Lecture 6 - Effect of Heat on Liquids & Gases Flashcards
What IMF are in solids?
Solids have strong IMF
- they are closely packed with strong attractions
- low energy state
- when a liquid loses energy it becomes a solid
What IMF are in liquids?
- if you add energy to a solid the energy of the molecules increases and the distance between the molecules becomes larger and can overcome the IMF to become a liquid
- liquids are flow and take on the shape of their container, definite volume
- when a solid gains energy it becomes a liquid
What IMF are in gases?
Gases have high energy
- weak IMF
- almost no attraction to one another
What happens when heat (energy) is added to a substance?
The heat increases the distance between the molecules and overcome the IMF.
-molecules with more energy will move away from other molecules.
What type of motion is vibrational motion?
Bending, stretching
What type of motion is rotational motion?
rotating, spinning
What type of motion is translational motion?
Linear - from point A to point B
Is kinetic energy uniform through a liquid?
NO! some particles may have more KE (more movement) and some particles may have less KE (less movement) within the liquid. The particles with the most KE may be able to jump out of the liquid phase and into the gaseous phase.
Take home point: KE is not uniform for all molecules within a liquid.
What is the average KE of molecules in a liquid called?
Temperature
What is temperature?
the average KE of molecules in a liquid
What is the average KE of molecules in a liquid called?
Temperature
What is does it mean to say a volatile gas/liquid?
It means that it liquid can exist in the vaporized state.
You increase the vapor by increasing the heat.
Or you can increase the vapor by choosing a liquid with weaker IMF.
Are oxygen and nitrogen volatile gases?
No! They exist naturally as a gas and need to cooled to freezing temps to be a liquid form. therefore they are not volatile because they do not exist as both a liquid and a gas at the same temp.
What is the relationship between vapor pressure and IMF?
the weaker the IMF, the higher the Vapor Pressure
What is room temp?
20 degrees C
What is body temp?
37 degrees C
What is temperature?
-thermal state of a substance which determines whether it will give heat to another substance or receive heat from another substance.
What is temperature in terms of KE?
temperature is the average KE
Is temperature uniform throughout a surface?
No, heat can form a gradient with something that is cooler and something that is warmer. The warmer one has more KE because the temperature is higher and the KE energy of those molecules bouncing around can be transferred to a cooler substance if they can come in contact with one another
What is heat?
Heat is a form of energy that can be transferred from a hotter substance to a cooler substance.
- the energy is in the form of KE which resides in the molecules of a substance
- HEAT IS A THERMAL GRADIENT
How does heat flow?
Heat energy flows from an area of increased heat to an area of lower heat energy?
-this is called heat exchange
What is thermal conductivity?
- measurement of a substance’s ability to conduct (exchange) heat
- copper/bronze vaporizer housings have increased thermal conductivity
- some substances are better at conducting heat than others
How is heat transferred?
Heat is transferred by a molecule with a lot of KE (energy of motion) bumping into something with less KE and giving that molecule some of its energy –> transferring some energy
What is kinetic energy?
KE is the energy of motion
What is the formula for KE
KE = [Mass X velocity(squared)]/2
How does an increase in heat affect kinetic energy and velocity?
An increase in heat causes an increase in kinetic energy and therefore an increase in velocity
What is liquid in terms of flowing ability and shape?
- a liquid is a substance that flows freely but is of constant volume, having a consistency like that of water or oil
- takes the shape of the container
what type of motion is present in liquids?
translational motion
Rank the IMF from greatest to least for solids, liquids, and gases
greatest IMF = solids
middle IMF = liquids
least IMF = gases
Rank temperature (aka average KE) for solids, liquids, and gases from greatest to least
greatest KE/average temp = gases
middle KE/average temp = liquids
lowest KE/average temp = solids
Do liquids and gases take on the shape of their container?
Yes! Liquids and gases take the shape of their container and flow freely. The molecules are in translational motion but they are closer together in a liquid than in a gas.
Rank the KE from greatest to least for solids, liquids, and gases
KE greatest = gas
KE middle = liquid
KE least = solid
Do gases have a set volume?
no
Do gases take on the shape of their container?
yes
what type of motion is present in gases?
translational motion, from point A to point B
How strong are the IMF for gases?
weak IMF in gases
In comparison to solids and liquids, what is the temperature (average KE) of gases?
higher temperature aka higher KE compared to solids and liquids
What distinguishes a gas from the vapor?
FOR A GAS, ALL MOLECULES ARE IN THE GASEOUS STATE UNDER NORMAL CIRCUMSTANCES (ROOM TEMP, 1 ATM PRESSURE)
Is vapor a state of matter?
No, vapor is not a state of matter
What is vapor?
A vapor is a molecules from a liquid or solid that has jumped into the gaseous state.
Are vapors gases?
No - these vapors are not gases.
THEY ARE MOLECULES IN THE GASEOUS STATE.
Do gases and vapors have the same properties?
No, vapor molecules have slightly different properties from gas molecules despite the fact that they are both in the gaseous state.
What is the property that distinguishes vapors from gases? YOU NEED TO KNOW THIS!!!***
*!!!! A VAPOR IS THE PORTION OF A SUBSTANCE IN ITS GASEOUS STATE THAT CAN BE CONDENSED TO A LIQUID BY INCREASING THE PRESSURE WITHOUT REDUCING THE TEMPERATURE!!!
Vapor is an equilibrium between what two phases?
Vapor describes an equilibrium between molecules in the liquid and gas state.
How are vapors formed?
Vapors are formed when liquid (or solid) molecules gain enough KE to break IMF and move to a gaseous state.
What does volatile mean?
liquids that are volatile have molecules that more likely to move to the gaseous state
Do volatile liquids have an equilibrium?
Yes - volatile liquids have an equilibrium between the number of molecules in the liquid state and those in the gas state
What is vapor pressure?
vapor pressure is the ratio of substance molecules in the gas to liquid state
True or False: Vapors are gases.
FALSE! Vapors are molecules in the gaseous state. They are NOT gases.
When is equilibrium reached between a liquid and a gas?
- when molecules of a liquid evaporate in a closed container, they can’t escape back into a liquid
- when the rate of evaporation - the rate of condensation, the gas is at equilibrium with the liquid
What is vapor pressure?
the pressure the gas molecules exert at equilibrium is defined as the “vapor pressure”
Are the inhalation gases actually gases?
NO! they are volatile liquids with molecules in the gaseous state, they are vapors NOT gases.
is vapor pressure affected by atmospheric pressure?
NO! vapor pressure is not affected by atmospheric pressure. VAPOR PRESSURE IS A FUNCTION OF TEMPERATURE and IMF
-the vapor pressure of water at a fixed temperature is the same at sea level as it is on mount Everest
Is boiling point affected by atmospheric pressure?
Yes - boiling point is affected by atmospheric pressure. the boiling point would be lower as atmospheric pressure is lower at higher altitudes.
What two factors constitute the vapor pressure of a substance?
temperature and IMF factor into the vapor pressure
What is vaporization?
vaporization is the conversion of a volatile liquid to a vapor
what happens to the particles during vaporization?
the particles escape the liquid phase and go into the gaseous state
is the process of vaporization an endothermic or exothermic reaction?
endothermic process with a rate determined by the temperature of the liquid
IS VAPORIZATION A CHEMICAL OR PHYSICAL CHANGE?
VAPORIZATION IS A PHYSICAL CHANGE
when does vaporization stop?
vaporization ceases due to cooling unless heat is applied to the system
What three things determine the vapor pressure?
know this
- polarity of the liquid (increase polarity = decrease in VP because greater IMF)
- mass (increased mass = decreased VP)
- temperature (increased temp = increased VP)
Water at 20 degrees C has what VP in mmHg?
H2O at 20 degrees has a VP of 17.5 mmHg (OR temp, room temp)
Water at 37 degrees C has what VP in mmHg?
H2O at 37 degrees has a VP of 47 mmHg (body temp, alveoli temp, water vapor pressure of the lung)
Water at 100 degree C has what VP in mmHg?
H2O at 100 degrees C has a VP of 760 mmHg (this is the boiling point!!)
Anytime the temperature has a VP that equals 760 mmHg, what is that called?
the boiling point
the boiling point is the temperature at which the substance goes from liquid to gas and it is the temperature at which the VP = 760 mmHg
The higher the temp, the _________ the VP, the __________ the KE.
The higher the temp, the greater the VP, the greater the KE.
An increase in IMF, will _____________ the VP.
An increase in IMF, will decrease the VP because the IMF cannot be overcome at the given temp.
What is the latent heat of vaporization?
latent heat of vaporization is the amount of heat absorbed to convert a liquid to gas at its boiling point
- amount of heat absorbed to convert liquid to gas at boiling point