This quiz will test your knowledge from the previous lesson and your prior learning.

Identify the properties of liquids. (Choose 2 answers)

Which change of state turns a liquid into a gas?

Which change of state turns a gas into a liquid?

Which of the following happens when a substance is heated?

Which statement best describes the movement of particles in a liquid?

What happens during freezing?

Changes of State

﻿Hi, I'm Miss Mason and welcome to today's lesson on investigating changes of state. Please make sure you have got a pen or a pencil, a piece of paper or a notebook, and ideally you want a ruler as well. If you need to take a few moments to pause the video and get them please do so now. Once you have all the necessary equipment, please write down today's title, investigating changes of state, and you may wish to add today's date. Please make sure your phone is on silent and turned over, so you're not tempted to have a look at it, whilst watching this video, and try and minimise any of the distractions around you as well. Let's go into this lesson with a positive attitude, and remember not to give up, even if you find things a little bit tough. So let's run through today's plan of action. Firstly, you're going to be recapping some of the information, you should already know about state changes. Then we're going to talk about how these changes of state might be investigated, and how they can be presented in heating and cooling curves. We'll then talk a little bit about, melting and boiling points, and hopefully by the end of today's lesson, you'll be able to determine states of matter, based on their melting and boiling points. Let's get started with our recap then. There's four questions on the screen, two of which have got some scaffolding, or helpful bits, for you. Pause the video now, and have a go at those four questions. Restart the video whenever you're ready. Let's see how you got on. So on the next slide, the answers will be revealed, and I'll just quickly talk you through them, but first of all, let me give you a chance to read them. You might want to pause the video here, because there's quite a lot to read. So the full changes of state you should have identified, melting, boiling, condensing, and freezing, well done, if you've got that. Next question asks you, whether a change of state is a chemical or physical change, and you have to give reasons for the answer you give. You should have said, that a change of state is a physical change, because no new products are formed, particles are just rearranged or repositioned, and a change of state is also reversible, which means it can't be a chemical reaction. Number three, you are asked describe what happens to the particles, in a substance when it melts, and you were given some sentences already, just with some missing words, I'll read out in full what you should have had. The substance starts off as a solid. Its particles gain kinetic energy as they are heated, which allows them to break free, from the forces of attraction that bind them together. They form a new arrangement and change state into a liquid. Give yourself five big ticks, 'cause hopefully, you got all of those missing words or phrases, correct. Number four was very similar, but it just asked you to describe, what happens to the particles in a substance, when it freezes this time. So you should have said, the substance starts off as a liquid, it's particles lose kinetic energy as they are cooled, which causes the bonds between the particles to reform, this results in a new arrangement, and a change of state into a solid. I'm hoping you've got another five big ticks there. That brings us to the end of our recap section. So, on the board, you should be able to see, that there are three pieces of equipment, that we would probably need to use, if we were going to carry out an investigation, into changes of state. So you can see a beaker, it's got some water in. A thermometer, which allows us to measure temperature, and a bunsen burner, which allows us to heat up substances. Now, investigating changes of state experiments, generally tend to be fairly simple. You would normally start off, with an ice cube in a beaker, and a thermometer in a the beaker as well. And you would gradually heat up that ice cube, until it changed state to become a liquid. You could then continue to heat it up, until it change state into a gas. So during that time, the ice cube will have gone through two changes of state, melting and boiling. And all the while that was happening, you would have left your thermometer in the beaker, to measure the temperature throughout. And it's really important, that we are able to take accurate temperature measurements, so that we can understand what's going on, in terms of temperature during these changes of state. I got some example results to show you now, and we're going to have a look, at what they might look like on a graph. So here we have a results table, showing us what happens to the temperature, of the substance over a period of time. The temperature was measured every 30 seconds, and you can see, that as the substance was being heated, that temperature gradually increased. Now, if we were to plot this in a graph, it would look something like this, you can see, that there are periods where the temperature is increasing, that is where the line, or the kind of pattern of the cross is, is steep, and then you can see, there are areas on the graph where, the cross has seemed to flatten up. Now, that happens for a reason, the areas where, the cross is seem to be following a diagonal pattern, are the areas where temperature is increasing, during this time, there is not a change of state going on. However, the areas of the graph that are flat, represent the time and temperature, at which a change of state is happening, here, and here. And we know there are two changes of state, when heating up an ice cube, are going to be melting and boiling. Now, let's think about, the states of matter that occur, between each of these changes of state. So obviously our ice cube starts off as a solid, it then melts, which is the flat section of this graph, to become a liquid, and it will then boil, to go on to become a gas, and this type of graph, with this type of representation is called a heating curve. What I would like you to do, is just complete a quick sketch of this graph, on your piece of paper or in your notebook and label it as a heating curve. It would also be a good idea, to label the sections, where we change your state is occurring and also label what that change of state is, and the state of matter in between, just like I've got on the board. Now let's take the time, to take a look at the opposite of a heating curve. Something that we would call a cooling curve. So instead of heating up a substance, and causing it to melt and boil, this time will be cooling it down, but I would like you to see, if you can add the correct labels onto this graph. Which change of states are occurring and where? And which changes, no, sorry, which states of matter, would be present in between each of those? Pause the video here, have a think, jot down some ideas and then restart it when you're ready. Our first change of state, happens here, and that is condensing. Our second change of state, happens on the other flat section of the graph, and this is freezing. So in our heating curve, we had melting and boiling, on the flat sections of the graph, now on this cooling curve, we've got condensing and freezing. What about the states of matter then? If this substance condenses, after its temperature has been decreased for a while, then it must've started off as a gas. After that change of state, the condensing, it will become a liquid, and once it has frozen, it can be labelled as a solid. Well done if you managed to get all of those. It's your job now, to copy and complete the following sentences, based on what you've just learned, about heating and cooling curves. Please pause the video and then restart it, when you're ready to find out the answers. Let's see how many you managed to get right. I'll just read through, what the correct answer should have been. Changes of state can be represented either, in a heating curve or a cooling curve. The sloped sections on these graphs represent, one state of matter and a changing temperature. The flat sections on these graphs, represent a change of state under constant temperature. In fact, that's something I forgot to mention on the graph lines, during a change of state, the reason why the graph has a section that is flat, is because, during a change of state there is no temperature change, the temperature remains constant, hence the flat area on the graph. Well done if you managed to get all of those right. Let's move on to our next activity. Here's another independent task for you to try. Let's read through what's in the white box, so that we can fully understand what needs to be done. Describe what is happening at each stage of this graph, in terms of temperature, arrangement, and movement of particles. Write at least three bullet points. When you're ready to begin, pause the video, have a go and then restart the video, when you think you've completed it. Let's see how you got on. I have split up, my answer into the four different stages. So, at stage A, I've said the temperature increases, there is no change of state, and the substance remains a solid, don't forget you're given that bit of information, the substance starts off as a solid. Compare, my section A to your section A, and add anything that you haven't got, and take the bits you have. For stage B, I've said melting occurs, particles move into a random arrangement, forces of attraction are broken, and the temperature stays constant. Compare it to yours, tick or correct anything that needs to be corrected. Stage C, the substance is now a liquid, temperature increases and there is no change of state, remember, anytime a section of the graph is diagonal, that is when the temperature is changing, but the state stays the same. Finally section D, this is where boiling occurs, particles move away from each other, forces of attraction are broken, and the temperature stays constant, do a final comparison of my stage D and yours, and then give yourself a big round of applause, for completing that activity. Well done. What we need to start thinking about now, is the specific temperatures, that different substances melt and boil at. We'll start off by discussing water, the melting point of water, is zero degrees celsius, this is the temperature at which solid turns into a liquid, so an ice cube would melt to become water. The boiling point is a hundred degrees celsius, this is the point at which, water would turn into water vapour or gas. What we need to be able to figure out, is what state of matter, water would be in at different temperatures, based on its melting and boiling point. The easiest way to show this, is a number line, which is why this big scale is on the slide. Firstly, we can label where the melting point of water is. I've just told you that the melting point of water, is zero degree celsius. We also know, that the boiling point is a hundred degrees celsius. So that's the first step I would take, label those on the number line. We need to realise that anything below zero degrees celsius or any temperature below that, would cause water to stay in its solid state of matter, so any temperature below zero, would cause water to be a solid ice. Once it passes zero degrees celsius, water will be a liquid, and it will stay that way, up until it reaches its boiling point, a hundred degrees celsius. So that makes up our next section of the number line. Once water reaches a hundred degrees celsius, its boiling point, it will become a gas. So, any temperature above that, will cause water to be in its gas state of matter. You might be asked questions, about what state of matter water would be in, at different temperatures, for example, at 40 degrees, at 120 degrees at minus 20 degrees, and you need to be able to say, what state of matter it would be in at those temperatures. So let's try and put that into a bit of practise now, there are three temperatures in this table, and we need to decide, what state of matter water would be in, at each of those temperatures. Remember, the melting point of water, is zero degrees celsius, and the boiling point of water, is a hundred degrees celsius. So if we go back to that number line, what state of matter would water be in, at 40 degrees celsius? Water would be, a liquid at 40 degrees celsius, because 40 degrees is somewhere between, water's melting point on its boiling point. The reason being, water doesn't boil until a hundred degrees. What about minus 13 degrees celsius? What state of matter would water be in then? Few seconds to think about that. You should have said water would be a solid, remember, water doesn't melt and become a liquid, until zero degree celsius. So at minus 13 it would still be a solid, our final temperature, 105 degrees celsius. Think about what state of matter we might end up with. And the correct answer is gas. Water boils to become a gas at hundred degrees celsius. So by the time it reaches 105 degrees, it should already be a gas. Well done, if you were able to predict, all of those before I gave you the answers. A key point to remember, this is just an added extra, is that room temperature is generally around 22 degrees, the reason I'm telling you this, is because some exam questions, or questions that you hear in school, or in other videos, may ask you, what state of matter, something would be in at room temperature. And it's your job to know, that room temperature is around 22 degrees, that might be worth jotting down on your piece of paper. This slide is going to give you some independent practise, so instead of me talking through, the of matter at different temperatures, and the reasons for this, you're going to be doing this on your own. Now, it's not water that we're talking about this time. The substance you've been given is ethanol, which is pure alcohol, and there were two points at the top, telling you the melting point and the boiling point, of this substance ethanol. You've got a series of temperatures in the table, and I would like you to predict, what state of matter ethanol would be, at each of those temperatures, and provide your reason why. Take your time with this, pause the video and then restart it, when you're ready to hear what the answers are. Okay, let's go through it. So, at 40 degrees you should have said, ethanol which melts at 114 degrees, sorry, minus 114 degrees and boils at 78 degrees. The state of matter at 40 degrees, should be a liquid, reason is, ethanol does not boil until 78 degrees. Next temperature is minus 13, again, ethanol would be a liquid, that's because ethanol melts at minus 114 degrees, which means it will already have changed state, from a solid to liquid, at minus 13 degrees. Next temperature, is 105 degrees, and ethanol would be a gas at this point, because it boils at 78 degrees. Temperature number four, is minus 200 degrees, this state of matter would be a solid, and the reason for that, is that ethanol doesn't melt until 114 degrees, and I keep saying that, minus 114 degrees and minus 200 degrees, is a lot, lot colder than that. Next temperature, 75 degrees, state of matter should be a liquid, reason is, ethanol boils at 78 degrees. So we weren't far away from that, but it hadn't quite reached its boiling point. Finally, room temperature, I've written this in the table, to make sure you were listening, to the information I gave you on the previous slide, room temperature is approximately 22 degrees, so think about what state of matter, ethanol would be in at this temperature. I'm hoping you all said liquid, and the reason for that, is ethanol does not boil until 78 degrees, massive well done for that activity, I know it's a bit tricky to get your head around, but I'm sure you all did fantastically. It's a good idea to get plenty of practise with this. So I'm going to give you a few more examples to try. Please read this information on the board. Then try to answer this question. The state that aluminium will be in at 730 degrees, is a liquid. Well done if you got that, you needed to read through the information, to find out the melting and boiling points, before you are able to decide the state of matter. Similar question coming up, still talking about aluminium, but you've got a different temperature to consider now. At 230 degrees aluminium would be a solid, because it doesn't melt until 660 degrees. Next question. Hopefully you've said the state of matter, at 1,350 degrees would be a liquid, remember, aluminium doesn't become a gas, until it reaches a massive 2,470 degrees. Next question. The correct answer is gas, well done if you got that, that was a tough one. Moving on to a different substance here, read through the information carefully, because it's changed now, and then answer this question. The state it will be in, oxygen will be in, at minus 230 degrees, is solid, that's because it doesn't melt to become a liquid until minus 218 degrees, which is hotter than minus 230 degrees. Next up. Your answer should have been a gas, this is because oxygen boils, at minus 189 degrees celsius, and minus 80 degrees, is hotter than this. So oxygen would already be a gas at that point. Next up. At minus 215 degrees oxygen would a liquid, fantastic effort if you've got that. You've now got, one multiple choice question to have go at, before we move on to your final independent task. Which of the following substances, would be a gas at room temperature? There are four substances on the board, I want you to have a look at them, melting and boiling points, and decide which of them would be a gas at room temperature. Pause the video if you need to, and then restart it, when you think you've got the right answer. The correct answer, should have been substance B, that's because it must've become a liquid, at minus 210 degrees and then boils to become a gas, at minus 196 degrees. Remember, room temperature is around 22 degrees, so substance B would have boiled long, long before that, and therefore it would be a gas. Your final task of today's lesson, is going to be slightly similar to what we did earlier on, it's your job to identify which state, each of the following substances would be in at 70 degrees, and you need to give reasons for your answer. You've got four substances, listed in the first column of the table, and you're given details, of their melting and boiling points, and you need to think about what state of matter, each of them will be in at 70 degrees and why? Pause the video here, write down your answers, and then start the video again, to see how many you got right. Correct answers coming up. Starting off with nitrogen, at 70 degrees, nitrogen would be a gas, this is because it boils, turns from a liquid to a gas at minus 196 degrees celsius. Big tick if you managed to get that one. The next substance was sodium, and that would be a solid at 70 degrees, because it doesn't melt until it reaches 98 degrees celsius. Another big tick if you got that one. Our third substance, was oxygen and like nitrogen, it would be a gas at 70 degrees, and that's because it boils at minus 189 degrees. Final substance was ethanol, and at room temperature that will be a liquid, because it doesn't boil until it reaches 78 degrees celsius. I wonder how many you got right. I bet it was a lot, well done. You've done incredibly well this lesson, and that brings us to the end of today's learning. I'd like you to read through today's notes, and either highlight or circle, the three most important things, you think you've learned today. Once you've done that, exit the video, and complete the exit quiz to review today's learning. Once again, thank you so much for being a part of this lesson, and I look forward to seeing you again. Bye.

This quiz will test your knowledge from this lesson and your prior learning.

A flat section on a heating or cooling curve graph shows...

What is the melting point of ice?

In a chemical reaction, if the mass of one reactant is 10g and the mass of the other reactant is 15g, what must the overall mass of the products be?

What is meant by the term 'condensing'?

Substance X has a melting point of 30°C and a boiling point of 75°C. In which state of matter will it be at room temperature?

Substance A has a melting point of 15°C. Substance B has a melting point of -8°C. Substance C has a melting point of 45°C. Which of these substances will remain a solid at room temperature?

Changes of state (Part 2)

Interpret melting point and boiling point data

Plot secondary data showing changes of state

This lesson looks at how changes of state can be investigated and how to determine the state of matter based on melting and boiling points

Science

Y7 Science

Key Stage 3

Year 7

Miss

Investigating changes of state

Particles

Chemistry

THEME

UNIT

Solids, Liquids and Gases

Diffusion

Gas pressure

Solutions

Review 1

Pure and impure substances

Separating mixtures

Rock salt

Distillation

Chromatography

Solubility

Solubility Practical

Case Study of Masataka Taketsuru

Review 2

If a substance melts at -100°C and boils at -50°C, what state will it be in at room temperature?

What is the correct definition for a 'mixture'?

Which separation technique is used to separate soluble solids from a solution?

How is melting/boiling point different between pure and impure substances?

Which separation technique is used to remove insoluble solids from a solution?

Which of the following pieces of equipment are necessary for carrying out filtration?

Which of the following is the correct description for 'filtering'?

Which state of matter can be described as being able to flow, change shape to fill its container and cannot compressed?

What is distillation used for?

What is a 'solute'?

Which of the following is the correct definition for 'solubility'?

What is a solvent?

What does distillation separate liquids based on?

What is meant when a solution is described as being 'saturated'?

What happens to the arrangement of particles during freezing?

What is the name given to the technique that can separate solutes from a mixture based on their solubility?

Lesson overview:Investigating changes of state

Particles: