The Scientific Method in Action
Lab 1: Collect Reliable Data
Observation of a burning candle.
We found that there is MUCH to see in what appears to be a simple object. See Observations of the candle in Lab 1.
Lab 2: Classify the Data. Melting order of substances.
We wondered if the liquid around the wick of a burning candle is just melted wax or is it a new substance created by the chemical reaction of burning.
We found that we agreed that there was a definite order of melting of the substances we tested.
So we Made an Hypothesis that every pure substance has a definite melting temperature.
Lab 3: Testing the Hypothesis by further experimentation.
We determined the Melting Point and the Freezing Point of a pure substance and found that there was indeed a constant melting and freezing point and that they were the same temperature.
And, WOW, we found a surprise discovery... The plateaus on the warming and cooling curves for the pure substance are phase changes. All of the energy is used to change the structure of the molecules without changing the temperature!
Lab 4: More experimentation on the Nature of Burning.
We found that the time that a candle will burn in an enclosed space is proportional to the volume of the space. This gave us two ideas on burning:
... The flame dies because it uses up something necessary for burning (like oxygen). OR
... The flame dies because it is "poisoned" by a substance (like CO2).
So, we tested the gases emitted by the burning candle
...The limewater test detected CO2 being emitted.
... The cobalt chloride test detected water being meditated by the burning candle.
Remember both H2O and CO2 are used as fire extinguishers.
Then we placed the burning candle in a glass cylinder in a beaker of water. The water rose 1/5 of the way up into the cylinder. "Ah ha", we remarked, oxygen is 1/5 of the atmosphere. But then we realized that other factors were complicating the issue. Heated air expanded emitting bubbles, and CO2 is soluble in water, etc.
Hence, we shall need more testing to "prove" that oxygen is the main factor in burning.
And we noticed that CO2 is not really poisonous inasmuch as it is present in mouth to mouth resuscitation and in photosynthesis.
We hypothesized that CO2 extinguishes fires by excluding oxygen as when we put out a candle with CO2 gas. And we hypothesized that water puts out a fire by both excluding oxygen and cooling the fuel below activation energy.
More experimentation is needed.
Lab 5: Finding the heats of Combustion and Solidification.
We herein measure the heat energy of burning a candle and of freezing wax. And calculate the heat of the phase change of the melting and freezing of wax.
And we found the Heat of Combustion in calories/gram and the Heat of Solidification in calories/gram.
From the ratio, we found that the heat of combustion is a hundred times more than the heat of melting! Combustion is a chemical change in which substances are destroyed and new substances are formed, and the heat of melting is a physical change that merely changes the crystal structure without changing the chemical composition.
We are now ready to proceed to Chemical Formulae and Chemical Reactions!
The Formula Club is coming!!