $10,$ and then multiply them together to find how many Earthlike planets there are in our galaxy. Express this number in words (thousands or millions, etc.).

Narayan Hari

Numerade Educator

Problem 33

The universe is a million trillion seconds old. Write this number in ordinary (not powers of 10 ) notation.

Donald Albin

Numerade Educator

Problem 34

Put these in order from lightest to heaviest: water molecule, oxygen atom, raindrop, hydrogen atom, glucose molecule, electron, DNA molecule.

Donald Albin

Numerade Educator

Problem 35

Put these in order from lightest to heaviest: $\mathrm{H}_{2}$ molecule, methane molecule, fine dust particle, hemoglobin molecule, proton, glucose molecule.

Donald Albin

Numerade Educator

Problem 36

How old are a baby's atoms? Are they older than an old person's atoms? What about a baby's DNA molecules?

Donald Albin

Numerade Educator

Problem 37

One sheet of paper is about $0.1 \mathrm{mm}$ thick. An atom is about $10^{-10} \mathrm{m}$ across. About how many atoms thick is one sheet of paper?

Donald Albin

Numerade Educator

Problem 38

The average weight, per atom, of the atoms in your body is about $10^{-26} \mathrm{kg}\left(2 \times 10^{-26} \mathrm{pounds}\right)$. About how many atoms are there in your body?

Donald Albin

Numerade Educator

Problem 39

The smallest dust particle visible to the unaided eye measures about $0.05 \mathrm{mm}$ across. About how many atoms across is this? In other words, if we line up atoms side by side, about how many would it take to make a line of atoms 0.05 mm long?

Supratim Pal

Numerade Educator

Problem 40

Referring to the preceding exercise: Assume the small dust particle is shaped like a cube. About how many atoms does it contain?

Donald Albin

Numerade Educator

Problem 41

What is the chemical reaction formula for burning hydrogen gas in air? What substance is created by this reaction?

Donald Albin

Numerade Educator

Problem 42

For safety, gas-filled balloons are filled with helium instead of hydrogen. What does this tell you about the behavior of helium in the atmosphere?

Donald Albin

Numerade Educator

Problem 43

Gasoline is a hydrocarbon fuel. What are the two main compounds created when gasoline burns in a car engine?

Donald Albin

Numerade Educator

Problem 44

$\mathrm{NO}_{\mathrm{X}}$ (nitrogen oxide and nitrogen dioxide) is one pollutant from automobiles. What elements must combine to form $\mathrm{NO}_{\mathrm{X}} ?$

Donald Albin

Numerade Educator

Problem 45

Gasoline contains neither oxygen nor nitrogen. So where must these elements come from when $\mathrm{NO}_{\mathrm{X}}$ is formed in car engines?

Donald Albin

Numerade Educator

Problem 46

Are there any molecules in your body that you could claim are "your" molecules, unique to your body and probably unlike any other molecules in the universe?

Donald Albin

Numerade Educator