Chapter 3 Resource: Matter and its Changes

Name Date Class
2
Evidence of Chemical Change
Is peanut brittle nothing but sugar with peanuts in it Or does something happen to the sugar during
cooking When heated, sugar becomes a light brown syrup to which you can add peanuts. When
cooled, it hardens into a shiny, brown candy, not into the white crystals that you started with. If a
friend called while you were heating the sugar, you might come back to the stove to find nothing but
a black mass left in the pan. You can’t get the sugar back from the black mass because it isn’t sugar any
more. It’s a different substance and just one example of chemical changes that happen around you.
Strategy
You will observe and describe chemical reactions.
You will identify signs of chemical reactions.
Materials
Laboratory
Activity
plastic spoons (5)
baking soda
self-sealing plastic bag
calcium chloride
plastic medicine bottle, small
water
paper towel
50-mL or 100-mL beakers (2)
cornstarch
droppers (2)
tincture of iodine
Epsom salts
(magnesium sulfate)
test tubes (2)
washing soda
(sodium carbonate)
petri dishes (2)
dull, copper penny
salt
vinegar
Hands-On Activities
Copyright © Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.
Procedure
Part A
1. Put 1 spoonful of baking soda into the
plastic bag. Using a second spoon, put 2
spoonfuls of calcium chloride into the
bag, and use that spoon to mix the substances
together.
2. Fill the medicine bottle half full of water.
Use a paper towel to wipe off any water on
the outside of the bottle. Carefully place the
bottle into the bag, so it remains upright.
3. Hold the bottle in position from the outside
of the bag. Have a partner zip the bag,
squeezing out as much air as possible. Be
sure the bag is tightly sealed.
4. Tip the bag to spill the water into the mixed
chemicals. Hold the bag and observe any
changes. Record your observations in the
table in the Data and Observations section.
Part B
1. Add water to a beaker until it is about half full.
2. Add 2 spoonfuls of cornstarch to the water
and stir.
3. Use a dropper to add about 20 drops of tincture
of iodine to the water. Stir it a few times.
WARNING: Iodine is poisonous if swallowed.
Keep your hands away from your mouth.
4. Allow the beaker to sit for about 2 minutes.
Observe what happens and record your
observations in the table in the Data and
Observations section.
Matter and Its Changes 13