Honors Chemisty Chapter 3
A 15.75-g piece of iron absorbs 1086.75 joules of heat energy, and its temperature changes from 25°C to 175°C. Calculate the specific heat capacity of iron.
0.46 J/gxoC
Standard conditions of temperature and pressure are
0C and 101 kPa
How many bars do we usually use for cold objects?
1 bar
How many bars of energy do solids have?
1 bar
The temperature of an unknown piece of metal with a mass of 30.00 g changes from 25.0 °C to 35.0 °C when the metal absorbs 350.0 J of energy. What is the specific heat of the metal?
1.17 J/g°C
If I heat up 2 pans of water one has 100 mL in it and one has 1000mL. Which one heats up the fastest?
100 mL
The specific heat(c) of copper is 0.39 J/g °C. What is the temperature change(∆t) when 100 Joules of heat(Q) is added to 20 grams?
12.82 °C
How many bars do we usually use room temperature?
2 bars
How many bars of energy do liquids have?
2 bars
A sample of iron receives 50.J of heat energy that raises the temperature of the iron 25.0°C. If iron has a specific heat of 0.10 J/g°C, what is the mass of the iron sample?
20 g
If a piece of aluminum is heated from 30.0oC to 50.0oC, what is the value of ΔT?
20o C
How many Joules of energy are required to change 10 gram of liquid water from 20 C to 90 C?
2926 J
How many joules of heat are needed to raise the temperature of 10.0 g of aluminum from 22°C to 55°C, if the specific heat of aluminum is 0.90 J/gx°C?
297 Joules
What temperature in Kelvin is room temperature?
298 K
Calculate the heat absorbed by 105.0 grams of water when it is heated to cook spaghetti. The initial temperature of the water is 20.0°C, and the final temperature of the water is 99.0°C. The specific heat of water is 4.18 J/g•°C.
34673 J/g°C
How many bars of energy do gases have?
4 bars
You have 20 g of water with specific heat of 4.18 J/g°C. The temperature changes from 25° C to 20° C. How much heat energy (Q) moves from the water to the surroundings?
418 J
When the external pressure is 505 kPa, what is the vapor pressure of water at its boiling point?
505 kPa
When a piece of aluminum foil is taken out of the oven and cools from 100° to 50°, What is the change in temperature?
50°
A 0.3 g piece of copper is heated and fashioned into a bracelet. The amount of energy transferred by heat to the copper is 66,300 J. If the specific heat of copper is 390 J/g 0C, what Is the change of the copper's temperature?
566.7 °C
A material was cooled from 100ºC to 40ºC. What is the temperature change?
60ºC
If the specific heat of water is 4,186 J/kg∙°C, how much heat is required to increase the temperature of 1.2 kg of water from 23 °C to 39 °C?
80,371.2 J
If heat is released by a chemical system, an equal amount of heat will be
Absorbed by the surroundings
Winds are caused by differences in _____.
Air pressure
How does heat flow?
Always from hot to cold
According to the kinetic-molecular theory, collisions between molecules in a gas
Are perfectly elastic
What happens to the rates of condensation and evaporation if the temperature increases?
At first, there will be more evaporation and then there would be more particles which would lead to more condensation until it leads to a new equilibrium.
What is the instrument used to measure air pressure?
Barometer
When the vapor pressure of a liquid is equal to the atmospheric pressure, the liquid begins to do what?
Boil.
When the atmospheric pressure equals the equilibrium vapor pressure ___ occurs.
Boiling
How are conditions of pressure and temperature, at which two phases coexist in equilibrium, shown on a phase diagram?
By a line separating the phases.
What is a device used to measure the heat absorbed or released during a chemical or physical change?
Calorimeter
What is temperature measured in?
Celcius, Kelvin, Farenheight
E(ch) is what?
Chemical energy
The symbol for specific heat is .......
Cp
As you climb up a mountain what happens to the air pressure?
Decreases
Change from Gas to Solid is called.......
Deposition
What are examples of things that go from a solid to a liquid?
Dry ice
Is it hard or easy to evaporate liquids with weak inter molecular forces?
Easy
A process that absorbs heat is called an
Endothermic process
What is it called when the rate of condensation equals the rate of evaporation?
Equilibrium (there is no net change which means that it is stable).
What happens to the oxygen molecules as altitude increases?
Fewer molecules
Small molecules are usually at what state at room temperature?
Gases
What state of matter has the most energy?
Gases
What state of matter is at the highest amount of energy?
Gasses
Q=mH(f)
H(f) is the heat of fusion, melt or freeze
Q=mH(v)
H(v) is the heat of vaporization, boiling or condensing
What is energy being transferred as?
Heat
Endothermic
Heat is absorbed (inside)
Exothermic
Heat is released (outside)
How must energy flow into a system?
Heating
Using the heat equation, what would the formula look like if we were solving for change in temperature?
Q / (m Cp) = ∆T
During a phase change, the temperature of a substance
Remains constant
Students make ice cream to investigate matter and its properties. The students add salt to the ice cream maker so that the mixture will change from a liquid to a solid. Which conclusion provides the most important reason salt is used to make ice cream solidify?
Salt lowers the freezing point of water.
What are particles in a gas best described as?
Small, hard spheres with insignificant volumes.
Freezing goes from what state to what state?
Solid to liquid
What state of matter is at the lowest amount of energy?
Solids
Why do some molecules evaporate?
Some molecules have enough energy to break free from the old of its neighboring molecules to evaporate
A chunk of ice whose temperature is -20C is added to an insulated cup filled with water at 0C. What happens in the cup?
Some of the water freezes, so the chunk of ice gets larger
The amount of energy required to raise the temperature 1ºC for every kilogram is called____?
Specific Heat
The heat required to raise the temperature of a SUBSTANCE by 1∘C
Specific Heat
The lower the boiling point, the stronger or weaker the inter molecular forces?
Stronger
Example of an endothermic phase transition
Sublimation
The direct change of a substance from a solid to a gas is called what?
Sublimation
What is it called when a solid turns directly into a gas?
Sublimation
Heat of Vaporization
The amount of heat required to boil 1 g of a substance at its BP
Heat of Fusion
The amount of heat required to melt 1 g of a substance at its MP
Temperature
The average kinetic energy of particles
Consider an iron cube and an aluminum cube. If the two cubes were at the same temperature, how would the average kinetic energy of the particles in iron compare with the average kinetic energy of the particles in aluminum?
The average kinetic energy of the aluminum particles would be greater.
What does temperature determine?
The direction of heat flow
What is Q?
The heat that is transferred to the surrounding objects
Do the molecules evaporate when you put a lid on a cup of water?
The molecules do not stop evaporating, but it instead bounces and periodically a vapor molecule that is moving slowly will bump in the water surface and stick. This is called condensation.
What are the water vapor molecules doing inside of the cup and what is it called?
The molecules exert a vapor pressure on the sides of a cup.
How does increasing the amount of salt added to the ice affect the freezing and melting points of water?
The more salt, the lower the freezing and melting points of water.
What water molecules evaporate?
The ones at the surface and are moving fast enough
What statements are part of the kinetic molecular theory?
The particles of a gas move independently of each other, move rapidly, and are relatively far apart,
What happens to particles when they are heated?
They speed up and spread out
What would be the effect on the particles if more heat is supplied to the system?
They would speed up
How is energy transferred?
Through the collisions of the particles
All phase changes (changing states) requires energy to be added or taken away. True or false?
True
In an exothermic phase transition, heat energy is transferred from the system to its surroundings. True or false?
True
The specific heat is the amount of energy needed to raise the temperature one degree Celsius of 1 gram of a substance. True or false?
True
What is it called when a liquid goes to a gas?
Vaporization
Water has a specific heat of 4184 J/KgºC. Wood has a specific heat of 1760 J/KgºC. What material needs more energy to raise the temperature 1ºC
Water
Why is water a liquid at room temperature?
Water molecules have a strong attraction for each other (would have to heat it up more to separate the particles)
Formula for solving specific heat problems
q = mcΔT
A high specific heat means...
It requires more energy to change temperature
What unit do you use to measure Thermal Energy?
J
What is the equation for kinetic energy?
KE = ½ mv squared
What does temperature measure?
Kinetic Energy
For a skillet, used for cooking, do you want a high or low specific heat?
Low, so that it will change temperature quickly
Why does a liquid's rate of evaporation increase when the liquid is heated?
More molecules have enough energy to overcome the attractive forces holding them in the liquid.
Chemical energy
Only if a new substance is formed (atoms reargued with atoms)
What happens to particles at higher temperatures?
Particles in an object move faster
Which are the first particles to evaporate from a liquid?
Particles with the highest kinetic energy
E(ph) is what?
Phase energy
What is the symbol for Thermal Energy?
Q
What is thermal energy given off as when heat is given or taken away?
Q
What happens to vapor pressure when you add a solute to a solution?
It lowers the vapor pressure
What happens to vapor pressure when you add salt to water?
It lowers the vapor pressure.
How do you make the water molecules evaportate faster?
Increase the number at the surface and increase the number moving fast enough.
How do you increase the number of molecules at the surface?
Increase the surface and increase the temperature.
Water could be made to boil at 105C instead of 100C by
Increasing the external pressure
What happens to the average kinetic energy of the water if the fastest molecules leave?
It decreases.
What happens to the rate of evaporation of a liquid as the liquid is cooled?
It decreases.
What happens to the temperature of a liquid as it evaporates?
It decreases.
If energy is added to a boiling liquid, what happens to the temperature of the liquid?
It does not change.
If a liquid is sealed in a container and kept at constant temperature, how does its vapor pressure change over time?
It increases at first, then remains constant.
As the temperature of a liquid increases, what happens to its vapor pressure?
It increases.
Why is salt added to roads & walkways in the winter?
It is added to lower the freezing point and prevent ice from forming.
In equilibrium between the liquid state and the gas state, what is true about the rate of evaporation?
It is equal to the rate of condensation.
What is the definition of vapor pressure?
The pressure exerted by the vapor phase of a substance at equilibrium with its liquid phase for a given temperature.
The amount of heat transferred from an object depends on
The specific heat capacity, initial temperature, and the mass of the object
The strength of inter molecular forces varies between liquids, therefore they will have _____.
The strength of inter molecular forces varies between liquids, therefore they will have
How does sweat cool you down?
The sweat evaporates by taking heat from your body and changing from a liquid to a gas
If the rate of boiling equals the rate of condensation...
The system is in equilibrium
Boiling point
The temperature at which a substance boils
Melting point
The temperature at which something melts
An increase in temperature of a contained liquid causes the vapor pressure to do what?
The vapor pressure above the liquid to increase.
When gaseous water condenses to liquid water, what happens to the energy?
The water releases energy to the surroundings.
What happens when you put a lid on a cup of water?
There is no condensation and it is evaporating, as more and more water vapor forms, more condensation appears.
E(th) is what?
Thermal energy
If two objects have reached the same temperature they have reached:
Thermal equilibrium
Which is moving faster, the water vapor or the liquid water if the room is equal to 25 °C, the vapor is equal to 25 °C, and the water is equal to 25 °C?
They are the same.
Depositing / Deposition
When a gas goes directly to a solid
Condensation
When a gas goes to a liquid
Boiling
When a liquid goes to a gas
Freezing
When a liquid goes to a solid
Subliming / Sublimation
When a solid goes directly to a gas
Melting
When a solid goes to a liquid
Are you adding or removing heat when it goes from a solid to a liquid to a gas?
You're adding heat (Endothermic)
Are you adding or removing heat when it goes from a gas to a liquid to a solid?
You're removing heat (Exothermic)
