Energy and States of Matter Chapter 11 23-October
Suggested HW
11.11, 11.17, 11.21, 11.23, 11.29, 11.31, 11.33, 11.39, 11.43, 11.45, 11.51, 11.57, 11.59,
11.61, 11.63
Lecture 9
1
Gases, Liquids, and Solids
3
Gases • Very little interaction
between molecules • Lots of motion = lots of
kinetic energy • Low density • Large compressibility • Will expand to fill a
container
Liquids • Potential and kinetic
energies are roughly equal
• High density • Little compressibility • Definite volume and
shape
Solids • Maximum interaction
between molecules • Dominated by potential
energy • High density • Very little compressibility • Definite volume and
shape
Kinetic Theory of Matter
4
Matter is composed of tiny particles that are always in motion
Kinetic Energy – energy that is possessed by an object because of particle motion Increases with temperature
Transferrable upon contact with another particle
Potential Energy – energy that is stored because of positioning Intermolecular Forces are important examples of potential energy
Objects at high temperatures have high kinetic energy
'E = Efinal - Einitial
Changes of State
5
Endothermic Process Any physical or chemical process that REQUIRES
energy
Heat (energy) is necessary to melt ice and
boil water
Changes in state are characterized by changes
in energy ('E)
'E = Efinal - Einitial
Egas > Eliquid > Esolid
Changes of State
6
Exothermic Process Any physical or chemical process that PRODUCES
energy
Heat (energy) is produced when
condensation or freezing occurs
'E = Efinal - Einitial
Energy and Changes of State
7
Liquid Solid + Heat Exothermic
Solid + Heat Endothermic
Liquid
Gas Liquid + Heat Exothermic
Liquid + Heat Endothermic
Gas
If a chemical or physical reaction is exothermic, the reverse reaction is endothermic
Specific Heat and Heat Capacity
8
The specific heat is the amount of heat needed to raise the temperature of one gram given substance by 1˚ C.
Units Æ J/(g ˚C)
Heat Capacity is about the same but it is for a specific amount of the substance.
Units Æ J/ ˚C
Molar Heat Capacity Æ Heat Capacity per mol of substance
Units Æ J/ mol ˚C
Solids and Liquids have different Specific Heats and Heat Capacities
J = Joules Æ unit of energy
1 calorie = 4.184 J
Heat change = mass * specific heat * change in temperature q = mC'T
Sample Problem
9
Solid aluminum has a specific heat of 0.908 J/(g ˚C).
1. Calculate the heat capacity of 16 g of aluminum.
2. Calculate the Molar Heat Capacity of aluminum
Sample Problem
10
1. How much heat is required to raise the temperature of 16 g of aluminum from 20 ˚C
to 82 ˚C?
2. How much heat is needed to change the temperature of 16 g ofwater from 20 ˚C to 82 ˚C (specific heat = 4.18 J/(g ˚C))?
Sample Problem
11
If a 16.0 g chunk of Al (150 ˚C) is dropped in 100 g of water at 20˚C, how much will the temperature of the water change?
Sample Problem
12
If a 750 g chunk of gold (C = 0.13 J/(g ˚C) at 234 ˚C is dropped into 10 kg of water at 4˚C, what will the final temperature of the solution be?
How much energy was transferred?
Changes of State and Energy
16
Q Æ heat absorbed or consumed C Æ specific heat in specified physical state
M Æ mass
'T Æ change in temperature 'Hfusion Æ heat of fusion(melting)
'Hvap Æ heat of vaporization (boiling)
Solid
Liquid
Gas
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