Lesson 5 - Classifying Chemicals Using Properties
Vocabulary
matter, mechanical mixture, mixture, properties, pure substance,
solution
Matter can be classified as either a mixture or a pure substance. Mixtures contain at
least two substances. If you can see the different parts of the mixture it is called a
mechanical mixture.
Ex. Soil, granola cereal, concrete
If the substance appears to be one substance, it is called a solution.
Ex. Vinegar, pop, coffee
Properties of mixtures depend on the proportions of the parts. Have you ever made
lemonade using too much powder? That'll make ya pucker!
Ex. Sweetness of pop, hardness of cement
Pure substances have properties that are always the same. You can identify an
unknown substance by testing its properties.
Ex. Salt, carbon, gold
Click on the item that is not a mechanical mixture?
Which item is a solution?
What made it possible for you to determine whether or not
it was a mechanical mixture? What about the other
substances? Is it hard to tell them apart?
Of course. It is hard to determine whether they are solutions or pure substances by
just looking at them. You must take into consideration all of their physical properties.
Remember...Properties are characteristics that you can use to describe or identify
different substances!
Can you name three properties that would be useful or
helpful in determining whether they are solutions or pure
substances?
We can check whether the melting point, boiling point or density on the labels match
the information in the table below. If they do match, we can say the the substances
are more than likely a pure substance.
In the following lab you will examine samples of unknown substances. While you
examine these substances you need to try and classify them as either a mechanical
mixture, a solution or a pure substance.
Make sure you read and then write out the lab before you begin. Remember to follow
the safety precautions of working in the lab and have all of your materials prepared
before you start!
LAB 5: CLASSIFYING CHEMICALS WITH DATA (Write out the lab).
PROBLEM: How can you classify unknown materials as mechanical mixtures,
solutions or pure substances?
HYPOTHESIS: How do you think it is going to turn out? Use the facts you already
know to come up with a guess that might really make sense.
MATERIALS:
-12 samples of unknown materials
-data table about properties of pure substances (See below).
TABLE: PROPERTIES OF SOME PURE SUBSTANCES
PURE
SUBSTANCE
MELTING POINT
(0C)
BOILING POINT
(0C)
ethanol
(alcohol)
-115
78
aluminum
660
sodium
bicarbonate
(baking
soda)
copper (II)
sulphate
(bluestone)
Substance
decomposes(break
apart) rather than
change state.
Substance
decomposes(break
apart) rather than
Substance
decomposes(break
apart) rather than
change state.
Substance
decomposes(break
apart) rather than
change state.
Substance
decomposes(break
apart) rather than
DENSITY APPEARANCE
(g/cm3)
clear
0.8
colourless
liquid
2.7
silverycoloured
solid
2.2
white solid
2.3
blue solid
crystals
change state.
change state.
3500
3930
3.5
colourless
solid crystals
carbon
(graphite)
4000
3930
2.3
grey-black
solid
copper
1084
2336
9.0
shiny reddish
solid
18
Substance
decomposes(break
apart) rather than
change state.
1.2
colourless
thick liquid
1535
3000
7.9
grey solid
lead
327
1750
1.3
blue-grey
solid
calcium
carbonate
(limestone)
Substance
decomposes(break
apart) rather than
change state.
Substance
decomposes(break
apart) rather than
change state.
2.9
grey-white
solid
naphthalene
80
216
1.2
white solid
sodium
chloride
(table salt)
801
1465
2.2
white solid
2.2
white solid
1.6
white solid
2.1
yellow solid
carbon
(diamond)
glycerol
(glycerine)
iron
Substance
calcium
decomposes(break
hydroxide
apart) rather than
(slaked lime)
change state.
sucrose
(sugar)
170
sulphur
113
Substance
decomposes(break
apart) rather than
change state.
Substance
decomposes(break
apart) rather than
change state.
445
tin
232
2270
7.3
water
0
100
1.0
silveryyellowish
solid
clear
colourless
liquid
Download Properties of Pure Substances
PROCEDURE:
1. Write out the lab and make sure you have two observation tables. (a rough copy
and a good copy to submit with your lab). Observation table
2. Examine each sample and describe its properties. Make sure to note information
on the labels.
**Remember. . . DO NOT OPEN THE VIALS!**
ANALYSIS:
1. Compare the properties of the unknown materials to the pure substances on the
data table. Classify each unknown substance as a mechanical mixture, a solution or a
pure substance.
2.
a) If an unknown sample is a pure substance, identify the pure substance.
b) If an unknown sample is a mechanical mixture or a solution, identify what pure
substances it might contain.
CONCLUSION: You must say what you found out during the lab. You figure out
whether your results agreed with your hypothesis or not. Put everything you
observed together and try to make some sense out of it.
**Hint** The conclusion should answer the problem.