See.:
Name:
_
Experiment: Understanding Mixtures and
Solutions (B. Science 10-2-2b)
purpose: To learn that mixtures are a physical not
~ chemical change. To explain the effects of
particle size, temperature, & stirring on a solid in
po/ution.
sulfur iron
magnet
Materials: Part A:
beaker
plastic bag
Part 8: cold water
100 mL graduated cylinder
stirring rod
~ot water 3 paper towels
6 - 200 m L beakers
6 sugar cubes
Methods: PART A:
_______
-_-n·iiiii--··
••u •••
·-·iiiii-iiiii·
~-.
MIXTURES ARE
RESULT OF A PHYSICAL CHANGE
1. Place about 5 g of sulfur and 5 g of iron on a paper towel next to each otheL
2. Now mix the two elements, note if a chemical reaction is occurring.
3. Now take a magnet, place a plastic bag around it ahd hold it near the mixture.
Make observations.
4. Is this a chemical or a physical separation.
P,~RT 8:
Explain why.
SOLID IN SOLUTION
1. Add 80 mL of hot water to the first two beakers. Add 80 mL of cold water into the
noxt four beakers.
2. Obtain six sugar cubes. Crush three of them on separate paper towels.
3. Add sugar samples to each beaker as indicated on the table in the results section.
\Alhen adding each sample, observe closely and record the time required for the sugar
to completely dissolve. When no sugar particles are visible, record the time in the
table. Observe each sample one at a time for no longer than 3 minutes.
Ai3sults: Part A: MIXTURES ARE A PHYSICAL CHANGE
2. chemical reaction: '--'3. Observation:
4. Type of change:
explain:
P,rut B: SOLID IN SOLUTION
SUGAR SAMPLE
WATER CONDITIONS
TIME TO DISSOLVE (sec)
1
crushed
~ho~t~
_
cube
~ho=t~
_
1
1
crushed
=..co='.=d
_
1
cube
~co_'_d
_
crushed
cold. stirred
1
cube
cold. stirred
1
Conclusions:
--
1. How does particle size affect the rate of sugar dissolving in water?
2. How does temperature affect the r~te of sugar dissolving in water?
3. How does stirring affect the rate of sugar dissolving in water?
4. Describe the quickest way of dissolving a sugar cube in water.
'n
_
e
See.:
Name:
_
5. According to your data which single factor - particle size, heating, or stirring - best
increases the rate of sugar dissolving?
Discussion:
1. Explain the molecular bases for using a food blender to grind solids into a solution.
2. Besides people liking their tea or coffee hot, why do people make their tea or coffee
in hot water?
3. Some solutes dissolve better when the solution is heated. others dissolve better when the solution is
cooled. The following exercise illustrates the importance of temperature in dissolving substances in a
solution. Listed below are the approximate amounts of two different solutes that will dissolve in 100 g of
water at several different temperatures. To more easily compare how temperature affects the solubility of
these two solutes, prepare a graph of these data. The horizontal, or X, axis of your paper should be
temperature. The vertical, or y, axis should be grams of solute dissolved per 100 grams of water. Put both
solutions on the same graph but use a different color for each substance. Be sure to make the intervals
between values a size that fills most of the graph paper. After preparing your graph, use the solubility lines
to answer the following questions. (label axis and the two lines).
180
220
209
21
18
10
9
197
204
16
14
7C••Sulfate
239
185
190
230
12
8
(approximate
grams
Sucrose
dissolved
HnOIl
100
g H2O)
dissolved
per
Cerium
100 gper
H2O)
Ce2(SO.h
Temperature
...
grams
a. At 33°C, which solution would have the most solute dissolved?
b. Which substance is most soluble at 33°C?
c. If you wanted more sucrose to dissolve in water, such as sugar dissolving in tea,
would you heat the solution or cool it?
d. If you wanted more cerium sulfate to dissolve in water, would you heat the
solution or cool it?
e. Between 50C and 100C, which solute shows the greatest change in the amourt thf2t
can be dissolved in 100 g of H20?
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