Notes

Kajal Patel
September 13, 2016
Period 7
Qualitative Observations of a Chemical Reaction
Purpose: Carefully observe and interpret a chemical reaction.
Apparatus: Lab apron, safety glasses, 250-mL beaker, 125-mL Erlenmeyer flask, wooden square, metric ruler, chemical scoop, rubber stopper, candle, matches, a toothpick, string, aluminum foil, limewater solution, cobalt chloride paper, Bunsen burner
Procedure:
1. Note appearance, odor, feel, and measure the length of the unlighted candle.
2. Heat the bottom of the candle and secure it to a wooden square on your lab table. Light the candle and allow it to burn for several minutes. Note any changes. Briefly describe the burning candle.
3. Blow out the flame and immediately place a lighted match in the “smoke” about 2 cm above the wick. See Figure 1-1. Note the result.
4. Use a chemical scoop to transfer a small amount of liquid from the bowl of the candle onto the lab table. Try to light it and note the result.
5. Place a toothpick into the soft candle next to the unlighted wick to form a wooden wick. Light the toothpick and note the result.
6. Place a length of string about 4 cm long on the wooden square. Light it and observe its behavior.
7. Make a slit it in a small piece of aluminum foil. See Figure 1-2. Light the candle. Place the foil between the base of the flame and liquid in the candle bowl. Note the behavior of the flame.
8. Invert a 250-mL beaker over the lighted candle. See Figure 1-3. Note any substance that collects on the inside of the beaker. Test the liquid with cobalt paper
9. Invert a 125-mL Erlenmeyer flask over the lighted candle for several minutes. Remove the flask, turn it right side up, and add about 10 mL of the clear limewater solution. Stopper and shake the flask. Note any change in the limewater solution.
Lab safety: In this experiment, you will be working with an open flame. Tie back long hair and secure loose clothing. Also wear safety goggles and a lab apron or coat at all times when working in the lab. Be sure all matches and burned materials are completely extinguished before they are discarded.
Results/Data:

Before
During
After
1
The candle has a white color, a smooth feel, and no odor. Height: 10.0 cm including the wick.
Diameter: 7.0 cm
The candle kept its white color, smooth feel, and was still odorless. The wick has darkened black.
Height: 10.0 cm including the wick.
Diameter: 7.0 cm
The candle is still white, smooth and odorless. The wick is black and the candle has become shorter.
Height: 6.5 cm
Diameter: 7.0 cm
2
The candle remained white, smooth, and odorless.
The flame of the candle is causing the wax to melt into a bowl at the surface of the candle.
The candle stuck to the wooden square. The wax in the candle bowl has cooled.
3
The candle flame is burning and the wax is melting.
The candle relighted when the match was held above the smoke from the blown out candle.
The lighted candle remains on the wooden square.
4
Wax from the lighted candle is collecting in the wax bowl.
When put against a flame, the wax does now light. It remains in its liquid state.
After the flame was turned off, the wax began to cool and harden back into a solid state.
5
The toothpick is placed into the unlighted candle.
The toothpick is burning and the flame is moving down at a medium pace.
The toothpick is only half way burnt and the flame lasted about 15 seconds.
6
The 4 cm string is unlighted and dry.
The flame burning the string is moving very fast.
The string does not burn all the way. The flame lasted approximately 3 seconds.
7
The lighted candle is burning. There is no foil placed yet.
Dark smoke is rising from the top of the flame. The flame dies out in about 5 seconds.
The candle is not lighted and the atmosphere smells smoky.
8
The beaker is clean and dry. Cobalt chloride paper is blue.
Water droplets form on the inside edge of the beaker. This is known from testing the substance with cobalt chloride paper.
The beaker dries and the cobalt chloride paper now shows the color pink.
9
The flask is clean and dry. The candle is lighted.
There was no change in physical appearance of the gas filled flask.
The clear limewater solution appeared milky in the flask.
Conclusions:
1. In the unlighted candle, only the solid phase is present. In the lighted candle, the solid, liquid and gas phases appear. The ???
2. The wick absorbs the liquid wax and brings it up to keep the flame going. The wick should be naturally absorbent. When the aluminum is placed between the liquid and the wick, the flame goes out. The aluminum block the wick from absorbing the liquid wax. The wick is not part of the chemical reaction.
3. Water vapor and carbon are the two substances indicated by the cobalt chloride and limewater tests. Yes it is possible that other substances are produced when the candle burns..??
4. Fire is used to start the burning of the candle. The reaction gave off heat.
5. An example illustrating the difference between observation and interpretation:
You observe there are pictures of flowers, mountains, and sunsets on your friend’s bedroom walls.
You interpret that she enjoys nature and the outdoors.