Post-Lab Notes: Chemical vs. Physical Changes
Station
Event
1
Observe water boiling in a
beaker on a hot plate.
Boiling points:
Distilled water: 100° C
Tap water: 102° C
Salt water: 106 ° C
2
3
4
Add 50 mL of acetic acid
solution (vinegar) to 5 g
sodium bicarbonate
(baking soda) in a 500-mL
Erlenmeyer Flask. Light a
wood splint and lower it
into the bottle.
Wax + Heat
Find the mass of the test
tube and wax. Melt wax in
a test tube over a flame.
Mass again.
Read about the Law of
Conservation of Mass
Observe NaCl under
magnification.
Add 0.5 g table salt (NaCl)
to 300 mL of water. Stir.
Repeat with sucrose
(C12H22O11)
Observations/Inferences/
Explanations
Observations: bubbles form in the water as liquid water
turns to steam.
Inferences: Molecules of water are gaining KE, therefore
moving faster. As the liquid water vaporizes, the volume
increases. (Charles’ Law)
Explanations: A change in the state of matter is occurring;
temperature is a measure of the average kinetic energy of
the particles of a substance; this is a demonstration of the
increase of average KE of the particles; kinetic theory of
matter.
Boiling Point Elevation:
Adding substances to water raises the boiling point, so tap
water and salt water have more dissolved substances than
distilled water, and this raises the boiling point.
Chemical or
Physical? Why?
Physical
Change
Observations: bubbles formed; the flame goes out when
lowered into the flask
Chemical
change
Inferences: A gas is produced; the gas is not oxygen -the
gas does not support combustion
A new
substance is
formed that
does not burn
Explanations: A new substance is formed (CO2 gas);
Oxygen is required for a flame to burn; the gas produced is
NOT oxygen
Observations: The wax melts. When it cools, it is still wax;
The mass before melting = mass after melting
Inferences: Particle motion increases with the increase in
temperature.
Explanations: The identity of the wax did not change.
Melting is a physical process
Law of Conservation of Mass applies to both chemical and
physical changes. (mass before = mass after the process)
Observations:
Sodium chloride: white, translucent, box-shaped crystals
(when magnified)
the salt does not immediately dissolve, but will dissolve
after agitation. Salt + water can form a solution.
Sucrose – the crystals were not as regularly-shaped as the
sodium chloride crystals were. Sugar dissolved quickly in
the water.
solubility
Give examples of types of
solutions
The ability of one substance to dissolve in another, or
solubility, is affected by temperature, agitation, & the
nature of the substances being dissolved
Salt water, sugar and water both form solutions
Inferences: salt and water can form a solution; the
particles are too small to be filtered out
Explanations: A mixture can be separated through
physical means. Salt DOES NOT separate from water
through filtration. In a solution, the particles are dissolved.
To separate this mixture, it must be evaporated, or distilled
through vaporization at the boiling point
Change in the
state of matter
does not change
the identity of
water; it is still
H2O, just in the
form of water
vapor
Physical
Change
Wax is the
same identity
Physical
The substances
do not lose their
identities; they
can be
separated
through
physical means
(distillation or
evaporation).
5
6
7
8
Define:
solution
solute
solvent
Add 1-2 drops of 0.1M
AgNO3 to 1-2 drops of
FeCl3 in a test tube.
Mossy Zinc + hydrochloric
acid
Zn + HCl 
Light a wood splint. Let it
burn for a few seconds.
Lower the glowing splint
into the bottle.
Observations: Each compound was initially clear ( 2
solutions); AgNO3 was clear and colorless; FeCl3 was clear
and yellow; when mixed, a light yellow cloudy substance
formed (change in color and clarity); if you look closely,
you can see little white particles in the liquid
Inferences: a new substance was formed
Explanations: the new substance is a precipitate (an
insoluble solid compound that forms when solutions of
certain ionic compounds in solution react). Balanced
Equation:
3AgNO3 (aq)+ FeCl3 (aq)
3AgCl(s) + Fe(NO3) 3 (aq)
Observations: zinc is grey and dull; HCl is clear and
colorless; bubbles form; the test tube felt hot (exothermic
reaction – gives off heat); a lit splint will ignite and “bark”
inside the test tube
Inferences: a gas is produced that is combustible
copper__________
zinc____________
iron____________
aluminum_______
lead____________
Explanations: hydrogen gas is formed and is highly
reactive
Zn (s) + 2HCl (aq)  ZnCl 2 (aq) + H2
Observations: The H2O2 is clear and colorless; the KI is a
white powdery compound; when mixed, it turns orange,
bubbles are formed, a glowing splint is ignited. The
reaction produces heat (exothermic)
If the flask is stoppered, pressure increases as the gas is
produced, and the stopper will eventually pop off – be
careful!
Inferences: a gas is produced that supports combustion=
oxygen gas
Explanations: The reaction has multiple steps; oxygen gas
is formed in one of the steps
Pure Substances:
(include observations)
Elements:
reddish-gold metallic, small pellets;
grey; dull; metallic, irregular shape_______________
dark brown, magnetic, “iron filings”____________
silvery grey, light metal,_low density_____
cube, soft (irregular shape), grey, heavy metal, dense, cube
_sodium chloride, NaCl
_sucrose, C12H22O11____
_ CaCO3_____________
Compounds:
_solid, white, granular, small cubes______________
_solid, white, granular, less regularly-shaped than NaCl_
_solid, white powder________________________
100 mL Hydrogen
Peroxide and ½ tsp.
Potassium Iodide in a 250mL Erlenmeyer flask.
Light a wood splint. Let it
burn for a few seconds.
Lower the glowing splint
into the bottle.
Classifying Matter
(list names of samples)
sodium carbonate solution
(NaCO3 dissolved in water)
brass_________________
steel_________________
_beans________________
_clay________________
_rocks & minerals_____
Homogeneous Mixtures:
_clear, colorless, “poison”_(aqueous solution)_________
_gold-colored; alloy – a solid mixture of copper and zinc
_grey, silvery metal with rust; made of iron, carbon, small
% of other metals elements_________________________
Heterogeneous Mixtures:
_multi-colored ______________________________
_red, soft, moldable, particles are visible___________
_various colors, textures________________________
Chemical
A new
substance was
formed
Chemical
A new
substance was
formed
Chemical
A new
substance was
formed that
supports
combustion
Explanations:
Pure substances
cannot be
broken down by
physical means.