Chapter 2
Matter and Energy
Chapter 2
Matter and Energy
Table of Contents
Section 1 Energy
Section 2 Studying Matter and Energy
Section 3 Measurements and Calculations in
Chemistry
Chapter 2
Section 1 Energy
Objectives
• Explain that physical and chemical changes in
matter involve transfers of energy.
• Apply the law of conservation of energy to analyze
changes in matter.
• Distinguish between heat and temperature.
• Convert between the Celsius and Kelvin
temperature scales.
Measuring Temperature
Temperature: measure of the
average kinetic energy or energy of
motion
 Use Celsius scale (but SI in Kelvin).
 Water freezes at 0ºC
 Water boils at 100ºC
 Body temperature 37ºC
 Room temperature 20 - 25ºC
0º C

Measuring Temperature
Kelvin starts at absolute zero (-273º C)
 1 K = 1ºC
 ºC = K - 273
 K = ºC + 273
 Kelvin is always bigger (good tip).
 Kelvin can never be negative.

273 K
Chapter 2
Visual Concepts
Temperature and Temperature Scale
The flow of energy -heat:
Energy and heat:
heat
1. Thermochemistry- concerned w/ the _____
change that occur during _______
chemical rxn
_____
___.
doing work
supplying
2. Energy- capacity for _____
___ or ________
heat
_____
3. Heat ( q )- energy that transfers from one
object to another due to temperature
difference (ex. coke in a fridge)




only changes in heat can be detected!
flows from warmer  cooler object until objects
have the same temperature
this energy that transfers is thermal energy
Joule (J) the SI unit of heat and energy
Exothermic and
Endothermic Processes

Essentially all chemical reactions, and changes
in physical state, involve either:
release of heat (exothermic),
or
absorption of heat (endothermic)

Exothermic - heat
flowing out of a system
into its surroundings:
 freezing
 condensing
 system loses heat
as the surroundings
heat up

 melting
 boiling
 system
Ex. water freezing,
raining, &
CH4 + 2O2  CO2 + 2H2O + Heat
gains
heat as the
surroundings cool
down


Endothermic - heat
flowing into a system
from its surroundings:
Ex. ice melting,
sweating, &
CaCO3 + heat  CaO + CO2
Energy
C + O2  CO2 + 395 kJ
C + O2
395kJ
C O2
Reactants

Products
Energy
CaCO
 CaO
CaCO
CaO
+ CO+2 CO2
3 + 176
3 kJ
CaO + CO2
176 kJ
CaCO3
Reactants

Products
Chapter 2
Conservation
Section 1 Energy
of Energy in a Chemical Reaction
Chapter 2
Section 1 Energy
Energy and Change, continued
Energy Can Be Transferred in Different Forms
• Energy exists in different forms, including
•
•
•
•
•
•
chemical
mechanical
light
heat
electrical
sound
• The transfer of energy between a system and its
surroundings can involve any one of these forms of
energy.
Chapter 2
Section 1 Energy
Heat, continued
Transfer of Heat May Not Affect the Temperature
• The transfer of energy as heat does not always result
in a change of temperature.
• For example, consider what happens when energy is
transferred to a mixture of ice and water.
• As energy is transferred as heat to the ice-water mixture, the
ice cubes will start to melt.
• The temperature of the mixture remains at 0°C until all of the
ice has melted.
Chapter 2
Section 1 Energy
Heat, continued
Transfer of Heat May Not Affect the Temperature,
continued
• Once all the ice has melted, the temperature of the
water will start to increase until it reaches 100°C.
• As the water boils, the temperature remains at 100°C
until all the water has turned into a gas.
• The temperature remains constant during the
physical changes in this system.
Chapter 2
 Heating
Section 1 Energy
Curve for Water
Heat Capacity


Heat Capacity: the amount of heat needed to increase
the temperature of an object exactly 1 oC
Heat Capacity of a substance depends on two factors:

specific heat capacity (Cp )- the amount of heat it
takes to raise the temperature of 1 gram of the
substance by 1 oC at constant pressure
 also
called “Specific Heat”
cal/g°C
J/g°C (or J/gK)
water
1.00
4.18
aluminum
copper
silver
gold
0.22
0.093
0.057
0.031
0.90
0.39
0.24
0.13
Chapter 2
Visual Concepts
Specific Heat Capacity
To solve for heat capacity (q)…
q = mCp T





To calculate, use the formula:
“q” is heat, unit- J or cal
“m” is mass, unit- g
“T” = change in temperature,
(T = Tf -Ti ) unit- oC
“Cp”or “C”= Specific Heat Capacity
units: J/(g oC) or cal/(g oC)
Same eq’n, different look!

q = m · Cp · T

Cp =
q
m · T

T =
q
m · Cp

m=
q
Cp · T
(T = Tf -Ti )
Example Problems
1.
It takes 24.3 calories to heat 15.4 g of a metal
from 22 ºC to 33ºC. What is the specific heat of
the metal?
given: q = 24.3 cal
T = Tf -Ti =33 – 22 = 11ºC
m = 15.4 g
Cp = ??
q = m Cp T
q
(24.3 cal)
Cp =
=
m T
(15.4 g)(11 ºC)
=
0.14 cal/(g oC)
Chapter 2
Section 1 Energy
Energy and Change, continued
Endothermic and Exothermic Processes, continued
• Energy can be absorbed by the surroundings or
released to the surroundings, but it cannot be created
or destroyed.
• The law of conservation of energy states that
during any physical or chemical change, the total
quantity of energy remains constant.
• In other words, energy cannot be destroyed or
created.
Chapter 2
Visual Concepts
Law of Conservation of Energy
Demo: Burning Water
Predict why the water appears to have gone
on fire.
 Does water burn?
 What liquids do you know burn?
 Of the liquids named above, which liquids
are less dense than water?
 When fighting a fire created by gasoline
burning, is it wise to try to get the fire out
with water from a fire hose? Why not? What
should be used instead?

Chapter 2
Section 2 Studying Matter and
Energy
Objectives
• Describe how chemists use the scientific method.
• Explain the purpose of controlling the conditions of
an experiment.
• Explain the difference between a hypothesis, a
theory, and a law.
Chapter 2
Section 2 Studying Matter and
Energy
The Scientific Method
• The scientific method is a series of steps followed to
solve problems, including
• collecting data (asking questions)
• formulating a hypothesis
• testing the hypothesis
• stating conclusions
• A scientist chooses which set of steps to use
depending on the nature of the investigation.
Chapter 2
Visual Concepts
Scientific Method
Chapter 2
 Scientific
Section 2 Studying Matter and
Energy
Method
Chapter 2
Visual Concepts
Comparing Theories and Laws
Chapter 2
Section 2 Studying Matter and
Energy
Scientific Explanations, continued
Theories and Laws Have Different Purposes,
continued
• For example, the law of conservation of mass
states that the products of a chemical reaction have
the same mass as the reactants have.
• This law does not explain why matter in chemical
reactions behaves this way; the law simply describes
this behavior.
• Keep in mind that a hypothesis predicts an event, a
theory explains it, and a law describes it.
Chapter 2
Visual Concepts
Models
Test Prep:

In order to advance to the level of a
theory, a hypothesis should be
1.
2.
3.
4.
obviously accepted by most people.
a fully functional experiment.
in alignment with past theories.
repeatedly confirmed by experimentation.

Matter is made of atoms that have positive
centers of neutrons and protons
surrounded by a cloud of negatively
charged electrons. This statement is
1.
2.
3.
4.
a theory.
a hypothesis.
an inference.
an observation.
Chapter 2
Section 3 Measurements and
Calculations in Chemistry
Objectives
• Distinguish between accuracy and precision in
measurements.
• Determine the number of significant figures in a
measurement, and apply rules for significant figures
in calculations.
• Calculate changes in energy using the equation for
specific heat, and round the results to the correct
number of significant figures.
Uncertainty in Measurement
1.
Accuracy, Precision, Error:
a.
b.
c.
d.
e.
2.
Accuracy: measure of how close the measurement
comes to the true value
Precision: how close a repeated measurement is to
one another
correct value
Accepted Value: ______
____ based on reliable
resources
Experimental Value: value measured
_________ in the lab
acceptedvalue - _____
exp’t value
Error = _______
Significant Figures in Measurement:
a.
b.
c.
d.
Sig. fig.: all digits that are known plus one estimated
________
digit
Addition/Subtraction- round to the least decimal
______ place
Multiplication/Division- round to the least _______
sig. fig.
the very end
Round off to the correct sig fig at __________.
Chapter 2
Visual Concepts
Accuracy and Precision
Chapter 2
Visual Concepts
Significant Figures
Significant Figures

Nonzero digits are always significant
46.3ml 3 sig fig
 6,295g 4 sig fig


Zeros between nonzero digits are significant
40.7L 3 sig fig
 87,008 km 5 sig fig


Zeros in front of nonzero digits are not
significant
0.0009785 m 4 sig fig
 0.0009 kg 1 sig fig

Significant Figures cont’d

Zeros both at the end of a number and to the right
of a decimal point are significant



85.00g 4 sig fig
9.004891000 10 sig fig
Zeros both at the end of a number but to the left of
a decimal may not be significant

IF, a zero has not been measured or estimated, it is not
significant


2,000 ml 1 sig fig
IF, a decimal point is placed after zero, it indicates that
the zeros are significant

2,000. ml 4 sig fig
Significant Figure Calculation

In addition and subtraction of numbers, the
result can be no more certain than the least
certain number in the calculation.

Answer can NOT have more digits to the right of
the decimal point than the measurement with the
SMALLEST number of digits.
 3.95+2.598+213.5984
= 220.1464 --> 220.15
Significant Figures Calculation

In multiplication and division, the answer can
NOT have more significant figures than there
are in the measurement with the smallest
number of significant figures.

If a sequence of calculation is involved, do not
round until the end
 12.257
(5sigfig)
X
1.162 = 14.2426234  14.24
(4 sigfig)
(4 sigfig)
Chapter 2.1 Section Review

What is energy?


State the law of conservation of energy


Energy is the capacity to do some type of work
Total quantity of energy remains constant in any physical
or chemical change. Energy can not be created or
destroyed
How does heat different from temperature?


Temperature = measure of kinetic energy of the particles
in an object
Heat = energy that is transferred between two objects
because of a difference in their temperature

What is a system?


A system consists of all the components that are
being studied at a given time
Convert between following Kelvin
temperatures to celsius temperature
273K = 0 °C
 1200K = 927 °C
 0K = -273 °C
 100K = -173 °C


Is breaking an egg an example of a physical or chemical
change?


Is cooking an egg an example of physical or chemical
change?


Chemical change, chemical properties of the egg are changed by
the transfer of energy as heat
What happens in terms of the transfer of energy as heat
when you hold a snowball in your hands?


Physical change, chemical composition of egg remains the same
Energy is transferred as heat from the hand, which is at a higher
temperature, to the snowball, which is at a lower temprature
Why is it impossible to have a temprature value below 0K?

Reducing kinetic energy of particle to zero is impossible

If energy is transferred to a substance as
heat, will the temperature of the substance
always increase?

The temperature of the substance will not
increase if it is undergoing a change of state
Chapter 2.3 Section Review

Perform the following calculations, and
express the answers in correct number of
sig.figs.
0.8102 m x 3.44m = 2.79 m2
 94.20g/3.16722 mL = 29.74 g/mL
 32.89g + 14.21 g = 47.10 g
 34.09L – 1.230 L = 32.86 L


Calculate the specific heat of a substance when
63J of energy are transferred as heat to an 8.0g
sample to raise its temperature from 314K to 340K.
Givens
m= 8.0g
q= 63 J
ΔT= Tf – Ti
= 340K – 314K
= 26K


Equation
q= mCpΔT
Cp = q/ (m ΔT)

Plug in the equation
Cp = 63J / ( (8.0g )(26K))
= 0.30 J./ gK

Express the following in the proper number of
sig.figs.
129g/29.2mL = 4.42 g/mL
 (1.551 mm)(3.260mm)(4.9001 mm) = 24.78 mm3
 35000kJ/0.250s = 1.4 x 10^5 kJ/s


A clock gains 0.020s/min. How many seconds
will the clock gain in exactly 6 months,
assuming 30 days are in each months?
Express in scientific notation.

If you measure the mass of a liquid as
11.50g and its volume as 9.03mL, how many
significant figures should its density value
have? Explain the reason for your answer.

Density = mass/volume
= 11.50g / 9.03mL
(4 sigfig) (3 sigfig)
therefore, should only have 3 sig figs.
Chapter 2
Section 3 Measurements and
Calculations in Chemistry
Determining the Number of Significant
Figures
Sample Problem A
A student heats 23.62 g of a solid and observes that its
temperature increases from 21.6°C to 36.79°C.
Calculate the temperature increase per gram of solid.
Chapter 2
Section 3 Measurements and
Calculations in Chemistry
Determining the Number of Significant
Figures
Sample Problem A Solution
Calculate the increase in temperature by subtracting
the initial temperature (21.6°C) from the final
temperature (36.79°C).
temperature increase = final temperature  initial temperature
36.79°C  21.6°C = 15.19°C = 15.2°C
Chapter 2
Section 3 Measurements and
Calculations in Chemistry
Determining the Number of Significant
Figures
Sample Problem A Solution, continued
Calculate the temperature increase per gram of solid
by dividing the temperature increase by the mass of
the solid (23.62 g).
temperature increase temperature increase

gram
sample mass
15.2°C
 0.644 °Cg
23.62 g
The answer is rounded to three significant figures.
Chapter 2
Section 3 Measurements and
Calculations in Chemistry
Scientific Notation, continued
Scientific Notation with Significant Figures
1. Use scientific notation to eliminate all place-holding
zeros.
2. Move the decimal in an answer so that only one
digit is to the left, and change the exponent
accordingly. The final value must contain the correct
number of significant figures.
Chapter 2
Standardized Test Preparation
Understanding Concepts

1. Which of the following determines the temperature
of a substance?

A.
charge on ions

B.
color

C.
motion of particles

D.
total mass of material
Chapter 2
Standardized Test Preparation
Understanding Concepts

1. Which of the following determines the temperature
of a substance?

A.
charge on ions

B.
color

C.
motion of particles

D.
total mass of material
Chapter 2
Standardized Test Preparation
Understanding Concepts

2. Which of these processes is an endothermic
physical change?


F.
an explosion

G.
melting of butter

H.
condensation of a gas

I.
formation of a solid when two liquids are
mixed
Chapter 2
Standardized Test Preparation
Understanding Concepts

2. Which of these processes is an endothermic
physical change?


F.
an explosion

G.
melting of butter

H.
condensation of a gas

I.
formation of a solid when two liquids are
mixed
Chapter 2
Standardized Test Preparation
Understanding Concepts

3. Which of the following definitely indicates an error
in an experiment?

A.
hypothesis not supported

B.
results contradict a theory

C.
unexpected results

D.
violation of a scientific law
Chapter 2
Standardized Test Preparation
Understanding Concepts

3. Which of the following definitely indicates an error
in an experiment?

A.
hypothesis not supported

B.
results contradict a theory

C.
unexpected results

D.
violation of a scientific law
Chapter 2
Standardized Test Preparation
Understanding Concepts

4. Every chemical change involves

F.
the formation of a different substance.

G.
the vaporization of a liquid.

H.
separation of states of matter.

I.
the release of energy.
Chapter 2
Standardized Test Preparation
Understanding Concepts

4. Every chemical change involves

F.
the formation of a different substance.

G.
the vaporization of a liquid.

H.
separation of states of matter.

I.
the release of energy.
Chapter 2
Standardized Test Preparation
Understanding Concepts

5. Use the concept of specific heat to analyze the
following observation: two pieces of metal with
exactly the same mass are placed on a surface in
bright sunlight. The temperature of the first block
increases by 3°C while the temperature of the second
increases by 8°C.
Chapter 2
Standardized Test Preparation
Understanding Concepts
 5. Use the concept of specific heat to analyze the
following observation: two pieces of metal with
exactly the same mass are placed on a surface in
bright sunlight. The temperature of the first block
increases by 3°C while the temperature of the second
increases by 8°C.

Answer: Because the temperatures of the objects
differ under the same conditions, they must have
different specific heats, so they are made of different
metals.
Chapter 2
Standardized Test Preparation
Understanding Concepts

6. Describe the scientific method.
Chapter 2
Standardized Test Preparation
Understanding Concepts

6. Describe the scientific method.

Answer: The scientific method is a series of steps
followed to solve problems, including collecting data,
formulating a hypothesis, testing a hypothesis, and
stating conclusions.
Chapter 2
Standardized Test Preparation
Interpreting Graphics

Use the graph below to answer questions 9–12.
Chapter 2
Standardized Test Preparation
Interpreting Graphics

9. What is happening during the portion of the graph
labeled Heat of Vaporization, in which temperature
does not change?

A.
No energy is added to the water.
B.
Added energy causes water molecules to
move
closer together.
C.
Added energy causes the water molecules
to move farther apart.
D.
Added energy causes the water molecules
to change from the solid state to the gas state.



Chapter 2
Standardized Test Preparation
Interpreting Graphics

9. What is happening during the portion of the graph
labeled Heat of Vaporization, in which temperature
does not change?

A.
No energy is added to the water.
B.
Added energy causes water molecules to
move
closer together.
C.
Added energy causes the water molecules
to move farther apart.
D.
Added energy causes the water molecules
to change from the solid state to the gas state.



Chapter 2
Standardized Test Preparation
Interpreting Graphics

10. For a given mass of water, which of these
processes requires the greatest addition of energy for
a 1°C temperature change

F.
heating a gas

G.
heating a solid

H.
heating a liquid

I.
changing a solid to a liquid
Chapter 2
Standardized Test Preparation
Interpreting Graphics

10. For a given mass of water, which of these
processes requires the greatest addition of energy for
a 1°C temperature change

F.
heating a gas

G.
heating a solid

H.
heating a liquid

I.
changing a solid to a liquid
Chapter 2
Standardized Test Preparation
Interpreting Graphics

11. How does the temperature change between the
beginning of vaporization and the end of vaporization
of water?

A.
temperature decreases slowly

B.
temperature does not change

C.
temperature increases slowly

D.
temperature increases rapidly
Chapter 2
Standardized Test Preparation
Interpreting Graphics

11. How does the temperature change between the
beginning of vaporization and the end of vaporization
of water?

A.
temperature decreases slowly

B.
temperature does not change

C.
temperature increases slowly

D.
temperature increases rapidly
Chapter 2
Standardized Test Preparation
Interpreting Graphics

12. On what portion of this graph are water molecules
separated by the greatest distance?
Chapter 2
Standardized Test Preparation
Interpreting Graphics

12. On what portion of this graph are water molecules
separated by the greatest distance?

Answer: The right side of the graph, which shows the
conditions of water in the gas phase.