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Combustion

Ämne: Engelska, Övrigt
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Hypothesis exp 1: I predict that the candle will burn more efficiently when tilted upside-down, and less efficiently when held straight up.I predict that the paper mug will not burn and that the water from the cup will not leak out.

I also predict that the light will go out when the jug is put over it.

Hypothesis exp 2: I predict that nothing will happen when we sprinkle the filings over the Bunsen burner

I predict that the steel wool will light when we hold a candle to it.

Hypothesis exp 3: I predict that there will be an explosion and that the lid will fly off.

Hypothesis exp 4: I predict that the wool will loose mass. I also predict that the wool will burn well.

Hypothesis exp 5: I predict that the light will go out before we have poured the liquid on it. In other words I predict that a gas will make the fire go out.

Hypothesis exp 6: I predict that a lot of foam will be formed and that a gas will but the fire will go out by a gas that can not be seen.

Results exp 1: When we held the match upright it went out very quickly. However, when we held it upside down it burned very quickly and did not go out until the fuel was gone.

N/A

The light went out after approximately 1 second after we put the glass over it.

Results exp 2: The iron filings lit up and it looked like a sparkler.

The Steel Wool melted, like hair does when lighted.

Results exp 3: There was a large bang and the lid of the can flew off.

Results exp 4: The steel wool gained mass. It melted like hair does when we put the match to it.

Results exp 5: When we made the mixture, thick foam formed. Then we poured it in the glass, but before we where able to pour it on the candle, the candle went out.

Results exp 6: When we made the mixture foam poured over the beaker, when it came close enough to the light it went out, without the foam touching the candle.

Conclusion:

All these experiments fall under the combustion reactions. Combustion reactions are chemical reactions. In everyday life, we call this burning. In a combustion reaction, there are redox reactions. Redox means reduction (and) oxidation reactions. This is when either oxygen or electrons are either taken away or given. For oxidation to take place, reduction is needed. They are in other words depending on each other. In several of the experiments, we have learnt that fire needs oxygen to burn. For example when we put the glass over the fire. The fire quickly went out. It did, however burn for a second or two before going out. This is because the small quantity of oxygen inside the glass is used up.

We did an experiment where we held two matches differently. First, we held a match straight up. The match quickly went out because the heat was travelling upwards and there was no fuel for it to burn on. Then we held a match upside down, this went better, and the match burned up very quickly. This is because now the match was held upside down, the flame went upward but now there was a fuel for it to burn on.

Combustions are exothermic reactions but a small quantity of heat is needed to get the reaction going. This is called the trigger energy. Each fuel needs a different amount of trigger energy. The heat makes the atoms in the fuel move. The heat is then transported through the whole object.

In the third experiment, we witnessed an explosion. An explosion is actually a combustion reaction that happens very quickly. An explosion must take place faster than 2000 m/s

We did two experiments which where about fire extinguishers. I did not know really how a fire extinguisher worked before. The aim of a fire extinguisher is to replace the oxygen needed for the burning to take place with CO2. This would stop the burning because there would be no oxygen to feed the fire. The CO2 is produced in the fire extinguisher. It is a neutralization reaction. One acid is mixed with an Alkali. When this happens there is always a salt and a gas produced, in this case CO2.

We also did two experiments where we put Eamon in a big TV box. In this experiment, we saw how much heat the body actually produced. Burning (combustion) is taking place inside us all the time. Combustions often need high temperatures but in the body there is a catalyst that is present at the reactions but it does not interfere with the reaction. The catalyst makes it possible to have combustion at lower temperatures.

From this experiment, I can also conclude that solids burn with a glow as gases burn with a flame. When we did the experiment where we sprinkled small iron filings over the fire, we saw sparks. This is how fireworks are made. Different metals give out different colors. So depending on what colors we want to see when the firework explodes we put in different metals.

Discussion:

There are some general rules for combustion:

-When burnt all fuels are oxidized
-All combustion reactions are exothermic and redox reactions
-For combustion to take place, a fuel, a oxidizing agent and heat is needed
-The oxidized reactant is called the reducing agent
-The reactant is called the oxidizing agent
-Before being combusted the reactant needs to reach its point of ignition
-All combustion reactions give out non-metal oxides
-To extinguishes fire: remove one or more of the necessary requirements

These are some ways to speed up a combustion reaction:

-A catalyst
-Using purer Oxygen
-Pulverizing reactant
-Mixing the fuel with the oxidizing agent
-Increase the temperature

In everyday life, we use combustion more than we think. In the winter many of us combust wood to get heat. Also, when we light a candle there is combustion.

A rocket blasts off from its launching pad at Cape Canaveral, Florida. Most of the rocket is filled with liquid fuel and a liquid oxidizing agent. The fuel and oxidizing agent mix and ignite in the combustion chamber; the presence of the oxidizing agent ensures that the fuel burns far more efficiently than it could if it depended on the surrounding air for oxygen.

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