Introduction: (Initial Observation)
What is fire? why is it hot? How is it made and how can it be extinguished? Learning about the fire and the factors causing or affecting fire can help us to control the fire as we need and benefit from that safely.
In this project you investigate the nature of fire in order to identify the factors affecting fire.
Burning is a common way of creating heat energy. Since heat energy is what we are looking for, it is important to learn more about the burning process and know how can we create the most heat energy from certain amount of fuel.
It is also important to know the flame, other properties of fire and even byproducts of burning. We can work on many different projects related to fire and burning. We have decided to know what factors effect burning.
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 is an experimental project in order to give student an understanding of the process of combustion. Learn that Fuel and oxygen are both necessary for a combustion. Discover that about 20% of the air is oxygen. Gain knowledge of some types of oxidation reactions.
This project requires adult supervision and safety considerations.
Now you are playing with fire. It is dangerous and can be fatal. If you are a beginner, do it while supervised by a fire safety trained adult. Also do it in a safe place. My favorite place for such experiments is a large concrete room with enough safety equipment and fire extinguisher. My second choice is an open area away from vegetation, wood, building or anything else that may catch on fire. Always do fire and chemical experiments as small as possible and keep your experiment area away from your supply area. Wear safety glasses and protecting clothing.
Information Gathering:
Find out about fire and burning. Read books, magazines or ask professionals who might know about the factors affecting or causing fire. Keep track of where you got your information from.
Fire Tetrahedron
In order for fire to occur four things must be present, Oxygen, Fuel, Heat, and a Chemical Chain Reaction. This is represented by the Fire Tetrahedron. When any of the four items are removed, the fire will go out. Fire extinguishers function by removing one of the four components of the Fire Tetrahedron.
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.
Question/ Purpose:
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 gain an understanding of the process of combustion and gain knowledge of some types of oxidation reaction. During this project you will discover that oxidation is an exothermic reaction.
Following are some specific questions that can be studied in this project:
- Does the amount of air affect the process of burning?
- Does availability of fuel affect the process of burning?
- What percentage of air is oxygen? (Experiment 8)
Identify Variables:
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.
Following is how you may define variables for question number 1.
Independent variable is the amount of air. Dependent variable is the time a candle continues to burn with each amount of air. Controlled variable is air temperature. Constants are the type fuel (candle wax), method of burning.
Following is how you may define variables for question number 2.
Independent variable is the availability of fuel. Dependent variable is the time a candle continues to burn with each amount of air. Controlled variables are air and air temperature. Constants are the type fuel (candle wax), method of burning.
Hypothesis:
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 are some sample hypothesis for question number 1.
Sample 1: Air does affect burning. More air has more oxygen and more oxygen can cause more burning. My hypothesis is based on my gathered information.
Sample 2: Air has no affect on burning. Air is almost everywhere but we don’t have fire everywhere. So air can not be a factor for burning. My hypothesis is based on my common sense.
This hypothesis is being tested in experiment 1.
Following is a sample hypothesis for question number 2.
Availability of fuel does affect the process of burning. My hypothesis is based on my observation of gas stoves that turn off when we close the gas valve.
This hypothesis is being tested in experiment 2.
Following are some additional hypothesis that can be tested in this project.
- When the color of the flame is red, it indicates incomplete burning of the fuel
- Incomplete burning of fuel creates smoke
- When the color of the flame is blue, it indicates complete burning
- The temperature of red flame is less than temperature of a blue flame
- Complete burning creates the highest amount of heat energy
Experiment Design:
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.”
Here you see an introductory experiments followed by 8 investigative experiment.
Introductory Experiment :
Strikes the match and lights the candle. Hold the yellow part of the flame under the bottom of one of the saucers. Blow out the match and examine the underside of the saucer. Follow the same procedure, using candle, lighter, and burning paper. Discuss what was observed. (Whenever the flame came in contact with a cool dish, a black substance was deposited. Moisture also was present.)
Look at a dictionary (www.dictionary.com) for the words fire, flame, combustion,
fuel, and ignition. Anything that will burn can be called a fuel. Most fuels contain carbon, hydrogen, or both. When carbon burns incompletely, which is usually the case, it glows with a yellow color. A flame is made of tiny particles of very hot carbon. When the particles cool quickly, as they did on striking the cool saucer, they were deposited as black carbon.
When they cool more slowly, as above an open flame, they join with the atoms of
oxygen from the air and become carbon dioxide (CO2), a colorless gas. The moisture formed on the saucers, because every flame gives of water vapor. This is because the fuel contains hydrogen, which reacts with oxygen in the air to
form water vapor.
Pours 6-8ml of hydrogen peroxide into a test tube. Add 1/2 teaspoon dry yeast into the test tube. The yeast will react with the hydrogen peroxide releasing oxygen. Immediately light a wooden splint. Blow out the flame gently, so that the splint is still glowing. Stick the splint into the test tube. It will re-ignite, and if enough oxygen is present, a popping sound may occur. Discuss and conclude that although oxygen itself does not burn, it must be present to have fire, which is an oxidation reaction.
Materials that you use for introductory experiment are:
- wooden matches
- small candle
- lighter
- paper
- saucers
- test tube
- dry yeast
- wooden splint
- steel wool pad
- 1/4 cup vinegar
- cooking or outdoor thermometer
- jar with lid (The thermometer must fit inside the jar)
Another activity (optional):
Place the thermometer inside a jar and close the lid. Record the temperature after five minutes. Soak one-half of the steel wool in vinegar for two minutes. Squeeze excess liquid from steel wool, and wrap it around the bulb of the thermometer. Place the thermometer with the steel wool inside the jar and close the lid. Record the temperature after five minutes. The temperature rises. The vinegar removed the protective coating from the steel wool, allowing the iron in the steel wool to rust. Rusting is a slow combination of iron with oxygen, which is an oxidation reaction. Oxidation is an exothermic reaction, and heat is always released.
Investigative experiments
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 air affect burning?
Introduction: In this experiment you try burning of candle with two different amounts of available air. You will measure the time the candle continues to burn for each of the air quantities.
Procedure:
- 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 above activity, 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 repeat this experiment with 2, 3, 4 or 5 different containers with different volumes. Containers may be made of glass or clear plastic so that you can see the flame.
Your results table may look like this:
| Volume of the air | Time the candle continued to burn (Seconds) |
| 1 cup | |
| 3 cups | |
| 5 cups |
Make a graph:
To make a bar graph, use one vertical bar for each container volume you try. The height of the bar will represent the time candles continue to burn.
Note:
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.
Control Experiment:
The control experiment can be an identical candle that you light up, but do nothing with that. Continuous burning of the control candle shows that any change in the burning of the experimental candle is caused by the changes you made in the amount of air available to the flame.
Experiment 2:
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 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.
Experiment 3:
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.
Experiment 4:
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)
Experiment 5:
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)
Experiment 6:
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)
Notes:
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.
Experiment 7: What materials are flammable?
Procedure:
Lighten a candle and test small samples of different materials to see which ones are flammable and which one can burn. 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.
Enter your results in a table like this:
| Sample | Flammable | Can burn | Non-flammable |
| Paper | |||
| Wood | |||
| Cotton Fabric | |||
| Nylon Fabric | |||
| Aluminum Foil | |||
| Sugar Cube | |||
| Dry Leaves | |||
| Fresh Leaves | |||
| Glass | |||
| Steel Nail | |||
| Plastic Foam |
What criteria is being used to distinguish flammable vs. non-flammable? What does “can burn” mean?
Flammability is the ease with which a substance will ignite, causing fire or combustion. Materials that will ignite at temperatures commonly encountered are considered flammable. Examples of flammable liquids are gasoline, ethanol, and acetone. Diesel fuel is in one of the less heavily regulated flammability categories, and biodiesel is considered nonflammable with a flash point usually over 300 °F (150 °C) even though it will combust inside a diesel engine. Paper, wood and aluminum foil are also considered nonflammable, but they can burn.
Another more technical definition for flammability is this:
Any substance with a flashpoint of 100 °F (37.8 °C) or less is considered flammable.
What is a flashpoint?
Flashpoint is the temperature in which a substance inflames by a spark (or by a brief exposure to a very small flame).
For example the flashpoint of acetone is -18ºC and the flashpoint of ethanol is 12ºC. In other words acetone can inflame with one spark if the temperature is -18ºC or higher. Ethanol can inflame with one spark if the temperature is 12ºC or higher. The flashpoint of mineral oil is usually more than 178ºC. So mineral oil is not flammable, but it can burn.
The flash point is an important characteristic of every substance. The flashpoint of a substance is the temperature in which the substance will inflame if exposed to one spark. Substances that do not inflame with one spark at a warm room temperature (100 °F (37.8 °C)) are considered nonflammable.
* All flammable materials can also burn, so you place Y in two columns. Materials such as iron nail cannot burn and are nonflammable.
Experiment 8:
In this experiment we intend to test and measure the percent of oxygen in the air. The first thing that comes to our mind and is suggested by some websites, is letting a candle burn all the oxygen in a container and loss of volume represents the amount of oxygen. But this is not right. First reason is that when oxygen burns, the same amount or more water vapors and carbon dioxide and carbon mono oxide gases are produced. So there will be no loss of volume of air. The other problem is that flame will also heat up the air and expands the air, so after burning stops, air contracts because it cools off.
The percentage of oxygen present in a quantity of air can best be measured by using wet steel wool. Steel wool will react with oxygen and rust.
Procedure: Wash the steel wool with methyl alcohol or a similar solvent to remove any grease. Rinse it with water and push it into the bottom of a test tube. Turn the test tube upside down in a cup of water.
In about 24 hours all the oxygen will be combined with the steel wool and become rusted iron (Iron Oxide). Whatever gas is left in the test tube is not oxygen. This is a fairly effective way of finding the percentage of oxygen in air.
To determine the percentage of oxygen in air, see what percent of test tube is filled with water.
Additional experiments:
We may design our experiments using solid, liquid or gas fuels.
To start we decide to use a candle. Candles are made of paraffin wax that is a long chain of hydrocarbon. So it’s chemical formula is very similar to natural gas, gasoline and mineral oil, but it has a larger molecule. That’s why it is a solid in room temperature. Even though candles are solid, what actually burns is liquid or melted wax. The wick of the candle sucks up the melted wax until it reaches to flame and then burns. To see the effect of oxygen ratio in burning a candle we need to control the oxygen that gets to the candle. We need to construct a box with adjustable openings close to the bottom for entrance of the air and openings close to the top for exiting of the gasses and moisture caused by burning. By modifying the opening, we observe the flame and measure the produced heat energy.
Safety Precautions:
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:
- a large metal tray
- a short candle
- some matches
- a clear glass cup
- a clear glass jar
- a few sheets of paper (about 5″ x 8″ each)
- a thin copper or steel wire.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
Calculations:
No calculation is required for this project.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
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 third experiment showed that oxygen by itself is not enough for fire and it needs a fuel to burn. Experiments 4, 5, 6, and 7 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.
Conclusion:
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.
Following are some additional ideas about fire related projects. Each idea needs a hypothesis and an experiment that can test that hypothesis. If you want to focus your research on any of the following, contact me so I can suggest you some experiment design.
1. Is there any relation between the color of flame and its temperature?
Once I visited a glass factory and I noticed that they use a device to remotely measure the temperature of the molten glass. This device looked like a gun or barcode scanner that supermarkets use. What they did was aim it toward the mass of molten glass inside the furnace to read the temperature. I don’t know if the device worked based on heat radiation or light emitted from molten glass, but it gave me the idea that we might be able to measure the temperature of flame based on it’s color. See details
2. What is the effect of oxygen in burning?
If you pump too much gas in your lawn mower before you start it, chances are it will not start. It seems that if the fuel and oxygen don’t have the proper ratio, fire does not start. I have also seen some cars that smell like gasoline while they drive. In my opinion something that smells like gasoline, most likely is gasoline. So these cars are not burning their gasoline fully (efficiently) and part of their gasoline is being dumped in to the air through their muffler. This gave me the idea to know what is the proper ratio of fuel and oxygen for best burning.
3. What is the effect of temperature in burning?
In cold weather when we try to burn some liquid fuel, we get a lot of smoke. In other words part of our fuel will be converted to smoke, wasted and polluting the environment. Liquid or gas fuels can be preheated if necessary. Can we get a better burning, less smoke and more heat energy by pre-heating the fuel?
4. How can we control the fire and burning process?
Fire can go wild. Overheat can burn what we don’t expect and cause explosion or uncontrolled fire. As much as controlled fire is helpful for us, uncontrolled fire is harmful and dangerous. We have seen shows that performers walks on fire and put fire in their mouth, hands, without being burned. How do they do that. Experiments can be designed to reveal the art and science of controlling fire.
Possible Errors:
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.
References:
Visit your local library and find books related to fire, fire safety and fire chemistry.
Following are some web-based resources
Fire Safety
Fire Chemistry
Fire Works
Other resources:
Steven J. Pyne. Fire: A Brief History. Seattle: University of Washington Press, 2001. xxvii + 204 pp. Illustrations, maps, bibliography, index. $18.95 (paper), ISBN 0-295-98144-X.
Reviewed by: Sylvia McGrath , Stephen F. Austin State University.
Published by: H-Environment (July, 2003)
