Chapter 12: Solids, Liquids, and Especially Gases

The States of Matter

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Figure 12.1: “Squeezing” air out of a bottle.

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Courtesy Ken Karp

Figure 12.2: Solid, liquid, and gas.

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Figure 12.3: At its melting point, the chemical particles of a crystalline solid leave the orderly lattice and achieve a greater freedom of movement in the liquid melt.

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Figure 12.4: Liquids evaporate as molecules with high translational energies escape from the liquid into the vapor.

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Particles of a gas Move rapidly in straight lines. Have kinetic energy that increases with an

increase in temperature. Are very far apart. Have essentially no attractive (or repulsive)

forces. Have very small volumes compared to the

volume of the container they occupy.

Kinetic Theory of Gases

Figure 12.9: Molecular motion in an ideal gas.

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• Gases are described in terms of four properties: pressure (P), volume (V), temperature (T), and amount (n).

Properties of Gases

• A barometer measures the pressure exerted by the gases in the atmosphere.

• The atmospheric pressure is measured as the height in mm of the mercury column.

Barometer

A. The downward pressure of the Hg in a barometer is _____ than/as the weight of the atmosphere.

1) greater 2) less 3) the same

B. A water barometer is 13.6 times taller than a Hg barometer (DHg = 13.6 g/mL) because

1) H2O is less dense

2) H2O is heavier

3) air is more dense than H2O

Learning Check

A.The downward pressure of the Hg in a barometer is 3) the same as the weight of the atmosphere.

B. A water barometer is 13.6 times taller than a Hg barometer (DHg = 13.6 g/mL) because

1) H2O is less dense

Solution

A gas exerts pressure, which is defined as a force acting on a specific area.

Pressure (P) = Force Area

One atmosphere (1 atm) is 760 mm Hg. 1 mm Hg = 1 torr

1.00 atm = 760 mm Hg = 760 torr

Pressure

• In science, pressure is stated in atmospheres (atm), millimeters of mercury (mm Hg), and Pascals (Pa).

Units of Pressure

A. What is 475 mm Hg expressed in atm?1) 475 atm2) 0.625 atm3) 3.61 x 105 atm

B. The pressure in a tire is 2.00 atm. What is this pressure in mm Hg?1) 2.00 mm Hg2) 1520 mm Hg3) 22,300 mm Hg

Learning Check

A. What is 475 mm Hg expressed in atm?2) 0.638 atm485 mm Hg x 1 atm = 0.638 atm

760 mm HgB. The pressure of a tire is measured as 2.00 atm.

What is this pressure in mm Hg?2) 1520 mm Hg2.00 atm x 760 mm Hg = 1520 mm Hg

1 atm

Solution

Figure 12.5: Composition of dry air.

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Figure 12.6: The regions of the atmosphere.

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Figure 12.7 Atmospheric pressure at sea level, 760 mm-Hg, 14.7 lb/in.2

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Figure 12.8: The Torricelli barometer.

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• Gases are described in terms of four properties: pressure (P), volume (V), temperature (T), and amount (n).

Properties of Gases

Pumping air into a tire increases its pressure.

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Courtesy Pat Lanza Field/Bruce Coleman, Inc.

Pressure and Volume (Boyle’s Law)

The pressure of a gas is inversely related to its volume when T and n are constant.

If volume decreases, the pressure increases.

Boyle’s Law

Figure 12.10: The effect of pressure on a gas.

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Robert Boyle, discoverer of the relationship between the pressure and volume of a gas.

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Courtesy Science Photo Library/Photo Researchers

Figure 12.11: Boyle’s Law: the pressure-volume relationship for a fixed quantity of gas maintained at constant temperature.

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PV in Breathing Mechanics

• When the lungs expand, the pressure in the lungs decreases.

• Inhalation occurs as air flows towards the lower pressure in the lungs.

PV in Breathing Mechanics

• When the lung volume decreases, pressure within the lungs increases.

• Exhalation occurs as air flows from the higher pressure in the lungs to the outside.

Temperature and Volume

Figure 12.15: Charles’ Law and the kinetic-molecular theory of gases: At constant pressure, as the temperature increases, so does the volume.

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• The Kelvin temperature of a gas is directly related to the volume (P and n are constant).

• When the temperature of a gas increases, its volume increases.

Charles’ Law

William Thomson, Lord Kelvin, devised the Kelvin temperature scale, in which temperature measurement begins at absolute zero and moves upward in Celsius degrees.

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Figure 12.13: Celsius and Kelvin (absolute) temperature scales.

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Figure 12.14: Charles’ Law: the temperature-volume relationship for a fixed quantity of gas maintained at a constant pressure.

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• The pressure exerted by a gas is directly related to the Kelvin temperature of the gas at constant V and n.

Gay-Lussac’s Law: P and T

Use the gas laws to complete with 1) Increases 2) Decreases A. Pressure _______ when V decreases.

B. When T decreases, V _______.

C. Pressure _______ when V changes

from 12.0 L to 24.0 L.

D. Volume _______when T changes from

15.0 °C to 45.0°C.

Learning Check

Use the gas laws to complete with 1) Increases 2) Decreases

A. Pressure 1) Increases, when V decreases.

B. When T decreases, V 2) Decreases.

C. Pressure 2) Decreases when V changes

from 12.0 L to 24.0 LD. Volume 1) Increases when T changes from 15.0 °C to 45.0°C

Solution

• The volume of a gas is directly related to the number of moles of gas when T and P are constant.

Avogadro's Law: Volume and Moles

Review

Figure 12.10: The effect of pressure on a gas.

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Figure 12.15: Charles’ Law and the kinetic-molecular theory of gases: At constant pressure, as the temperature increases, so does the volume.

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• The volume of a gas is directly related to the number of moles of gas when T and P are constant.

Avogadro's Law: Volume and Moles

Partial Pressure (Dalton’s Law)

• In a mixture of gases, the partial pressure of each gas is the pressure that gas would exert if it were by itself in the container.

Partial Pressure

• The total pressure exerted by a gas mixture is the sum of the partial pressures of the gases in that mixture.

PT = P1 + P2 + .....

Dalton’s Law of Partial Pressures

• The total pressure of a gas mixture depends on the total number of gas particles, not on the types of particles.

Partial Pressures

Henry’s Law

• According to Henry’s Law, the solubility of a gas in a liquid is directly related to the pressure of that gas above the liquid.

Figure 12.16: The gas laws and a carbonated drink.

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A combination of the laws of gases, including their low solubility in a warm liquid, causes this to happen when you shake a bottle of warm soda before you open it.

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Courtesy Ken Karp

Because of their higher ratio of surface area to volume, small bubbles of gas transfer their oxygen to water more effectively than large bubbles.

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Courtesy Miller Brooks, Perfecto Manufacturing

A tank of compressed gas furnishes oxygen at a partial pressure high enough to allow normal breathing underwater.

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Courtesy Frank Viola/Comstock Images

Figure 12.17: The lungs and the alveoli.

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Blood Gases

• In the lungs, O2 enters the blood, while CO2 from the blood is released.

• In the tissues, O2

enters the cells, which release CO2 into the blood.

Figure 12.19: Partial pressures and gas flows to and from the blood.

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Blood Gases

• In the body, cells use up O2 and give off CO2.

• O2 flows into the tissues because the partial pressure of O2 is higher (100 mm Hg) in oxygenated blood, and lower (<30 mm Hg) in the tissues.

• CO2 flows out of the tissues because the partial pressure of CO2 is higher (>50 mm Hg) in the tissues and lower (40 mm Hg) in the blood.

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Which of the three common states of matter – solids, liquids, or gasses – (a) maintain their own volumes, no matter what container holds them; (b) maintain their own shapes, no matter what container holds them?

QUESTION

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Name or describe (a) a moving object (other than a fan blade) that possesses rotational energy, (b) a moving object (other than a vibrating spring) that possesses vibrational energy, and (c) a moving object that possesses translational energy. Now name or describe a moving object that possesses simultaneously any two of these three forms of kinetic energy.

QUESTION

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As shown in Table 12.1, sodium chloride and potassium iodide boil at much higher temperatures than do water, ethyl alcohol, and propane. What kind of bonding – covalent or ionic – occurs in each of these compounds? What do these boiling points indicate about the relative strengths of the forces of attraction between ions of ionic compounds and between molecules of covalent compounds?

QUESTION

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What would you expect the average barometric pressure to be at an altitude of 5500 m (18,000 ft)?

QUESTION

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What characteristics would the atoms or molecules of a real gas have to have in order for the gas to behave exactly like an ideal gas?

QUESTION

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The volume of a quantity of a gas held at constant temperature and 760 mm – Hg pressure is 100 mL. What pressure does it take to reduce the volume to 95 mL?

QUESTION

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A gas kept at constant pressure has a volume of 10 L at 25°C. At what Celsius temperature would the gas have a volume of 20 L?

QUESTION

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Suppose we start again with a balloon filled to a volume of 1 L at a pressure of 760 mm –Hg and a temperature of 27 °C – the same initial conditions as in the first example of this section? Now suppose we again reduce the external (or atmospheric) pressure to 300 mm-Hg. To what Celsius temperature would we have to cool the balloon to keep its volume at 1 L?

QUESTION

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When gaseous oxygen and gaseous hydrogen react to form water, in what volume ratio do the hydrogen and the oxygen react? (As in the Example, writing a balanced equation for the reaction helps.)

QUESTION

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Suppose you had 10L of a gas composed of individual hydrogen atoms. Then, at constant temperature and pressure, these individual hydrogen atoms combined to form diatomic hydrogen molecules, H2. What would be the volume of this gaseous H2?

QUESTION

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Fish, which consume oxygen just as all other animals do, survive on atmospheric oxygen that dissolves in water. Name a gas present in water in a greater concentration of oxygen. Explain.

QUESTION

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Aside from temperature, what is one factor that determines how much N2 can dissolve in a given quantity of water? What is one factor that determines how fast the N2 dissolves?

QUESTION

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Two gases constitute 99% of the (dry) air we inhale: nitrogen (78.1%) and oxygen (20.9%). Four gases make up virtually all of the air we exhale: nitrogen (74.9%), oxygen (15.3%), carbon dioxide (3.7%), and another gas that accounts for just over 6% of our exhaled breath. What is this fourth gas that makes up an even larger fraction of our breath than does carbon dioxide, and where does it come from?

QUESTION

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What do you think would happen if you inverted a warm bottle in the water and placed a towel soaked in cold water around it? Explain.

QUESTION