Chemical
Reactions
and
Energy
Changes
Exploring key indicators of
chemical change
LESSON AT A GLANCE
Chemical Change
Indicators of Chemical Change
Energy Changes in Chemical Reactions
THINK-PAIR-SHARE
Can you think of an example
of a chemical reaction
you see in your daily life?
How can you determine
if a chemical reaction has
occurred? Name one
sign to look for.
Today, you’ll learn to...
Describe what a chemical change is.
DID YOU KNOW?
Identify indicators of chemical change. The famous
‘elephant toothpaste’
experiment, where a
foamy eruption occurs,
Investigate and identify energy changes demonstrates a rapid
chemical reaction. It forms
in different chemical reactions. when hydrogen peroxide
comes into contact with
yeast.
CHEMICAL
CHANGE
It refers to a process in which burning of wood
one or more substances are
transformed into entirely new
substances with different
properties.
rusting of iron
What indicators should
you look out for to determine
if a chemical change is
taking place?
cooking of egg
Indicators of Chemical Change
Gas Production
Some chemical reactions
result in the formation of
gas or gases.
formation of carbon dioxide when
baking soda mixes with vinegar
Indicators of Chemical Change
Solid Production
Other chemical reactions
result in the formation
of a solid substance
formation of iron oxide
or precipitate*.
that adheres to the
surface of the material *Precipitate is an insoluble solid
that forms out of a solution.
Indicators of Chemical Change
Colour Change
A chemical change also
occurs when there is a
noticeable change in
the colour of a substance
during a chemical reaction. change in colour in
potassium permanganate
when oxalic acid is added
Indicators of Chemical Change
Temperature Change
Another sign that a chemical
change is occurring is when
there is a noticeable change
in the temperature during a
chemical reaction.
change in temperature
as the wood burns
Identify what chemical change
TRY THESE! indicator is shown in each scenario.
chalk formation magnesium
digestion of
reacting of tooth ribbon reacting
food in our
to vinegar decay with hydrochloric
stomach
acid
Y
R KE
SWE
AN
Identify what chemical change
TRY THESE! indicator is shown in each scenario.
GAS PRODUCTION COLOUR CHANGE GAS PRODUCTION COLOUR CHANGE
chalk formation magnesium digestion of
reacting of tooth ribbon reacting food in our
to vinegar decay with hydrochloric stomach
acid
Energy Changes in Chemical Reactions
BURNING OF WOOD
EXOTHERMIC
These are chemical reactions that release energy in
the form of heat or light. When an exothermic reaction
occurs, it often feels warm or hot to the touch.
PHOTOSYNTHESIS
ENDOTHERMIC
These are chemical reactions that absorb or take in
energy from the surroundings. When an endothermic
reaction occurs, it often feels cool or cold to the touch.
THINK ABOUT THIS!
List at least three (3) examples of exothermic and
endothermic reactions you encounter daily.
EXOTHERMIC ENDOTHERMIC
Add example here. Add example here. Add example here.
Add another Add example here. Add another
example here. example here.
PLE
SAM ER
W
ANS
THINK ABOUT THIS!
List at least three (3) examples of exothermic and
endothermic reactions you encounter daily.
EXOTHERMIC ENDOTHERMIC
Burning of a candle Reaction between Melting of ice
a strong acid and
water
Rusting of iron Evaporating liquid Cooking an egg
water
REVIEW
CHEMICAL CHEMICAL ENERGY
CHANGE CHANGE CHANGES
INDICATORS ON CHEMICAL
It is a process in
REACTIONS
which one or Some indicators
more substances are gas production, It can either be
are transformed solid production, exothermic, if it
into entirely new colour change and released energy,
substances with temperature or endothermic,
different change. if it absorbed
properties. energy.
CHEMICAL REACTIONS: A CLOSER LOOK
Make a list of at least five
different observations where
you suspect a chemical change
is occurring.
For each observation, identify
and write down the specific
indicator (gas production, solid
production, colour change or
temperature change) that
suggests a chemical change
is taking place.
