Hello, my name's Mrs. Clegg and I'm pleased to be studying with you today about chemical reactions.

And in particular we'll be looking at oxidation.

This lesson is part of the unit "Understanding Chemical Reactions" and here are our outcomes for today's lesson.

So by the end of it, you should be able to describe oxidation reactions, including combustion, rusting, and name the products of some oxidation reactions.

Here are our keywords for today, so I want you to listen out for these.

Oxidation, oxide, rusting and corrosion.

And here are those keywords written into a sentence.

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

An oxide is a compound containing oxygen that is formed during an oxidation reaction.

Rusting refers to the corrosion of iron or steel in the presence of water and oxygen.

And corrosion is when a metal reduces in size due to a chemical reaction.

You might want to note down some of those definitions so that you can refer to them during the lesson.

I've split today's lesson into two parts.

The first part is oxidation and the second part we're gonna look in detail at an oxidation reaction, rusting.

So let's get started with oxidation.

So first of all, what is oxidation? Well oxidation is when a substance reacts to combine with oxygen, for example, combustion and rusting.

When metals react with oxygen, they produce metal oxides and we can represent this as a general equation.

Metal plus oxygen reacts together to produce a metal oxide.

Now if we look at the mini video going on there, you can see magnesium burning in oxygen.

So the reaction for that would be magnesium plus oxygen react together to provide magnesium oxide.

Another example would be aluminium and oxygen producing aluminium oxide, and sodium metal reacting with oxygen which would produce sodium oxide.

So let's have a quick check.

Complete the statement.

Oxidation is when a substance reacts with- Which one of those would you put? Well done if you said oxygen.

Let's do another one.

So name the product formed when the metal lithium reacts with oxygen.

Well done if you said lithium oxide.

The speed or rate of an oxidation reaction can vary.

It can be very fast, i.

e.

in seconds or it can be quite slow, over many years.

So fireworks combusting, they happen really quickly, don't they? That reaction happens really fast.

But Roman coins, copper coins, they've been in the ground for a long time and they oxidise, but it takes a long time.

It's very slow.

So complete this statement.

Oxidation happens- Which of those would you say was correct? Well done if you said at different rates.

Now let's think about non-metals.

Non-metal elements can undergo oxidation to produce non-metal oxides.

So if we think about some non-metal elements, things like carbon or nitrogen, sulphur, let's have a look at some of those.

So carbon and oxygen react together to form carbon dioxide, nitrogen and oxygen form nitrogen dioxide.

So we've got the non-metal element reacting with oxygen to form a non-metal oxide.

Non-metal compounds can also undergo oxidation to produce oxides and other compounds.

And water is an oxide of hydrogen, H2O.

So let's have a look at a couple of reactions.

So we've got methane, which is a non-metal compound, reacting with oxygen to form carbon dioxide and water.

And we've got ethanol, which is a non-metal compound, reacting with oxygen to form ethanoic acid and water.

And we can just have a look at the symbol equations there and we can see the oxides being formed there.

And this one a little bit more complicated, but we can see we've got another compound, ethanoic acid, which contains oxygen, and we've got water.

For nonmetal atoms, we can tell how many oxygen atoms are actually in the oxide by the name of the oxide.

So let's have a look at this table.

So if there's one oxygen atom in the oxide, the prefix will be mono.

So carbon monoxide has the formula CO, which means one carbon and one oxygen.

If there's two oxygens in the atom, in the oxide, then it's di, the prefix is di.

So it's carbon dioxide.

And there you can see CO2, because there's two oxygens.

The little subscript 2 means there's two oxygens.

And then we can also have three oxygens in the oxide.

So sulphur trioxide.

And four, dinitrogen tetroxide.

and five, arsenic pentoxide.

You wouldn't be expected to remember those, but you can work it out by looking at the prefix.

So mono, di, tri, tetr and pent.

So let's have a quick check.

So what would the product be when non-metal sulphur reacts with oxygen? Well done if you've said sulphur dioxide.

And we also know therefore that there are two oxygen atoms in the oxide.

Let's have another check.

A gas jar contains pure oxygen.

A small piece of heated sulphur is lowered into the gas jar.

The sulphur burns brightly.

What substance or substances are produced? Well done if you said sulphur dioxide, SO2.

We know it's got to be sulphur dioxide.

It can't be A, because there was no carbon present and it can't be C, because there is no carbon present either.

Let's have another check.

So select the correct statement or statements.

Water is made up two hydrogen atoms bonded to one oxygen atom.

Well done if you said A, water has the formula, H2O, so it is an oxide.

And another check question.

So there are five oxygen atoms in phosphorus trioxide with the formula P2O5.

Is this true or is this false? Well done if you noticed it was false.

Which of these statements would help you say why that statement was false? So well done if you noticed it was A.

In the question it says phosphorus trioxide, but tri means three.

So the name, that it can't be that if the formula is P205.

The name should actually be diphosphorus pentoxide because there's five oxygens bonded to two phosphorus atoms. Well done.

So now you're going to complete the oxidation practical and your teacher will give you three metal samples to test.

Copper, magnesium and iron.

So what I want you to do, is observe the metal sample's appearance and note it in a results table.

You're going to heat the metal sample now in a blue Bunsen flame and note any observations in your results table.

Then you're going to remove the metal sample from the flame and observe its appearance again and record this in your results table.

And then repeat steps two and three again for the other two metal samples.

Here's a sample table for you to complete.

Pause the video and come back when your table is full.

So your results table may be similar to this.

So iron, when you looked at it before heating, is like a grey metal wool.

It glows red or orange, and you get orange sparks which sort of form crumbles.

And after heating the metal is darkened.

Magnesium is like a shiny grey metal strip and it burns with a very bright white flame.

And after heating, you've got like a white powder or ash formed.

Copper is shiny orange or brown or copper coloured.

It glows bright red and it doesn't melt or burn.

And afterwards it's like a black, dark grey colour.

And when it's cooled down, you can actually scrape off the surface to reveal the copper coloured metal underneath.

So what I'd like you to do now, is match up the word equations with the oxidation reactions.

So here are the word, here's part of the word equation and here's the product.

So you need to match up the reactants with the product.

You might like to pause the video and join us when you've done it.

So let's have a look.

So iron plus oxygen would form iron oxide, magnesium and oxygen forms magnesium oxide, copper and oxygen form copper oxide, phosphorus and oxygen would form phosphorus pentoxide, carbon and oxygen forms carbon dioxide and sulphur and oxygen form sulphur dioxide.

You could practise working out how many oxygen atoms are in the oxide as well there.

So let's move on to the second part of our lesson today.

Rusting.

Now the rusting of iron is a much more complicated oxidation reaction, which takes place between iron, oxygen, and water.

Rusting is a series of reactions and the chemical name for rust is actually iron oxide.

And the formula of rust is this.

So we've got two iron atoms. Fe is iron, so two iron atoms and three oxygen atoms. Rusting is a specific type of corrosion and the surface of the metal is damaged by the chemical reaction.

And here's the word equation.

Iron plus oxygen plus water react together to form iron oxide.

Let's have a quick check.

Name the two reactants needed for iron to rust.

Well done if you said oxygen and water.

The rusting process corrodes iron, and many mixtures of metals that contain iron.

For example, steel.

So iron plus oxygen plus water gives rust or iron oxide.

And to try and stop or reduce rusting, we treat metal by painting it, by oiling it, or sometimes we coat it with another metal or we change the mixture of the metal, and we paint oil or coat with another metal to actually act as a barrier to try and stop the oxygen and water actually coming into contact with the iron.

So Task B.

Andeep has planned an experiment to determine what makes iron rust.

He sets up the following test tubes and leaves them for two weeks.

So he is got an iron nail in the first tube with some boiled or distilled water, which means there's no dissolved oxygen in the water.

And you can also see there's some air in the top there, which would contain oxygen.

In tube B, we've got boiled distilled water again.

So we've got no oxygen in the water and there's actually a layer of oil on top of the water to stop air from getting into the water.

And in C, Andeep is using a chemical called anhydrous calcium chloride.

And what that does is remove water from the air and he's used dry air which contains oxygen.

So if we look at the tubes.

Tube A, the nail has got oxygen and it has got water.

Tube B has got water but no oxygen.

And tube C has got no water but has got oxygen.

So what I'd like you to do is use the table to make a prediction of what Andeep will see in each of the tubes after two weeks.

And to write a conclusion for his experiment.

Pause the video and come back when you've finished.

So let's have a look and see what the results would show us.

So in tube A, it is likely that the nail would rust.

In tube B, there would be no rust on the nail.

And in tube C, again, no rust on the nail.

So what is the conclusion that you can write for this experiment? For rusting to occur, both water and oxygen must be present because only tube A rusted.

Well done if you got that correct.

So the conditions for rusting are that both water and oxygen must be present.

So question two, a car is made from steel, which is an iron base metal.

And so it is painted to stop it rusting.

Explain how painting stops the car from rusting and explain what would happen if the car got scratched, including the type of reaction that would occur.

So pause the video and come back when you've completed the task.

How did you get on? Let's have a look at the answers then.

So for part A, your answers should include the following.

The paint will stop oxygen from the air and it will stop water from the rain be able to react with the oxygen.

And we need both water and oxygen for rusting to happen.

And part B, if the car was scratched, oxygen from the air and water from the rain will react with the iron causing rusting to happen.

And the final bit, what type of reaction is that? This is an oxidation reaction.

Fantastic.

If you've got all of that, well done.

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

So let's look at the summary of today's lesson.

When a substance reacts to combine with oxygen, this is called oxidation.

Examples of oxidation are combustion and rusting.

One of the products of oxidation is always an oxide, but the other products can vary.

And remember we talked about water being an oxide of hydrogen.

Rusting requires both oxygen and water to be present.

We looked at the reactions with nail and, where we'd removed oxygen or we'd removed water and we saw what happened if you remember.

And rusting can be stopped by coating the surface of the iron base metal.

We might coat it with oil or with paint or with a different type of metal altogether.

So well done.

I hope you're feeling a lot more confident about what oxidation reactions look like and what they need to happen.

Well done and I'll see you next time.