Lab : Physical and chemical properties
A physical change is one in which the substance itself is not changed (although it may look
different). Melting is a physical change. Water is still H2O, whether it is solid (frozen) or liquid
(melted). In a chemical change, such as burning, however, the substance is changed into a new
substance. Wood, a compound made of Carbon, Hydrogen and Oxygen becomes H2O, CO2 and
Carbon when burned. It not only looks different after it is burned, it is different.
Physical properties can be determined without changing the identity of a substance. Some
common physical properties are color, hardness, odor, density, solubility, melting point and
boiling point. The substance is the same before and after checking these properties.
Chemical properties describe how substances make chemical changes. “Iron rusts,” “Wood
burns” or “Gold doesn’t tarnish” are examples of chemical properties. Some indications of a
chemical change are 1) color change, 2) production of a gas, 3) formation of a solid precipitate, and
4) energy changes (light given off, getting hot or cold). Chemical changes also tend to be 5) not
easily reversible. Notice, however, that the physical change of boiling makes a gas, and melting,
freezing and boiling involve energy changes.
In this experiment you will examine a variety of substances and describe their physical
properties. You will then cause several changes to take place in these substances. Based on your
observations, you will decide whether these changes are chemical or physical.
Equipment
Safety goggles
magnet
spot plate
2 beakers
funnel
filter paper
glass stirring rod
evaporating dish
Materials
S
sulfur powder
Fe
iron filings
NaHCO3 sodium bicarbonate
NaCl
sodium chloride
ring stand
ring clamp bunsen burner wire screen
watch glass
crucible tongs
3 small test tubes
Mg magnesium ribbon
Sand
C12H22O11 sucrose (sugar)
3 M HCl
hydrochloric acid
Safety
1. WEAR SAFETY GOGGLES AND APRONS!!
2. The hydrochloric acid (HCl) is Corrosive. If you spill acid on the lab bench sprinkle it with
baking soda (sodium bicarbonate) until the bubbling stops, then wipe up with a damp paper
towel. If you spill acid on your skin then wash the area with cold water. If you get acid in
your eyes, flush with running water in the eyewash for 15 - 20 minutes.
3. Do not look directly at the intense light of the burning magnesium.
4. Before using the bunsen burner, make sure hair is tied back and loose clothing is confined. Let
your partner light the burner if you are wearing fake fingernails. Never leave the burner
unattended!! Be careful with the burner. Burns are the most common lab accident.
Procedure
Part A: Physical properties
1. The substances listed in the Data Table are in small cups at your station. Examine each
substance carefully. Record your observations of the physical appearance of each substance in
the Data Table. Is it a powder, crystal, solid chunk, etc? What is its color?
2. Test the effect of a magnet on each substance by passing the magnet around the outside of the
plastic cup. DON’T dip the magnet directly into the material. Record your
observations.
3. Test the Solubility of each substance in water . Using your plastic pipet, add 1 mL of
water to 6 wells in your spot plate. Add a very small amount of each
sample (enough to cover the tip of the stick) to separate wells and stir
with a toothpick. If the sample completely dissolves in the water, so the
water is clear, the substance is Soluble in water. Record as S in the Data
Table. If the substance doesn’t dissolve, or the water stays cloudy, the
substance is Insoluble in water. Record as I in the Data Table. Wash
out the Spot plate very well with lots of water. You don’t have to test the Magnesium. It’s
Insoluble.
Part B: Causing a Physical or Chemical change
4. a. Combine a small amount of iron filings (Fe) and sulfur (S) on a clean piece of paper. Mix
carefully so the sulfur doesn’t get into the air (the sulfur powder is very irritating). Record
the appearance of the combination in the Data Table.
b. Move a magnet under the paper below the combination. Record your observations in the
Data Table. Give this mixture to your teacher for use in Part C.
5. a. Combine a small amount of the sodium chloride (NaCl) and sand on a clean piece
of paper. Mix and Record your observations.
b. Transfer the combination to a 100 mL beaker. Add about 30 mL of tap water
and stir with a stirring rod. Record your observations.
c. Filter the mixture as follows. Fold a piece of filter paper in quarters. Open to
form a cone and insert into a plastic filter funnel. Wet the paper slightly to
hold it in place. Place the filter funnel in a 250 mL beaker. Pour the salt/
sand/water combination into the funnel. The liquid that passes through the
filter is called the filtrate. Examine both the wet residue in the filter paper and
the filtrate. Record your observations. Discard the filter paper in the trash.
d. Pour about 10 mL of the filtrate into an evaporating dish. Set this dish
on a wire screen on the ring stand. Using a Burner, heat the dish gently
until the liquid has completely evaporated. (You can go on and do the
next several procedures while you boil off the water. ) Allow the dish to
cool. Examine the residue in the dish and record your observations.
Wash the glassware in the sink.
6. Place a watch glass on the lab bench close to your burner. Light the burner.
Use crucible tongs to grasp one end of a large (5 cm) strip of magnesium
ribbon (Mg). Hold one corner of the strip in the burner flame until the
magnesium ignites. DO NOT look directly at the the burning magnesium!!
Place the “burnt magnesium” on the watch glass. Compare the appearance
of this product with that of the original magnesium ribbon. Record your
observations. SAVE the burnt magnesium for procedure 7.
7. a. Put the unburned small (1 cm) strip of magnesium (Mg) into a small test tube.
b. Transfer a small amount of the burnt magnesium into a second small test tube. Try to get
just the burnt part of the sample. Avoid getting any unburnt magnesium into the second
tube.
c. Use your spot plate as a rack for the 2 test tubes. Add 10 drops of 3 M hydrochloric acid
(HCl) to each tube. CAUTION: the hydrochloric acid is very corrosive!! Feel the bottom of
the test tubes. Record your observations in the Data Table.
8. Place a small sample of sodium bicarbonate (NaHCO3) in a clean test tube. Place the tube in
your spot plate. Add 10 drops of 3 M Hydrochloric acid (HCl) to the tube. Touch the bottom
of the tube. Record your observations. Wash the contents of all three tubes down the sink
with lots of water.
Part C: Causing a Physical or Chemical change (Teacher Demo)
9. Your teacher will combine the iron/sulfur combinations prepared in Step 4 in a clean, dry test
tube. Observe for changes while the test tube is heated over a burner for several minutes. This
heating is done in a fume hood because the gases produced can be toxic. Note any odor
produced, the new appearance of the heated combination and any other observations you
think are important. Record in the Data Table.
10. Your teacher will place a small amount of sucrose (C12H22O11 ) in a small, clean, dry test tube.
Observe for changes while she heats the sucrose in a burner flame for 1 – 2 minutes. Note any
odor produced, the new appearance of the burned sucrose and any other observations you
think are important. Record in the Data Table.
11. Wash all equipment. Put away your equipment properly. Leave the materials and any
borrowed equipment in the tray on the bench top (magnet, funnel, filter paper). Be sure to
wash your hands when done.
Lab: Physical and Chemical properties: Names ___________________________________
Data Table Part A
______________________ Mods ______
Substance
Crystal, powder,
chunk etc. ?
Color
Effect of magnet?
Solubility in water
(S or I)
S, Sulfur
Fe, Iron
NaHCO3,
Sodium Bicarbonate
NaCl,
Soldium Chloride
C12H22O11, sucrose
Sand
Mg, Magnesium
Data Table:
System
4. Fe and S,
a. Mixed
b. Tested with
magnet
5. NaCl & sand
a. Mixed
b. Mixed with
water
c. Filtered
d. Filtrate
(liquid)
evaporated
Part B and C: Observations
Chemical or Physical
change? Reason!!!!
Data Table:
System
Part B and C: Observations
Chemical or Physical
change? Reason!!!!
6. Mg
Large piece
burned in air
7. a. Mg
small piece +
3 M HCl
7. b. “Burnt” Mg
(product from #6)
+ 3 M HCl
8. NaHCO3
+ 3 M HCl
TEACHER DEMO
9. Fe and S
heated
10. C12H22O11
heated
Questions : (You probably already answered Q1 in the Data Table)
1. In your Data Table for Parts B and C above, indicate if each change you observed was a
Physical Change or a Chemical change. Give specific reasons for your answers!
2. Classify the following as a heterogeneous mixture, homogeneous mixture, compound or
element.
iron _______________
sulfur _______________
iron + sulfur (no heating) ____________
iron + sulfur (heated) ____________
sodium bicarbonate (NaHCO3) _________
sucrose (C12H22O11)_____________
sand _________________
sand and salt _________________