Lab Report: Identifying Physical and Chemical Changes
Nelson Science Perspectives 10 section 5.2
Amazing Student
September 17, 2012
Mrs. Volkmann
SNC 2D
Purpose:
To collect evidence and then use it to identify physical and chemical changes.
Hypothesis:
I predict the following:
Change 1 will be a chemical change
Change 2 will be a chemical change
Change 3 will be a physical change
Change 4 will be a chemical change
Change 5 will be a chemical change
Change 6 will be a physical change
Materials:
See textbook “Nelson Science Perspectives 10” page 180
Procedure:
See textbook “Nelson Science Perspectives 10” pages 180-181
Observations: (could be called “results” – don’t explain anything)
Change
#
1
Summary
Magnesium ribbon (Mg)
added to hydrochloric
acid (HCl)
Description Before Change
Mg – solid, metal, grey
medium lustre, malleable,
ductile, opaque
Description Of Change
Test tube felt warm
bubbles
HCl – liquid, transparent,
colourless, low viscosity,
odourless
2
Burning splint placed
near mouth of test tube
Mg ribbon disappearing
Liquid is still colourless and
clear
Bubbles still rising through
liquid.
“pop” sound when burning
splint placed near mouth
of test tube
3
Copper (II) sulfate
(CuSO4) added to water
CuSO4 – solid, blue, powder,
odourless, opaque
CuSO4 dissolved in the
water and created a blue
solution (transparent, blue,
low viscosity)
Water – liquid, colourless,
transparent, low viscosity,
odourless
4
Steel wool added to
CuSO4
Steel Wool – solid, grey,
metal, ductile, medium
lustre
CuSO4 – liquid, blue,
transparent, low viscosity
5
Add sodium hydroxide
(NaOH) to test tube
from change 4
NEXT, add hydrochloric
acid (HCl)
6
Lauric acid (C12H24O2) is
heated and then cooled
Test tube has greenish blue,
transparent, liquid
NaOH – liquid, transparent,
colourless, low viscosity,
odourless
HCl – liquid, transparent,
colourless, low viscosity,
odourless
Lauric acid – solid, white,
powdery, opaque, brittle,
flowery odour
Test tube felt warm
Dark red solid appears as
steel wool disappears
Solution in test tube turns
greenish blue (still
transparent, low viscosity)
AFTER NaOH – when NaOH
drops hit the greenish blue
solution, brown precipitate
formed
AFTER HCl – brown
precipitate disappeared
and solution became
colourless and transparent
When HEATED – turned
into a colourless,
transparent, low viscosity,
liquid, which smelled like
soap
When COOLED – turned
into a white, opaque,
brittle, solid that smells
like soap
Analysis: (could also be called “discussion” – explain results)
Part 1: Textbook Questions and Answers (See “Nelson Science Perspectives 10” page 181)
a) The following table classifies each change as either physical or chemical and justifies
why based on the observations:
Change #
1
2
3
4
Type of Change
Chemical
Chemical
Physical
Chemical
5
Chemical
6
Physical
Justification
Increased temperature and bubbles/new gas
“Pop” showed evidence of hydrogen gas present
Solid dissolving in a liquid
New colour of the solution (greenish-blue) and new
colour solid (reddish-brown) appeared
Brown precipitate formed when NaOH added, then
disappeared when HCl added
Melting and freezing (change of state)
b) Change 6 was the most difficult to classify because when I saw the solution go back to a
solid, it looked a little different than it started, it wasn’t powdery anymore, so I thought
at first maybe a new substance was created. But then I heated it up again and realized
that it was definitely just a change of state that was happening in change 6.
c) One example from my everyday life when a physical change is reversible is when I boil
water on the stove in a pot. The liquid water turns into a gas as it boils, but when the
gaseous water hits the lid of the pot, it condenses and turns back into liquid water.
One example from my everyday life when a physical change is NOT reversible is when I
chop up carrots for dinner. After chopping them I can’t put them back together, so the
physical change is irreversible.
d) The chemical change in this activity that was reversible occurs in change 5. A brown
precipitate was formed when NaOH was added in change 5. Then when HCl was added
in the second part of of change 5, the precipitate disappeared. Therefore a new
substance was created (chemical change) and when HCl was added that chemical
change was reversed (the precipitate disappeared)!
In order to reverse this change again (and create the precipitate once more) you could
add more of the NaOH, which created the precipitate in the first place.
e) When I heard the “pop” sound in change 2, it showed that hydrogen gas was present.
This is obvious because the starting reactants were Mg and HCl, so if a gas was created,
and elements can’t just magically appear, then it must have been H that turned into a
gas. We know it wouldn’t have been Cl because that gas is deadly and wouldn’t be
created in a science classroom!
Part 2: Sources of Error
There are sources of error in this lab, meaning there are parts of the procedure where errors
could occur, and thus create errors in the observations and results.
Sources of error in this lab include the following:
Change #
1
2
3






Source of Error
Amount of hydrochloric acid added to test tube
Amount of magnesium ribbon added to the test tube
Trouble lighting the Bunsen burner could create a problem because all of
the gas from the test tube could escape before you get the burning split to
the mouth of the test tube
Amount of water added to the test tube
Amount of copper(II) sulfate added to the water
Some solution could spill if the test tube stopper wasn’t in properly
4



5




6
Size of steel wool ball added
Some solution could spill if the test tube stopper wasn’t in properly
Not waiting long enough for the new reddish-brown solid to form and to
settle in the test tube
Amount of sodium hydroxide added to test tube
Adding enough hydrochloric acid to make the brown precipitate disappear
If water wasn’t warn enough the lauric acid wouldn’t melt
If the cool water was too warm the lauric acid wouldn’t solidify again
Conclusion:
In conclusion, this lab allows you to collect evidence and use that evidence to classify each of
six changes.
There are pieces of evidence that can suggest either a chemical or a physical change. For
example in this lab, the following clues suggested a chemical change: bubbles/gas produced,
heat produced, colour change, and precipitate formed. The following clues suggested a physical
change: dissolving and change of state.
My hypotheses were all correct. Change 1 was a chemical change, change 2 was a chemical
change, change 3 was a physical change, change 4 was a chemical change, change 5 was a
chemical change, and change 6 was a physical change.