Introduction: (Initial Observation)
Fire is one of the first human discoveries and we still use it every day in different forms. At home we use fire to cook, to create hot water and for heating in winter.
At work, fire is used to manufacture glass, metals, ceramic, chemicals and petro-chemical products.
Fire is helpful if it is controlled and becomes a disaster when it goes wild and when we lose control of it. This project is an important step towards knowing fire, its potential, and its weaknesses. A piece of paper that can simply burn, can also be used to extinguish fire. It all depends on how we use it and what we know about it.
This project requires adult supervision and safety considerations.
Find out about fire, its uses and dangers. Read books, magazines or ask professionals who might know in order to learn about the effect of air on fire. Keep track of where you got your information from.
Start with looking up the words fire, air and oxygen in an encyclopedia. Wikipedia.org is a free online encyclopedia.
Following are samples of information that you may find:
Also visit the website of U.S. Fire Administration.
There you will find training and educational opportunities for the Fire Service, allied organizations and individuals working together in disasters and emergencies. Also available are fire statistics, publications, public fire education campaign materials, and information on fire service funding opportunities. Federal travelers will find a directory of approved, fire-safe hotels and for the general public, they offer information on home fire safety.
You may also make a fire triangle and use it as a part of your display.
Information gathered from books indicates that fire needs two key elements to start. One is a fuel and the other is oxygen. Fuel is anything that can burn. Natural gas, gasoline, alcohol, coal, charcoal and wood are examples of fuels. Oxygen is a gas that exists in air and in some chemicals such as Hydrogen Peroxide.
Fire also needs some heat in order to start and continue. Many fuels do not ignite unless they are warm. For example, a small spark can ignite gas and gasoline, but it does not ignite charcoal, candle, and wood.
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
Problem: Every year wild fire (or out of control fire) cause death and destruction of property in many places in the world. We need to know how fire is made and how it can be controlled in order to prevent its harms, while getting benefit from its heat.
The purpose of this project is to know the effect of air on burning fire. We want to know if fire needs air to burn and how does the amount of air affect the time a fire lasts.
Additional related questions are:
1. Can we have fire without oxygen?
2. How much oxygen does a fire need?
3. Ways to extinguish fire safely
4. How does fire harm us?
5. How can we protect ourselves from fire accidents?
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
We will use a candle as a source of fire for this project. Candle uses paraffin wax as a fuel, so it is not a highly combustible substance and is easier to work with.
Variables are defined as follows:
- The independent variable (also known as manipulated variable) is the amount of air available to the fire.
- The dependent variable (also known as responding variable) is the length of time the candle continues to burn. The size of the flame may also be considered as a dependent variable.
- Constants are the source of fire and the experiment procedures.
- Controlled variable is the room temperature and air conditions. (Do all experiments in the same room)
Please note that controlled variable is not the same as a control experiment. See the control experiment in the experiment section.
For the five question suggested above, possible hypothesis are as follows:
1. I think we cannot have fire without oxygen. One reason is that if fuels could burn without oxygen, they could as well ignite inside their own container and we had no way of stopping such fires.
2. The amount of oxygen depends on the amount of fuel that will burn.
3. Fire can be extinguished by interrupting the oxygen or fuel.
4. Fire creates heat that will burn our body cells. In other words heat can be dangerous regardless of its source.
5. We can protect ourselves by knowing flammable and non-flammable material and also knowing the ways that heat and fire expand.
Following experiments are designed to help us find answers to our questions. You may come up with a similar experiment of your own. We use a large metal tray as our test area for all of the recommended experiments.
Experiment 1: Does fire need air?
Introduction: In this experiment we restrict the air available to a burning candle to see if it affects the flame and burning time.
- Light up a short candle in the center of a metal plate and do nothing with that. This will be your control (required in scientific method).
- Light up another short candle on the center of the tray. Wait a few minutes until the fire is hot and large. Turn a glass cup upside down, and lower it over the burning candle and let it rest on the tray. How long does it take for the flame to go out? (Record the size of cup and the number of seconds that candle continued to burn.)
- Repeat the step 2, but this time use a jar or any thing larger than a cup so it holds more air. Record the size of the jar and the number of seconds that candle continued to burn.
The reason that we repeat the same process with a larger jar is that larger jar holds more air, so it will have more oxygen and if the candle continues to burn longer in the larger jar, we may conclude that it burned longer because it had more oxygen to burn.
- Repeat the step 2 with one more cup or jar that is larger than the first two. Record the size of the jar and the number of seconds that candle continued to burn.
Record your results in a table like this:
|Air volume ( volume of cup, jar or beaker)||Burning time in seconds|
|Unlimited (Control, no cover)|
While doing the above two steps, did you notice any thing else in the cup or jar? Did you notice some water condensation in the cup or jar? Where does the water come from?
There must be something in the candle that when it burns, it produces water. Do you know what is it called? It is called Hydrogen. Hydrogen is an important element in many fuels including natural gas, gasoline, wood, and cotton. As a mater of fact most of these fuels are made of only two elements that are carbon and hydrogen. The only difference is the ratio of carbon to hydrogen and the way that those carbons and hydrogen atoms are connected to each other.
You may need a control experiment to show that no unknown factor has been affecting the experimental fire.
Light up another candle identical to your experimental candle and do nothing with that.
This candle will be your control experiment.
In this way you will be sure that no other external factor is affecting the size of flame or burning of your experimental candle.
Make a graph:
Make a bar graph to show the relation between the air volume and the burning time. Make one vertical bar for each cup or cover you used. Write the volume of the cup under each bar. For example you may have bars named 300, 1000, 3000.
The height of each bar represent the number of seconds the candle continued to burn. you may use 1cm for each second. For example if the candle burns 20 seconds, then the bar is 20cm tall.
Experiment 2: Does fire need fuel?
Get a tin ,copper, or steel wire. Take the wire and make a loose knot. Place it around the wick as close as it can be to the candle. Next, turn on the candle and allow it to burn for a few minutes. Now, tighten the knot by pulling the wire from both ends. This will cut off the fuel route of the candle. What happens to the flame (record the results)?
For experiment 2 you could also use a forceps to stop the melted wax from going up and reaching to the flame. If you are able to apply enough force to completely stop the wax from going up in the wick, the flame goes off; otherwise it will just shrink and become smaller.
Take your metal tray and lay a sheet of paper flatly at the bottom of the tray. Use a lighted match and attempt to burn the middle of the paper while it is still on the tray. What happens (record the results)? We do this experiment with two purposes. The first is to see if a flammable object exposed to oxygen and the flame only from one side burns easily. The second is to see if fire can easily transfer downward.
Hold a sheet of paper horizontally above the metal tray. Use a match and expose the fire to the middle of the paper from the top. What happens? Does the paper burn easily when the fire is exposed from the top? (Record the results)
Hold a sheet of paper horizontally above the metal tray. This time, use a match and expose the fire to the middle of the paper from the bottom. What happens? Does the paper burn easily when the fire is exposed from the bottom? (Record the results)
Hold a sheet of paper vertically above the metal tray. Use a match and expose it to the lowest part of the paper. How fast does it ignite? (Record the results)
In Experiment 6, you should have the fastest ignition and burning. This is a clear example of why curtains and skirts are the most common starters of fire accidents.
Lighten a candle and test small samples of different materials to see which ones are flammable. To do this test, you can put the samples on the tip of a metal fork or use a metal tweezers. Some of the items that we suggest to test are paper, wood, small pieces of different fabrics, aluminum foil, plastic, plastic foams, glass, sugar cubes, dry leaves, and fresh leaves.
Do your experiments in a place away from furniture and other flammable materials. Do it as small as possible and try to use the largest metal tray that you can access. If you do not have a metal tray, you can cover a large plastic tray with aluminum foil. Have a bucket of water handy as a fire extinguisher. All these experiments should be supervised by an adult. Take some pictures and use the pictures for your display and reports. You may be allowed to perform experiments number 1 and 2 at your display table in school. Ask your teacher for permission.
Materials and Equipment:
For this experiment you will use:
1.) a large metal tray
2.) a short candle
3.) some matches
4.) a clear glass cup
5.) a clear glass jar
6.) a few sheets of paper (about 5″ x 8″ each)
7.) a thin copper or steel wire.
Results of Experiment (Observation):
Write your own results.
For primary, elementary, and intermediate levels, this project does not need any calculations, but if senior students decide to do this experiment, you may calculate how much oxygen is needed to burn certain amounts of fuel. To do that, you weigh the candle and then light it on in a large container and leave it till it goes off. Then you weigh the candle again to see how much weight it has lost. That will be the weight of paraffin wax that is burned. You will also know the size of the container and use these numbers to calculate how much air or how much oxygen is required to burn a unit weight of paraffin wax.
Example: You may light up a small candle with known weight in a 20-liter glass container and seal the container to prevent air leak. After a while the oxygen in the container will finish and the candle extinguishes. Weigh the candle again. You may notice that the candle has lost 3 grams of its weight. By now you know that 3 grams of candle wax requires 20 liters of air to burn. Since only 1/5th of the air is oxygen, you may say that 3 grams of candle requires about 4 liters of oxygen.
So one gram candle requires 1.3 liters of oxygen.
How do I measure the volume of glass?
If the glass is cylindrical, measure its volume by multiplying the height by the base area. Otherwise use a measuring cup to fill up the glass with water and count how much water it holds.
Summery of Results:
Experiments number 1 showed that more oxygen results longer burning and as soon as the container runs out of oxygen, the fire goes off. We may not have fire while there is no oxygen.
The second experiment showed that oxygen by itself is not enough for fire and it needs a fuel to burn. Experiments 3, 4, 5, and 6 show that the direction of the flame is effective on expansion of fire or transfer of fire from one object to another. Magicians use these techniques to hold fire on the palm of their hands and since the heat goes up, their hand does not burn.
Experiment number 7 showed what objects can ignite and the result is in the following table.
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
Visit your local library and find some books related to fire, fire safety or fire chemistry.
List your all your references (printed or online) in this section of your report.