Introduction: (Initial Observation)
We use the heat of fire to cook meals, make hot water, melt metals, form glasses and build varieties of products.
Although beneficial in most cases, fire can cause disasters when it is out of control. Every day thousands of fire accidents occur in homes, work places, savannas and forests with no obvious reason.
By understanding what is needed to start fire, we can start controllable fire as needed, and prevent unexpected and uncontrollable fire.
In this project you identify and examine material and conditions needed for fire to start.
Warning: Adult supervision and support is required for experiments of this project.
Start with close observation of lighting up a candle or a match. Write down your questions. Decide what you are going to do about this project.
Following are some sample questions:
Why matches are made of wood or paper? Why candles are made of wax? Is it because wood, paper and wax are flammable? What other material around your home are flammable?
Make a list of what you are going to do. This is a sample:
1. Examine different household material to find out which materials are flammable.
2. Test the effect of heat on starting fire.
3. Test the effect of fuel on starting fire.
4. Test the effect of air on starting fire.
Gather information about fire and how it starts. Read books, magazines or ask professionals who might know in order to learn about the material and conditions required to start fire. Keep track of where you got your information from.
Following are samples of information that you may gather by reading books or interviewing a professional such as a chemist or a fireman.
What is fire?
Fire is the result of fast burning of a fuel. Fuel is any material that can burn. Wood, oil, paper, gasoline, and alcohol are samples of fuels. Burning is a chemical reaction between a fuel and the oxygen in the air.
What is needed for fire to start?
To start fire, you need fuel (something that can burn), oxygen (About 20% of air is oxygen) and heat. You usually need heat to start the fire. The heat of fire is often enough for the fire to continue.
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 what is needed to start the fire. Do we always need a match, a lighter or another fire in order to start a new fire? Can presence of fuel, oxygen and heat cause spontaneous combustion of bushes, papers and other flammable material?
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 heat.
Dependent variable (also known as responding variable) is fire.
Constants are fuel and air.
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:
Heat can cause fire where fuel and air are available. My hypothesis is based on my gathered information.
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.”
You can do many different experiments to test the effect of heat on fuel. Almost in all such experiments you use a heat source and a fuel. The heat source can be a hot iron, a hot test tube, a hot electric stove or even a hot spot of sunlight formed by a large magnifier. Fuel is usually a strip of plain paper or newspaper.
Experiment 1: Can the heat of sunlight be used to start fire?
Background: Brush fires and forest fires are very common in dry – hot areas. The cause of such fires are often unknown. I suspect that some of such fires may be caused by glass bottles and tin cans that people throw away. The reflection of sunlight by metal cans and the refraction of sunlight by glass or plastic bottles may create very bright and hot spots. It is possible that such hot spots can cause fire on brushes. In the following experiment you may test the effect of a hot spot on flammable material.
Introduction: A magnifier glass can refract the sunlight beams and bring them to a focal point. This creates a very bright and hot spot. In this experiment you may use a large magnifying glass and test the effect of focused sunlight on a solid fuel such as paper. This test will show if heat can start fire.
On a warm, dry, sunny day, wear your sunglasses and go to an open space, away from buildings, brushes and other flammable material. You will need a large magnifier glass and newspaper.
Roll up a newspaper and place it on the ground. Sit back to the sun and hold the magnifier glass over the newspaper. Move the magnifier up and down until the light spot is as small as possible. Keep the light spot in one position for about a minute.
What happens? Does the newspaper catch fire?
Can the heat of sunlight cause fire where fuel (newspaper) and oxygen (from air) are present?
Does rolling up the newspaper help the fire to start easier? Why? Is it because more air is available to a rolled newspaper?
Additional / Optional Experiments:
Repeat this experiment with other fuels such as wood chips, cotton balls, cotton fabric, wool fabric and charcoal.
Extinguish the flame as soon as possible. Wind can blow burning papers away and land them on other flammable material.
Do this experiment outdoor on soil or on a concrete surface. You may optionally use a metal tray to place it under the newspaper or use it to extinguish the fire.
As extra precautions you may keep a bucket of water, a bucket of sand or a fire extinguisher handy.
Using a concave mirror:
In this experiment you could use a concave mirror instead of a lens (or magnifying glass).
Reflection of sunlight by a concave mirror is a focused spot similar to what was formed by the magnifying glass. Concave mirrors are the mirrors that make objects appear larger. Some concave mirrors are sold by beauty suppliers and are used for personal grooming.
Experiments involving fire create smoke, bad odor and risk of fire. All such experiments must be performed in a fire proof open space or in a fireproof room with proper ventilation. Some additional experiments that may test the effect of heat on starting fire are:
- Use a test tube clamp and hold an empty test tube over the flame of a gas stove for about 2 minutes. Then carefully drop a strip of paper in the test tube. What happens? Does the heat of test tube cause the paper to catch in fire?
2. Turn on a hot plate and set it to its highest temperature. After about five minutes, drop a cotton ball or a piece of paper over the hot surface. Does it start fire.
You may also perform experiments to show that cooling the environment can extinguish fire. For example cooling a burning candle with blocks of ice can put off the flame.
Materials and Equipment:
This is a sample list of material. You may make a different list of material based on the experiments that you choose to do.
- Wood Chips
- Cotton Ball
- Cotton Fabric
- Magnifying glass with 10cm in diameter.
- Concave mirror
- Hot plate
- Test tube
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.
No calculations are 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.
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.