Hello, my name's Mrs. Clegg.

Welcome to our lesson today.

We'll be learning about combustion, which is a chemical reaction.

This is part of the unit called understanding chemical reactions.

So here's our lesson outcome today.

By the end of the lesson, you should feel much more confident in describing the process of combustion and burning and be able to name the products of these reactions.

Here are some of our key words that I want you to listen out for today.

Combustion, oxidation, burning, fuel and molecule.

Here, they're written into a sentence.

So in combustion, fuel reacts with oxygen to release energy and requires fuel, oxygen, and heat to start the reaction.

Oxidation is a type of reaction in which oxygen bonds to the elements of the reactants.

Burning is a type of combustion where substances react with oxygen and produce visible flames.

Fuel is a substance that releases its stored energy when it undergoes combustion.

And finally, a molecule is made up of two or more atoms chemically bonded together and these are usually non-metal atoms. Today's lesson's been divided into two parts.

First of all, we're going to look at burning in combustion, and then we'll look at the equations for combustion.

So let's get started with the first part of our lesson.

Burning and combustion.

Combustion's a chemical reaction and to happen, combustion needs three things.

Fuel, oxygen, and heat.

So burning is a campfire burning.

It is a combustion reaction.

And burning is where fire or flames are produced.

So you can see those nice flames in the campfire there burning away.

Now combustion here we've got charcoal.

So combustion of charcoal, oxidation is happening, but there are no flames and it's not burning.

So there's the difference between burning and combustion.

Many reactions need heat to get them started.

Safety matches for example, they will only light when the heat from friction of the rough surface on the box causes a reaction between the chemicals on the match head and the chemicals in the rough surface surface.

So there we've got some safety matches and they're being struck to actually light.

We can show the things that are needed for combustion in a triangle called the fire triangle.

So fuel, oxygen, and heat, that's the fire triangle.

So remember, for combustion to happen, we need these three things.

If one of the size of the triangle is removed, then the combustion reaction will actually stop and the fire or burning will also stop.

So let's have a quick check.

What three things are needed for combustion to occur? Well done if you said D.

Heat, oxygen and fuel, well done.

Substances or fuels that can easily catch fire are labelled as flammable.

So flammable substances easily catch fire.

So you might have seen some items around the house that have got symbols on them.

This is a trainer waterproofing spray can, and you can see the symbols there warning us that this is a hazard and this symbol is the hazard symbol to show it's flammable.

It will easily catch fire.

Remember the fire triangle? We need those three things, fuel, oxygen, and heat.

The hazard symbols help us to stay safe by helping us to know that we need to take precautions to stop accidents from happening.

For example, this particular spray needs to be kept away from heat to avoid a fire taking place.

The amount of heat that is required for combustion to get started varies.

So magnesium needs heat from a blow torch or a bunsen burner to actually start the reaction with oxygen.

And there we've got a video of magnesium reacting with oxygen, bright white light.

And then it stops.

Why does it stop do you think? So once the reaction has started, it will continue without you needing to continue to heat it.

But it stops when the fuel or the oxygen is used up.

So if we think about the fire triangle, the oxygen that's needed for the combustion reaction, it doesn't always have to come from the air.

So here we've got a rocket burning fuel and rockets use oxidising chemicals to provide the oxygen that are needed for combustion to happen.

And we have special hazard symbols that show substances that can provide oxygen for a reaction, and they look like this.

So if you see a symbol like that, it shows that this is an oxidising chemical which can provide the oxygen needed.

So an explosion is where the combustion reaction takes place really quickly.

So think about a sparkler.

That happens really quickly, doesn't it? And if we look at the wrapping of sparkler, you'll see a hazard symbol like this, which is the hazard symbol for the risk of explosion occurring.

So it tells us to take precautions and make sure that that explosion doesn't happen when we don't want it to.

So let's have a quick check.

Heat from a blow torch or a Bunsen burner is needed to start all combustion reactions.

Is that true or is that false? Well done if you said false.

Now let's have a look at two statements to see if you can justify your answer.

Which one of these would you choose? Well done if you said A.

Some reactions just happen with the heat from friction such as matches.

Which is the correct image of the fire triangle, A, B, or C? Well done if you said B.

Let's just have a quick look.

So A, fire, oxygen, and heat.

So fire and heat are really the same thing.

So we need the fuel for the combustion to occur.

And C, we've got fuel, we've got heat, and then we've got carbon dioxide.

Well, carbon dioxide is what is produced usually as a result of burning.

So fire extinguishers put out fires by removing one or more of the sides of the triangle, fuel, oxygen or heat.

So if we put water on a fire, we're cooling the fuel and removing heat from the fire.

Some fire extinguishers put fires out by removing two or more a size of the fire triangle.

So if we put foam on a petrol fire, it covers the burning liquid with a layer of foam and that removes the supply of oxygen, but it also represents the release of flammable vapours, the fuel, and it cools the fuel and removes heat from the fire.

And this is a carbon dioxide extinguisher and it works by removing oxygen from the fire, it cools the fuel and removes heat from the fire.

So some fire extinguishers can remove two or three sides of that fire triangle.

Let's have a quick check.

So putting water on a fire will do what? What does it remove? Well done if you said heat.

Let's have another quick check.

Which of these is the correct hazard symbol that would be placed on a substance that is a source of oxygen? Well done if you said A.

That is the hazard symbol for oxidising chemicals.

B is the sign, the hazard risk of being flammable.

And C, if you remember, was the hazard symbol for a risk of explosion.

So let's move into task A.

So this black powder is made of carbon and carbon is able to burn.

This black powder is copper oxide and it is made when copper reacts with oxygen as an oxidation reaction.

So the question is, does copper oxide burn? And give reasons for your answer.

So how did you do? Let's look at the answers.

So copper oxide does not burn and the reason the copper oxide does not burn is because the copper has already combined or reacted with the oxygen.

Oxidation has already happened.

These two students are talking about combustion and burning.

I'm going to show you some statements in a moment and I want you to say whether the statements are only about burning only about combustion or both burning and combustion.

So here are the statements.

You might like to pause video and come back when you've made your decisions.

Let's look at the answers.

So no flames are seen is combustion.

Only combustion.

Remember the charcoal? Products other than oxides are sometimes formed.

That is true for both combustion and for burning.

Flames are seen.

That's only for burning.

Remember the campfire burning? It's a reaction with oxygen.

So that's oxidation and that is both.

Both burning and combustion are oxidation reactions.

And an oxide is always produced would be both, burning and combustion.

So question three, label the sides of the fire triangle.

So well done if you've got all three.

It doesn't matter which order they're in.

So fuel, oxygen, and heat.

As long as you've labelled with those three in any orientation, it doesn't really matter.

Well done.

Question four.

Match the statements about fire extinguishes to the parts of the fire triangle that it removes.

So we've got three statements there and we've got the three parts of the fire triangle.

So match the statements.

Pause the video, come back when you're ready.

And so the foam fire extinguisher produces foam that cools the fuel, forms a layer on top of the fire, as well as stopping the fuel-forming vapours.

Would be fuel, it would be heat, and it would also be oxygen.

So this type of fire extinguisher removes all three parts of the fire triangle.

A water filled fire extinguisher cools the fuel of fire.

So that would be heat is removed.

And a carbon dioxide fire extinguisher forms a layer of non-flammable gas over the fire and cools the fuel.

So that would be oxygen being removed and it would also be heat being removed.

Well done.

Fantastic if you've got all of those questions correct.

Let's move on to the second part of our lesson now.

Combustion equations.

So many of our fuels are carbon and hydrogen based.

They only contain hydrogen and carbon atoms and we call those hydrocarbon fuels.

Examples of these are methane, propane, petrol.

Petrol is mainly octane.

And the general equation for hydrocarbon fuel that's burning is this.

So hydrocarbon fuel plus oxygen react together to form carbon dioxide and water.

So a specific example might be ethane and oxygen react together to form carbon dioxide and water.

So there's the symbol equation and you can see that ethane just contains carbon and hydrogen atoms. C2H6.

Water is often formed in chemical reactions if oxygen and hydrogen atoms are present.

So in a gas boiler, methane and oxygen react together to form carbon dioxide and water.

And you might have seen outside on buildings, a vent coming out of the wall.

And then you can see the water being formed as a product of the reaction.

And here's the equation, the simple equation.

So CH4, that is methane.

If we look, we can see where the hydrogen and the oxygen atoms are being rearranged to form water.

So the hydrogen from methane and the oxygen from oxygen itself are rearranged to form water, a new product.

So we know a chemical reaction has occurred.

And carbon dioxide is often formed in chemical reactions if oxygen and carbon atoms are present.

So again, if we look at the equation above, we can see where the carbon and the oxygen, atoms are being rearranged to form the new product, carbon dioxide.

Let's have a quick check.

So which reactions would you expect to see water being formed as a product? So have a look at these.

There might be more than one answer.

So well done if you chose A and B.

So if we look at C and D, we know that it can't possibly be them because there's no hydrogen atoms present.

Let's have another check.

So which reactions would you expect to see carbon dioxide as a product? So have a look.

Well done if you said A and C, 'cause you can see that carbon is present and oxygen is present.

It can't be B and it can't be D because there's no carbon.

So let's have a look at carbon dioxide and water.

They're both really small molecules, they're both formed very easily and they both have very strong bonds between their atoms. So here's the carbon dioxide molecule.

You can see there's one carbon and two oxygens bonded together in a carbon dioxide molecule.

And here's water.

You can see there's two hydrogen atoms and one oxygen atom bonded together.

So let's have a quick check.

Find the correct statement or statements about carbon dioxide and water.

Well done if you said A and D.

They have strong bonds between their atoms and they're small molecules that are easy to form.

So in task B, what I'd like you to do is match up the statements to the keywords and you can use the keywords more than once.

So here are the statements, and here are the keywords.

So pause the video and come back when you're ready.

Remember, you can use the keywords more than once.

Okay, how did you do? So let's have a look.

So.

Often formed in chemical reactions if oxygen and hydrogen atoms are present will be water.

Formed when a substance reacts with oxygen is going to be an oxide.

Happens quickly or over many years, that's oxidation.

Remember fireworks and remember Roman coins, the copper in the coins oxidising over many, many, many years.

So it can happen really quickly or really slowly.

Small, easily formed molecule with strong bonds between the atoms. So that could be water and it could also apply to carbon dioxide.

The process of reacting with oxygen is oxidation.

And then finally, often formed in chemical reactions.

If oxygen and carbon atoms are present would be carbon dioxide.

Well done.

Absolutely great work if you've got all of those correct.

So next, you're going to carry out a practical to investigate how the burning time of a candle changes with the volume of air or oxygen.

So you're going to get a beaker, a candle, some adhesive putty, a heat resistant mat, a stop clock.

You're going to light the candle and start the stopwatch straight away as soon as you put the beaker over the top, then you're gonna stop the stopwatch when the candle goes out and record your result.

And then you're going to repeat the experiment using different sized beakers.

So you've got a different volume of air present.

And here's a results table that you could use to record your results.

We've got the size of the beaker in centimetre cubed and we've got the time taken for the candle to go out in seconds.

Remember, you don't need to put the units in every row of the results table 'cause they're in the heading.

So pause the video and come back when you've completed your results table.

So now, could you write a conclusion for your experiment looking at the results that you've collected? And here are some statements to help you.

The candle which burned for the longest was in the mm beaker because.

So we're asking you to find out which candle burned the longest and then give a reason why.

The candle went out when.

So what did you notice? So pause the video and come back when you're ready.

Let's have a look.

So the candle, which burned for the longest time was going to be in the largest beaker that you used, or you might have actually written the specific volume that you used.

So here's the answer.

And the reason why the because, there was the greatest quantity of oxygen available for the candle to burn.

And the candle went out when all the oxygen had been used up in the combustion reaction.

Remember that side of the fire triangle would've been removed.

Absolutely brilliant if you got those correct.

So we've come to the end of our lesson now.

So let's have a look at the summary.

So here are the main points of our lesson today.

The term burning describes the reaction of substances with oxygen and is most commonly used to refer to visible flames.

Remember the campfire burning.

Water is often formed in chemical reactions if oxygen and hydrogen atoms are present.

Carbon dioxide is often formed in chemical reactions if oxygen and carbon atoms are present.

Carbon dioxide and water both consist of small molecules that form easily with strong bonds.

Well done today and I look forward to working with you again for the next lesson.