Burning House Lab Report

According to the National Fire Protection Association more deaths occur due to smoke inhalation than any other means (see figure 1).

Figure 1: Deaths during house fires.

When a fire occurs in a home, occupants can quickly be overcome by smoke and unable to reach nearby exits. Planning and practice can help you survive

In this experiment we will be looking at the effects that combustion has on the air around it and the bi-products that it produces in a confined space.

I will be asking the question of why fire fighters have to crawl in a burning building and what must be done when someone is stuck in a burning building.

The experiment will showcase the following chemical reaction:
Fire + Oxygen + Hydrocarbons => Carbon Dioxide

The lower levels of the room thus has more oxygen than the higher levels of the room. Figure 2: A fireman crawling in a burning house.

3 Experiment
3.1 Introduction

In order to do the experiment I will be using two candles and a glass jar. The candles will be different lengths; one tall and the other short. I will look at all the bi-products produced and what happens to the air inside the jar.

The candles will represent the fire in a building and the glass jar will represent the building. This will then give me the effect of a burning building. I will see which candle dies out first and why.

3.2 Materials
For this experiment we will use the following materials (see figure 3):
• Long candle (15cm).
• Short candle (7cm).
• Candle holder.
• Glass jar (7 litre).
• Fire lighter.
• Two towels.
• Ruler and marker.
• Hacksaw.
•

Candle wax has the following states:
• Melting point = 470C -650C
• Boiling point = 1880C
• Flash point = 1980C (where candle wax starts to burn)

3.6.2 What happens to the air inside the jar?
Now that you have a fire, warm gases start to be produced. When the hydrocarbon starts to breakdown/up it breaks up into hydrogen and carbon. The hydrogen mixes with the oxygen (O2) to form water vapour (H2O) and carbon to form carbon dioxide (CO2).

The water vapour condenses on the cold surface of the jar to form water.
3.6.3 Why do the candles die out at different times?

Figure 7: Candles being smothered in the Candles in a Jar experiment

Carbon dioxide and other gases are warm gases which expand. As the warm gases expand the remaining oxygen is pushed down to the bottom of the jar (more space for warm air). There are also now more particles of carbon dioxide and water vapour than oxygen.

Candles die out once about 30% of the oxygen content has been used up.

Figure 8: Gasses produces during combustion in a confined space.
The candles die out at different times because the carbon dioxide expands pushing the remaining oxygen down to the bottom of the jar. The carbon dioxide reaches the long candle before it reaches the short