1. Topic IV Physical Behavior of Matter
Regents Chemistry
Topic IV Physical Behavior of Matter

2. Different Phases of Matter
An element, compound or mixture can exist in the form of a solid, liquid or a gas
Solid – rigid form, definite volume and shape, strong attractive forces and crystalline structure
Liquid – not held together as well, can move past one another, no definite shape but definite volume
Gas – minimal attractive forces, no definite shape or volume, expand to shape of container

3. Other Phases
Vapor – is the gaseous phase of a substance that is a liquid or a solid at normal conditions: ex: water vapor
Plasma – is a gas or vapor in which some or all of the electrons have been removed from the atoms. ex: In a planet’s core!

4. Heating and Cooling Curves
Heating Curves: Constant rate of heating of a substance over time – endothermic process!

5. What Can We Learn From a Heating Curve?
AB: heating of a solid, one phase
present, kinetic energy increases
BC: melting of a solid (melting), two
phases present, potential energy
increases, kinetic energy remains
constant
CD: heating of a liquid, one phase

6. What Can We Learn From a Heating Curve?
DE: boiling of a liquid (Vaporization),
two phases present, potential
energy increases, kinetic energy
remains constant
EF: heating of a gas, one phase
present, kinetic energy increases
***We can tell when the kinetic energy remains constant
because the temperature is not increasing!***

7. Cooling Curves
Shows the constant rate of cooling of a gas at high temperature – an exothermic process

8. Summary of a Cooling Curve
AB: cooling of a gas (vapor), one phase
present, kinetic energy decreases
BC: condensation of the gas (vapor) to
liquid, two phases present, potential
energy decreases, kinetic energy
remains constant
CD: cooling of a liquid, one phase

9. Summary of a Cooling Curve
DE: solidification (freezing) of a liquid,
two phases present, potential
energy decreases, kinetic energy
remains the same
EF: cooling of a solid, one phase
present, kinetic energy decreases

10. Substances That Do Not Follow the Curves
Some substances change directly from a solid to a gas – Sublimation
Example: CO2 changes from a solid to a gas a normal atmospheric pressure
Some substances change directly from gas to a solid – Deposition

11. Practice Problem
Which portions of the graph represent times when heat is
absorbed and potential energy increases while kinetic
energy remains constant?
worksheet

12. Regents Chemistry
Temperature Scales

13. Temperature Scales Celsius ° C Kelvin K Fahrenheit ° F
Based on boiling point/freezing point of water
Kelvin K
Based on absolute zero
Fahrenheit ° F
Used in U.S. and Great Britain

14. Conversions Key Equations °C = 5/9 (°F - 32) °C = K - 273
Celsius to Kelvin
K = °C
Fahrenheit to Celsius
°C = 5/9 (°F - 32)
Kelvin to Celsius
°C = K
Celsius to Fahrenheit
°F = 9/5(°C) + 32
**Add the conversions on the right to your worksheet

15. Practice Problems Convert 10 °C to °F
°F = 9/5(°C) = 9/5 (10 °C) + 32
= 50°F
Convert 25°C to K
K = °C

16. Worksheet Add the Fahrenheit and Celsius conversions to worksheet
Finish worksheet using p from text
Answer problems on p. 52 #71-76 on worksheet - write out question and answer
Homework: p.52 #77,78,79 (a-e)

17. Regents Chemistry
Measurement of Heat Energy

18. Energy and Energy Changes
Energy is the capacity to do work. In other words, it allows us to do things!
Energy surrounds us and is involved in all of life’s daily functions.
It comes in many forms!

19. Energy and Energy Changes
Energy can be used to change the temperature of a substance
As we heat a substance (put in heat), the vibration of molecules in a substance increases.
Example: When a solid is heated, the molecules vibrate until they break free and the substance melts.

20. Specific Heat Capacity
The specific heat capacity of a substance is the amount of heat required to raise 1 gram of the substance by 1 degree Celsius
For water it is J / g• K
Compared to other substances, water has a very high specific heat..what does this mean?

21. Specific Heat Capacities
Check out the specific heat capacities of different substances!

22. Measurement of Heat Energy
Question: You pool absorbs how many much heat energy when it warms from 20 °C to 30 °C?
It easy is we use a formula on our reference tables!
q = mCT

23. This means what?.. q = mCT q = amount of heat absorbed or lost
m = mass in grams
C = specific heat
T = difference in temperature

24. Back to our problem… q = mCT
Question: You mini - pool containing 100,000 g of water absorbs how many much heat energy when it warms from 20 °C to 30 °C?
q = mCT
q = (100,000 g)(4.184 J / g• K) (10 °C) =
q = 4,184,000 Joules!

25. Rearranging the formula..
You need to be able to solve for any of the variables in the equation
q = mCT

26. Making it easy..
If we are finding the heat change during the melting or boiling phases, we can use the Heat of Fusion or the Heat of Vaporization..
Why?? Because temperature remains constant during these periods!

27. Heat of Fusion and Vaporization
Heat of Fusion – amount of heat energy required to melt a unit mass of a substance
For water : HOF = 334 J/g
Heat of Vaporization – amount of energy required to convert a unit mass from liquid to vapor phase
For Water: HOV = 2260 J/g

28. Practice Problem q = 255 g x 334 J/g = 85, 170 J
How many joules are required to melt 255 g of ice at 0°C?
q = m x Heat of Fusion
q = 255 g x 334 J/g = 85, 170 J

29. Measuring Heat Change
Calorie = the amount of energy(heat) required to raise the temperature of one gram of water by one Celsius degree.
1 Calorie (cal) = Joules (J)
Metric system
SI system

30. Converting Calories to Joules
Convert 60.1 cal of energy into joules
60.1 cal X J = J
1 cal = J
1 cal

31. Converting Joules to Calories
Convert 50.3 J to cal
1 cal = J
50.3 J X 1 cal =
12.0 cal
4.184 J

32. Kilojoules and Kilocalories
The prefix kilo means 1000
energy is often expressed in kilos because the numbers are large
We can use Dimensional Analysis to convert.
4.0 J x 1 kJ
= kJ
1000 J

33. Converting kilojoules to kilocalories
1 cal = J
1000 kcal = 4184 kJ
500.0 kJ x
1000 kcal
= 2092 kcal
4184 kJ

34. Regents Chemistry
Behavior of Gases

35. Behavior of Gases
Scientists construct models to explain the behavior of substances
Gas laws are used to describe the behavior of gases
We will focus on the kinetic molecular theory, which describes the relationships among pressure, volume, temperature, velocity, frequency and force of collisions

36. Kinetic Molecular Theory
Major Ideas:
1. Gases contain particles (usually molecules or atoms) that
are in constant, random, straight-line motion
2. Gas particles collide with each other and with the walls of
the container. These collisions may result in a transfer of
energy among the particles, but there is no net loss of
energy as the result of the collisions.
Said to be “Perfectly Elastic”.

37. Kinetic Molecular Theory
3. Gas particles are separated by relatively great distances.
because of this, the volume occupied by the particles
themselves Is negligible and need not be accounted for.
4. Gas particles do not attract each other.

38. Relationship Between Pressure and # of gas Particles
Kinetic Molecular Theory explains why gases exerts pressure
Gas particles collide with each other and the walls of the container
Thus pressure is exerted on the walls
The greater the number of air particles, the greater the pressure
Pressure and number of gas molecules are directly proportional

39. Relationship Between Pressure and Volume of a Gas
If you compress the volume of a container, the particles hit the walls more often and pressure increases. The reverse is also true!

40. Relationship Between Temperature and Pressure of a Gas
Temperature of a substance is defined as the measure of the average kinetic energy of the particles
Kinetic Energy is given by the formula KE = ½ mv2
So, as the temperature rise, the average kinetic energy of the particles increase
Increase is not due to mass, but an increase in velocity of the particles, causing them to hit the walls of the container with greater force (pressure)

41. Relationship Between Temperature and Pressure of a Gas
At constant volume, as the temperature of the gas
Increases, the pressure it exerts increases

42. Relationship of Temperature and Volume of a Gas
At constant pressure,
As the temp of the gas
Increases, the volume
It occupies increases

43. Relationship Between Temperature and Velocity
As temperature increases, the kinetic energy of the particles increase
What causes the increase in temp?
The increase in velocity of the particles
The higher the average velocity of the particles, the greater the temperature
KE = ½ mv2

44. Combined Gas Law Equation
P and V
must be in
the same units
and T must
be in Kelvin!
P1V1
P2V2 T1 T2
This law can be used to solve problems involving
the gas properties of temperature(T), volume(V)
and pressure(P), whenever two or more of these
properties are involved

45. Common Units of Variables
Standard temperature and pressure (STP) is defined as
One atmosphere of pressure and a temperature
of 0 C (273K)
Pressure is defined as force per unit area.
In chemistry, pressure is expressed in units of:
torr, millimeters of mercury (mm Hg), atmospheres (atm)
and kilopascals (kPa).
Normal atmospheric pressure is:
760 torr, 760 mm Hg, 1 atm and kPa

46. Ideal vs. Real Gases The KMT describes Ideal gases, but real gases
behave differently in two ways
1. Real gas particles DO ATTRACT at low temperatures
Ex: ozone!
2. The volume real gas particles occupy at high pressures becomes important..
Real behaves most like ideal at high temperatures and low pressures

47. Gas Law Sample Problem
worksheet

48. Regents Chemistry Agenda 2/26/04 Thursday Review Gases worksheet
Discuss Quiz for tomorrow
HW: STUDY!

49. #1

50. #2