PHYSICAL AND CHEMICAL PROPERTIES OF MATTER



PHYSICAL AND CHEMICAL CHANGES

OF MATTER

Background Information:

Each kind of matter has certain characteristics that distinguish it from all other kinds of matter. These are called properties. The chemist divides these properties into two categories, physical and chemical properties.

Physical properties can be investigated without changing the composition of the substance. These properties are divided into two groups called INTENSIVE and EXTENSIVE properties. Intensive properties do not depend on the size of the sample while extensive properties will change depending on the sample size. Physical properties are qualities that describe the appearance of a substance, or anything that would be described by your senses.

Chemical properties cannot be investigated without undergoing a chemical change in a substance. Chemical properties describe an interaction of the substance with some other substance. When a substance undergoes a chemical change, it will lose it’s own physical properties and develop new physical properties that represent the new substance that is formed. The following are some evidences of a chemical change:

a. Appearance of a substance (solid, liquid, or gas) d. change in color

b. Change in energy (absorption or production) e. Presence of a new odor

c. Explosion or flammability

Problem: Can you determine the physical and chemical properties of aluminum?

Hypothesis: Write a hypothesis for this lab based on the problem.

Procedure: DAY ONE:

Part A: Physical Properties (Make up a data table for this part)

Take a piece of aluminum foil and measure/observe the following physical properties:

a. Length,

b. Width,

c. Height (the height is 0.00152 cm)

d. Mass

e. Color

f. Malleability

g. Ability to dissolve in water

Part B: Chemical Properties

You will be making observations that might indicate that a chemical change is occurring.

1. Take the piece of aluminum foil given to you in part A and cut into two even pieces so that they measure (approximately) 3.00 cm X 4.00 cm.

2. Rub one piece on both sides with steel wool.

3. Cut both pieces of foil so that they measure (approximately) 1.50 cm X 4.00 cm. Two pieces of foil will be rubbed while two pieces will remain unrubbed.

4. Place 5 mL of 6 M NaOH (strong base) in two separate test tubes.

5. Drop one piece of rubbed foil into one test tube and one piece of unrubbed foil into the other test tube at the same time. Make sure they are in the NaOH. Make any observations of what is happening in the two test tubes. Is there any difference in the reactions of the two test tubes?

6. Place 5 mL of 6M HCl (strong acid) into a test tube.

7. Light your Bunsen burner and get a wood splint ready to use.

8. While one partner drops the piece of unrubbed foil into the test tube and places his/her thumb over the mouth of the test tube, the other partner will be lighting the wood splint.

9. When the partner holding the test tube feels pressure, quickly remove your thumb from the test tube and have the other partner insert the flaming wood splint. Make observations about what has occurred.

10. End of day one lab. Return the unused piece of foil to your teacher and clean up your lab area completely.

DAY TWO:

11. Place 5 mL of HCl and a piece of aluminum foil (gotten from your teacher) into a test tube. When the reaction is over, pour the contents into an evaporation dish. Add about 3 mL of water to the evaporating dish.

12. Slowly heat the evaporating dish with your Bunsen burner until no liquid remains in the dish. Turn off the Bunsen burner. Make any observations about the contents remaining in the dish.

13. When the evaporating dish has completely cooled to your touch, add 10 mL of water and completely dissolve the solid that is present.

14. Transfer the contents to a clean test tube and make observations.

15. Add a few drops (4-5) of ammonia to the test tube and make observations on the contents of the test tube.

16. End of day two. Clean up your lab area completely.

Observations and Data (two parts):

1. Make a table that lists the physical properties that you recorded.

2. Throughout the lab procedure, there are places where you are to record data and observations (#5, #9, #12, #14, #15). Make a table or some other graphic organizer to display this information neatly and in an organized fashion.

Calculations and Analysis (two parts):

1. Calculations for volume, density, and percent error. Be sure to write the formula, plug in the numbers and give your answers with the correct number of significant figures with units. The actual density is 2.699 g/cm3.

2. List the evidences for a chemical reaction for EACH step #5, 9, 12, 14, and 15. Not all are chemical reactions.

Conclusions:

Part One:

Write a short paragraph indicating if your hypothesis was proven or disproved. Explain why. Also discuss the accuracy of your density calculation. Discuss at least two potential errors in your density calculation.

Part Two:

Answer the following questions:

1. Using what you saw in lab, why would you say that properties such as color, mass, and density are considered physical properties?

2. Using what you saw in lab, why would you say that properties such as reaction with an acid and reaction with a base are considered chemical properties?

3. Divide the properties in Part A into intensive and extensive properties.

4. Propose a hypothesis that will explain the difference in the reaction of the rubbed and unrubbed pieces of foil. (Write it in an “If….., then…” statement form.)

5. What is the name of the gas produced when the foil reacted with the HCl? What is your evidence?

6. Where did the gas come from (from which compound)?

7. Would the concentration of the acid or the base affect the reactions you observed? Explain how.

Extra Credit (2 points each)

8. What is the name of the powder that was left after the liquid evaporated in the dish? (Think about what chemicals went into the reaction to begin with)

9. What is the name of the new substance produced when ammonia was added at the end? (Think about what chemicals were there to begin with)

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