Why is the match flaming upwards
"Fire and Flame" - experiments
The choice of experiments depends entirely on the teaching situation and the contributions of the students. We can only provide a list of suggestions here.
For example, the evidence of water in green foliage made in the 2nd lesson was not originally planned and is not listed here.
The experiments listed here can be done at home, but: Always outside and on the stone floor!
An adult must be able to intervene!
|Fire needs heat|
Water and metal steal the heat from the fire
|Heat rises to the top|
|Fire needs air|
|Fire only consumes part of the air|
|Most of the time, gases burn from the fuel|
|Finely divided things burn faster|
A cheap, easy-to-use and reliable fire extinguisher was available at all stations for emergencies: a pot lid.
At station 2, the experiment with the match was added when it turned out that some elementary school students were afraid of the matches. That fear quickly vanished when they learned how to hold a match safely.
This is what is done in the experiments:
- Cool metal weakens the candle flame:
You hold a cool metal plate or a knife sheath vertically in the flame so that the fire continues to get air.
Although a lack of oxygen cannot be the reason, one observes at first that the flame becomes smaller, sometimes even goes out. If the metal has become hot after a few seconds, the effect can no longer be observed.
This experiment works best with a metal, fine-meshed sieve or a slotted spoon, as is used in the kitchen to lift dumplings out of the cooking water, instead of a metal plate. If you hold the sieve / slotted spoon in the flame in such a way that the flame could actually continue to burn through the mesh / a hole, the fire will still go out or at least become very weak.
- Paper cooking pot:
Water cools the fuel so that it cannot ignite.
A small box is folded out of paper or you take an empty matchbox. This is placed close to a burning tea light. The covers of matchboxes can serve as supporting pillars.
The box will burn after a short time.
Repeat the experiment, but now fill the box with some water.
the heat from the candle flame is used to evaporate the water. Only when all the water has evaporated does the box start to burn.
- 1.Fuel catches fire when the heat source is below it:
You try to light paper that you hold in your hand with a burning match coming from different directions.
You are only really successful if you approach the flame from below the paper.
Because every fuel itself has to be heated to the ignition temperature before it can catch fire. The flame of the match gives off its heat upwards (hardly to the side and not downwards), so it can only preheat fuel that is above it.
- Tea bag rocket:
For this classic you need cheap tea bags. You should try the experiment yourself beforehand, because not all types of paper work. The experiment works best when the ambient air is cool.
The closure and the paper label are released from the bag. The content is emptied. The remaining shell is set up as a tube and twisted a little bit at the top to look like a rocket at launch. Now you light the top.
The fire is slowly working its way down. When it's almost down, the rest of the bag and attached ash lift off, still burning. On good days, the rocket flies over three meters and goes out in flight.
- Delete a match:
If you hold a burning match horizontally like most people do, you have to blow it out if you don't want to burn your fingers. Children often unintentionally blow out the candle that has just been lit at the same time.
A match also goes out if you hold it burning vertically with your pointed fingers upside down.
The flame, which is large at the beginning, creeps downwards, becoming weaker and weaker. Good matches leave two to three millimeters of unburned wood when it goes out.
- Loosely crumpled newspaper burns better than tightly twisted newspaper:
Let the children try this out for themselves. Adults are familiar with this supposed banality, but not yet children.
- Fire under glass:
The students light their tea lights. Now put different sized glasses (e.g. jam, cucumber, horseradish glasses) over the burning tea lights and watch how the flames slowly go out.
As an extension, the students can stop the time until the flame is out and relate it to the volume of the extinguishing vessel.
the greater the amount of air available, the longer the candle burns.
Unfortunately, the measurement results are often so imprecise that the linearity of the dependency cannot be recognized.
- Syringes pop:
You can buy 10 ml disposable syringes including the cap for a few cents in pharmacies.
First you let the students draw air into the syringe, think about what is now in the syringe, seal it so that the air cannot get out and push the plunger in.
The air is difficult to compress. If you let go of the piston, it will move outwards again by itself.
Now the students try to pull up a closed, empty syringe.
It's difficult. If you let go of the piston, it snaps - plop - back.
If the plunger is held under tension, the syringe is immersed in water and the cap is removed under water,
Then water gets into the syringe very, very quickly.
The water takes up the space that the air occupied in the first part of the experiment.
- "Water elevator":
The students light their tealights and let them float in a shallow water vessel while they are burning. Now put a glass over it.
When the flame has gone out and the glass cools down, you will see water rising into the glass.
With this experiment you can roughly estimate how much oxygen is in the air if you take a standing cylinder as a glass and measure how high the water rises proportionally. The carbon dioxide produced during combustion is absorbed by the water. Certainly complete absorption can be achieved by using lime water (caution pH 12.4!).
But even with water alone, the mean value of 10 experiments is quite good at 1/5 oxygen content in the air.
When an object catches fire, it is often not the solid object itself that burns, but gases that escape from it in the heat. A classic example of this are steppe plants that outgass essential oils. In the past, many children learned to do this under the Christmas tree. Or have you never enjoyed the small jets of flames when a single fir tree needle explodes in a candle flame?
- 1. Flame jump:
This experiment works best with a pure beeswax candle. If necessary, but not nearly so well, an Advent wreath candle will do the same. Tea lights don't work at all.
You let the candle burn for a while so that a hot wax lake can form below. Now someone carefully blows out the candle. A second immediately holds the flame of a match or lighter in the rising wax vapor.
The flame “flies” along the steam cord from the match to the candle wick. With pure beeswax candles, the flame can bridge a distance of up to 10 cm, so that even less closely observing students can see the effect.
- Flambéed handkerchief:
Soak a handkerchief - or a banknote - with an approximately 1: 1 mixture of tap water and denatured alcohol and hold it by one corner with a pair of crucible tongs. Have a water container ready to extinguish the fire. Now you light the bottom (not the top!, See above).
The evaporating alcohol catches fire all over the surface. You can recognize this by the blue flame. Only when all the alcohol has been burned and all the water has evaporated in the heat does the fabric begin to burn with a yellow flame.
If the flambé does not work, there is too much water in the mixture and more alcohol has to be poured into it. But you shouldn't use pure alcohol because the water is needed to cool the fabric while the alcohol burns around it.
There are always severe burns because alcohol is underestimated in its flammability and no thought is given that the vapors will already catch fire.
Alcohol is not a grill lighter !!!!
There are two reasons:
1. the air gets to the fuel particles better
2. the heat is passed on faster
- Example cotton:
A scrap of cotton fabric and some cotton wool are set on fire.
The fabric burns off slowly, the wadding quickly fizzles.
- Dust explosion (in school with moss spores, in reality in mills with grain flour or wood flour):
In a commercially available device, the finest bear moss spores are atomized in the air above a candle flame by a blast of air.
With a large jet of flame it flings the lid of the vessel upwards.
- Gas explosion (feared in reality in the event of leaks in the gas pipeline and illegal extraction of oil from pipelines)
A commercially available apparatus is used to produce an explosive gasoline / air mixture that is ignited by means of an electrical spark.
Private individuals sometimes rinse gas canisters with water. Because the gasoline does not mix with the water, very little gasoline remains in the canister - just enough to explode as a gasoline / air mixture in a warm place.
- Fat fire:
The teacher heats cheap salad oil or frying fat until it steams vigorously. Now the steam can be ignited with a match.
From a safe distance you can now try to extinguish the fire with water from a squirt bottle.
Note: the pan burns, just put the lid on!Up
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