Kitchen Chemicals

The chemical and physical prop= erties of a substance make up a sort of fingerprint that characterizes the substan= ce. In this ChemLab, you will test four unknown sol= ids using three different liquids. The unknowns are common materials that you&#= 8217;d probably find in your kitchen. The results of your tests will give you the information you need to unravel the compositions of mixtures of two solids = and three solids.

OBJECTIVES

• Observe the chemical and physical reac= tions of four common kitchen materials with three test reagents.

• Compare and interpret = the reactions of the test reag= ents with five two-solid and three-solid mixtures of the common kitchen material= s.

• Infer the composition of each of fiv= e unknown mixtures by comparing their reactions with those of the known materials.

HYPOTHESIS:

MATERIALS

microplate

3 thin-stemmed pipets

3 test tubes

spatulas

tooth picks

SAFETY PRECAUTIONS

<= ![endif]>

Wear an apron and goggles. Do = not touch or taste any of the solids or liquids, even though you may believe you know their identities.

PROCEDURE

1. Place the 3 microplates on a sheet of white paper or book cover.

2. Label three long columns of we= lls on the microplate I, II, and III. La= bel nine rows of wells on the microplate A, B, C= , and D, and 1 through 5.

3. Add a small amount of each mat= erial to the row of three wells that has the appropriate letter or number.

4. If you use the same spatula fo= r each material, rinse and dry it before dipping into the next solid to avoid contaminating one material with another.

5. Observe and record the color a= nd texture of each of the nine materials in the data table.

6. From the test tubes of reagent liquids, draw into the bulb of each pipet the liquid corresponding to the l= abel number on that pipet.

7. Add 3 drops of liquid I to each of the nine materials in colum= n I.

8. Stir= each well using a different toothpick. Discard in the trash.

9. Observe any changes that take = place, and record them in the data table.

10. Repeat using liquid II = and then liquid III.

11. Record observations in the data table.

SOLID<= /p>	COLOR<= /p>	TEXTURE	REACTION WITH LIQUID 1<= /o:p>	REACTION WITH LIQUID 2<= /o:p>	REACTION WITH LIQUID 3<= /o:p>	NAME
A =						SALT
B						BAKING SODA
C =						BAKING POWDER
D =						STARCH
1 =
2 =
3 =
4 =
5 =

ANALYZE AND CONCLUDE

1. Interpreting Data What properties and reactions characterize each of the four kitchen solids?

2. Drawing Conclusions = Can you positively identify the solids that are contained in any of the five mixtures? If so, identify the solids and explain your conclusions.

3. Making Inferences If you are unable to conclusiv= ely identify the solids in any of the mixtures, what are their likely identitie= s? Explain

APPLY AND ASSESS

1. Two of the four original solid= s, baking powder and baking soda, are often used in making baked goods. What characteristic probably makes them useful in baking? Which solids display t= his characteristic?

2. Baking powder is a mixture of = two or more compounds, and it reacts with water or any other liquid that contains = water. Baking soda is a single compound that reacts with acidic solutions but not = with water. Which of the solids do you think is baking powder? Explain.

3. One of the solids is an organic compound you may have learned about in a biology course. It produces a char= acteristic color when combined with iodine.

Which solid gave this reaction= ? What is the identity of this compound?