chemistry quarantine, chemistry chapter 10

What are the three assumptions we make when using the kinetic theory relating to gases?

1. All matter is made of tiny particles, 2. Particles are in constant motion, 3. Collision between particles are elastic

Pouring liquid nitrogen on a balloon decreases the volume of the balloon dramatically, as shown in the photograph in problem 52, pg. 290. Afterwards, the balloon reinflates. Use the kinetic theory to explain these events. (the temperature of liquid nitrogen is

196 celsius)- The volume of the gas is proportional to its temperature, so when the liquid nitrogen comes in contact with the particles of the balloon the volume of the gas particles decrease.

Express the following pressures in kPa:

799 mm Hg 106 kPa 9010 Pa 9.010 kPa 2.34 Atm 237 kPa

What is the relationship between kinetic energy and temperature?

A substance absorbs heat and the particles start to move faster from the average kinetic energy therefore the temp increases.

Why does increasing the temperature of a liquid increase its rate of evaporation?

Added heat increases the average kinetic energy of liquid particles which makes the molecules break away faster

Would you expect an equilibrium vapor pressure to be reached above a liquid in an open container? Why? (10.2)

An equilibrium is unlikely to happen as the particles could escape the container during evaporation.

What causes atmospheric pressure and why is it lower at the top of a mountain than it is at sea level?

Atmospheric pressure is caused by gravity pushing on air particles. It is lower at the top of a mountain because the air is less dense.

What instrument do we use to measure atmospheric pressure?

Barometer

What is the difference between boiling point and normal boiling point? (10.2)

Boiling point is the temperature of which the vapor pressure is the same as the external pressure.

Use figure 10.11 on pg.279 to find the boiling point of each liquid:

Ethanoic acid at 100 kilipasticals 120 C Chloroform at 80 kilipasticals 53 C Ethanol at 20 kilipasticals 40 C

Explain how liquids and gases differ in terms of compressibility? (10.2)

Gases can be compressed because there is space between the particles, but for liquids they can't because they do not have that gap in between the particles.

Vacuum

If no gas particles are present, there can be no force. This is called a Vacuum.

vapor pressure

If particles evaporate in a closed container, the gas particles above the liquid collide with the container creating a pressure we call Vapor Pressure.

What is STP in kelvin and Atmospheres? 273 K and 1 atm

In kelvin and kPa? 273 K and 101.3 kPa In kelvin and mmHg? 273 K and 760 mmHg

What do we mean by elastic collision?

It means that no energy is gained or lost in a collision.

List 3 different units we use to measure pressure.

Millimeters of mercury, atmospheres, kilapastical

mm Hg.

Millimeters of mercury-mm Hg

Solid

Molecules are held close to each other by their attractions of charge. They will bend and/or vibrate, but will stay in close proximity. The molecules have an ordered arrangement.

Gas

Molecules are in continual straight-line motion. The kinetic energy of the molecule is greater than the attractive force between them, thus they are much farther apart and move freely of each other.

Liquid

Molecules will flow or glide over one another, but stay toward the bottom of the container. Motion is a bit more random than that of a solid. They have enough kinetic energy to slip out of the ordered arrangement of a solid.

How does perspiration help cool your body on a hot day?

On a hot day your sweat evaporates from your skin taking your body heat with it.

In terms of particles (distance apart and motion) describe solids vs liquids vs gases.

Particles in solids are close together and have low energy. Liquids are closer together but in a random arrangement with medium energy.

Pascal

SI unit for pressure is the pascal (Pa)

Stp

STP is considered to be 0 celsius and 1 atm.

Define STP and give it's values in kelvin and kPa.

Standard temperature pressure kelvin 273.15 and kPa 101.325

By what factor does the average kinetic energy of gas molecules in an aerosol container increase when the temperature is raised from 300K to 900K? (10.1)

The average kinetic energy of gas molecules in an aerosol container increases by 3.

How would the average kinetic energy of water molecules be affected when you pour hot water from a kettle into cups that are the same temperature as the water? (section 10.1)

The average kinetic energy would stay the same.

kinetic energy

The energy an object has because of its motion is called Kinetic Energy

A cylinder of gas is heated from 275 K to 1375 K. By what factor does the average kinetic energy of the gas particles increase?

The factor of 5

kinetic theory

The kinetic theory explains the relationship between particles and their motion.

Explain why the boiling point of a liquid varies with atmospheric pressure.

The lower atmospheric pressure the easier it is for particles of liquid to escape and the higher the pressure the harder it is for particles to escape so they require more energy and the boiling point will go up.

Phase Changes or Changes of State

The process of changing state requires that energy be absorbed or released. It is usually measured in calories. One calorie is the amount of heat required to raise the temperature of 1 gram of water 1 degree C.

Water

The range of temperatures found on Earth's surface and the physical properties of water allow water to occur commonly and in abundance in all three phases: solid, liquid, and gas. Phase changes usually refer to the changes of state of water on Earth.

boiling point

The temperature at which the vapor pressure of a liquid is just equal to the external pressure.

Use figure 10.11 on page 289 of the text to determine the temperature at which water will boil in an open container when the atmospheric pressure is 400 mm Hg.

The water will boil at about 80 celcius.

What are three units we use to measure pressure?

Three units are pascal (Pa), kilopascal (kPa), and mm Hg.

Explain vapor pressure and dynamic equilibrium. (10.2)

Vapor pressure is the pressure that a liquid will apply in a vapor form against the atmosphere. Dynamic equilibrium is the balance between evaporation and condensation.

When you remove the lid from a food container that has been in the freezer for a long time, you discover a large collection of ice crystals on the underside of the lid. Explain what has happened? (10.4)

Water from the food went through sublimation and condensed to the top of the lid.

Describe what happens, at the particle level, when a solid is heated to its melting point. (10.3)

When a solid is heated to its melting point the vibrations of the particles are very strong and when it reaches its certain temperature it breaks down and melts.

(goes with question 18) How can you determine the vapor pressure in each container?

You can determine it by measuring the right side. If it's higher it means more pressure and if it's lower it means less pressure.

Atmosphere

atm

Vaporization

conversion of a liquid to a gas or vapor

Barometer

device used to measure atmospheric pressure

Is the average kinetic energy of the particles in a block of ice at 0 degrees C the same or different from the average kinetic energy of the particles in a gas

filled weather balloon at 0 degrees C? Explain.- They both have the same average kinetic energy. All substances have the same average kinetic energy at a certain temperature even if they have different physical states.

Define gas pressure

force exerted by a gas per unit area results in the constant collision of many tiny gas particles

Gas pressure

force exerted by a gas per unit area.

Absolute zero

if the volume of a substance decreases as temperature decreases, it would stand to reason that at some point, the volume would get so small that it would be nothing! This is what we call Absolute Zero. 0 K or -273 C.

Kinetic energy

is energy that an object has because of its motion. The Kinetic Molecular Theory explains the forces between molecules and the energy that they possess. This theory is based on three theories about matter. • Matter is composed of small particles (atoms, molecules, and ions). • The space the molecules occupy (volume) depends on the space between the molecules and not the space the molecules occupy themselves. • The molecules are in constant motion. This motion is different for each of the three states of matter. They are colliding with each other and the walls of their container. When the molecules collide with each other, or with the walls of a container, there is no significant loss of energy. Absolute zero is the temperature used to describe when all movement is as slow as it can possibly be.

Mass

is the measure of the heaviness of a substance, usually is weighed in grams. The characteristics of atoms in the material determine the mass. The more tightly packed they are, the greater the mass

• Evaporation

is the process in which a liquid is changed to gas. Water can change from liquid to vapor only when energy is available. Evaporation requires energy, usually in the form of heat in the atmosphere. When you take energy from an object, it gets cooler. The heat energy went into the water molecules and caused them to speed up and evaporate. When water evaporates from a surface, the amount of water vapor in the air increases.

Density

is the ratio of mass to volume. To determine the density of a substance, divide its mass by its volume. Water has a density of about 1, and objects that sink in water, such as steel, have a higher density. In contrast, steel's density is about 8.

Temperature

is the term used to explain how hot or cold an object is. Temperature is the average kinetic energy of particles in the substance. Water molecules at 0o C. have lower kinetic energy than water at 100o C.

Define Kinetic energy

kinetic energy refers to motion

• Freezing

occurs when a liquid is changed to a solid

• Sublimation

occurs when a solid is changed directly to a gas (e.g., ice cubes shrinking in a freezer)

• Melting

occurs when a solid is changed to a liquid

• Condensation

occurs when water changes from gas to liquid by condensation. The water molecules release their stored heat energy and form fog or clouds.

• Deposition

occurs when water vapor (gas) changed to a solid (e.g., frost in a freezer compartment)

The volume

of a substance is the three-dimensional space it occupies. It is measured in cubic centimeters or millimeters. One cubic centimeter equals 1 millimeter. When scientists set up the metric system, they set those quantities up that way to make science easier.

Atmospheric pressure

results from the collision of air molecules with other objects. at sea level is 101.3 kPa.

Define atmospheric pressure

results from the collision of the air molecules with other objects

melting point

temp. at which a solid changes to a liquid

Gas

term used for a substance that is normally a gas at room temperature. Ex. oxygen, helium etc.

Vapor

term used for the gas state of a substance that is normally a liquid or solid at room temperature. Ex. water vapor.

normal boiling point

the boiling point of a liquid at a pressure of 101.3 kPa.

Why is the equilibrium that exists between a liquid and its vapor in a closed container called a dynamic equilibrium? (be specific)

the equilibrium refers to balance and dynamic refers to many factors.

Evaporation

when a liquid changes to a gas at the surface of a liquid that is not boiling, it's called evaporation.