HOUSEHOLD CHEMISTRY
Problem
How can you identify a common household chemical by comparing its properties with the properties of known
materials?
Introduction
We use chemicals every day to cook, bake, and sometimes to feel better. The chemical and physical properties
of a substance make up an identification tag for each substance. A chemist can use these properties to identify
an unknown substance or to determine the contents of a mixture of substances.
When substances are mixed together two things can happen:
1) Nothing. The substances are mixed but no change occurs.
2) Formation of new substances. The substances interact to produce one or more different substances.
This process is called a chemical reaction.
How do you know if a chemical reaction has occurred? Important clues that a chemical change has happened
are: a change in color, odor or temperature, the production of a gas, or the formation of a precipitate (solid).
In this experiment you will mix several pure substances commonly found in your kitchen with water, vinegar,
and a methanol solution containing iodine and observe the interactions.
Prelaboratory Assignment
 Read the introduction and procedure before you begin.
 Answer the Prelaboratory Questions.
1) What is the difference between a physical and a chemical property?
2) What is the difference between a physical and a chemical change?
3) List 5 clues used to tell whether a chemical reaction has occurred.
 Create a Data Table with the following headings (to neatly record your observations/data):
Solid
Materials
Apparatus
Safety googles
Lab apron
3 disposable pipettes
Masking tape
Marking pen (Sharpie)
8 Plastic Dixie cups
Scoopula/spatula
24-well test plate
Color
RXN with Water
RXN with vinegar
RXN with iodine
Reagents
1% iodine solution in methanol
Vinegar
Salt
Baking Soda
Baking Powder
Sucrose (sugar)
Starch
2 unknown mixes (supplied by your instructor)
1 unknown substance
Safety
None of the chemicals (known to chemists as reagents) are hazardous except for iodine and the methanol
(solution). Common sense procedures should be followed:
1) Wear safety goggles and an apron at all times in the laboratory.
2) Wipe up all spills with large amounts of water.
3) Wash your hands thoroughly before you leave the laboratory.
Methanol is flammable.
4) Avoid extreme heat and flame at all times.
Iodine is a skin and eye irritant and it is toxic to many internal organs. Prolonged or repetitive exposure(s) may
result in organ damage (especially to the lungs and/or nervous system).
5) Avoid contact with skin and eyes at all times. Wash skin immediately and thoroughly if contact occurs.
6) Flush eyes immediately and for 15 minutes in the eye wash if a splash to the eyes occurs. Seek medical
attention if irritation persists.
7) Seek immediate medical attention if inhaled or ingested.
Procedure
1) Label five small Dixie cups: 1, 2, 3, 4, 5. Label three more cups: M1, M2, U (M = mix; U = unknown).
Note: this may be already done for you (depends on how nice your instructor was this morning).
2) Label three pipettes: water, vinegar, and iodine.
3) Place a small amount of each substance, mix, and unknown in the properly labeled cups from the stock
bottles containing each substance.
Note: this may also be done for you already.
4) Record the initial color of each substance in your data table (that you created).
5) Place your 24-well plate flat on the lab bench so that the long edge is vertical toward you. Use masking tape
to create an X and Y axis label just above and to the side of the plate.
Place a mark on the tape marking the row that each substance will go in and the column that each reagent
will go in.
6) Place a small amount of pure substance 1 in the first three wells of the first row (across). Repeat this step
with three sample of pure substance 2 in the second row. Continue this process until you have placed three
samples of each pure substance to be tested (1-5) in the wells in the same order as in your data table.
7) Record the color of each sample in your data table (for any pure substance, mix, or unknown that you have
not already done so for).
8) Draw the correct liquid into each pipette from the containers supplied by your teacher. (They are at the
front and back of the lab.) Carefully place these with their tips up in an empty beaker to hold them until you
are ready to use the liquids.
9) Add 2-3 drops of water to each substance in the first column (vertical) of your test plate. You should add the
water to the first sample and then record your observations in your data table. Repeat for each substance.
Do NOT do the entire column and then record your data; you may miss a reaction!
Be sure to note any/all changes that occur.
10) Repeat step 9 using the vinegar and iodine solutions for column 2 and 3. When you are finished, rinse out
your well plate and shake it dry as best as possible. Run ample water when you rinse out the plate.
11) Repeat steps 5-10, using samples of the mixtures and unknown obtained in your Dixie cups.
Clean-up
1) Rinse the well plate out thoroughly and shake it dry. Wipe it out with a paper towel if necessary to remove
remaining film. Leave out on your lab towel to dry.
2) Wash your lab area with water and wash your hands thoroughly with soap and water before leaving the lab.
Analysis and Conclusions
Complete this section in your “Lab Report Sheet” provided by your instructor.
Lab Report for Household Chemistry
Name(s) ___________________________________
Prelaboratory Questions
___________________________________
1) What is the difference between a physical and a chemical property?
2) What is the difference between a physical and a chemical change?
3) List 5 clues used to tell whether a chemical reaction has occurred.
Data/Observations (draw/insert data table here)
Analysis and Conclusions
1) Compare your data for the pure substances with the data for each of the two solid mixtures.
Which of the pure substances shows behavior that is similar to what you saw with the two-solid mixtures,
M1 and M2?
If you cannot positively identify your mixture(s), discuss the possibilities for the mixtures. Explain thoroughly.
2) Based on your answer to question 1, what is the identity for each of your two solid mixtures?
Mixture 1 is ______________________________ and ______________________________
Mixture 2 is ______________________________ and ______________________________
3) Compare your results for the unknown mixture, U, to the observed characteristics of each pure substance.
Can you identify any of the pure substances as a component of the unknown? Explain (in detail).
4)
What is the major component of the unknown mixture, U; commonly used as an upset-stomach and pain
reliever? Compare your results to the ingredients on the package (see teacher for label).
5) Two of the pure substances (baking powder and baking soda) are used to make baked products.
What chemical property makes these substances useful in baking (explain what they do when reacted)?
How is this property useful in baking?
Which two of the five pure substances exhibit this property?
6) Baking soda reacts with acidic solutions, but not with water.
Identify which of the 5 pure substances is baking soda and which is baking powder. Explain (using your data
and observations, not because you were “given”/told which they were at the onset).
7) One of your pure substances produced a characteristic color (blue-black) when it reacted with the iodinealcohol solution. Starch is an organic compound you probably encountered in your biology course.
Identify which of the pure substances is starch. Explain (using your data/observations).