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LAB: Classifying Substances
Intro: To use what you have learned about chemical and physical changes to describe four substances and
their properties based on changes they undergo.
PURPOSE:
Describe the physical properties of four substances. Identify physical and chemical changes. Classify four
substances by their chemical properties.
MATERIALS
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baking powder
baking soda
spot plate
cornstarch
iodine solution
plastic spoons (4)
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stirring sticks
sugar
vinegar
water (H2O)
goggles
PRE-LAB
1. Hypothesis: Given what you know about chemical changes will any of the following powders undergo
a chemical change with water: baking powder, baking soda, cornstarch, or sugar?
2. Hypothesis: will any of the following powders undergo a chemical change with vinegar: baking
powder, baking soda, cornstarch, or sugar?
3. Hypothesis: will any of the following powders undergo a chemical change with iodine: baking powder,
baking soda, cornstarch, or sugar?
PROCEDURE
1. Use Table 1 and Table 2 to record your data.
2. Start with the baking powder.
 Use a spoon labeled baking powder to place a small amount of baking powder into three cups of
your spot plate.
 Use just enough baking powder to cover the bottom of each cup.
 Look at the baking powder.
 What color is it?
 What is its texture? Does it look smooth, or rough?
 Write your answers in Table 1 in the column labeled “Unmixed.”
3. Work with the baking powder in the first cup of the spot plate.
 Use the squirt bottle to add 30 drops (about 1.5 mL) of water to the baking powder in the first cup.
 Stir with the stirring stick.
 Look at the mixture.
 What is the color? Does a reaction take place?
 Write what you see in Table 1 in the column labeled “Mixed with water.”
 Clean your stirring stick.
4. Now work with the baking powder in the second cup of the spot plate.
 Add 1/2 dropper full of vinegar to the second cup of baking powder.
 Stir.
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Write what you see in Table 1 in the column labeled “Mixed with vinegar.”
Clean your stirring stick.
5. Next, work with the baking powder in the third cup of the spot plate.
 Add 5 drops of iodine solution to the third cup of baking powder.
 Caution: Be careful when using iodine. Iodine will stain your skin and clothes.
 Stir.
 Write what you see in Table 1 in the column labeled “Mixed with iodine solution.”
 Clean your stirring rod.
Table 1 Observations
Substance
Baking powder
Baking soda
Cornstarch
Sugar
Unmixed
Mixed with
water
Mixed with vinegar
Mixed with iodine
solution
6. Repeat steps 2–5 for each of the other substances (baking soda, cornstarch, and sugar).
 Use a clean spoon with the correct label for each substance.
7. Analyzing Data In Table 2, write down the following for each substance:
 The type of change you saw—physical or chemical
 The property that the change demonstrates—reactivity or solubility
Table 2 Changes and Properties
Substance
Baking powder
Baking soda
Cornstarch
Sugar
Mixed with iodine
Mixed with water Mixed with vinegar solution
Change Property Change Property Change Property
ANALYSIS QUESTIONS
1. Making Predictions Suppose that you have a mixture of two substances.
a.
The mixture turns black when it is mixed with iodine and bubbles when it is mixed with water
and vinegar.
b.
What two substances are in the mixture? (Hint: Use two of the substances from this
experiment.)
2. Drawing Conclusions Reactivity is a chemical property. Tell which liquid each of the four
substances reacted with, if any. Explain how you know that there was a chemical reaction. What is the
difference between a chemical change and a physical change?