Observations Of Physical And Chemical C

Observations of Chemical and Physical Changes
Hands-On Labs, Inc.
Version 42-0182-00-03

Abstract:

Observations:

Exercise 1: Observations of a Chemical Change
Data Table 1. Chemical Reactions.
Well
Chemical #1 (4 drops)
Chemical #2 (4 drops)
Observations:
Chemical Change (Y/N)
A1
NaHCO3
Sodium Bicarbonate
HCl
Hydrochloric Acid

A2
NaOCl
Sodium Hypochlorite
KI
Potassium Iodide
Observation 1:
+ Add 2 drops of starch
Observation 2:

A3
KI
Potassium Iodide
Pb(NO3)2
Lead Nitrate

A4
NaOH
Sodium Hydroxide
C20H14O4
Phenolphthalein

A5
HCl
Hydrochloric Acid
C20H14O4
Phenolphthalein

A6
NaOH
Sodium Hydroxide
AgNO3
Silver Nitrate

B1
AgNO3
Silver Nitrate
NH4OH
Aqueous Ammonia
Observation 1:
+ Absorb in paper towel and expose to sunlight
Observation 2:

B2
NH4OH
Aqueous Ammonia
CuSO4
Copper Sulfate

Questions
A. Suppose a household product label says it contains sodium hydrogen carbonate (sodium bicarbonate). Using your results from Data Table 1 as a guide, how would you test this material for the presence of sodium bicarbonate?

B. Write the chemical equation for the reaction in well A6.

C. One of the reactions you observed resulted in this product: NaCl + H2O + CO2(g). What well did this reaction occur in? Describe how your observations for this reaction support your answer.

D. You found a sample of a solution that has a faint odor resembling vinegar (an acid). To verify that it is vinegar, you add a few drops of phenolphthalein. The sample turns pink. From this result, can you assume this sample is indeed vinegar or contains some vinegar? Explain your answer using your results from Data Table 1.

E. While performing a starch test on several different cookie brands, four tests result in the typical black color of starch presence, but the fifth gives a yellow-brown color. How might you interpret this result?

F. You have read that a new brand of hair tonic is supposed to contain lead (an ingredient in Grecian Formula®). Devise a simple test to confirm the presence or absence of lead in that hair tonic. Use your observations in Data Table 1 to describe a positive result for this test.

G. Is cutting a cake into 8 pieces a chemical or a physical change? Explain your answer.

H. When a soda is poured into a glass and the soda bubbles, is it the result of a chemical change? Explain your answer.

I. In well B1, what was the reactant in the second step? Did this reactant cause a chemical change? Use your observations to support your answer.

J. Think about how phenolphthalein acts as an acid/base indicator. Do your observations in well A5 support this or contrast what you would expect to happen? Explain your answer.

K. Identify the following as examples as either Physical or Chemical changes:
a. Baking muffin batter to make muffins.
b. Combining dry ingredients (flour, salt, sugar, baking soda) to make muffins.
c. Shredding paper.
d. Burning paper.
e. Cooking tomatoes to make tomato sauce.
f. Chopping tomatoes.
g. Peeling apples.
h. Apple slices turning brown in the air.

Exercise 2: Heating and Combustion
Data Table 2. Heating and Combustion.
Chemical
Initial Observations
Heating Observations
Burning Observations
Mg

Zn

CuCO3

Cu(NO3)2

Questions
A. Describe the similarities and/or differences between heating and burning the magnesium metal. Did either heating or burning produce a chemical change? Explain your answer using the observations collected in Data Table 2.

B. Describe the similarities and/or differences between heating and burning the mossy zinc metal. Did either heating or burning produce a chemical change? Explain your answer using the observations collected in Data Table 2.

C. Describe the similarities and/or differences between heating and burning the Cu(NO3)2. Did either heating or burning produce a chemical change? Explain your answer using the observations collected in Data Table 2.

D. Describe the similarities and/or differences between heating and burning the CuCO3. Did either heating or burning produce a chemical change? Explain your answer using the observations collected in Data Table 2.

E. How would you describe the differences between heating and burning? Use your experiences in the experiment to describe these differences.

F. Which of the four chemicals that was heated produced a physical change? Support your answer with observations made and recorded in Data Table 2.