Lesson video

Hello, my name is Mrs. Collins, and I'll be guiding you through the learning today.

This lesson forms part of the Unit Materials and is called Chemical reactions: the displacement of metals.

We're gonna be learning today about how we can use the reactivity series to make predictions about whether metals will be displaced or not in a chemical reaction.

So let's get started.

During today's lesson, we are going to explain what happens when one metal displaces another metal from salt, as well as how carbon can be used to extract metals from their ores.

The keywords for today's lesson are displacement reaction, metal salt, aqueous solution, reactivity series, and ore.

Now, some of those words will be familiar to you, but a lot will be new.

So pause the video here, read through the definitions, and write down any notes.

Today's lesson has been divided into three separate parts.

So first of all, we're going to look at the theory behind displacement reactions.

We are then going to take a look at a practical activity.

And then, we'll explore extracting metals.

So let's get started with displacement reactions.

So a displacement reaction occurs when a more reactive element takes the place of a less reactive element in a compound.

For example, a more reactive metal will displace another that is less reactive from its metal salt in an aqueous solution.

Now, copper sulphate is a really good example of a metal salt, and this has got a blue colour, and you may well have used this during your science lessons.

And an aqueous solution is formed when a substance is dissolved in water.

So if we dissolve copper sulphate in water, it will form a blue solution, and that will be an aqueous solution.

So we can say that's copper sulphate solution, or that is aqueous copper sulphate.

So during this displacement reaction, a more reactive metal will displace a less reactive metal from its metal salt.

And if we look, we are going to use these balls to represent the different substances within that chemical reaction.

So we've got the metal there, which is the first purple circle, we've got another metal, which is a pink circle, and then the salt is the blue circle.

So the first metal is purple, and that is more reactive than the pink metal.

So it displaces the pink metal from the metal salt.

So you can see that happening in the balls at the bottom.

So let's have a go at a question based on the learning that we've covered so far.

So what I'd like you to do is read through those statements and decide which one best finishes off the sentence.

So pause the video here and complete the sentence.

So, hopefully, you've recognised that the correct answer is A.

In a displacement reaction, a more reactive element takes the place of a less reactive element in a compound.

Well done if you've got that correct.

So when magnesium is added to aqueous copper sulphate, a displacement reaction occurs.

Remember, aqueous means that that copper sulphate has been dissolved in water.

So we can say it's copper sulphate solution.

So if we add magnesium to a copper sulphate solution, a displacement reaction occurs.

So here, we've got the blue copper sulphate solution.

We've added magnesium powder to that reaction, and we're going to observe it to see if there's a change in temperature.

So the blue copper sulphate solution, the grey magnesium is added, and then if we watch very carefully, we can see that there's a slight increase in temperature.

You watch the thermometer there.

So slight increase in temperature.

So let's write down our observations for that reaction.

So first of all, we've got that blue colour solution.

If we watched it for long enough, we'd see that it gradually fades over time and becomes colourless.

The grey metal solid will turn into an orange-brown solid.

And the temperature will increase slightly from room temperature, which is about 20 to 21 degrees Celsius, up to 25 degrees Celsius.

So an increase of approximately four or five degrees Celsius.

But what do these observations actually mean? How can we interpret them? So first of all, the blue copper sulphate has been replaced by colourless magnesium sulphate.

So we've got blue copper sulphate solution being replaced by colourless magnesium sulphate solution.

The grey magnesium is being replaced by an orange-brown copper metal.

And we know that the reaction is exothermic because the temperature has increased.

And this is because energy is being released to the surroundings, and that increases the temperature.

We can write an equation for this reaction.

So we've got magnesium and copper sulphate.

And we know that the magnesium has displaced the copper from its salt, so we know it's formed magnesium sulphate and copper.

So you can see there that the magnesium has displaced the copper from the compound.

So this is a displacement reaction.

If you remember from a previous lesson, we talked about the reactivity series, and that the higher up in the list a metal is, the more reactive it is.

And we can use the reactivity series to predict whether a displacement reaction is going to take place.

So a more reactive metal, remember, will displace a less reactive metal from its salts in solution.

So we know that magnesium will displace copper because it's higher in the reactivity series than copper.

So let's look at a couple of other examples.

So zinc will displace silver from a solution of silver chloride.

And if you look in the list, zinc is higher up in the reactivity series than silver.

And here's another example.

Copper will not displace calcium from a solution of calcium nitrate, and that's because copper is less reactive than calcium, so it can't displace calcium from its compound.

So let's have a go at a question based on that new learning.

And this time, we've got a true or false question.

So magnesium will displace lead from a lead sulphate solution to form magnesium sulphate and lead.

You may need to check the reactivity series.

So we are interested in magnesium and lead, and I'm just gonna flick back to the previous slide so that you can see the reactivity series.

So I want you to look out for magnesium and for lead in the reactivity series.

I'll just give you a moment to do that and then we'll go back to the question.

So is that statement true or false? And then justify your answer using the two statements at the bottom.

So pause the video here and answer the question.

So, hopefully, you've recognised that that statement is actually true, and it's true because magnesium is more reactive than lead.

So it's higher in the reactivity series than lead.

So well done if you've got that question correct.

Now, let's have a go at task A.

Here we've got a practical that's taken place.

So we've got copper sulphate solution and an iron nail has been placed in that.

So some copper sulphate solution was poured into a test tube, an iron nail was added, an orange-brown solid gradually appeared.

Who do you agree with and why? So what I'd like you to do is to pause this video, read through those four statements, decide which one of those statements you agree with, and then explain why that's the case.

So let's go through the answers.

So the person who's actually correct is Laura.

So the reaction has made copper and copper is insoluble.

So this shows that a displacement reaction has taken place.

Alex is not quite right because the copper has not come from the nail, it's actually come from the solution.

Remember, it's copper sulphate solution.

Aisha's not right either because she says, "The iron nail made the copper in the copper sulphate solution become insoluble." Well, that the fact that the copper is insoluble is an observation.

It doesn't explain the result, which comes from the displacement reaction.

And Jun is also incorrect because this is an observation, again, and it doesn't explain the results.

So well done if you've got that answer correct.

We are now going to take a look at question two.

So a coil of copper wire has been placed into a solution of silver nitrate.

I want you to read through those three statements, decide which one is correct, then complete the word equation, and then make a prediction about what would happen if the copper wire was placed in a solution of sodium nitrate.

For part C, you might want to find a reactivity series of metals to refer to.

Let's go through the answers.

So, hopefully, you recognise that the product of the reaction between copper and silver nitrate is silver, which is insoluble.

So that explains the appearance of the solid silver.

Completing the word equation, you've got copper and silver nitrate.

So we know the copper displaces the silver from the silver nitrate.

So the first product is copper nitrate.

And we know because the silver's been displaced, it forms that insoluble metal, silver.

Then for the prediction, well, it would stay the same.

No reaction will take place because copper is less reactive than sodium.

So well done if you got that correct.

We are now going to move on to part two, the displacement reactions practical.

So displacement reactions can be used to confirm the position of a metal in the reactivity series for metals.

So this is the experiment that we're going to do, and you can see the equipment there.

And I just want to draw your attention to the spotting tile, which is that white piece of plastic, and it's got dimples in it so you can carry out the reaction in those dimples, and we're gonna see that a little bit later on.

So what this does is it allows metals and salt solutions to be combined quickly and accurately, and it also uses less of the reactants, and that makes it easier for us to spot when a reaction takes place.

So in this experiment, we are going to use the following metals, magnesium, iron, and zinc.

And we are going to use the metal salt solutions, copper sulphate, zinc sulphate, magnesium nitrate, and iron sulphate.

And notice in the list, we've got salt solutions for each of the three metals that we are using, but we've also got copper sulphate as well.

So I'm just going to pop up the reactivity series of metals here.

And what I want you to do is use that series to predict which metal will be the most reactive and which metal will be the least reactive in this experiment.

So take a look at those three metals, look at the reactivity series.

Which one do you think will be the most reactive? And which one do you think will be the least reactive? I'll give you a moment to answer that question.

So remember, the higher up in the list of metals the metal is, the more reactive it is.

So magnesium is most reactive and iron is least reactive.

So well done if you've got that correct.

Using a dropper pipette, each row of the spotting tile is filled with a different aqueous solution.

And you can see that in this diagram here.

It's a good idea to place a piece of paper underneath the spotting tile because then you can label the different solutions.

And that's important because you can see copper sulphate and iron sulphate are both coloured solutions, so it's really easy to tell which one's which.

But the zinc sulphate and the magnesium nitrate are both colourless, and that means it's easy to get them mixed up.

So using a spatula, the same metal is added to the aqueous solution in each column of the spotting tile.

We're going to make careful observations and we're going to note them down.

We are looking particularly for signs of colour changes, that's either to the solid or the solution.

And we're also looking for effervescence.

And if you remember back to a previous lesson, that means fizzing.

So in a moment, we're going to watch the reaction taking place.

And as it's happening, I want you to try and make as many observations as you can.

It's obviously a little bit more difficult than it would be if you were doing it in real life, but we are going to go through the results together.

So in the first row, we are adding magnesium here, and then in the second, we're gonna add iron, and the third, we're gonna add zinc.

So we're just gonna watch to see if there's a reaction taking place for each of those.

Now, as I mentioned, it's actually quite difficult to see that taking place, but I've actually got a photograph here of the results.

So have a look at them and see if you can complete the table, putting a tick where a reaction has taken place and across for no reaction, and you need to do your best.

So we are looking out particularly for effervescence, any potential change in colour, and to see if a reaction's taken place.

So I'll give you a moment to do that.

Now, if we have a look at the copper sulphate solution, first of all, we can actually see that all three metals have actually reacted with the copper sulphate solution.

It's a little bit difficult to see, but that actually has happened.

For the zinc, only the magnesium has worked.

So there's only a reaction between the magnesium and the zinc sulphate.

For the magnesium nitrate, we're not interested in the magnesium reacting with the magnesium nitrate, because, obviously, the magnesium can't displace the magnesium.

But it doesn't react.

So iron doesn't react with magnesium nitrate and zinc doesn't react with magnesium nitrate.

And then in the last column, both metals react with iron sulphate.

So the magnesium and the zinc both react, but the iron obviously, again, we're not interested in.

So just check that next to your results.

Have you got the same results as I have? Now, we need to think about interpreting the results.

What do those results actually tell us? So first of all, the magnesium metal has displaced all the three other metals from their salt solutions, and that means that magnesium must be more reactive than those three metals.

Iron has displaced copper from copper sulphate, so that means iron must be more reactive than copper, but it hasn't displaced zinc, it hasn't displaced magnesium.

That means it must be less reactive than magnesium and less reactive than zinc.

And then the zinc metal has displaced the copper from the copper sulphate and the iron from the iron sulphate.

And that means what we can do is use that information to actually work out which one is the most reactive and which one is the least reactive.

So interpreting the results.

As we've discussed, the order of decreasing reactivities, that's the most reactive at the top, the least reactive at the bottom, is magnesium, zinc, and iron.

And we could actually add copper to the bottom of that, if we wanted to.

And if we check with a reactivity series of metals, we'll see that it actually agrees with it.

And that's how we worked out the activity series of metals.

We carried out a whole series of practicals like this to see which metals were the most reactive.

Now, we can write word and symbol equations for these displacement reactions, and we're going to show a couple of those.

So magnesium and zinc sulphate forms magnesium sulphate and zinc.

So the magnesium, you can see there, has displaced the zinc from the zinc sulphate, and that has formed magnesium sulphate.

And then the zinc is left as an insoluble metal.

And then we've got the symbol reaction.

And then iron and copper sulphate.

So, again, iron is more reactive than copper, so it's displaced the copper from the copper sulphate to form iron sulphate.

So when a displacement reaction does not take place, we can still write that down, and we can write it down like this.

So copper plus zinc sulphate has no reaction.

So let's have a go at a question and see if we can apply the knowledge that we've just learned.

So which of these displacement reactions will take place? Look at the list of reactions, take a look at the reactivity series, and make a prediction.

So pause the video here and see which ones you think will take place.

If you want to extend it, you could also work out what the products might be.

For the first one, that reaction will take place because zinc is more reactive than copper.

Next one, magnesium and zinc sulphate.

And that's because magnesium, again, is more reactive than zinc.

Copper will not react with iron sulphate because copper is less reactive than iron, so it cannot displace the iron.

So well done if you got that correct.

Let's have a go at task B.

So we've got question one here.

Some students are carrying out a displacement reaction practical to find out the order of reactivity of the metals, magnesium, copper, and tin.

So what you need to do is describe what a displacement reaction is.

So what's the definition.

Draw a circle around the metal salts they should use in the experiment.

So look at the metals and decide which metal salts they ought to use.

Then say why it's better to carry out the experiment in a spotting tile rather than test tubes.

So, what are the advantages of using a spotting tile? And how will the students know if a reaction has occurred? So pause the video here, answer the questions, and I'll see you when you're finished.

Okay, let's go through those questions then.

So what is a displacement reaction? So this is a reaction where a more reactive element takes the place of a less reactive element in a compound.

Remember, metals is just an example of this.

There are other elements that actually carry out displacement reactions too.

So if you've just talked about metals, do change that to elements.

Then, draw a circle around the metal salts they should use in the experiment.

Now, because they're using magnesium, copper, and tin, it would make sense to use copper sulphate, magnesium sulphate, and tin chloride.

Now, on to C.

Now you will have potentially some of these listed, but maybe not all of them.

And you may also have ones which are not on the list too.

So there are lots of different advantages.

So just check which ones you've got next to my list.

So a spotting tile allows the chemicals to be easily and accurately combined.

It uses less of the reactants than test tubes.

It's easy to label the metals and the solutions by standing the spotting tile on a sheet of paper.

And it's easier to make observations as all reactions can be observed at the same time.

And then how will the students know if a reaction has occurred? We are looking for signs of a chemical reaction.

So we are looking for maybe a change in colour of the solution or the metal, we can look for a temperature change, and we can also look for effervescence.

So well done if you've got that question correct.

Let's move on to question two.

We're going to use the reactivity series for metals to complete the following word equations for the following displacement reactions.

So look carefully at the reactivity series of metals, decide where the metals are and whether a displacement reaction will happen, and then work out what the products will be.

Pause the video now and have a go answering the question.

So let's go through the answers.

Firstly, A, calcium and zinc sulphate.

Now, calcium is higher in the reactivity series than zinc, so it will displace zinc from the zinc sulphate.

So we end up with calcium sulphate and zinc.

Next one, iron and silver nitrate.

Iron is higher in the reactivity series than silver, so it will displace silver in the reaction, and we end up with iron nitrate and silver.

Now, lead is lower in the reactivity series than the sodium chloride, so there will be no reaction for this.

Now, you could have written no reaction, or you could have written lead plus sodium chloride.

Either of those would be correct.

And then aluminium and tin chloride.

Aluminium is higher than tin in the reactivity series, so it will displace tin.

We end up with aluminium chloride and tin.

So well done if you've got those answers correct.

Right, so let's move on to part three of the lesson, which is extracting metals.

Now, a metal ore is normally a rock that contains metals or metal compounds that can be extracted.

And here are some examples of different types of metal ore.

You won't need to know them off by heart, but it's quite useful to know some of them.

The most common one that you'll come across in science is haematite, which is an iron ore.

So based on what we've just covered, which of the statements gives the best description of a metal ore? So read through those three statements and decide which one is the best description.

Pause the video here and have a go answering the question.

So let's go through the answer.

And you should have identified that it's C, a rock that contains a metal in a form that can be extracted.

Now, not all rocks contain metal.

Usually, the metal is found as a metal oxide inside the rock, but not always.

So the best answer to that question is C.

Now, carbon can be used to extract some metals from their ores if carbon is more reactive than the metal.

So again, it's a displacement reaction.

If carbon is more reactive than the metal, it will displace the metal from its compound.

This normally happens inside a blast furnace.

So carbon is more reactive than iron, so it can displace iron from an iron ore inside a blast furnace.

So this is how we get iron from rocks from their metal ores.

So carbon is very cheap and easy to find and it's really useful for metal extraction.

Now, you don't need to know this reaction in a lot of detail.

But in actual fact, the source of carbon that we use in the reaction is called coke.

But in the chemical reaction, we call this carbon.

So let's have a look at the chemical reaction that takes place when we use carbon to extract iron from its ore.

So we've got the iron oxide and we've got the carbon.

We know that carbon is more reactive than iron, so it will displace the iron from its compound.

So we end up with carbon dioxide and iron during this reaction.

We can also extract iron from its iron ore by reacting it with a more reactive metal like aluminium.

And when we do this, it's called a thermite reaction.

And the mite reaction is another example of a displacement reaction, and it's very, very exothermic and it's used to join railway lines in real life.

So the equation for this reaction is aluminium plus iron oxide forms iron and aluminium oxide.

So you can see, the aluminium is more reactive than the iron, so it's displaced the iron from the compound to form aluminium oxide.

And then you've got the iron leftover.

Now, if we want to extract lead from its ore, we need to crush it, heat it, separate it, and roast it.

And we actually, again, can react this lead oxide that's formed at the end with carbon.

Because carbon is more reactive than lead, we can use it to extract lead from its compound.

So the equation for this reaction would be carbon plus lead oxide.

The carbon displaces the lead to form carbon dioxide, and then you are left with a metal lead afterwards.

So it's a really good means of extracting lead from its ore.

Carbon is included in the reactivity series for metals as a reference point.

So those metals below carbon in the reactivity series can be extracted from their ores using carbon.

So if carbon is more reactive than the metal, it can be used to extract the metal from its ore.

But any metal which is more reactive than carbon, carbon cannot be used to extract it.

So we can use the reactivity series to predict whether carbon can be used to extract a metal from its ore.

An alternative method of extraction called electrolysis, which uses electricity, is needed for those more reactive metals.

So let's have a look at the reactivity series of metals here.

We can see, you've got the very reactive metals at the top and the very unreactive metals at the bottom.

And you can see that carbon has been included, and that'll help us.

So let's summarise what we've learned so far about extraction of metals.

So those metals above carbon cannot be extracted from their ores using carbon.

So we have to use electrolysis for those metals.

The metals below carbon, we can use carbon to extract them.

If carbon is more reactive than those metals, we can use it to extract them from the ores.

And then metals like gold and platinum are found as pure metals.

So we don't need to use an extraction technique, we can just dig them up because they're found purely as gold and platinum, not in compounds.

So let's have a go at a question based on that learning so far.

True or false? Aluminium can be extracted from its ore using carbon.

So we need to know where aluminium is in the reactivity series.

So decide if that is true or false, and then justify your answer.

So pause the video here, maybe look at a reactivity series, and then I'll see you when you've answered the question.

So the answer to the question is actually false.

And this is because aluminium is more reactive than carbon.

So carbon cannot be used to extract it because aluminium is too reactive.

So we'd need to use electrolysis in this case.

So let's have a go at task C.

So you've got the reactivity series of metals there, so make sure you use that to help you answer the question.

Number one, name a metal ore.

See if you can remember the name of one of the metal ores.

Two, explain why carbon is included in the reactivity series.

And then three, draw a circle around the metals that can be extracted from their metal ores using carbon.

So pause the video here and answer the question.

Welcome back.

So let's go through those questions one at a time.

So name a metal ore.

So well done if you manage to remember one of these.

So you've got malachite, galena, and haematite with the examples we used earlier on, but you may know others, particularly if you pay "Minecraft." So often, they use the name of actual metal ores in that game.

Number two, why is carbon included in the reactivity series? It's included as a reference point for extracting metals from their ores.

So the key bit there is reference point.

And then part three, draw a circle around the metals that can be extracted from the metal ores using carbon.

So remember, they've got to be metals that are below carbon in the reactivity series.

So we've got zinc, iron, and copper.

So well done if you've got those answers correct.

Now, we've got two more questions to have a go answering.

And again, you might need to refer to the reactivity series to answer them.

So question four, suggest why an alternative method of extraction is needed to extract a very reactive metals from their ores.

And then question five, some carbon was mixed with copper ore and was heated.

At the end of the reaction, an orange-brown deposit was observed.

So there was an orange-brown solid observed during the reaction.

Part A, name that deposit.

So what was it? And B, write a word equation for the reaction.

So pause the video here and answer those questions.

Let's go through the answers.

So question four, suggest why an alternative method of extraction is used.

The metals are more reactive than carbon, so cannot be displaced by carbon.

So you need to mention the reactivity of carbon in your answer.

Then you've got carbon being mixed with copper ore.

So remember, it's copper ore, so therefore, the carbon is displacing the copper from its ore.

So the orange-brown deposit is copper metal.

And then a word equation for the reaction would be copper oxide plus carbon forms copper plus carbon dioxide.

So normally, in an ore, it's a metal oxide that's formed.

So well done if you got that correct.

Here is a summary of what we've learned during this lesson.

So a more reactive metal will displace another that is less reactive from its salt in solution.

In a displacement reaction, magnesium displaces copper from copper sulphate to form magnesium sulphate and copper.

Displacement reactions can be used to confirm the position of a metal in the reactivity series for metals.

A metal ore is typically rock that contains metal in a form that can be extracted.

And carbon can be used to extract some metals from their ores when carbon is more reactive.

Thank you very much for joining me today in this lesson.