Chemistry Chapter 13
What is the difference between boiling and evaporation?
-Boiling: When a liquid is heated to a temperature at which particles throughout the liquid have enough kinetic energy to vaporize, the liquid begins to boil. -Evaporation: Vaporization that occurs at the surface of a liquid that is not boiling. During evaporation, only those molecules with a certain minimum kinetic energy can escape from the surface of the liquid.
What is the difference between melting point and freezing point?
-Melting Point: The temperature at which a substance changes from a solid to a liquid; the melting point of water is 0°C. -Freezing Point: the temperature at which a liquid changes into a solid -The Melting and Freezing Points of a substance are the same temperature.
What is the difference between vapor pressure and atmospheric pressure?
-Vapor Pressure: A measure of the force exerted by a gas above a liquid in a sealed container; a dynamic equilibrium exists between the vapor and the liquid -Atmospheric Pressure: The pressure exerted by atoms and molecules in the atmosphere surrounding Earth, resulting from collisions of these particles with objects
How does normal pressure compare with pressure above/below sea level?
Pressure decreases from normal as the height above sea level increases. Pressure increases from normal as the depth below sea level increases.
How does high/low atmospheric pressure change boiling point?
The lower the pressure the lower the boiling point. As the pressure lowers, it means it takes less vapor pressure to equal the atmospheric pressure, hence a lower boiling point.
Sketch a phase graph. Label: solid, liquid, gas, temperature, pressure, normal melting point and normal boiling point, triple point. Define triple point.
*LOOK TO NOTES FOR GRAPH* Triple Point: the point on a phase diagram that represents the only set of conditions at which all three phases exist in equilibrium with one another
How many different crystal systems are there and how do they differ?
-7: Galena, Zircon, Topaz, Gypsum, Amazonite, Tourmaline, Calcite -Crystal Systems differ in: angles of the faces and number of edges of equal length on each face
Absolute Zero
-Absolute zero (0 K, or -273.15° C) is the temperature at which the motion of particles theoretically ceases. -Particles would have no kinetic energy at absolute zero. -Absolute zero has never been produced in the laboratory.
What is absolute zero?
-Absolute zero (0 K, or -273.15° C) is the temperature at which the motion of particles theoretically ceases. -Particles would have no kinetic energy at absolute zero. -Absolute zero has never been produced in the laboratory.
What is the difference between boiling point and normal boiling point?
-Boiling Point: The temperature at which the vapor pressure of a liquid is just equal to the external pressure on the liquid -Normal Boiling Point: The boiling point of a liquid at a pressure of 101.3 kPa or 1 atm
Explain why it takes longer to boil an egg in Denver than it does in Alton.
-The temperature at which the vapor pressure of the liquid is just equal to the external pressure on the liquid is the boiling point (bp). -At a lower external pressure, the boiling point decreases -At a higher external pressure, the boiling point increases -Sea Level: Atmospheric pressure at the surface of water at 70C is greater than its vapor pressure. Bubbles of vapor cannot form in the water, and it does not boil. At the boiling point, the vapor pressure is equal to atmospheric pressure. Bubbles of vapor form in the water, and it boils. Atop Mount Everest: At higher altitudes, the atmospheric pressure is lower than it is at sea level. Thus the water boils at a lower temperature.
What happens to the temperature of a liquid as it evaporates? Which particles evaporate first?
As liquid evaporates, it cools. The particles that have the highest kinetic energy and temperature evaporate first.
What causes air pressure?
Atmospheric pressure results from the collisions of atoms and molecules in air with objects
Which states of matter can be compressed?
Gas (Chapter 14)
Would average kinetic energy be higher in water that is 100°C or steam that is 100°C? in water at 90°C or water at 100°C?
Kinetic energy is directly proportional to Kelvin temperature. 100+273=373K 90+273=363K -it would be higher in steam since steam is a gas, and gases have the highest energy -Greater in 100 than 90 (water)
What is the SI unit of pressure?
Pascal (Pa)
Which temperature scale is directly proportional to the average kinetic energy of molecules?
The Kelvin temperature of a substance is directly proportional to the average kinetic energy of the particles of the substance.
Normal Boiling Point
The boiling point of a liquid at a pressure of 101.3 kPa or 1 atm
Vaporization
The conversion of a liquid to a gas or vapor
Kinetic Energy
The energy an object has because of its motion
Atmospheric Pressure
The pressure exerted by atoms and molecules in the atmosphere surrounding Earth, resulting from collisions of these particles with objects
Sublimation
The process in which a solid changes to a gas or vapor without passing through the liquid state
Melting Point
The temperature at which a substance changes from a solid to a liquid; the melting point of water is 0°C.
Boiling Point
The temperature at which the vapor pressure of a liquid is just equal to the external pressure on the liquid
Evaporation
Vaporization that occurs at the surface of a liquid that is not boiling
What is dynamic equilibrium? Explain how and when dynamic equilibrium is reached?
-In a system at constant vapor pressure, a dynamic equilibrium exists between the vapor and the liquid. The system is in equilibrium because the rate of evaporation of liquid equals the rate of condensation of vapor. -An increase in the temperature of a contained liquid increases the vapor pressure. -The particles in the warmed liquid have increased kinetic energy. As a result, more of the particles will have the minimum kinetic energy necessary to escape the surface of the liquid.
When does boiling occur? When does sublimation occur? What is the element that we saw sublimate and depose in a demonstration?
-When a liquid is heated to a temperature at which particles throughout the liquid have enough kinetic energy to vaporize, the liquid begins to boil -The temperature at which the vapor pressure of the liquid is just equal to the external pressure on the liquid is the boiling point (bp). -The change of a substance from a solid to a vapor without passing through the liquid state is called sublimation. Sublimation occurs in solids with vapor pressures that exceed atmospheric pressure at or near room temperature. -When solid iodine is heated, the crystals sublime, going directly from the solid to the gaseous state. When the vapor cools, it goes directly from the gaseous to the solid state
What are the units for normal atmospheric pressure?
1 atm=760 mmHg=101.3 kPa
Write three pressure unit conversion problems using atm, mm Hg, and kPa. Solve them.
1 atm=760 mmHg=101.3 kPa
List the points of the kinetic theory.
1. The particles in a gas are considered to be small, hard spheres with an insignificant volume. 2. The motion of the particles in a gas is rapid, constant, and random. 3. All collisions between particles in a gas are perfectly elastic
If the external pressure is 200 kPa, what would the vapor pressure of water be that is boiling?
200kPa, because at boiling point, external pressure equals vapor pressure.
Vapor Pressure
A measure of the force exerted by a gas above a liquid in a sealed container; a dynamic equilibrium exists between the vapor and the liquid
Kinetic Theory
A theory explaining the states of matter, based on the concept that all matter consists of tiny particles that are in constant motion.
Barometer
An instrument used to measure atmospheric pressure
List the three allotropes of carbon and describe many ways they differ.
Diamond: Each carbon atom in the interior of the diamond is strongly bonded to four others. The array is rigid and compact. Graphite: The carbon atoms are linked in widely spaced layers of hexagonal (six-sided) arrays. Fullerene: In buckminsterfullerene, 60 carbon atoms form a hollow sphere. The carbons are arranged in pentagons and hexagons.
