This quiz will assess knowledge which you have learnt throughout this topic

What is another word for finite?

What are the 3 fossil fuels?

What is the purpose of life cycle assessments (LCAs)?

What is the first stage of a LCA?

Potable water is safe to drink.

Which of the following cannot be used in the sterilisation of water.

What are the 2 methods of desalination?

Why is distillation not the preferred method for obtaining potable water?

Review Lesson

﻿Hello and welcome to the next lesson in our using resources topic. Today's lesson is a review lesson on all the triple only content. Please make sure that you have a pen and a piece of paper ready, and that your phone is on silent and at one side so that you don't get distracted. So once you're ready, let's go. So in today's lesson, we're going to recap some of the key content of the triple only course. So we're going to start off by looking at rusting and then we will move on and look at alloys and their importance. We will look at polymers and we will finish off the lesson by recapping the Haber process. So let's start with rusting. What is rusting? Remember rusting is the corrosion of iron. So rusting only applies to iron. And there are two substances which are required for rusting to occur. Rusting requires oxygen and it requires water. And rust is a form of iron oxide. So we have the equation here, which is what takes place when rusting happens. So iron plus oxygen plus water will form hydrated Iron three oxide. And we've got a picture here which shows some rusting iron. So what we've got here is an experiment which shows that oxygen and water are both needed for rusting to occur. So in test tube one, we have got air and we've got water. And what will happen if you leave it for a period of time, the iron nail would show rusting. Test tube two, we have boiled water and we have a layer of oil on top of the boiled water. Now, what this means is that the iron nail is exposed to the water which it sits in, but it doesn't have any access to any air and therefore any oxygen. So in test tube two, if we were to leave it for a period of time, we wouldn't see any rusting of the iron nail. And then test tube three there is air present, but there is no water. And test tube three has these little crystals of calcium chloride. And what happens is the calcium chloride crystals are able to absorb any water vapour from the air and therefore the iron nail has no water being exposed to it at all. And so in test tube three, no rusting occurs once again. So how can rust be prevented? There's a series of different measures that can take place, but they basically involve coating of iron with different substances. Remember steel is an alloy of iron. So steel is made up of iron and typically carbon. And therefore steel can rust because it's got iron in. So we could coat our iron or steel with paint. So we're providing a barrier between the iron and steel and the oxygen and water. We could coat it with oil or grease. We could coat the iron or steel with plastic. We could use a less reactive metal to coat the iron or steel or we could use a more reactive metal such as zinc. And you may remember the process of sacrificial protection that takes place if the iron or steel is covered with zinc, because what happens is that the zinc reacts with the oxygen or the water or both instead, and gets oxidised as opposed to the iron reacting with the water or the oxygen and becoming oxidised. So that's called sacrificial protection. And how all of those methods work is by providing a barrier between the iron and the air and the water. So what we're going to do is a series of quick fire questions to check you understand what we've covered so far. So, what is rusting? Well done if you selected corrosion of iron. Rusting only applies to iron. What is needed for iron to rust? Well done if you selected oxygen and water. Remember that's what the experiment that we looked at showed us. Rust can be prevented by coating the iron object with oil. Well done if you selected true. Remember it helps to form a barrier between the iron and the oxygen and water. So what I would like you to do, you've got two application questions here. I would like you to pause the video and have a go at answering these questions. Now, part two, question number two is describing a simple experiment that could be done to prove that the presence of water causes an iron nail to rusts more quickly. Include what you would expect to find. Okay. So you're thinking back to the experiment slide which I talked to you through. Okay. And if something's rusting more quickly, you obviously need to have something to compare to. So please pause the video now, have a go at answering those questions and then press play once you have finished. Okay. So please pause the video now to mark your work. Particularly for question two, make sure you add in anything which you didn't get and then press play once you are finished. Okay. So let's move on and let's recap what we learned about alloys. So why are metals alloyed? Remember pure metal in metallic bonding, what happens is the positively charged metal ions form essentially nice, neat rows. And what happens are these rows of metal ions are able to slide over each other really easily. And so this is why pure metals are actually quite soft. So remember an alloy is when you mix a metal atom with atoms of a different element. And to be honest, normally it is another metal. And so, as we can see in this picture here, our original metal is denoted by the circles, the orange circles with the positive charging. What's happened when this metal has been been alloyed, another type of metal atom has been added in, and we can see this by the black circles with the positive charging. Now, what you can see is that the layers, the rows of positive metal ions have been disrupted by these larger size metal atoms. And what that means is that the layers of atoms can no longer slide over each other as easily. And that is why metals are harder. Sorry, alloys of metals are harder than pure metals, okay? Because the other metal atoms, which have been added disrupt the layers of metal ions, and therefore they can't slide over as easily and therefore they are much harder than the pure metal. Some examples of alloys and their uses. So we have bronze. Bronze is made up of both copper and tin and a property of bronze is that it's resistant to corrosion and therefore it's suitable to be used in statues, decorative items and ship propellers. Brass is also made up of copper, but it's also made up of zinc as well. Now the properties of brass is that it's very hard but it's workable. Therefore it can be used in door fittings, in taps and in musical instruments. We are then going to move on and we're going to look at steel. So we have high carbon steel. So this is when we have iron with one to 2% carbon. So we have more carbon atoms have been added compared to in a minute when we look at low carbon steel. So the properties of high carbon steel is that it's strong, but it's brittle. And it's used in cutting tools and metal presses. Low carbon steel is iron with less than 1% carbon. Therefore it's softer because our iron atoms are less disrupted and it's easy to shape. And low carbon steel is used in the manufacturing of cars, machineries and ships. And then we have stainless steel. So this is iron mixed with chromium and nickel. And stainless steel is resistant to corrosion and it's hard and it's used commonly in cutlery and in plumbing. So we're going to do a series of quick fire questions to check what we've just done. So, alloys are much softer than pure metal. Well done if you selected false. They are much harder than pure metal. Brass and bronze both contain copper well done if you selected true. Bronze is used to make musical instruments. Well done if you selected false. It is brass which is used to make musical instruments. So we have got three application questions for you to do about alloys. I would like you to pause the video now, answer the questions and then press play once you have finished. So let's mark your work. Please pause the video now to mark your work. Make sure you add in anything which you didn't get correct. And then press play again once you are finished. So next up, we're going to look up polymers. Now, remember polymers are large molecules which are made from monomers, which are smaller molecules. Now the properties of polymers depend on the monomers which they are made from and the conditions under which they were made. Now the polymers often share some common properties. So polymers are often chemically unreactive. They're are normally solids at room temperature and they're normally strong and hard-wearing. Now what we're going to look at is polythene. And we're going to look at the properties of polythene, when it's made under different reaction conditions. So low density polythene is made under a high pressure and with a trace of oxygen being present. And in low density polythene, the polymer chains are branched. And this means that the polymer chains are unable to pack as closely together. We then have high density polythene. So high density polythene uses a catalyst at 50 degrees Celsius. And there is a slightly raised pressure. In high density polythene, the chains are straighter, and this means that more polymer chains can pack closely together, hence it's called high density polythene. And high density polythene has a higher softening temperature, than low density polythene and it is also stronger. So we're now going to look at two different types of polymers in relation to what happens when they are heated. So we've got thermosetting polymers. Now, when you heat thermosetting polymers, sorry, they don't melt when they are heated. The reason why they don't melt when they're heated is because between the polymer chains, there are strong covalent bonds. Now these covalent bonds that happen between the polymer chains are called cross-links. But what does happen with thermosetting polymers is at very high temperatures, the polymer will start to char. So that means it will start to blacken at very high temperatures. We're then going to look at thermosoftening polymers. Now these soften quite easily when they are heated. The reason for this is, between the chains, there are weak intermolecular forces. And what happens is when the polymer is heated up, the intermolecular forces between the chains break, this means that you can remould the polymer. And then once the polymer cools down, once the temperature drops, the intermolecular forces reform between the polymer chains. So what we're going to do now is a series of quick fire questions to check you understand what we've just covered. So, polymers are made up of monomers. Well done if you selected true. All polymers have the same properties. Well done if you selected false. Low density polythene forms lots of branched chains. Well done if you selected true. Remember the branched chains mean that the polymer chains can't pack closely together. High density polythene is formed using a catalyst. Well done if you selected true. And the chains in high density polythene are randomly branched and can't pack closely together. Well done if you selected false. Remember in high density polythene, the polymer chains are straighter, and this means that the polymer chains can pack close together. So we have got six recall questions on polymers. I would like you to pause the video now, answer the questions and then press play once you are finished. Okay. So let's mark your work. Please pause the video now, mark your work, correct anything you didn't get right and then press play once you are done. Okay. So the final thing we're going to look at in this lesson is the Haber process. So remember the Haber process is a way of making ammonia from nitrogen and hydrogen. And it was first devised by this guy, Fritz Haber about a hundred years ago. So, what do we need in order to make ammonia? So we need nitrogen, which we get from the air and we need hydrogen, which we get mainly from natural gas. And the diagram here shows the covalent bonds present in ammonia because nitrogen and hydrogen are both nonmetals and therefore it is covalent bonding that happens. So what we've got here is the equation for the Haber process. So nitrogen and hydrogen react together and they form ammonia. Now remember what that arrow means, that arrow means that it is a reversible reaction. So what that means is that ammonia can break down and it can form nitrogen and hydrogen. What we have here is the balanced symbol equation for the Haber process. So, one mole of nitrogen reacts with three moles of hydrogen to form two moles of ammonia. And I'm just going to go through the stages of the Haber process. So first thing that happens is that nitrogen and hydrogen are pumped through pipes. The nitrogen and hydrogen pressure is then increased to 200 atmospheres. The pressurised gases then are heated to 450 degrees Celsius and they're passed through a tank, which has an iron catalyst. During that process, ammonia is then made. What then happens is the mixture is cooled. So it's a mixture of ammonia and unreacted nitrogen and unreacted hydrogen. So the mixture is cooled and what happens is that the ammonia liquefies and it's then able to be removed. The unreacted nitrogen and hydrogen are then recycled. So they get recompressed and reheated before they've returned to the reaction vessel. And remember the conditions, so 200 atmospheres pressure, 450 degrees Celsius, and the presence of an iron catalyst. The pressure and the temperature are a compromise in the conditions. And if you are a higher tier student, you will have watched the video hopefully where we look at why the 200 atmospheres and 450 degrees Celsius is a compromise in making ammonia. So, a series of quick fire questions. So the raw materials in the Haber process are nitrogen and hydrogen. Well done if you selected true. The chemical formula for ammonia is NH2. Well done if you selected false. The chemical formula for ammonia is NH3. The reaction in the Haber precess is a reversible reaction. Well done if you selected true. The conditions used in the Haber process are 200 atmospheres and 450 degrees Celsius. Well done if you selected true. Unreacted nitrogen and hydrogen are disposed off in the Haber process Well done if you selected false. Remember they get recycled and they get reused in the reaction vessel. So, a recap of the key points from this lesson. So both oxygen and water are needed for iron to rust. Remember rusting only applies to iron. Alloys are harder than pure metals because the regular layers are disrupted by different sized atoms. Polymers are made from monomers. Thermosoftening polymers are able to be remoulded once heated. Remember that's because the weak intermolecular forces between the polymer chains are broken. And then finally, ammonia is made in the Haber process from nitrogen and hydrogen, the conditions used are 200 atmospheres, 450 degrees Celsius and an iron catalyst. Well done on another brilliant lesson. Please make sure that you now click next to complete the end of lesson quiz for this lesson.

This quiz will assess your knowledge from this topic.

What is needed for rusting to take place?

Rust can be prevented by coating the iron object with paper.

Pure metals are harder than alloys.

Which of these is a use of bronze?

Which of the following is not a property of a polymer?

Thermosetting polymer chains are fixed together by strong covalent bonds.

What are the raw materials for making ammonia in the Haber process? (Select 2)

What catalyst is used in the Haber process?

Review lesson

This lesson will review the key concepts for this unit. We will recap rusting, alloys, polymers and the Haber process.

Chemistry

Y11 Chemistry

Key Stage 4

Year 11

Review lesson: Chemistry content

Using Resources

UNIT

Finite resources

Life cycle assessments

The importance of recycling

Phytomining and bioleaching

Rusting

Alloys

Polymers

Glass, ceramics and composites

Safe drinking water

Required practical on potable water

Wastewater treatment

Making ammonia and the Haber Process

The economics of the Haber Process

Making fertilisers in the lab and in industry

Exam skills: Compare and evaluate

Case study: Kitty Hach Darrow

Under normal pressure, what temperature does water boil at?

Aerobic respiration requires oxygen

Plants use nitrogen to make proteins.

How do plants absorb nitrate ions?

What pressure is used in the Haber process?

What happens to unreacted hydrogen and nitrogen in the Haber process?

Which type of copper ore contains a low percentage of copper?

What is used to extract copper in phytomining?

What is used to extract copper in bioleaching?

Displacement is used to extract copper from solution. What type of reaction is displacement?

Lesson overview:Review lesson: Chemistry content

Using Resources: