You need these materials:
2 metal caps (e.g. softdrink bottle caps), or foil boat
Ceramic saucer
Dish or bowl (metallic, ceramic, or clay)
1⁄4 teaspoon white sugar
1⁄4 teaspoon table salt
Candle
Matches
Tongs
16
Safety:
• Perform this activity in a fireproof work area.
• Be sure to wear safety goggles while making close observations, tie your hair
back if you have long hair, and always be aware of where the flame is with
respect to your clothing—do not lean over the flame.
• Burning candles are open flames that can cause burns. Liquid wax is hot
and can also cause burns to the skin.
Procedure:
A. a) Light the candle and let 3-4 drops of wax fall into the center of the dish
or bowl. Press the candle into the melted wax and hold it upright until
the wax solidifies.
b) Place the bottom of the saucer over the lighted candle for 10 seconds.
What do you observe?
B.
a) Put the sugar and table salt separately in the metal caps.
b) Hold the metal cap with sugar using the tongs and heat it over the
lighted lamp for 2 minutes. Observe what happens.
c) Do the same with the table salt in the other cap. Observe what happens.
Observations:
A. a) Describe the appearance of the substance that deposited at the bottom
of the saucer.
b) What is this substance called?
B.
Sample Observation after heating
a. Sugar
b. Table salt
c) How do you compare the appearance of the sugar with that of the table
salt after heating?
d) Compare the effect of heat on sugar and table salt.
Answers
A. The candle have no flame anymore.
a) The substane is black in colour and if i touch it i feel it like smooth dust.
b) The circular blackish ring that is formed on the glass plate/slide. It indicates the deposition of unburnt carbon particles present in the luminous zone of the flame.
B.
a) The sugar have melted down to a liquid form and turned a light brown color. Once the sugar had been heating for a while, it have turned black and started producing wisps of smoke. Once I transferred the sugar from the flame to the metal dish, the sugar would be blackish brown, solid and surrounded by black soot.
b) Some salts decompose readily upon heating such as bicarbonates salts. While some salts are stable when heated such as sodium chloride. However, if the cation in a salt has a high polarising power towards especially carbonates, hydroxide and nitrates ions, the salt will decompose to form a more stable salt.
c) The sugar became blackish brown but the salt is still white or transparent .