Chemistry 1/2: Chemical & Physical Changes in Matter Lab                   

  Introduction:

Matter can be classified in different ways using physical and chemical properties.  Some physical properties are color, odor, density, hardness, structure, solubility, melting point, and boiling point.  Chemical properties are determined by the reaction of a substance with other substances.  Examples of chemical properties are the following: reacts with acids, reacts with oxygen in the air, decomposes on heating, and is acidic or basic.

            Chemical and physical properties must not be confused with chemical and physical changes.  Physical change refers to a transformation of a substance in which only physical properties change, with the chemical properties remaining constant.  Chemical changes produce new compounds which have different chemical and physical properties that the starting substances.

Objectives: 

In this lab you will investigate the differences between chemical and physical changes in matter by performing four experiments and classifying the changes as chemical or physical.  You will compare and contrast physical and chemical changes in matter.

Equipment: 1 stained test tube ñ ring stand & ring ñ forceps ñ crucible ñ clay triangle ñ dropper ñ glass slides-

test tube rack ñ spatula ñ Bunsen burner ñ test tube holder ñ dissecting microscope ñ well plate

Procedures:

I. Heating copper. 

1.       Obtain a clean dry crucible.  To dry the crucible, heat strongly for 2-3 minutes and allow to cool

2.       Roll some copper turnings into a large tight ball.  Place the ball in the crucible

3.       Mass the crucible and unheated copper together and record the mass to the nearest 0.001 gram. 

4.       Heat the crucible and copper over a hot flame for fifteen minutes.  Turn off flame and allow to cool.  Record the mass of the crucible and heated copper together to the nearest 0.001 gram.

5.       Dispose of the heated copper in the trash can. Only after it has cooled.

II. Heating a wood splint

1.       Obtain a wood splint and break it into small pieces.  Place the wood pieces in the appropriate test tube.

2.       Put the test tube in a test tube clamp on the ring stand and heat the tube strongly with a Bunsen burner for several minutes.

3.       Record your observations

4.       Dispose of the burnt wooden splint in the burnt matches cans

III. NaCl and water

1.       Dissolve a small amount of sodium chloride (NaCl) in about 10 drops of water.

2.       Place 2 drops of the solution on a glass slide.

3.       Hold the glass slide with a forceps and gently evaporate the liquid over a low Bunsen burner flame (Reduce the amount of gas and air to obtain a low flame).

4.       Let the slide cool, then examine the solid formed with the dissecting microscope.  Compare this solid with a fresh sample of NaCl.

5.       Record your observations

6.       Wash and dry the glass slide.

IV. Combining solutions

1.       Combine 5 drops of barium nitrate solution with 2-3 drops of sodium chromate in well #1. Barium nitrate is poisonous, avoid skin contact.  Record your observations in the data table.

2.       Combine 5 drops of iron (III) chloride solution with 1-2 drops of silver nitrate in well #2.  Avoid contact with silver nitrate.  Record you observations in the data table.

3.       Dispose of both well products in the solid waste container then clean and dry the well plates.

RETURN THIS TO THE INSTRUCTOR

Chemistry 1/2: Chemical & Physical Changes in Matter Lab                                            Name(s):

Data Tables

I. Heating Copper

II. Heating Wood

III. Evaporation of NaCl

IV. Combining Solutions

Conclusions:

1. What kinds of evidence normally indicate chemical changes?

2. What kinds of evidence normally indicate physical changes?

3. Explain why the evaporation of the sodium chloride solution is a physical change rather than a chemical change.

4. Explain why a chemical reaction would be needed to separate copper from the oxygen after the copper oxide was formed.

5. How would you tell if a material was a mixture or a compound?