Chapter 7 Notes
Section 7.1
Matter is made of tiny particles in constant motion
Atomic Theory
Greek philosophers (430 BC ) Democritus and Leucippus proposed that matter is made of tiny particles
called atoms. For 2,300 years atoms were an idea that few believed. In 1803, John Dalton revived the idea
of atoms, but lacked proof.
Brownian motion
In 1827, Robert Brown, a Scottish botanist, saw that the grains of pollen in water moved in an irregular,
jerky way. After observing the same motion, he concluded that all tiny particles move in the same way.
Evidence for atoms
In 1905, Albert Einstein proposed that Brownian motion is caused by collisions between visible particles
like pollen grains, and smaller, invisible particles. This was strong evidence that matter was indeed made of
atoms.
Historical Facts
Ancient Chinese ideas
A collection of ancient texts compiled by Confucius (551-479 BC) discusses the basic “building blocks” of
matter (metal, wood, water, fire, and earth). Some of the writings in these texts were already 1000 years old
when Confucius collected and preserved them in five volumes known as “The Five Classics.”
Ancient Indian ideas
In India, writings from the 6th century BC describe five elements — earth, water, fire, air, and ether — that
make up the universe. The writings explain that all objects such as stones, gold, silver, and trees, are made
up of the five elements.
Ancient Greek ideas
The Greek philosopher Empedocles of Acragas (495-435 BC) explained that everything we see is made up
of four basic elements: fire, water, air, and earth. Aristotle, another Greek philosopher, believed that
Empedocles’ explanation was the best way to understand why there are so many different types of matter.
Definitions:
An element is defined __________________________________________
_____________________________________________________________
An atom _____________________________________________________
_____________________________________________________________
An molecule _________________________________________________
_____________________________________________________________
An compound ________________________________________________
_____________________________________________________________
An mixture ___________________________________________________
_____________________________________________________________
Section 7.2
Measuring temperature
You are really measuring the amount of energy that a particular matter has at that
particular time.
Thermometer: an instrument that measures temperature (amount of energy).
The ________________________uses the expansion of colored liquid __________.
As the temperature increases, it expands and rises up a long, thin tube.
All thermometers are based on a physical property (such as color or volume) that
changes with temperature.
A _____________________________ uses a thermistor to measure temperature.
A _______________________________ in which chemicals that change color at
different temperatures. (Eg. aquarium “sticker” thermometers - outside of the tank)
Temperature Scales:
Water
F. P.
B. P.
Celsius:
0 C
100C
-273 absolute
zero
273 K
373 K
0 K absolute zero
Fahrenheit:
Kelvin:
Conversions between scales
Fahrenheit to Celsius
Celsius to Kelvin
Tc =
Tk =
Celsius to Fahrenheit
Kelvin to Celsius
Tf =
Tc =
TEMPERATURE CONVERSIONS
Convert The Following Temperatures into Celsius Degrees:
1) 45o F
2)
145o F
3)
22o F
4) - 95o F
5) - 45o F
Convert The Following Temperatures into Fahrenheit Degrees:
6)
45o C
7)
135o C
8)
5o C
9)
- 10o C
10) - 45o C
NOW CONVERT ALL OF THE ABOVE INTO KELVIN UNITS
More Temperature Conversion Practice:
1. 45 C = _______K = __________F
2. 298 K = _______C = _________F
3. 50 F = ________C = _________K
4. 0 F = _________C = _________K
5. 0C = _________F = __________K
6. 15 F = ________C = _________K
Temperature and energy
Temperature is a measure of the kinetic energy of individual atoms. Imagine
you had a microscope powerful enough to see individual atoms in a solid at
room temperature. You would see that the atoms are in constant motion. The
atoms in a solid material act like they are connected by springs (Figure 7.9).
Each atom is free to move a small amount. When the temperature goes up, the
energy of motion increases and the atoms jiggle around more vigorously.
Average motion
If you throw a rock, the rock gets more kinetic energy, but the temperature of
the rock does not go up. How can temperature measure kinetic energy then?
We already know the relationship between motion and kinetic energy for a
single object (or atom). For a collection of atoms, the situation is different.
The kinetic energy of a collection has two parts. The kinetic energy you know
comes from the average motion of the whole collection, like the motion of the
whole rock. The kinetic energy that comes from the average motion of all the
atoms together is not what temperature measures.
Random motion
Each atom in the rock is also jiggling back and forth independently of the
other atoms in the rock. This jiggling motion is random. Random motion is
motion that is scattered equally in all directions. On average, there are as
many atoms moving one way as there are moving the opposite way.
Temperature and random motion
Each atom in the rock has kinetic energy from its random motion, as well as
from the average motion of the whole rock. Temperature measures the kinetic
energy in just the random motion. Temperature is not affected by any kinetic
energy associated with average motion. That is why throwing a rock does not
make it hotter (Figure 7.10). When you heat a rock with a torch, each atom
jiggles back and forth with more energy but the whole rock stays in the same
place.
Melting and boiling
The higher the temperature, the higher the random kinetic energy of each
atom. Hot atoms move faster than cold atoms. If you heat a rock with a torch
long enough, the atoms get so much energy they start to break away from
each other. The rock melts. If you keep heating even more the liquid rock will
start to boil. In boiling some atoms have so much energy they leave the rock
altogether and fly off into the atmosphere.
The phases of matter
Solid, liquid, and gas
A ___________________ holds its shape and does not flow.
The molecules vibrate in place, but on average, don’t move
far from their places.
A ___________________ holds its volume, but does not hold its
shape — it flows. The molecules are about as close together as they
are in a solid, but have enough energy to exchange positions with
their neighbors. ______________ flow because the molecules can
move around.
A __________ flows like a liquid, but can also expand or contract to
fill a container. A ____________does not hold its volume. The molecules
have enough energy to completely break away from each other and are
much farther apart than molecules in a liquid or solid.
Intermolecular forces
These intermolecular forces have different strengths for different molecules.
The strength of the intermolecular forces determines whether matter exists as a solid,
liquid, or gas at any given temperature.
Phase Changes = the ________________ change of a substance from one
state to another at _______________ temperature and pressure
Phase changes involve potential energy between particles.
Heat of Vaporization = (H v )
Heat of Fusion =(H f )
Q=
Q=
Heat to Melt (or _________)
(Solid  Liquid)
Heat to Vaporize (or _________)
(Liquid  Gas)
Section 7.3
What is Heat?
____________________ is the sum of all of the kinetic energy of atoms or molecules
added up together.
Thermal energy depends on ________________and _____________________ .
Two pots of water which are both heated to 85o Celcius.
#1 has 1,000 grams of water
#2 has 2,000 grams of water.
Which takes more energy?
Why?
What is heat? It is the flow of _____________________________.
Heat is really is thermal energy ____________________________.
(If there is a difference in the temperatures)
*Heat always flows from the ____________________ (higher energy)
to the ____________________(lower energy). ***********
Units of heat and thermal energy
The joule is the metric unit for measuring heat.
- The average hair dryer puts out 1,200 joules of heat every second!
The calorie is defined as the quantity of heat needed to increase the temperature
of ____________ of water by _____________________.
- The unit used for measuring energy content of the food we eat is the kilocalorie,
which equals 1,000 calories.
The British Thermal Unit is defined as the quantity of heat it takes to increase the
temperature of ______________ of water by __________.
-The Btu is often used to measure the heat produced by heating systems
or heat removed by air-conditioning systems.
Specific Heat
The specific heat is the amount of energy that will raise
the temperature of one kilogram of material by one degree Celsius.
You need to add __________of heat to 1 kg of water to raise the temperature by 1°C.
You only need ___________ to raise the temperature of 1 kg of steel by 1°C.
It takes 9 times more energy to raise the temperature of water by 1°C than it does to
raise the temperature of the same mass of steel by 1°C. APPLE PIE !!!
****** Knowing the specific heat tells you how quickly the temperature of a
material will change as it gains or loses energy.
Why is specific heat different for different materials?
- Materials made up of heavy atoms or molecules have ______________________
compared with materials made up of lighter ones.
- This is because temperature measures the__________________________________.
- Heavy particles mean fewer molecules per kilogram. Energy that is divided between
fewer particles means more energy per particle, and therefore more temperature change.
Calculating energy changes from heat
Q = m c (T 2 – T 1 )
1. How much heat is needed to raise the temperature of a 250-liter hot tub from 20°C to 40°C?
The specific heat of water is 4,184 J/kg°C. (HINT: 1 liter of water has a mass of 1 kilogram.)
2. How much heat energy is needed to raise the temperature of 2.0 kilograms of concrete
from 10°C to 30°C? The specific heat of concrete is 880 J/kg°C.
3. How much heat energy is needed to raise the temperature of 5.0 grams of gold from 20°C
to 200°C? The specific heat of gold is 129 J/kg°C.
7.4 Heat Transfer
Heat conduction
Conduction occurs between two materials at different temperatures and when they are
_______________________each other. Eg. Holding a Hot cup of coffee.
Convection
Convection is the transfer of heat through the motion of fluids such as ___________
and ___________________.
Thermal radiation
is electromagnetic waves (including light) produced by objects because of their
temperature. All objects with a temperature above absolute zero (-273 °C or -459 °F)
emit thermal radiation.
Thermal radiation comes from atoms
Thermal radiation comes from the thermal energy of atoms. The power in
thermal radiation increases with higher temperatures because the thermal
energy of atoms increases with temperature (Figure 7.20). Because the sun is
extremely hot, its atoms emit lots of thermal radiation.
Objects emit and absorb radiation
The temperature of an object _________ if more radiation is absorbed.
The temperature _____________ if more radiation is given off.
The temperature adjusts until there is a ____________ between radiation absorbed
and radiation emitted. (_______________________)
The amount of thermal radiation absorbed depends on the surface of a material.
Black surfaces ________________ Mirrored surfaces ___________________
Thermal radiation can travel through the vacuum of space.
Conduction and Convection cannot carry heat through space because both processes
require matter to transfer heat.
Thermal radiation also travels fast (EM Waves) - at the speed of light.
Thermal Equilibrium =
As collisions continue, the molecules of the hotter material lose energy and the molecules
of the cooler material gain energy. The kinetic energy of the hotter material is transferred,
one collision at a time, to the cooler material. Eventually, both materials are at the same
temperature. When this happens, they are in _____________________________.
Thermal equilibrium occurs when two bodies have the ______________________.
No heat flows in thermal equilibrium because the temperatures are the same.
Heat: (Q)
Unit: Calories (cal) or Joules (J)
Thermal Equilibrium Q lost = Q gained
* Heat lost by the hot object = heat gained by the cold object
Q = m c (T 2 – T 1 )
Thermal Equilibrium Practice:
1. 0.5 kg of hot water at 90 o C is poured into 0.5 kg of cold water at 10 o C.
a. How much heat does the hot water contain?
b. How much heat does the cold water contain?
c. What is the Total Energy of the mixture?
d. What is the new temperature of the combined liquid?
2. Exactly 0.2 kg of hot water at 80 o C is poured into
0.1 kg of cold water at 20 o C.
a. How much heat does the hot water contain?
b. How much heat does the cold water contain?
c. What is the Total Energy of the mixture?
d. What is the new temperature of the combined liquid?
3. Exactly 1.2 kg of hot water at 95 o Celcius are poured into 0.8 kg of cold water
at 15 o Celcius.
a. How much heat does the hot water contain?
b. How much heat does the cold water contain?
c. What is the Total Energy of the mixture?
d. What is the new temperature of the combined liquid?
The rate of heat transfer
In nature, heat transfer always occurs from hot to cold until thermal equilibrium is
reached. The rate of heat transfer is proportional to the difference in temperature. If the
temperature difference is large, heat flows faster than when the temperature difference is
small.
Thermodynamics- the study of ____________.
1st Law of Thermodynamics – the total increase in thermal
energy of a system is the sum of the work done on it and the
heat added to it.
2nd Law of Thermodynamics - no machine can be made that
only absorbs energy by heat and then entirely transfers the
energy out of the engine by an equal amount of work.
 3rd law of Thermodynamics- Entropy
- a measure of a systems disorder
Systems with maximum disorder are favored.
Increasing disorder reduces the energy available for work.
The entropy of the universe increases in all natural processes.
Entropy can increase or decrease within a system.