Energy
Transformations
Mr. Carter’s Science Class
The 1st Law of thermodynamics
Write down the 1st Law
of Thermodynamics
from memory
 Matter and energy
cannot be created or
destroyed.
 They can change
forms, though.
Chemical Reactions
In chemical reactions
energy just changes
form from one form
to another.
 For example when a
candle burns the
energy stored in the
candle wax get
converted thermal
energy (heat) and
light.

All chemical reactions fit into 2
categories
Exothermic
Reactions
Endothermic reactions
Exothermic Reactions

Exothermic reactions
are reactions that
produce more energy
than they require

Example: the
chemical reaction that
takes place in a hot
pack to produce heat.
The chemical energy
stored in the hot pack
is converted to
thermal energy.

Endothermic Reactions

Endothermic reactions
are reactions that
require more energy
than they produce

Example: When you
boil a used-up hot
pack to make it
reusable.
The thermal energy
from the stove is
converted back into
chemical energy in
the hot pack.

4 important chemical reactions
1.
2.
3.
4.
Photosynthesis
Combustion
Aerobic Cellular Respiration
Fermentation
1. Photosynthesis
CO2 + H2O + sunlight → C6H12O6 + O2
 Balance the equation now.
 Photosynthesis is performed by autotrophs

 Autotroph=
bacteria.
plants, algae, and photosynthetic
1. Photosynthesis
Carbohydrates
are the product
 Oxygen is the
by-product

1. Photosynthesis
Carbohydrates are the primary energy
source for the majority of living things (us
included.
 Carbohydrates are also called sugars and
often taste sweet.
 Carbohydrates have an “–ose” suffix.

 Examples:
cellulose
sucrose, fructose, maltose,
2. Combustion
Combustion is the process of burning
carbon-and-hydrogen-containing
compounds (hydrocarbons)in the presence
of oxygen
 Hydrocarbon + O2 → CO2 + H2O + Energy

2. Combustion
Balance the equation for the combustion
of propane gas (C3H8)
 C3H8 + O2 → CO2 + H2O + Energy
 Name 4 things that humans use
combustion reactions for.

3. Aerobic Cellular Respiration

Cellular respiration is the process of
getting energy from the sugars in food in
the presence of oxygen.
C6H12O6 + 6O2 → 6CO2 + 6H2O + 36ATP
 Balance the equation now.

3. Aerobic Cellular Respiration




Cellular respiration happens
in the cells of an organisms
Cellular respiration
(breathing) is why most
organisms need oxygen
(including us)
This is why we need to eat
food (and mainly
carbohydrates).
Cellular respiration occurs in
the mitochondria of the cell.

For this reason, the
mitochondria are known as
the “powerhouses” of the
cell.
ADP
Adenosine
Triphosphate
 ATP is created
by adding a
phosphate
group to ADP.
This requires
energy.

ATP
ATP

ATP is “used
up” for
energy by
the cell and
converted
back into
ADP
(Adenosine
Diphosphate)
ADP
ATP or ADP?
ATP or ADP?
ATP or ADP?
ATP or ADP?

Create your own analogy!
4. Fermentation
Fermentation is the process of converting
sugars into ATP WITHOUT oxygen.
 Fermentation is also called anaerobic
cellular respiration
 C6H12O6 → CO2 + C2H6O + 2ATP
 Balance the equation now.

4. Fermentation
Fermentation is often
performed by yeast and
bacteria.
 Yeast produce CO2 gas as
they ferment, making
bread rise.
 Yeast also make beer
alcoholic (ethanol) and
foamy (CO2).

Fermentation
Some fermenting
bacteria produce Lactic
Acid instead of alcohol.
 Lactic acid makes
fermented foods taste
sour or tangy.
 Lactic Acid Fermentation
is used to produce “sour”
products like yogurt,
sour cream, kimchi,
pickles, sourkraut, etc.

4. Fermentation
Anaerobic cellular respiration also
occurs in our muscles during
VIGOROUS exercise.
 If your body is working so hard
that your lungs can’t keep up
(you can’t get enough Oxygen to
your muscles), your muscle cells
have to do anaerobic cellular
respiration
Aerobic

Anaerobic
What is Air?





Air is not a pure substance,
but a mixture of several
gases.
78% of air is Nitrogen (N2)
which is inert (does not
easily react with other
molecules).
21% of Air is Oxygen (O2)
0.9% of Air is Argon (Ar),
which is inert because it is a
noble gas
0.037% of air is Carbon
Dioxide (CO2)
Rising Carbon Dioxide





CO2 levels in the atmosphere
are increasing.
This is mostly because
humans are combusting fossil
fuels for energy and
transportation.
We are also cutting down
forests and replacing them
with cities and farms.
Forests REMOVE CO2 and
replace it with O2
Animals, like cows and
people, REMOVE O2 and
replace it with CO2
The greenhouse effect
CO2 is called a greenhouse
gas because it surrounds
the planet and “traps” heat
and light.
 This is called the
greenhouse effect and it is
causing global mean
temperatures to increase.
 The greenhouse effect also
causes the world’s climate
to get screwed up by
increasing global
temperatures.
