Ch. 5: *Chemical Reactions*

Ch. 5: “Chemical Reactions”
SR 5.1, pg. 153, #1-6
1. Identify which of the following is a
chemical reaction.
a. melting ice
b. burning a candle
c. rubbing a marker
on paper
d. rusting iron
a. NOT a chemical
b. chemical reaction
c. NOT a chemical
d. chemical reaction
2. List 3 signs that could make you think
a chemical reaction is taking place.
• gas given off
• formation of a precipitate
• energy change
• change in color
• change of identity of substances
3. List 4 forms of energy that might be absorbed
or released during a chemical reaction.
• heat
• light
• electricity
• sound
4. Classify the following reactions as
exothermic or endothermic.
a. paper burning
a. exothermic
with a bright flame b. endothermic
b. plastics becoming c. exothermic
brittle after being
left in the sun.
c. a firecracker
5. Predict which atoms will be found in
the products of the following reactions:
a. Mercury (II) oxide, HgO,
is heated & it
b. Limestone, CaCO3,
reacts with hydrochloric
acid, HCl.
c. Table sugar, C12H22O11,
burns in air to form
a. Hg & O
b. Ca, C, O, H, Cl
c. C, H, O
6. Critical Thinking
• Calcium oxide, CaO, is used in cement mixes.
When water is added, heat is released as CaO
forms calcium hydroxide, Ca(OH)2. What signs
are there that this is a chemical reaction? Which
has more chemical energy, the reactants or the
products? Explain your answer.
• Substances change identity, & energy is released.
The reactants have more chemical energy
because the energy of the reactants equals the
energy of the products plus the energy released.