Title: Unknown Substances Lab:
Introduction:
Statement of the Problem:
How can you identify a set of (nontoxic) unknown substances?
Scientists have used different indicators to determine unknown substances. These
indicators react differently to each substance tested. These results help the scientist
narrow down what possible substance they are dealing with in an experiment. Scientists
use their senses to determine the identity of unknown substances. (Except for Taste.)
Scientist use microscopes and magnifying glasses to help distinguish the appearance of
different unknown substances.
History: Baking Soda: Food historians believe the use of baking soda dates back to ancient
civilization and it is perhaps this age-old use of it which has prevented its demise as a chemical
additive.
Source:
http://www.recipes4us.co.uk/Specials%20and%20Holidays/Baking%20Powder%20and%20Sod
a%20Origin%20Uses%20Recipes.htm
Hypothesis: Unknown # 1 is….Unknown #2 is…. (Write a testable hypothesis. Each
unknown will react differently when exposed to different solutions.)
Materials:
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magnifying glass
1g of 4 unknown powders
1g unknown mixture
1 ml water (tap)
1 ml warm water
1 ml vinegar
1 ml iodine solution
5 Petri dish
4 Graduated cylinders
Triple-Beam Balance
4 Eye Dropper
Safety: Iodine is toxic and caution should be used when handling. Hot water can cause
burns, caution should be used when handling. Glass eye dropper can break and cause
cuts. Don’t Taste any substance in the lab.
Procedure: Taking 4 unknown substances and one unknown mixture, we used different
solutions to determine the true identity of each unknown. The solutions we used were:
vinegar, iodine solution, water and warm water. We placed each unknown in a Petri dish
and applied one drop of each solution to each unknown. We used a data table and wrote
down any changes that appeared. We used this information to identify each unknown.
1. Using an 8 ½ X 10 inch piece of paper make a template to keep the unknown
separated. Diagram 1.
2.
Results:
Unknown
1
Appearance
of
Substance
Water
Added
Warm
Water
Added
Vinegar
Added
Iodine
Added
Why color
change?
Predictions x
correct?
Identities
Salt
of
Unknowns
How do
you know?
Unknown
2
Sugar
Unknown
3
Corn
Starch
Conclusion: Refer to your lab report template.
Unknown
4
Mixture
x
x
Baking
Soda
Baking
Soda/Corn
Starch
Diagram 1
1
4
2
3
M
V
I
HW
W