Identifying Substances Using Properties
KU
/3
TI
/6
App
/5
Feb. 2016
Com
/3
Total
/17
Question: How can physical and chemical properties be used to identify substances?
Hypothesis: If the properties of an unknown substance are identified by testing and observation,
then the substance can be identified by comparing these properties to the properties of known
substances.
Materials:
Safety goggles
Numbered samples of five unknown solids
Small container with distilled water
Small container with dilute hydrochloric acid
Hand lens
Spot plate
Stirring rod
Before you begin, put on your safety goggles!!
Procedure:
1. Two very small samples of each of the five unknown solids were obtained and placed in separate
wells of the spot plate. The unknowns were placed in order so that it was known which was #1, #2,
etc.
2. Each sample was observed using a hand lens.
3. The colour, clarity and crystal shape of each unknown was observed and the description was
recorded.
4. A small amount of water was added to the first sample of each unknown. The samples were stirred
with a stirring rod.
5. Observations were made and the results were recorded.
6. A few drops of dilute Hydrochloric Acid (HCl) were added to each sample of the unknown solids.
7. Observations were made and the results were recorded.
Place a small amount of each unknown in the wells of the spot plate.
You need two samples of each so, put a small amount of unknown 1 in the first well in the first row of
wells and a small amount of unknown 1 in the first well of the second row. Repeat for each unknown.
1
Unknown
#1
2
3
4
5
Observations: (6 marks TI, 3 marks C – neatness and legibility)
Unknown Substance
Property
1
2
3
4
5
Colour
Clarity
Crystal shape
Solubility in
water
Behaviour in
acid
Identity of
solid
Analysis
The chart below shows some properties of five solids. Use this chart to determine the identity of your five solids.
Compare the results you obtained during the lab with the known results below.
Property
NaCl
sodium chloride
Colour
White
Clarity
Crystal
shape
Solubility in
water
Behaviour
in acid
Opaque or
translucent
Small cubes or
small irregular
crystals
Soluble
Dissolves
NaHCO3
sodium
bicarbonate
CaCO3
calcium
carbonate
NaNO3
sodium nitrate
Na2S2O3
sodium
thiosulphate
White
Off-white
White
White
Opaque
Opaque
Opaque
Opaque or
translucent
Powder
Powder
Small spheres
Hexagonal
prisms
Soluble
Insoluble
Soluble
Soluble
New gas is
formed –
tiny bubbles
appear
New gas is
formed – tiny
bubbles
appear
Dissolves
Creates a
cloudy yellow
substance
Discussion:
1. For each of the solids explain how you decided on its identity. (Which property or properties did
you use to identify the solid?) Write 5 sentences! (5 marks A)
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2. Which physical properties did you examine in this activity? (1 mark KU)
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3. Which chemical properties did you examine in this activity? (1 mark KU)
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4. Which sample(s) were the hardest to identify? Why? (1 mark KU)
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