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.
Safety note: This project requires adult supervision and safety considerations.
Find out about fire and how it is made. Read books, magazines or ask professionals who might know in order to learn about the factors or conditions that affect fire. Keep track of where you got your information from.
Following are samples of information you may find:
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.
The purpose of this project is to find out if fire needs air to bur. A more specific question for this project is:
How does the amount of oxygen affects the time a candle can burn?
This project will also help you to find answers to the following questions.
- Can we have fire without oxygen?
- How much oxygen does a fire need?
- Ways to extinguish fire safely
- How does fire harm us?
- 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.
The independent variable (also known as manipulated variable) is the amount of oxygen available to a burning candle.
Dependent variable (also known as responding variable) is the time a candle continues to burn. Flame size could also be a dependent variable; however, it is hard to measure.
Constants are the candle type and the size.
Controlled variable is the room temperature. Perform all experiments in the same day to ensure same room temperature for all your experiments.
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. Following is a sample hypothesis:
My hypothesis is that fire needs air to continue. A candle will burn longer if more oxygen is available to it.
Following are some additional sample hypothesis related to fire experiments:
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.
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Experiment 1: How does the amount of oxygen affect the burning time of a candle?
In this experiment we use candle as a source of fire. Candles uses paraffin wax as fuel, so it is not a highly combustible substance and is easier to work with. We use a large metal tray as our test area. We also use different size jars to limit the amount of air.
- Light on a 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 part 1, but this time use a jar or any thing larger than a cup so it holds more oxygen. (Record the size of jar and the number of seconds that candle continued to burn.)
- The reason that we repeat the first experiment 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.
- You may optionally repeat the part 1 with one more jar that is larger than the first two. In this way you have tried three different amounts of air for the same size candle.
While doing the above two experiments, 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, 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 are connected to each other.
Your results table may look like this:
|Volume of jar||Burning time in seconds|
The volume of the jar may be recorded in metric system (liter, milliliters) or English system (quart, gallon or cubic inches).
Make a graph:
Use the above results table and make a bar graph to visually present your results. Make one vertical bar for each size jar you try. Write the size of each the jar under the bar it represents. The height of the bars will show the time the candle continued to burn after you restrict the air using each jar.
Additional experiments related to fire
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 3 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 7, 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.
Light up 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 experiment number 1 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.
Summary of Results:
Experiments number 1 and 2 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.
Find books about fire, fire safety and fire fighting. List the books and websites you use in the list of references.