Physical and Chemical Changes
Lab Takeup
Intro to the lab
• Purpose: To observe changes and determine
whether they are physical or chemical
changes.
• Hypothesis: If a chemical change is observed,
one or more of the five clues for a chemical
change will be observed, because these are
clues that a new substance has been
produced.
Expected Results
Step Before
During and After
Physical or
Chemical?
1
-Copper penny, shiny
-Nitric acid, clear colourless
liquid.
Vigorous bubbling, reddish
brown gas produced. Nitric
acid begins to turn deep
blue/green colour.
Chemical. (gas
produced, colour
change)
2
-Water, clear colourless
liquid
Water boiled, some
condensed on the
watchglass, steam
produced.
Physical (change of
state).
3
-Magnesium, metal,
malleable, somewhat dull.
Sparks, then a bright flame. Chemical (colour
White powder left over
change, heat and
after reaction.
light produced).
4
-Potassium iodide,
transparent solution, slight
yellow colour.
-Lead nitrate, clear
colourless solution.
Yellow precipitate
produced instantly.
Chemical
(precipitate, new
colour).
Expected Results
Substance
Colour and Form
Solubility
Fusibility
Sucrose
Fine powder, crystalline,
white solid
Dissolves in water,
some powder
remained at bottom
of test tube.
Melts, then
caramelizes in tray.
Calcium
Shiny metal, small lump
Vigorous reaction
with water. Bubbles
produced, along with
a white precipitate.
Does not melt easily.
Conclusion
• Several changes were observed. The reactions
in steps 1, 3 and 4 were chemical changes.
They all displayed one or more of the 5 clues
for a chemical change as predicted in my
hypothesis. The change observed in step 2
was a physical change, as it did not display
these clues. It was easily reversed during the
experiment.
Conclusion continued
• In the second part of the lab, a couple of
unexpected chemical changes occurred.
• Solubility is a physical property, however
calcium underwent a chemical reaction with
water.
• Melting, which is also supposed to be a
physical change, was accompanied by a smell
and colour change, indicating that the sugar
had a chemical reaction with the air.
Sources of Error
• Observations made are subjective. One person
may classify a physical change as chemical
because of the gas bubbles produced. An
improvement to this would be to direct the
experimenter to observe reversibility in the
procedure.
• (I’ll be honest, since there is not a lot of
measurement in this lab errors are difficult to
find).
Questions
• This is where I would answer analysis
questions from the lab (if there were any) 
Class questions?
• You might want to look in to questions that the
class might have. Be creative, and try to think of
anything you might get asked.
• Ex: What was the yellow precipitate in Step 4?
– Lead (II) iodide was formed in a double displacement
reaction.
• Ex: Why did calcium produce a precipitate in
water?
– Calcium displaces hydrogen from water, producing
calcium hydroxide, which does not dissolve.
• Ex: Would the hydrogen “pop” if set alight?
– Yes, hydrogen is explosive.