Intro Quiz: Acids and metals

Video: Acids and metals

﻿Hi everyone. This is miss Fener, welcome to the lesson. This is lesson number five in the reactivity topic, and we're going to be focusing on the reactions between metals and acids. Before we get going, can you just make sure you put your phone on silent and you've removed all distractions from the room around you. Let's get started. So here's a list of the equipment that you're going to need for our lesson. An exercise book or some paper and a pen or a pencil. So if you haven't got that already, pause the lesson now and go and quickly collect it. Here is the agenda for our lesson. So we are on lesson five looking at acids and metals. And we're going to start off by having a look at what a chemical reaction actually is. And I'll tell you some of the observations that we might be able to see when it chemical reaction is taking place. Then we're going to have a look specifically, at the reactions between metals and acids. And then finally, I'm going to show you how we can describe the test for hydrogen gas. Observations of a chemical reaction. So what is a chemical reaction? We often talk about chemical reactions, but it's just as important to really know what they actually are. Chemical reaction is a process in which he new substance is formed. So anytime that we're forming a new substance, a chemical reaction has taken place. So when reactants are converted into products, a chemical reaction is taking place, we formed a new substance, a new product. There are four main observations that we might see when a chemical reaction is taking place. And the first is a change in colour. So if we have a look at this picture here of the bike chain, we'd usually expect bike chains to be a silvery colour, the colour associated with metals made of metal. We can see in the picture that this bike chain has turned a reddish brown colour, a rusty colour, and that's because a chemical reaction has taken place. The metal that the bike chain is made out of has turned into a new substance. It's reacted with the oxygen in the air, and it's formed iron oxide, which is rust and that rust is a new colour. So the new substance that has formed is a different colour, which is why we can see a colour change. And we'll often see this observation in a chemical reaction. The product being formed will be a different colour so we'll see a colour change in the reaction. So that's the first observation that we might see. The second one that we could see is a change in temperature. Now, some reactions are exothermic and some are endothermic. So you might see the temperature of the reaction increasing or decreasing. Sometimes this will only be very slightly or sometimes it will be really noticeable. But a change in temperature is the second observation that's associated with chemical reactions. The third observation is fizzing or the technical word for that, effervescence. Whenever we're seeing bubbles of gas being produced essentially often a chemical reaction will have gas produced as one of the products. So seeing these bubbles of gas being produced we know that the reactants are being converted into products. Now, if this gas is just being produced in the air we won't really be able to see it unless it's got a colour. But we can see it if the gas bubbles are being produced in a liquid, we'll see actual bubbles being formed. So if we see fizzing or bubbles of gas being produced, we can use this as one as the observations that chemical reaction has taken place. And the fourth one is a new substance being formed. This will always happen in a chemical reaction. And if it hasn't happened, a chemical reaction hasn't taken place. So in any reaction where we form new substance, we know it has been a chemical reaction. And the example that I've got here is an egg being cooked. Now we start with a raw rag, which looks very different to a cooked egg and that's because a chemical reaction has taken place. We've formed a new substance. We formed cooked egg or fried egg. It would be really difficult for us to get that raw egg back from that cooked egg which is another way that we can tell that it was a chemical reaction. It's really difficult to get the reactants back once we formed the products. Now if something isn't a chemical reaction is likely to be a physical change and it's really important that you know the difference between the two. A physical change is a process that causes a substance to change size, shape or state. So for example, you might take a substance and cut it into smaller pieces. All you've done there is a physical change. You've not formed a new substance. You've just created smaller pieces of a substance that you already had. Changing shape you might bend something into a new shape. So let's say you've got a malleable metal, You might it bend into a new shape. And again, you still just got the metal. It's just the metal in a new shape. You've not formed a new substance. And finally changing state, so for example, freezing or melting. If we take frozen water or ice and we melt it into liquid water, it's still just water. All that's happened is it's changed state. So we've still just got water, we haven't formed a new substance so it would be a physical change. Physical changes are usually reversible as well. So you can revert back to what you originally had. So for example, if I take melting my ice cube, as an example, I could easily then just freeze that water back into an ice cube, so it's reversible. Is this a chemical reaction or a physical change? Baking a cake, have a think and say the answer to your screen. Baking a cake would be a chemical reaction, well done. The reason that it's a chemical reaction is because we start with the separate ingredients and we end up with a new substance, cake. So we might start off with flour, eggs, and butter and we end up with cake. And we can't reverse that cake back into the ingredients. So it's a chemical reaction, we formed a new substance. Okay, the next one. Is boiling water in a pan a chemical reaction or a physical change? Say the answer to your screen for me. Great, it's a physical change because all we're doing is turning liquid water into water vapour. We've still just got water. We've not formed a new substance, and we could easily cool that water vapour back down to return it to liquid water again, so it's reversible. Really well done. And finally, is this a chemical reaction or a physical change? Magnesium burning in oxygen. Say the answer to your screen for me. It's a chemical reaction. The magnesium is burning and reacting with the oxygen in the air and it forms a new substance. When something burns, it forms new products and you can't get that original substance back again, it's burnt. In this case the magnesium will be burning with the oxygen in the air to form magnesium oxide. And we'd also see a colour change when this reaction take place. But because we formed a new substance, it has to be a chemical reaction. Time to you have a go at some questions on your own now using the information that you've just learned. You've got three questions, I'd like you to write down your answers on paper please. You can pause the lesson now and then resume the video when you're ready to carry on. Okay, let's go through the answers. So question one, the four observations that you might see when a chemical reaction takes place. You might see a change in colour, a change in temperature, bubbles of gas being produced and a new substance forming. Give yourself a big tick if you've got all those four, and if you missed any add them in now. Number two, reshaping a piece of metal is a physical change because no new product has been formed. You've just changed the shape of the metal. You haven't formed a new substance, that's physical change. Give yourself a tick if you got that one right and then add in any bits that you missed if you didn't get that fully correct. And number three, a piece of wood burning is a chemical reaction because a new product has formed. There was also a change of colour and a change in temperature. So we're seeing some of those observations they're associated with chemical reaction. Again, add in any bits that you missed or give yourself a big tick if you've got that one right. Well done let's move on. I guess that there's an opportunity now for you to have a go at a practical. Now this isn't essential and if you're unable to do it, for whatever reason, that is absolutely fine. I'd still like you to have a look through the practical and understand it and I've got some results for you to have a look at at the end. Do not try this without a parent or carers help. Make sure you clear space to work, pay close attention and be careful. So if you are going to be taking part in the practical, make sure that you go and speak to a parent or carer, and you're going to need this equipment. You'll need a cup, a spoon, a nail, some vinegar and some sandpaper or a nail file. There's the practical list again for you. So if you are going to be doing the practical, please pause the lesson now and go and collect that equipment. So the first step of the practical, the first thing that you need to do, is lightly sand or file the metal nail. So you're going to take your sandpaper and lightly file the outside of the nail. And what this is doing is just removing any products that might have formed on the outside of the nail, from it reacting with the oxygen in the air. So you just want to remove all that so it's the pure metal nail. So lightly sand that. Step two, you need to pour five tablespoons vinegar into your cup. Number three, place the filed nail into the vinegar. Wait 10 minutes. It should be about two minutes. You might need to wait slightly longer to see the reaction happening. Number four, I'd like you to write down your observations. Is this a chemical reaction or a physical change? You need to choose, which is it and why. So for those of you that weren't able to do the practical, this is the results that you would have seen. And for those of you that did do it, I hope these are the results that you saw. You can compare my picture to the results that you got. And what you can see here is our metal nail and at this point it is in the vinegar. And what is happening is it is reacting, it is a chemical reaction. It's forming a new substance and as it's doing so it's forming bubbles, it's fizzing, and you can see those bubbles along the edge of the nail. So I'm going to show you now exactly what that chemical reaction was. Oh yeah, that's what the nail is made of. That nail is made of iron was added to vinegar, which is ethanoic acid, that's its proper scientific name. So we've added our iron nail to our vinegar, which is ethanoic acid. And it's formed iron ethanoate which is a salt and hydrogen, and that's what those bubbles are that you can see, it's bubbles of hydrogen gas being produced. And we can also apply that reaction to different metals and acids. If we react to any metal with any acid, it will always form a salt and produce bubbles of hydrogen gas. So what we've done there is an example of a reaction between a metal and an acid. The reactions of metals and acids So there's that general equation again. If you react any metal with any acid, you'll form a salt and hydrogen, and that's what we call the general equation, because you can apply it to the reaction of any metal with any acid. Now depending on which acid we use for this reaction, we will form different salts. So for example, if the acid that we use is sulfuric acid, we will always produce a salt called a metal sulphate. So sulfuric acid produces a metal sulphate. Hydrochloric acid produces a metal chloride and nitric acid produces a metal nitrate. So they're the rules and I'd like you to pause the lesson here please to write those rules down as to what salt will form depending on which acid you use. So please pause the lesson now and write that down and then resume when you're ready to move on. Okay, so putting those rules into practise now then, if we're reacting the metal copper with different acids, I wanted to show you the different salts that would be produced. So for example, if we react to copper with the acid sulfuric acid, we will put produce copper sulphate. Remember sulphates are always produced when we use the sulfuric acid and hydrogen, hydrogen is always produced in these reactions. If we react copper with hydrochloric acid, we'll produce copper chloride because chlorides are always produced when we use hydrochloric acid, and hydrogen would also be produced. And then in the final one, if we react copper with nitric acid, the salt produced will be copper nitrate because nitrates are always formed when nitric acid is used and hydrogen will be produced as another product as well. So I want to check your understanding of that now. I need you to fill in the blank in this equation. You can say the answer to your screen for me. So sodium plus hydrochloric acid forms something chloride plus hydrogen, say the answer to your screen. The answer was sodium, well done. Sodium plus hydrochloric acid forms sodium chloride, that's the salt plus hydrogen. Here's another one for you to do. Magnesium plus nitric acid forms magnesium something plus hydrogen, say the answer to your screen. Well done, the answer was nitrate, magnesium nitrate. Zinc plus sulfuric acid form zinc sulphate plus, say the answer, great, the answer was hydrogen, hydrogen is always produced as well as the salt. Okay it's time for you need to have a go at some on your own. There are four equations here, all based on that reaction that we just looked at between metals and acids, I'd like you to have a go at copying these out and completing them. Make sure you write them down and you can pause the lesson now and then resume when you're ready to go through the answers. Okay, let's go through the answers. Number one, iron plus sulfuric acid will form iron sulphate plus hydrogen. Number two, zinc plus sulfuric acid will form zinc sulphate plus hydrogen. Number three, calcium plus hydrochloric acid will form calcium chloride plus hydrogen. And number four, potassium plus nitric acid will form potassium nitrate plus hydrogen. Give yourself a tick for any that you got correct and correct the ones that you got wrong. So here's another example of one of those reactions between a metal and an acid. Sodium, the metal reacting with sulfuric acid to form the salt sodium sulphate and hydrogen. Now we can turn these as well into symbol equations, which will look like this. So we've got sodium, reacting with H2SO4 to form the salt and hydrogen. And if we balanced that it would look like this. So now I've got the same number of atoms on the reactant side of the equation as I have on the product side. Describe the test for hydrogen gas. Which product is common to all reactions between a metal and an acid. Is it option one metal, option two hydrogen, option three acid or option four copper sulphate? Point to the the answer that you is correct now. The answer was the option two, hydrogen. Hydrogen is the product that is common to all reactions between metals and acids. So here's an example of a reaction between an metal and an acid. And as we said a minute ago, the product that all of these reactions have in common is hydrogen gas. So if we were wanting to know whether a reaction between a metal and an acid had taken place, we could look to detect that hydrogen gas, and if it was there, we'd know that the reaction had happened. So if we wanting to test for hydrogen gas, the first thing that would do is collect the hydrogen gas or the gas that we think is hydrogen. And the best way to do this is to put the reaction between the metal and the acid into a test tube like this. And you can pop a onto the top or your thumb if you're careful onto the top. And then as that hydrogen gas is produced, it's going to build up in the test tube. Step two, you'll put a lit splint into the gas. Now a splint is just a long wooden tube. It's longer than a match so it keeps your fingers away from the fire, so it's just a bit safer. So if you'd light one of these, like you can see in the picture and then quickly take the out of the top of the test tube and put the lit splint into the test tube. Okay, that's step two. Now, if hydrogen gas is present, a hydrogen will burn a squeaky pop and you'll hear a really loud squeaky pop noise. So if the hydrogen is present, it will burn with a squeaky pop, and if the gas wasn't hydrogen or there's no hydrogen there, it won't burn with a squeaky pop. So there are the three steps that we can do to check whether the reaction has taken place and hydrogen has been produced. And I'll like you to put these steps in the correct order for what we do to test for hydrogen gas. Pause the lesson now and resume when you're ready for the answer. Okay, let's have a look through the answer. First of all, you need to collect the hydrogen gas and you need to put a lit splint into the gas and finally the hydrogen if it's there, will burn with a squeaky pop, really well done. Write the three steps performed to test for the presence of hydrogen gas. I'd like you to make sure that in your answer, you include those four key words, collect, test tube, splint and squeaky. Pause the video to complete your task and resume once you're finished. There's the answer. Number one, collect the gas produced in a test tube. Number two, place a lit spent into the gas. And number three, if hydrogen is present, it will burn with a squeaky pop. Mark your answer and add in any bits that you missed. Share your work with Oak National. If you'd like to please ask your parent or carer to share your work on Instagram, Facebook or Twitter, by tagging @OakNational and #LearnwithOak. I'd love to see some of the results from the practical that you completed today. And that's the end of the lesson. Great work today, you've worked really hard. Please don't forget to complete the quiz once this video is over. Click on to the next slide and the quiz will be there waiting for you to take it. Next lesson we're going to be looking at the reactions between metal oxides and acids. See you next time.

Worksheet: Acids and metals

Exit Quiz: Acids and metals

Completed: Acids and metals

This lesson looks at the observations made when a chemical reaction takes place, before focussing specifically on the reactions between metals and acids. This lesson also contains a practical, providing the opportunity for you to complete one of these reactions yourself.

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Acids and metals

Introductory Quiz

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