Lesson video

Welcome to today's lesson.

It's called A Particle Model of Chemical Reactions, and it's part of the unit, atoms, elements, and compounds.

My name's Mrs. Mytum-Smithson.

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

This lesson, we're going to be drawing particle diagrams of reactants and products and show how they're rearranged by a chemical reaction.

If this all sounds a little bit strange, don't worry, because we're going to go through this step by step.

By the end of the lesson, you'll be an expert on particle diagrams. Today's keywords are reactants and products.

On the next slide, there's some definitions for these, so feel free to pause the video if you wish to read them.

Today's lesson consists of two learning cycles.

Firstly, we're going to learn about reactants and products.

Then, we're going to learn about atom rearrangement.

I'm sure you're keen to get going.

So, let's start with reactants and products.

When we have a chemical reaction, first thing we need to do is start with some reactants.

Sometimes it's one chemical, sometimes it's more than one, and these react in a chemical reaction.

So, let's have a little look.

So, we've got magnesium plus oxygen.

And then, usually, we'll draw an arrow and this arrow signifies that a chemical reaction has taken place.

And this is the product, so we've only got one product in this case and it's magnesium oxide, so this is a product.

This is the new chemical that's been formed in the chemical reaction.

So, we didn't start with magnesium oxide, we started with magnesium and oxygen.

When these react together, we get magnesium oxide.

Let's have a quick check for understanding.

Which circled part of the equation is showing the reactants? Pause the video now for some thinking time.

Press play when you've got your answer.

Well done if you said, A, sodium and chlorine are the reactants.

So, in this case, we've got two reactants and you can see that sodium plus chlorine makes the product, sodium chloride.

Well done if you got that right.

The examples that we've looked at already only showed one product form from a reaction, but sometimes there's two or more.

Let's have a look at the next one.

So, here's a reaction taking place between magnesium and hydrochloric acid.

These are the reactants.

And if you remember, we've got an arrow that we draw to show that a chemical reaction has taken place.

On the right-hand side of that, we're going to see the products.

So, the products in this case are magnesium chloride plus hydrogen.

Now, let's have a quick check for understanding.

How much do you know about products? What circled part of the equation shows the products? Pause the video now for some thinking time.

Press play when you've got your answer.

Well done if you said, D, the products are on the right-hand side of the equation.

So, in this case, the products for this reaction between lithium and water are that it makes lithium hydroxide and hydrogen.

Well done if you got that one correct.

The examples that we've looked at so far contain two reactants, but sometimes there's only one reactant and this might break down and produce two or more products.

Let's have a look at an example of this.

We've got calcium carbonate, so that's a reactant, 'cause there's only one reactant in this equation.

We've got the arrow, which shows that a chemical reaction has taken place.

And in this case, the calcium carbonate breaks down to produce two products, calcium oxide and carbon dioxide.

What I'd like you to do now is choose any of these correct answers that are about reactants.

So, reactants are written on the left-hand side in an equation, written on the right-hand side in an equation, the chemicals before a reaction takes place, the chemicals made after a reaction takes place.

Pause the video now, put down your answer or answers, and then press play when you want to reveal the answers.

Well done if you said that reactants are written on the left-hand side in an equation and that they are also the chemicals before a reaction takes place.

Well done if you got that right.

Here's task A.

I'd like you to sort the reactants and the products into the table for five equations.

What I'd like you to do is in the first column, you're going to write the question number.

In the second column, you're going to write all the reactants.

And then, in the final column, you're going to write the products.

So, here are the equations.

Zinc plus oxygen makes zinc oxide, carbon plus oxygen makes carbon dioxide, methane plus oxygen makes carbon dioxide and water, zinc plus hydrochloric acid makes zinc chloride and hydrogen, silver nitrate and copper makes silver and copper nitrate.

Pause the video while you complete that task, then press play when you want the answers.

Well done for working really hard on completing this task.

Let's go through the answers.

So, on the left-hand side, we've got reactants.

In this case, question one, there were zinc and oxygen.

That's what we started with.

And then, we only got one product for this reaction and that is zinc oxide.

And that's going to appear on the right-hand side of the arrow, that is the product.

Question two, we've got carbon and oxygen to start with.

So, they're our reactants.

And on the right-hand side of that arrow, we've got our product and that is carbon dioxide.

For question three, we've got methane and oxygen on the left-hand side of the equation.

So, before the arrow.

And then, on the right-hand side, we've got the products, carbon dioxide and water.

Question four, this time, we've got zinc and hydrochloric acid on the left-hand side before the arrow.

Then, when the chemical reaction has taken place, we're going to make zinc chloride and hydrogen.

And finally, we've got copper and silver nitrate.

And in this case, on the right-hand side of the arrow, we're going to make silver and copper nitrate.

So, they're our products.

Well done if you've got all five of those correct.

You're doing really well.

That's the end of our first learning cycle, reactants and products.

I'm hoping that you know lots about those now.

Now, we're going to go along and have a look at atom rearrangement.

This is a little bit more complicated, but I'm sure once you get it going with it, you'll be absolutely fine.

Some people think that chemistry is magic, and whilst it's a really interesting subject, there's nothing magical happening.

When a chemical reaction takes place, there's no new atoms that magically appear or disappear.

And we say that no new atoms are created or destroyed in a chemical reaction.

The atoms from the reactants are actually rearranged and chemically bonded in a different way to form the products.

So, for example, magnesium and oxygen makes magnesium oxide.

So, we're gonna have a look now at what happens when we draw atoms to represent these.

So, here's our atoms that we've drawn.

We've drawn magnesium atoms as these grey atoms and oxygen atoms as these red circles.

So, they're not actually red and magnesium atoms aren't actually grey.

But we're using these just to represent what's actually happening.

So, you can see we've got magnesium on its own, oxygen on its own.

And when the chemical reaction takes place, the magnesium now is bonded to an oxygen atom.

So, each magnesium atom is bonded to one oxygen atom.

Nothing magic happening, nothing magically appearing, nothing magically disappearing, it's just been rearranged.

Here's our magnesium oxide atom rearrangement diagram here.

So, we can see that the reactants that we started with are magnesium and oxygen and we ended up with magnesium oxide.

What we can do to double check this is we can draw a table that looks like this.

In the first column, we've got atom type.

In the next column, we've got the number of atoms in reactants, and then we've got the number of atoms in products.

So, what we can do is we can check here to make sure that no atoms have appeared or disappeared, and then we can know that our equation is correct.

So, here, we've got magnesium.

So, if we count up the number of magnesium atoms on the left-hand side in the reactants, we'll see that that's two.

There's two grey circles there.

Then, the number of atoms in the product, all we've got to do is count and we can count up to two.

So, there's two magnesium atoms there.

And then, for the oxygen, we've also got two oxygen atoms in the reactants.

We can see those there.

And then, we can see the oxygen atoms in the products abundant to the magnesium atoms and we can count those up there, and that's two.

So, the number of atoms in the reactants are just rearranged in the products.

There are the same number of each type of atom in the reactants and in the products.

Now, we're going to take a look at another example, iron and sulphur.

So, iron is represented by the chemical symbol, Fe, and sulphur is represented by the chemical symbol, S.

And we're going to react these together to make iron sulphide.

So, here's one of our reactants, iron.

You can see they're the iron atoms. We're going to react those with sulphur.

So, there's the sulphur atoms and we're going to make iron sulphide.

So, then, if we want to check that our atoms have just been rearranged and no atoms have been created or destroyed, what we can do is we can then count 'em up.

So, we can count up the number of atoms in the reactants for iron and we should get that to 12.

And we're going to have a look now at the number of atoms in the products and we are going to count those up too.

And you should have seen that there's also 12.

Then, with the sulphur atoms, you can see that there's 12 and the number of sulphur atoms in iron sulphide is also 12.

So, you can see that there are the same number of iron and sulphur atoms in iron sulphide.

No atoms are created or destroyed.

Here's a particle diagram for the reaction of methane and oxygen.

Methane is the gas that's in your gas cooker if you've got one of those at home, and it's just made up of one carbon atom bonded to four hydrogen atoms. And we are going to just see what happens when that burns.

So, when it reacts with the oxygen in the air.

So, here's methane and oxygen on the left-hand side, 'cause they're our reactants.

And then, on the right-hand side, we've got the products.

And the products for this are carbon dioxide, one carbon atom and two oxygen atoms. And then, we've got water, which is one oxygen atom and two hydrogen atoms. So, we're going to count them up to make sure that nothing is being created or destroyed.

So, if we count up the number of carbon atoms, we can see that we've got one on each side.

Then, we have a look at the hydrogen atoms. We can see that on the left-hand side in the reactants, we've got four.

And on the right-hand side in the water, we've also got four.

Then, all we've got to do is count up the oxygen atoms. So, in this case, we've got four oxygen atoms in the reactants.

And then, in the products, if you can see, you've got two oxygen atoms bonded to carbon.

And then, we've got the other two oxygen atoms that are bonded to hydrogen.

And when we count them up, it still equals what we started with.

So, we can confidently say that no atoms have been created or destroyed.

True or false, atoms are rearranged in a chemical reaction.

Is that true or is that false? Pause the video for some thinking time.

Press play when you've got your answer.

Well done if you said that that was true.

Now, I want you to justify your answer.

So, you've got no new atoms are formed in a chemical reaction or atoms can be created or destroyed during a chemical reaction.

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

Well done if you said no new atoms are formed in a chemical reaction.

Atoms cannot be created or destroyed during a chemical reaction.

Well done if you got that right.

Copper carbonate is a reactant that breaks down to form two products.

So, let's count up the number of atoms to make sure that no atoms have been created or destroyed.

So, on the left-hand side, we're gonna count the copper atoms represented by the symbol, Cu.

So, we've got one on the left-hand side in the reactants, and then we've got one on the right-hand side in the copper oxide.

Next, we're going to count up the carbon.

So, we've got one on the left-hand side in copper carbonate and we've got one on the right-hand side after the reaction, which is carbon in carbon dioxide.

And then, we count up the three oxygens on the left-hand side in the reactants.

And then, in the right-hand side, we've got one oxygen which is bonded with copper and two which are bonded with the carbon.

So, that makes a total of three.

And as you can see, we've got the same number of atoms in the reactants as the products.

They're just rearranged.

So, no atoms have been created or destroyed.

What I'd like you to do now is have a look at the atoms within that white box.

What could the products be from the reaction between hydrogen gas, so that's the Hs, and oxygen gas, that's the O.

So, once these have reacted together, what could you possibly get? Is it A, B, or C? Pause the video now for some thinking time and press play when you've got your answer.

So, well done if you said C, you're absolutely correct.

There's two water molecules there.

And if I have a look at the atoms, we could only get that from hydrogen and oxygen gas.

So, we've got four hydrogens and two oxygens.

And in C, you can see that we've got two water molecules.

Each water molecule is made up of one oxygen atom bonded to two hydrogen atoms. We've got two of them, so we've got two oxygens and four hydrogens.

So, they are the rearranged reactants.

It could not be A and it could not be B, because we have no carbon in the reactants.

So, if we've got no carbon in the reactants, we can't have carbon in the products.

Well done if you got that one correct, it was C.

Another quick check.

The number and type of atoms in the reactants are shown in the table.

What number is missing from the table showing how many copper, so that's Cu, atoms are in the products? Is it one copper atom, two copper atoms, or four copper atoms? Pause the video now for some thinking time.

Press play when you've got your answer.

Well done if you said two, it is indeed two.

If you've only got two atoms of copper to start with, you can only have two atoms of copper in the products.

Well done if you got that one right.

Here's task B.

The students have been talking about atoms. Select who you agree with.

You can agree with more than one student.

Those students that you don't agree with, I want you to correct their statement or statements.

So, Alex has said, "During a reaction, atoms might be destroyed." John said, "Some atoms may be created during a reaction." Lucas said, "The products are made of the same atoms as the reactants." Sam said, "The atoms in the reactants are rearranged to make the products." Pause the video now, and then press play when you've got your answers.

Well done for working so hard on completing that task.

If you said that Lucas and Sam were correct, you're absolutely right.

The products are made of the same atoms as the reactants and the atoms in the reactants are rearranged to make the products.

John and Alex were wrong, but hopefully you've corrected it.

'Cause now, Alex is saying during a reaction, no atoms are destroyed.

And John's saying, no atoms are created during a reaction.

So, well done for completing that task and I hope you got it correct.

What I'd like you to do for this task is complete the table to show the number of atoms in the reaction.

Pause the video now, complete the task, press play when you've got your answers.

Well done for completing the task.

Hopefully you've got it correct.

So, the rules are that no atoms are created or destroyed.

So, they should be the same number of atoms in the reactants and products.

So, zinc, if we've got one atom in the reactants, we're only gonna have one atom in the products.

The same with carbon.

If we've got one atom in the products, we must have one atom in the reactants.

And finally, the oxygen.

I'm sure you can count up and you can see that those three atoms in the reactants are still there because one's with zinc oxide and two are with carbon dioxide.

So, you should have written three there.

Well done for completing that task.

I hope you managed to get it correct.

Here's part three of task B now.

Sulphur reacts with oxygen, making sulphur dioxide.

The equation is S plus O2 makes SO2.

Draw a particle diagram to show this reaction.

Then, what I'd like you to do is complete the table showing the type and number of atoms for the reaction.

This might seem a bit tricky, so you might have to think a little bit before starting this task.

What I want you to do now is pause the video, complete the task, and press play and we'll go through the answers together.

Well done for completing that task.

I hope you found it okay.

So, here are our initial atoms. So, our initial ones are the reactants.

So, we've got one sulphur atom and two oxygen atoms. It doesn't matter what colour you've drawn them, you might not have had any colours available.

So, it's fine if you've just drawn circles with an S in it and circles with two Os in it.

We've got that arrow, which shows that a reaction has taken place and we should have rearranged them like this.

So, we've got one sulphur atom still, and we've got two oxygen atoms, and that sulphur dioxide.

If you have rearranged it any other way, so it's absolutely fine if you've rearranged it some other way, but all three atoms must overlap or they must touch and you mustn't have any extra atoms other than those three atoms. Well done if you managed to do that.

And here's our little table now, so we can check that no atoms have been created or destroyed.

So, we've got S for sulphur, O for oxygen.

Then, all we've got to do is count up the reactants and count up the products.

So, we've got one sulphur atom, one sulphur atom, so no sulphur atoms have been created or destroyed.

We've got two oxygen atoms to start with in the reactants, and we've got two at the end in sulphur dioxide.

So, we know that that's correct.

No atoms have been created or destroyed.

Well done if you've got all that correct.

Well done for working hard throughout this whole lesson.

This is part five of task B.

Don't worry, it's definitely the last one.

So, what I want you to do now is fill in the blanks using the words, reactants or products only.

So, those are the only two words, and you're gonna put them in these sentences.

So, something are the chemicals that react in a chemical reaction.

Something are the chemicals that are formed in a chemical reaction.

There's something after a chemical reaction contains exactly the same number of type of atoms as a something.

The atoms in the something after a chemical reaction are bonded differently to the same atoms in the something.

And the something that you can use is only reactants or products.

What I want you to do now is pause the video, complete the task, and then press play when you've got your answers.

Well done for completing part five of task B.

Let's go through the answers now.

Reactants are the chemicals that react in a chemical reaction.

Products are the chemicals that are formed in a chemical reaction.

The products after a chemical reaction contain exactly the same number and type of atoms as the reactants.

The atoms in the products after a chemical reaction are bonded differently to the same atoms in the reactants.

Well done if you got that right.

I think you've worked really hard.

Here's a summary for today's lesson.

Reactants are the chemicals that react in a chemical reaction.

Products are the chemicals that are formed in a chemical reaction.

The reactants and products in a chemical reaction contain exactly the same number and type of atoms. The atoms in the products of a chemical reaction are bonded differently to the same atoms in the reactants.

Well done for working hard throughout this lesson.

I know at times, it's been a little bit tricky to understand the concepts of reactants and products.

However, I'm sure that you are much more knowledgeable now than you were at the start of the lesson, and I hope to see you again in another lesson soon.