Lab Investigation: Chemical & Physical Changes in Matter

CHEMICAL & PHYSICAL CHANGES IN MATTER Before performing the lab in class, start writing your lab report by summarizing the following background information about physical and chemical properties and physical and chemical changes. Your “background” section should be 4-6 sentences. This will be checked off before you may perform the lab.

Background: Matter can be classified in different ways using chemical and physical properties. Some physical properties are color, odor, density, structure, solubility, and melting and boiling points. Chemical properties are determined by the reaction of a substance with other substances. Examples of chemical properties are the following: reacts with acids, burns or reacts with oxygen in the air, decomposes (breaks down) when heated, does not react with acids, or does not burn.

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 one or more of the physical properties change. The chemical composition of the substance (and therefore its chemical properties), remains the same. Chemical change refers to the production of new substances which may have physical and chemical properties different form the original substance.

Purpose: In this experiment, you will investigate the differences between chemical and physical changes in matter. You will perform 8 different activities and observe the changes that occur during each. You will then determine if your procedure resulted in a chemical or physical change.

Materials: Balance, Bunsen burner, test tubes, wood splint, sodium chloride (NaCl), water (H2O), Copper (Cu), crucible, scoopula, copper (II) nitrate (Cu(NO3)2, nitric acid (HNO3), barium nitrate (Ba(NO3)2), sodium chromate (Na2CrO4), iron(III)chloride (FeCl3), potassium thiocyanate (KSCN), iron (III) chloride (FeCl3), silver nitrate (AgNO3)

Procedure : Prepare a data table as directed in the data section. Complete activities 1-8 and record your observations in the data table. After recording your observations, classify each of the activities as either a physical or a chemical change (based upon your supporting evidence). CAUTION: SAFETY GOGGLES MUST BE WORN AT ALL TIMES DURING THIS LAB. Activity # 1. Heating a wood splint. Observe the demonstration by the teacher & record your observations.

2. Barium nitrate and sodium chromate. In a small test tube, add 5 drops of barium nitrate, Ba(NO3)2, solution, then add 3 drops of sodium chromate, Na2CrO4, solution.

3. Iron (III) chloride and potassium thiocyanate. In a small test tube, add 5 drops of iron(III)chloride, FeCl3, solution add 3 drops of potassium thiocyanate, KSCN.

4. Iron (III) chloride and silver nitrate. In a small test tube, add 5 drops of FeCl3 solution add 2 drops of silver nitrate, AgNO3, solution.

5. Sodium chloride & water. Place approximately 0.2 grams of sodium chloride in an evaporating dish and add 3 mL of water, stir the solution. Heat the dish until all the water has evaporated. After the dish has cooled, examine the residue. Record your observations. 6. Heating copper. Obtain a clean, dry crucible and a small amount of copper turnings from your teacher. Roll the copper turnings into a loose ball about 2 cm in diameter & place the ball into the crucible. Measure the mass of the crucible & copper. Heat the metal in the crucible over a hot flame for 5 minutes, cool, & remeasure the mass.

7. Heating Cu(NO3)2. CAUTION: Do not inhale the fumes & avoid skin contact. Using a scoopula, place a small scoop of copper(II)nitrate, Cu(NO3)2, into a large test tube. Heat slowly over a low flame for about one minute. Let the solution cool, then add 10 drops of nitric acid, HNO3. Heat gently for one minute.

8. Substance A and substance B. In a small test tube, add 5 drops of Substance A solution, then add 5 drops of Substance B solution.

Data: Copy the following table and fill it in as you perform the lab

Activity # Observations (Supporting Evidence) Type of Change 1) Heating Wood Splint

2) Ba(NO3)2 and Na2CrO4

3) FeCl3 and KSCN

4) FeCl3 and AgNO3

5) NaCl and Water

6) Heating Copper

7) Heating Cu(NO3)2

8) Substance A and Substance B

Analysis: Answer the following questions in complete sentences: 1. Give 3 different examples of evidence you observed in the lab that indicated a chemical change had taken place? 2. In activity #5, only a physical change occurred, but the substance appeared to have changed chemically. Describe this exercise and explain why it looked “chemical”. 3. Explain the difference between chemical properties and chemical changes.

Conclusion: 1. Choose one activity, from # 2-8 in the data table, that you classified as a chemical change. 2. Describe at least 2 physical properties, and 1 chemical property for the original substances. 3. Describe how these properties changed as a new substance was produced. 4. Choose one activity, from # 2-8 in the data table, that you classified as a physical change. 5. Describe at least 2 physical properties, and 1 chemical property for the original substances. 6. Explain how these properties helped you decide that a new substance was not produced.