Physical and Chemical Changes Lab

OBJECTIVE: To differentiate between chemical & physical changes

BACKGROUND:

When a physical change occurs, only the form of the substance changes. Chemical changes, however, result in the formation of new substances with different properties. Some general signs of a chemical change include a change of color or odor, the formation of a precipitate (solid), the formation of a gas, and a change in heat or light. In this lab, you will perform different activities and, based on your observations, determine whether a chemical or physical change has taken place.

SAFETY

• Before lighting the match, tie back long hair and secure loose clothing. After extinguishing the match, thoroughly douse it with water before placing it in the designated waste beaker.

• Do not ingest any chemicals.

• Absolutely no goofing or horseplay off.

PROCEDURE

Perform each of the following activities and carefully observe what happens. After each activity, complete your data table.

1. Lighting a match – Light a single match (refer to safety precautions listed above).

2. Lighting a candle: Light a single candle. Observe the candle for 45 seconds.

3. Heating Sucrose: Take a pinch of sugar and place it on the foil. Using the tongs, hold the foil over the candle for approximately 1 minute.

4. Crushing chalk – Use a mortar and pestle to crush a piece of chalk.

5. Mixing crushed chalk with vinegar – In a test tube, mix a small amount of the crushed chalk from Procedure #4 with vinegar.

6. Mixing crushed chalk with water – In a test tube, mix a small amount of the crushed chalk from Procedure #4 with water.

7. Dissolving sucrose in water – In a test tube, dissolve a small amount of sucrose in water.

8. Mixing CaCl2 and Na2CO3 solutions – In a test tube, combine several drops each of the calcium chloride and sodium carbonate solutions.

9. Blowing bubbles in BTB—In a beaker, pour 25 mL of BTB in the beaker along with 25 mL of distilled water in a beaker. Using a straw, blow bubbles in the solution for 1 minute.

10. Burning Steel Wool—Obtain a small piece of steel wool. Using the Bunsen burner, hold the piece of steel wool over the flame.

11. Food coloring and water—Fill a beaker with 50 mL of water, place 3 drops of food coloring in the water.

12. Ammonia and Alka Seltzer—Fill a graduated cylinder with 25 mL of Ammonia. Place 3 drops of Universal Indicator in the graduated cylinder and stir the solution. Drop ½ an alka seltzer tablet in the graduated cylinder.

13. NaOH and water—Dissolve 2-3 pellets of NaOH in approximately 5 mL of water inside a test tube. (Use your five senses on the test tube)

14. Phenolphthalein in NaOH—Add 2-3 drops of phenolphthalein to NaOH solution(from previous activity #13).

15. HCL to NaOH mixture—Add several drops of HCl to NaOH solution until an observation is noticeable.

16. Zinc and HCl-Add 1 piece of zinc to 1/3 full test of 0.5M HCl. See instructor for chemical.

17. Gas Collection of Zinc and HCl—Use a test tube and invert over previous activity #16 to collect gases and use a candle to check for gases.

18. Record and collect all observations in the table provided.