Transcript CHenergy and states of matter student

Matter and Energy
Matter and energy interact and cause
changes in matter.
Energy
Definition: ___________________
Is ___________
Is measured in the unit __________
Can be ____________ or __________
Potential Energy
________ that is _______ (i.e. in a
_________ _________).
Something has the “potential” to do
some kind of work
Example: the child at the top of the
slide has potential energy
REGENTS QUESTION:
Given the balanced equation:
F2 + energy → F + F
Which statement describes what occurs during
this reaction?
(1) Energy is absorbed as a bond is formed.
(2) Energy is absorbed as a bond is broken.
(3) Energy is released as a bond is formed.
(4) Energy is released as a bond is broken.
Kinetic Energy
________ of ________
Example: the child going down the slide
now has kinetic energy
REGENTS QUESTION:
The graph below represents the relationship between time and
temperature as heat is added at a constant rate to a sample of a
substance. During interval AB, which energy change occurs for the
particles in this sample?
(1)The potential energy of the particles increases.
(2) The potential energy of the particles decreases.
(3) The average kinetic energy of the particles increases.
(4) The average kinetic energy of the particles decreases.
So why do we want to study
energy?
Energy = __________
__________________
Having something do
work is great!
Examples: our bodies
need energy to do
work, our cars rely on
energy to do work, our
homes need to be
heated via energy,
etc…
Different types of energy…
______  is waves, visible or invisible
_________ involves moving electrons
_______ movement of molecules
__________ is contained in foods
__________ responsible for the sun
______ waves/vibrations of molecules
__________ involves moving objects
__________ opposing poles
REGENTS QUESTION:
Three forms of energy are
(1) chemical, exothermic, and temperature
(2) chemical, thermal, and electromagnetic
(3) electrical, nuclear, and temperature
(4) electrical, mechanical, and endothermic
Light
Responsible for colors
Responsible for sight
We have found ways to use light to
improve how much we can see and
what we see (example: TV)
Chemical and Electrical Energy
Energizes everything from
remote controls to cars.
Chemical Energy
Chemical energy from
crude oil (natural,
non-renewable
resources) is used to
heat our homes and
run factories that
produce consumer
goods.
Law of Conservation of Energy
_____________________________
_____________________________
Examples of Conservation of Energy
When you watch TV, it starts as _________
________ and converts to _______________
__________.
The ______________(or ____________)
goes into your eye and converts to ________
______ in your nerves and then to the brain.
The _______________(vibrations) go to your
ear drum where is vibrates sending ________
___________ to the brain.
REGENTS QUESTION:
Which quantities must be conserved in
all chemical reactions?
(1) mass, charge, density
(2) mass, charge, energy
(3) charge, volume, density
(4) charge, volume, energy
Summary:
What will we study in this unit?
What is heat? How is it different from
temperature?
How does energy relate to chemical
reactions?
How energy relates to phase changes?
REGENTS QUESTION:
Which temperature change indicates an
increase in the average kinetic energy
of the molecules in a sample?
(1) 15°C to 298 K
(2) 305 K to 0°C
(3) 37°C to 273 K
(4) 355 K to 25°C
Understanding Heat Flow
Heat (q) is defined as the __________
_______________________________.
Heat flows from ______  ________
What will happen if the two objects are
touching? (example)
REGENTS QUESTION
A student made a copper bracelet by hammering
a small copper bar into the desired shape. The
bracelet has a mass of 30.1 grams and was at a
temperature of 21°C in the classroom. After the
student wore the bracelet, the bracelet reached a
temperature of 33°C. Later, the student removed
the bracelet and placed it on a desk at home,
where it cooled from 33°C to 19°C.
Explain, in terms of heat flow, the change in
the temperature of the bracelet when the
student wore the bracelet. [1]
Heat Energy vs. Temperature
__________ is measure of the heat flow.
___________ is a measure of the ______
_____________ of the particles in matter.
REGENTS QUESTION:
The temperature of a sample of matter is
a measure of the
(1) total kinetic energy of the particles in the
sample
(2) total potential energy of the particles in
the sample
(3) average potential energy of the particles
in the sample
(4) average kinetic energy of the particles in
the sample
Heat Energy and Changes in Matter
In virtually all changes in matter,
energy is released or absorbed.
System vs. Surroundings (together they
make the universe).
Examples
REGENTS QUESTION:
A few pieces of dry ice, CO2(s), at 78°C are
placed in a flask that contains air at 21°C. The
flask is sealed by placing an uninflated balloon
over the mouth of the flask. As the balloon
inflates, the dry ice disappears and no liquid is
observed in the flask.
State the direction of heat flow that occurs
between the dry ice and the air in the flask. [1]
Write the name of the process that occurs as
the dry ice undergoes a phase change in the
flask. [1]
Exothermic Reactions (Changes)
___________ reactions
__________________
(i.e. explosions).
A good way to
remember this is to
associate “_____” with
“______”.
Has a –q value because
heat is leaving the
system.
__________________.
Endothermic Reactions (Changes)
_________ reactions ______________
A good way to remember this is to
associate “_______” with “________”.
Has a +q value because heating is
entering the system.
Heat is a ___________.
REGENTS QUESTION:
What occurs when two fluorine atoms
react to produce a fluorine molecule?
(1) Energy is absorbed as a bond is broken.
(2) Energy is absorbed as a bond is formed.
(3) Energy is released as a bond is broken.
(4) Energy is released as a bond is formed.
Activation Energy
Sometimes reactions can’t occur on their
own (they can be exothermic).
They need a little _______________to get
it started.
This energy is called __________________.
Can you think of a common example of a
reaction that requires activation energy?
Energy and Phase Changes
Energy of particles of matter relates to
the phase or state of matter (solid,
liquid, or gas)
Therefore, ______________________
_______________________.
Let’s review what we already know…
Phase Changes
Other
terms
Change in
phase
Endo or
Exo
Sign of
ΔH or q
Endo
+
Melting
Liquefying S  L
Freezing
Solidifying
L S
Exo
-
Vaporization
Boiling
LG
Endo
+
Condensation
_______
GL
Exo
-
Sublimation
_______
SG
Endo
+
Monitoring Energy in Phase
Changes
Have you ever sat and
watched a pot or kettle of
water boil?
Did you ever wonder how
energy from the stove
causes the water to
change phase?
Have you ever thought
about PE and KE changes
in the process of heating
water?
Heating Curve of Water
F
D
B
A
C
E
What changes in phase are
occurring…
____________________-
solid, ice
melting
liquid
boiling
gas
REGENTS QUESTION:
The graph below represents the uniform
heating of a substance from the solid to the
gas phase. Which line segment of the graph
represents boiling?
(1) AB—
(2) CD—
(3) BC—
(4) DE—
What changes in energy are
occurring…
AB- increase in KE (as evident by
increase in temperature)
BC- no change in KE, but continually
adding heat, so increase in PE
CD- increase in ____
DE- increase in ____
EF- increase in ____
REGENTS QUESTION diagram
REGENTS QUESTION:
A sample of a substance is a liquid at
65°C. The sample is heated uniformly to
125°C. The heating curve for the sample
at standard pressure is shown below.
Determine the boiling point of the
sample at standard pressure. [1]
State what happens to the potential
energy of the particles of the sample
during time interval BC. [1]
What is specific heat capacity?
The _________________________
______________________________.
C=____________(specific heat capacity
of water). Table ____
Heat of Fusion
Heat of fusion (Hf) = ______________
energy ___________ or __________
when _________ or ___________.
See Reference Table ___ for values
Ex: Hf H2O = __________
Heat of Vaporization
Heat of vaporization = _____________
or __________ when ____________ or
_____________.
See Reference Tables for values.
Ex: HVH2O = _____________
Kinetic Theory of Heat
Molecules and atoms are constantly in
motion, even in the SOLID phase.
They are said to have kinetic energy or
the energy of motion.
As the energy of the particles increases,
temperature increases.
Heat Calculations and
Phase Changes
One can calculate how much heat is absorbed
or released.
Potential energy
If the problem says…
Melt/freeze
Vaporize/ condense
At 0°C (melting/freezing point)
At 100°C (boiling/condensing point)
Use
Q = mHf (melting/freezing) or
Q = mHv (vaporization/condensation)
Kinetic energy
If the problem says…
Temperature changes
Increase in temp from __ to __
Decrease in temp from __ to __
Heat a liquid/solid
Cool a liquid/solid
Use
Q = mCΔT
Examples
How much heat is needed to melt 10.5
grams of ice at 0°C?
_________________
_________________
_________________
Examples
What mass of liquid water can be
vaporized if 680 J of heat energy is added
at 100°C?
_______________
_________________
_________________
Examples
How much energy is needed to increase
the temperature of 5.0 grams of water
from 0°C to 10°C?
________________
_____________________
_____________
Examples
What is the mass of water that can be
increased in temperature by 15°C by the
addition of 800 J?
_____________
___________________
___________________
Calorimetry
Used to measure amount of heat
released or absorbed during a
chemical/physical change that occurs in
water solution.
“calorimeter” is used to measure the
change in temperature of water
surrounding a reaction.
Cheap Calorimeter- insulation
REGENTS QUESTION diagram
REGENTS QUESTION:
Base your answers to questions1 through 3 on the information
below and on your knowledge of chemistry.
Starting as a solid at 25°C, a sample of H2O is heated at a
constant rate until the sample is at 125°C. This heating
occurs at standard pressure. The graph below represents
the relationship between temperature and heat added to
the sample.
1. Describe what happens to both the potential energy and the
average kinetic energy of the molecules in the H2O sample
during interval AB. [1]
2.Using the graph, determine the total amount of heat added to
the sample during interval CD. [1]
3. Explain, in terms of heat of fusion and heat of vaporization,
why the heat added during interval DE is greater than the heat
added during interval BC for this sample of water. [1]