Lesson video

Welcome to today's lesson on Compounds and their formations.

It's part of the unit Atoms, Elements, and Compounds.

My name is Mrs. Mytum-Smithson.

I'm really pleased that you've come along to learn with me today.

We'll go through the lesson step by step, and by the end of this lesson, you should be very confident with the content of it.

By the end of today's lesson, you should be able to explain the difference between a compound and an element.

Today's keywords are chemical compound, chemical bond.

On the next slide, there's some sentences that include these keywords.

If you wish to read them, just pause that slide and then when you're ready to start the lesson, just press play.

This lesson consists of two learning cycles: compounds and comparing compounds and elements.

Our first learning cycle is compounds.

Let's get going.

Many substances that exist are not elements, they're chemical compounds.

So an element is made up of one type of atom.

Let's look about chemical compounds.

So if you have a look at our two diagrams here, we've got some atoms, and you can see that they're joined to some other atoms that are different colours.

Different colours represent different elements.

So a chemical compound is where two or more different elements are chemically bonded, and they're formed when a chemical reaction takes place.

So here's a chemical bond, that's just the join.

So they're joined together by chemical bonds.

And a chemical bond is a strong force that holds those atoms together.

It takes a lot of energy to break that chemical bond.

I've got a quick check for understanding for you.

Which image or images could represent a compound? a, b, or c? What I want you to do is pause the video for some thinking time and press play when you've got your answer.

So well done if you said a and b.

a is made up of two types of atoms and they're overlapping, which shows that they've got a chemical bond.

Remember, a chemical bond takes a lot of energy to break.

And if you have a look at b, b also contains two different types of atoms, and they're overlapping to show that chemical bond.

c, although there's two different types of atoms there, they're not shown as bonded together because there's no overlap, they're not touching.

So well done if you said a and b.

Many everyday substances are compounds.

You've probably come across some of these.

So we've got water, carbon dioxide, and methane.

If you've got a gas cooker at home or perhaps you've cooked with one at school, you know that the methane is the gas that comes out of the cooker.

Compounds can be represented by spheres or circles, so three dimensions or two dimensions, using different chemical symbols.

So if you have a look, you can see that we've got the chemical symbols on these elements.

So water is made up of one atom of oxygen bonded to two hydrogen atoms, and carbon dioxide is one carbon atom bonded to two oxygen atoms. And if you have a look at methane, that's made up of carbon, one carbon atom and four hydrogen atoms are bonded to it.

These are single molecules of the compound.

So these are just one molecule of that compound.

So one molecule of water, one molecule of carbon dioxide, or one molecule of methane.

True or false? Compounds can be made from two or more different elements.

Is that true or is that false? Pause the video for some thinking time and press play when you've got your answer.

Well done if you said true.

Compounds can be made from two or more different elements.

Now I want you to justify your answer.

When elements react, they're bonded together to make a compound or elements are mixed together to make a compound.

Pause the video now for some thinking time, press play when you've got your answer.

So well done if you said that a reaction had to take place.

When elements react together, they're bonded together to make a compound.

Now I've got to check for understanding here.

Which image or images could represent a compound? Is it a, b, or c? Or you can pick more than one of these responses.

Pause the video now for some thinking time, press play when you've got your answer.

Well done if you said b.

b represents a compound.

This compound's called ammonia.

It consists of one nitrogen atom bonded to three different hydrogen atoms. You might have gotten caught out by a.

a is actually the same type of atom.

So, that's still an element.

And c, that's a monoatomic atom, so that's just on its own.

That's neon on its own.

So well done if you said b.

The students have been discussing compounds and chemical bonds.

What I want you to do is help Laura correct the students' definitions of compound and chemical bonds.

So here's Izzy.

Izzy's saying, "A compound is when two or more elements mix together." Alex is saying, "The atoms in a compound are not chemically bonded together." And Sam's saying, "Chemical bonds in a compound are weak and don't take much energy to break." Pause the video now.

Complete this part of the task and press play when you've got your answer.

Well done for working really hard and completing that task.

Let's see the students' answers.

A compound is where two or more elements react and chemically bond together.

So it's react, not mix.

Alex is saying the chemical bonds in a compound hold the atoms in a molecule together.

So chemical bonds hold the atoms together.

And finally, Sam.

Chemical bonds in a compound are strong and take a lot of energy to overcome and break.

So if you're gonna break those chemical bonds in a compound, it is gonna take a lot of energy to break them.

Well done if you've got all those three corrected correctly.

Here's part two of Task A.

What I want you to do for this task is sort these images into elements and compounds.

Explain how you sorted the elements from the compounds.

So first of all, look at the images.

Say to yourself, I know that that's an element, and you put that in the element column.

If not, it's a compound, and you put it in the compound column.

But what is it that you're thinking about whilst you're sorting them? I want you to just write a short sentence about how you know which is an element and which is a compound.

Pause the video while you complete this task and then press play when you've got your answers.

Well done for completing that task.

I hope you didn't find it too tricky.

So let's have a look.

So a is an element, and it's an element because we've only got one colour atom there.

So one type of atom is there.

b? So you can see that there's two different colours.

And that must be a compound because there's two different atoms chemically joined together.

And then we've got c.

That's one colour.

So it's representing one type of atom.

So that must be an element.

D, we've got two different colours here representing two different types of atom, so that must be a compound.

e, here we've got is we've got two different colours representing two different elements.

We've got two molecules of that substance there.

So that's a compound.

This one here, they're all the same colour.

So they're all one type of atom.

That must be an element.

And g, we've got two different colours representing two different types of atom.

So that's a compound.

And finally, and I hope this one hasn't caught you out.

Although there are two atoms there, they are the same colour, which means that they're the same type of atom, which means that that one is an element.

Now whilst you were doing that task, you were probably making some rules up in your head about how you know it's an element and how you know it's a compound.

So all the compounds have got two or more different types of atom, so different colours, and if you have a look, all the elements there have got one type of atom represented by one type of colour.

So well done if you manage to write something like that.

You've done really well to be able to sort elements and compounds.

Well done for completing the first learning cycle compounds.

We are now moving on to comparing compounds and elements.

What's very interesting about compounds is that they usually have very different properties to those of the elements that it's made from.

So we're going to have a look at now at an example.

This example is copper chloride, and we're going to see how it's formed from copper and chlorine reacting together that bond together to make that compound, which is copper chloride.

So if you have a look at the copper, the copper's like a reddy coppery coloured metal.

You've probably seen this around your house in water pipes.

We're going to add that and react it with chlorine.

Now chlorine is a pretty dangerous greenish/yellowish gas.

Probably haven't seen that.

We don't see very much of that around.

And what we're gonna do is we're going to carry out a reaction, and this reaction is going to produce copper chloride.

And copper chloride, as you can see here, is a totally different colour to what we've started with.

So you can see that copper chloride is like a bluey, greenish blue powder.

So that'll completely different to the elements that it's made from.

Now we're going to carry out an experiment.

So a small piece of magnesium is held in a flame.

The following table is used to record what happens.

So here's our observation.

So we're going to look at the state of matter.

So is it a solid state, a liquid state, or a gas state? What does it look like? So it's appearance.

Just a quick description there.

An electrical conductivity.

Will it conduct electricity or not conduct electricity? So let's see what happens.

So here's our magnesium metal here.

And we've got our oxygen, which is colourless.

So we haven't got a picture of it because we can't actually see it.

And we're going to carry out a reaction.

So let's watch this reaction now.

The reaction's taking place here.

You can see that reaction's taken place.

And now you can see the product.

So the product there is magnesium oxide.

So you can see that that magnesium oxide looks completely different to the magnesium and the oxygen that it came from.

Now let's complete our table with our information that we've got from observing the experiment.

So let's have a look.

Magnesium.

So it's solid, and it's silver, and it's shiny metal.

Oxygen, we know that that's a gas, and it's colourless, we can't see it.

That's why we didn't have a picture of it.

And the magnesium oxide is solid, and it's a white brittle powder.

So you could see that powder was formed.

Let's have a look at the electrical conductivity of magnesium and magnesium oxide.

So here we've got the simple equipment that we're going to use.

So we've got an LED bulb, and that's connected to a wire.

So we've got one wire connected to the LED bulb, and we've got a battery pack.

When that connects up, the LED bulb will light.

So if you put anything between the wire and the LED bulb, if it conducts electricity, it's going to light up that LED bulb.

So let's have a look.

So you can see there the wire is in connection with the magnesium.

When we put the LED bulb on, you'll see it lights up green.

So, magnesium conducts electricity.

There we go.

See it again.

Definitely conduct electricity.

Now let's have a look at the magnesium oxide.

So here we've got the wire connecting the magnesium oxide together.

However, you can see that it doesn't matter how many times it gets put into the magnesium oxide, there's no light.

So it shows that magnesium oxide does not conduct electricity.

So let's complete our table.

So oxygen doesn't conduct electricity.

I've just written no in there for you.

We'll have a look at the magnesium.

Yes, that did conduct electricity because the light lit up.

So the bulb lit up, showing that magnesium conduct electricity.

And then we've got magnesium oxide.

No, the bulb did not light up.

So the LED did not light up when we completed the circuit.

So, magnesium oxide does not conduct electricity.

So you can see that the properties of the magnesium oxide are different to the elements that it came from.

Let's have a check for understanding.

The magnesium burns with a bright white flame.

A chemical reaction takes place.

Which two of the options provided are evidence that a new substance has been formed? So how do we know that a new substance has been formed? Is it that the silver metal is after the reaction? You get white smoke, you get the appearance of a white solid.

So we're going to choose two of these options to show that a chemical reaction has taken place and a new substance has been formed.

Pause the video now for some thinking time and press play when you've got your answer.

Well done if you said that the white smoke and the appearance of a white solid showed that a reaction had taken place.

What I want you to do now is select two answers.

So the magnesium oxide formed will have.

Will it have the same properties as oxygen? Will it have the same properties as magnesium? Will it have different properties to oxygen, different properties to magnesium? I want you to select two answers there.

So pause the video while you select your answers, then press play when you ready for me to go through them with you.

So well done if you said c.

It's going to have different properties to oxygen, and it's also going to have different properties to magnesium.

Well done if you've got those two correct.

Now I've got to true or false statement for you.

Compounds always have the same properties as the elements they're made from.

Is that true or is that false? Pause the video now for some thinking time, press play when you've got your answer.

So well done if you said that that was false.

Now I want you to justify this.

So I've got two statements here.

You would have to test the compound to see its properties and compare them to the elements it's made from.

Or a compound never has the same properties as the elements it's made from.

Pause the video, have a little think, and then press play when you've got your answer.

Well done if you said you would have to test the compound to see its properties, and then you could compare them to the elements that it's made from.

Well done if you got that one correct.

You could conduct an experiment to see if compounds have different properties to the elements that made it.

So here's a list of equipment you would need if you want to see if sulphur and iron have got different properties to the compound formed, that's iron sulphide, when they react together.

So here's the equipment list that you need.

A boiling tube, sulphur powder, iron filings, a clamp and a stand, a magnet, a watch glass, a weighing boat or funnel, mineral wool, a Bunsen burner, heat resistant mat, and tongs.

So you must remember to follow the safety instructions from your teacher.

We could test the substances to see if they're magnetic.

And here's a method that allows you to do so.

So you add the substance to the watch glass and then you place some magnet underneath the watch glass.

So it's not touching the substance.

That way if it is magnetic, the substance doesn't get stuck to the magnet.

And then you're going to write down your observations.

So you're going to look carefully about what's happening, and you're going to write those observations down.

Here's a method that can be used for reacting sulphur and iron.

Let's go through the equipment.

First of all, you'll need a clamp and a clamp stand.

We've got a boiling tube, the sulphur and iron mixture, and mineral wool.

So the first thing we're going to do is we're going to write down the colour and state of matter observations for iron and sulphur.

Then we're going to test the iron and sulphur to see if they're magnetic.

We are going to set up the equipment as shown in the diagram.

We're going to heat it until a reaction takes place.

And then we're going to leave it to cool, and we're going to observe the colour and state of matter of the compound after it's cooled.

And then we're going to test the compound formed, so the iron sulphide, to see if it's magnetic.

Here's what I'd like you to do now.

I want you to complete this.

So iron reacts with sulphur to make iron sulphide.

You're either going to carry out the practical under your teacher supervision, or you're going to watch the video and complete the table with your observations.

So your observations, you're going to look at the state of matter, the colour, and if it's magnetic or not.

So you're gonna carry those out for iron, for sulphur, and finally for iron sulphide.

When you've completed your table, then you're going to say, what evidence can you see that a new substance, iron sulphide, has been made? So you're going to write a sentence or two about what evidence you've got.

Pause the video now, carry out your practical, or watch the video of the practical, then press play when you want to go through this task.

And here we've got our iron and sulphur reaction.

So the first thing we're gonna do is we're gonna test the iron filings to see if they are magnetic.

So you want to write down your observations now.

Then what we're gonna do is we're gonna look at the sulphur.

Again, write down your observations.

Now we're going to take a spatula, or two of iron filings.

Just a small amount, you don't need lots.

And then we're going to take the sulphur as well.

Equal amounts of sulphur and iron.

We put the magnet on there.

See what that does.

Now here comes the tricky bit.

Gonna take this weighing boat that we've put our elements in.

I'm gonna try and get all of the contents into the boiling tube without spilling them.

You could also use your funnel for this if you've got a funnel instead of a weighing boat.

We're going to get some mineral wool and place that in the top just to stop the reactants from escaping.

So it's just stop the iron and sulphur from escaping.

Then what we're gonna do is we're gonna heat it gently using a blue flame on a Bunsen burner just so that the elements start to react together to form that compound.

You can see the reaction's started to happen now.

The reaction's almost complete now.

You can see the change in colour.

Now we're going to wait till it's cooled.

So we're going to wait a few minutes also until it's cooled down.

Then we're going to remove the mineral wool.

Make sure that all the mineral wool comes out.

Now you're going to take your product, tip it out onto your watch glass.

That's iron sulphide there that you've made, a compound.

You're going to then test to see if it's magnetic.

Ideally you'd do this under the watch glass, but this demonstration shows it on top of the watch glass.

You're gonna write down your observations now.

How did you get on? I hope you've managed to get all of your observations done.

So we're going to go through these now.

So iron is a solid, and it is grey, and it is magnetic.

Sulphur is solid, it's yellow, and it's not magnetic.

And then you should have carried out your reaction or watched the reaction on the video.

And you can see that the state of matter.

So iron sulphide is solid, it's black, and it's not magnetic.

So what evidence have you got that a new substance has been made? So you know that a new substance has been made.

And you can see this because the colour has changed from being grey and yellow, and it's now black.

And also the iron was magnetic, but the iron sulphide is not magnetic.

So iron sulphides got different properties to the iron and the sulphur.

So well done if you've got that correct.

Sofia watched an experiment her teacher carried out.

When sodium reacted with chlorine, a bright yellow orange flame was seen and sodium chloride was made.

Here's her observation.

So she's got a state of matter.

So sodium was solid, chlorine was a gas.

And their colour, so sodium was shiny and silver when it was cut, and chlorine was a yellow/green gas.

And you can see that the sodium chloride that's been formed is a solid, and it's white.

So what evidence does Sofia have to show that the compound sodium chloride was formed? Pause the video now and then press play to go through the answers.

Well done for working hard and completing Sofia's answer for her.

So she said, "I know a compound, sodium chloride, was formed because, after the reaction, the compound was a different colour from the two elements that reacted together.

The compound was in the solid state and not in the solid and gas states like the elements from which it was made." So the two main things here that you're going to say are that the compound was a different colour and also it had changed state.

So there was no gas state associated with it.

Well done if you've worked hard and got that correct, you're doing really well.

Here's a summary of today's lesson.

A compound is made from two or more different elements chemically bonded together through a chemical reaction.

A compound may have different properties to those of each of the elements from which it is made.

Well done for working really hard this lesson.

I hope that you understand a little bit more about compounds now, and how we can show that the compounds have got different properties from the elements that they're made from.

Well done.