Download Evidence of Chemical Change

Evidence of Chemical Change
Background Information: All matter has physical and chemical properties
by which it can be classified. The physical properties useful to the scientist
are color, odor, density, hardness, structure, solubility, melting point, and
boiling point.
Chemical properties are determined by the reaction of a substance with
other substances. Examples of chemical properties are combinations with
acids and bases, reactions with oxygen and other active gases, and the
reactions of the substance with other compounds.
Changes in which the physical or chemical properties of a substance are
changed are considered physical or chemical changes.
To tell if a change is a chemical change or a physical change, ask yourself
this question: does the change alter the type of substance? If the shape,
size, or physical state is changed but the chemical composition, or type of
matter remains the same, the change is a physical change.
In a chemical change, which is also called a chemical reaction, the atoms of
a substance are rearranged. A chemical change requires that the new
substance have a chemical composition that is different from the
composition of the original substance.
Some signs of chemical changes are: color change, bubbling and fizzing (a
gas is produced), light or heat production (the release of energy), and the
formation of a solid.
Mass is not destroyed or created during any chemical change. The law of
conservation of mass states that the mass of what you end with is always
the same as the mass of what you start with.
Adapted from M. Poarch
http://science-class.net
Procedure:
(1) There are six stations set up around the room. Each station has a task
card with instructions and all of the supplies and materials you will need
to complete the task.
(2) As a team, move through each station, read the instructions of the task
card, and record you observations on this answer sheet.
Station # 1
Substance
Physical Properties
"Before"
Physical Properties
"After"
Observed Changes
Physical Properties
"Before"
Physical Properties
"After"
Observed Changes
Copper Penny
Salt
Vinegar
Station # 2
Substance
Cornstarch
Iodine
Water
Adapted from M. Poarch
http://science-class.net
Station # 3
Substance
Physical Properties
"Before"
Physical Properties
"After"
Observed Changes
Physical Properties
"Before"
Physical Properties
"After"
Observed Changes
Physical Properties
"Before"
Physical Properties
"After"
Observed Changes
Steel Wool
Vinegar
Station # 4
Substance
Baking Soda
Vinegar
Station # 5
Substance
Calcium
Chloride
Water
Station # 6
Substance
Physical Properties
"Before"
Physical Properties
"After"
Plaster of
Paris
Water
Adapted from M. Poarch
http://science-class.net
Observed Changes
Questions & Conclusions:
(1) Identify 4 signs that indicate that a chemical change has taken place.
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(2) For each station, describe the evidence that a chemical change took
place.
Pennies/Salt/Vinegar
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Cornstarch/Iodine/Water
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Steel Wool/Vinegar
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
Adapted from M. Poarch
http://science-class.net
Baking Soda/Vinegar
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
Calcium Chloride/Water
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
Plaster of Paris/Water
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
Adapted from M. Poarch
http://science-class.net
Pennies, Salt, & Vinegar
What to do:
(1) Use a dull, dirty penny for this investigation.
(2) Observe the physical properties of the penny. Record these
observations.
(3) Put the penny on the bottom of a Petri dish.
(4) Sprinkle salt over the top of the penny.
(5) Use a dropper to cover the penny with vinegar.
(6) Observe any changes in the penny.
(7) Record your observations on your answer sheet.
Adapted from M. Poarch
http://science-class.net
Cornstarch and Iodine
Note: IODINE IS POISONOUS - KEEP YOUR HANDS AWAY FROM YOUR
MOUTH!
IT ALSO MAKES A PERMENENT STAIN - IT WILL NOT COME OUT
OF CLOTHES OR OFF YOUR SKIN!!
What to do:
(1) Observe the physical properties of cornstarch. Record these
observations.
(2) Fill a beaker ½ full of water.
(3) Add 2 spoonfuls of cornstarch to the water and stir.
(4) Observe the physical properties of iodine. Record these
observations.
(5) Use a dropper to add 20 drops of iodine to the water. Stir a
times.
(6) Allow the beaker to sit for 2 minutes.
(7) Record your observations on your answer sheet.
Adapted from M. Poarch
http://science-class.net
few
Steel Wool & Vinegar
What to do:
(1) Observe the physical properties of the steel wool. Record
these observations.
(2) Put a small piece of steel wool in a plastic bag.
(3) Measure 10 mL of vinegar and pour into the plastic bag with
the steel wool and seal the bag.
(4) Allow the vinegar and steel wool to sit for about 3 minutes.
(5) Record your observations on your answer sheet.
Adapted from M. Poarch
http://science-class.net
Baking Soda & Vinegar
What to do:
(1) Put one teaspoon of baking soda in a plastic bag. Record these
observations.
(2) Measure 10 mL of vinegar.
(3) Combine the vinegar with the baking soda in the plastic bag
sealing it quickly.
(4) Record your observations on your answer sheet.
Adapted from M. Poarch
http://science-class.net
Calcium Chloride & Water
What to do:
(1) Put one teaspoon of calcium chloride into a plastic bag. Record
these observations.
(2) Measure 10 mL of water.
(3) Combine the water with the calcium chloride in the plastic bag
sealing it quickly.
(4) Record your observations on your answer sheet.
Adapted from M. Poarch
http://science-class.net
Plaster of Paris & Water
What to do:
(1) Put one teaspoon of plaster of paris in a plastic bag. Record
these observations.
(2) Measure 10 mL of water.
(3) Combine the water with the plaster of paris in the plastic bag
sealing it quickly.
(4) Record your observations on your answer sheet.
Adapted from M. Poarch
http://science-class.net