Lesson video

Hello, my name is Miss Couves.

I'm really excited for our lesson today.

In today's lesson, we're going to be investigating some chemical reactions.

I am so excited for the experiment that we're going to do together later.

Scientists investigate chemical reactions so they can find out more about how they work.

Today, we are going to be investigating the chemical reaction between vinegar and sodium bicarbonate.

Let's get started.

In today's lesson, we are going to start by recapping our previous knowledge.

Then we will learn about the reactivity and how we measure it.

We will look at the variables in scientific experiments, and then we will finally plan our own experiment into reactivity.

For today's lesson, you will need an exercise book or paper, and a pencil.

If you don't have one of these items, pause the video now and go and get them.

If you would like to have a go at the experiment, you will also need some vinegar, some bicarbonate of soda, a cup, and a spoon.

You will also need an adult to help you.

Let's start by recapping our knowledge.

Pause the video to complete the diagram in your notes.

Press play when you're ready to hear the answers.

Particles in solids are touching and in ordered rows.

In liquids, they are touching and arranged randomly.

And in gases, they are far apart, not touching, and moving very fast.

As we increase the temperature, particles have more energy.

Pause the video to write down the four state changes that we have learned about.

Press play when you're ready to hear the answers.

The change from a solid to a liquid is called melting.

The change from a liquid to gas is called boiling.

The change from a gas to a liquid is called condensing.

The change from a liquid to a solid is called freezing.

What is a physical reaction? A physical reaction is a change in the form or arrangement of a substance.

Why is glass smashing an example of a physical change? Glass smashing is an example of a physical change because the form of the glass changes from a large pane to lots of tiny shards.

But the type of substance doesn't change.

It is still glass.

Pause the video and write down why paper tearing is an example of a physical change.

What is a chemical change? A chemical change is a change that forms a new substance.

Let's think about the cake baking.

When the cake bakes, it produces a new substance.

The cake batter looks very different to the cooked cake, and they have different properties.

Because a new substance is formed, a chemical reaction has taken place.

What a bike rusts, the metal in the bike reacts with the oxygen in the air to form rust.

A new substance, rust, has been formed, so this is a chemical reaction.

What is formed in a chemical reaction? A chemical reaction forms a new substance.

Pause the video and write down why a match burning is an example of a chemical change.

A physical change is when the form of a substance or the arrangement of its particles changes.

For example, changes of state or dissolving.

They're easy to reverse and often result in a change in appearance.

A chemical reaction is when a new substance is formed.

For example, burning and rusting.

These changes are hard to reverse.

They often result in a change in appearance.

What is the same about chemical and physical changes? Both chemical and physical changes result in a change of appearance.

What is different between physical changes and chemical changes? A physical change is easy to reverse whereas a chemical change is hard to reverse.

A physical change changes the form of a substance whereas a chemical change produces a new substance.

In today's lesson, we're going to investigate reactivity.

Reactivity is how much a substance reacts.

A substance that is very reactive reacts very fast.

We call this a vigorous reaction.

My turn, vigorous.

Your turn.

A substance that is not reactive reacts very slowly or not at all.

How do we know that a reaction is taking place? There are three things we might see if a reaction is taking place.

These are bubbles forming, a colour change, and a temperature change.

Pause the video and write down three things we might see in a chemical reaction.

Press play when you're ready to continue.

We are going to look at the reactivity of two metals, magnesium and copper.

While I'm doing the experiment, I want you to think about these questions.

How do we know that a reaction is taking place? Which metal is most reactive? And how do you know? Let's have a look at the reaction between magnesium and acid, and copper and acid.

I am going to put some magnesium in this test tube and some copper in this test tube.

I'm going to put one piece of magnesium in the first test tube.

Have a look, what does the magnesium look like? Magnesium is a silvery-gray solid.

I'm going to put one piece of copper in the second test tube.

Have a look carefully.

What does copper look like? Copper is a orange metal.

In my reaction, I'm going to add the same amount of acid.

Watch carefully to see what happens when I add the acid to the magnesium.

Can you see that it is bubbling very fast? We call this a vigorous reaction.

How do I know that a reaction is taking place? I know a reaction is taking place because I can see the bubbles being produced.

These bubbles are being produced very fast, so magnesium is a reactive metal.

Have a look at copper.

I'm going to put the same amount of acid into my copper test tube.

What do you notice about the reaction of copper with acid? Can you see any bubbles? Copper is not reacting with the acid.

It is not producing any bubbles.

Is copper more or less reactive than magnesium? Let's look at them both together.

Magnesium is producing lots of bubbles.

Copper is not producing any.

Which one is more reactive? Magnesium is more reactive because it is forming the bubbles faster.

This is an experiment that you shouldn't try at home, so make sure you're watching carefully as I do the experiment.

What did we learn in our experiment? We learned that magnesium is more reactive than copper.

How did we know that magnesium was more reactive than copper? We knew magnesium was more reactive than copper because it produced bubbles faster.

In an investigation, we call the things that we could change variables.

What did we change in the experiment we just did? We changed the type of metal.

In an investigation, we have three types of variable.

Let's find out what they are.

The independent variable is the thing you change.

What is the independent variable? The independent variable is the thing you change.

The dependent variable is the thing you measure.

What is the dependent variable? The dependent variable is the thing you measure.

The control variables are the things you keep the same.

What are the control variables? The control variables are the things you keep the same.

In our experiment with magnesium and copper, what was the thing we changed? The thing we changed was the type of metal, so the type of metal was our independent variable.

What did we measure in our experiment with magnesium and copper? We measured the number of bubbles produced, so our dependent variable was the number of bubbles produced.

Our control variables are the things we keep the same.

What did we keep the same in our experiment? We kept the number of pieces of metal the same.

We kept the amount of acid the same.

Why do you think we needed to keep them the same? When we're doing an investigation, we need to make sure it's a fair test.

An experiment can only be a fair test if we only change one thing.

In this experiment, we changed the type of metal, so everything else had to be kept the same.

Pause the video and write down the three types of variable and what they represent.

Let's look at an example.

In this experiment, we reacted one gramme of each metal with 20 millilitres of vinegar.

We counted the number of bubbles produced for one minute.

What was the independent variable? The independent variable is the thing we changed.

What did we change in this experiment? The thing we changed was the type of metal.

What is the dependent variable? The dependent variable is the thing we measure.

What did we measure in this experiment? The control variables are the things that we kept the same.

What did we keep the same in this experiment? Pause the video and write down the independent variable, the dependent variable, and the control variables.

Press play when you're ready to see the answers.

The independent variable was the type of metal.

The dependent variable, the thing we measured, was the number of bubbles produced for one minute.

And the control variables, the things we kept the same, was the one gramme of each metal and the 20 millilitres of vinegar.

We used the same amount of metal and the same amount of vinegar.

Pause the video to answer these questions to check your knowledge.

Question one, what is the independent variable? Question two, what is the dependent variable? Question three, what are the control variables? Question four, how many variables should you change in an experiment? Pause the video and press play when you're ready to check your answers.

The variable you change in an investigation is called the independent variable.

The variable you measure in an investigation is called the dependent variable.

The variables that you keep the same in an investigation are called the control variables.

You should only change one variable in an investigation to make sure it is a fair test.

Pause the video to tick or fix your answers.

Press play when you're ready to plan our investigation.

Now we're going to complete our investigation.

If you would like to have a go, you will need some vinegar, water, bicarbonate of soda, a cup, and a spoon.

You will also need an adult to help you.

If you don't have these things, you can do your experiment with me.

Pause the video and copy this table into your notes.

Press play when you're ready to start the experiment.

Before we start, let's check we know what our variables are.

I'm going to read you the method.

Then I want you to pause the video and write down the independent variable, the dependent variable, and the control variables.

Number one, make the vinegar solution using the correct number of spoonfuls of water and vinegar.

Add a teaspoon of sodium bicarbonate to each one, and record the number of bubbles produced in the table.

We are going to use the words lots, some, few, many, and none to record the number of bubbles.

Pause the video and write down the variables in our experiment.

Press play when you're ready to check your answers.

The independent variable is the number of spoonfuls of water and vinegar.

The dependent variable was the number of bubbles produced.

And the control variable was the same amount of sodium bicarbonate.

Are you ready to start our experiment? Right, let's get started.

I am ready to start my experiment.

Can you see how I've set up my page? I've got my four containers that I'm going to do my experiment in, and I've written the values for the amount of water and vinegar next to them.

Pause the video and set your page up like mine.

When you're ready to start, press play.

The first thing we're going to do is make the vinegar solutions using the correct number of spoonfuls of water and vinegar.

In the first one, I need to put one spoonful of vinegar and three spoonfuls of water.

Here is my vinegar.

One spoonful of vinegar and three spoonfuls of water.

I'm going to stir it to make sure that it's mixed.

In the next one, I'm going to put two spoonfuls of vinegar and two spoonfuls of water.

Just stir.

In my third one, I'm going to put three spoonfuls of vinegar and one spoonful of water.

One, two, three.

And one spoonful of water.

Stir.

And then in my final one, I'm going to put four spoonfuls of vinegar.

What's the total number of spoonfuls I've put in each container? I've put four spoonfuls in each container.

Why do you think I've done that? I've put four spoonfuls in each container so I knew that each container has the same volume of solution.

It is one of my control variables.

The next thing I'm going to do is I'm going to add a teaspoon of sodium bicarbonate to each of them.

I'm going to write down whether I think that there are some bubbles, few bubbles, many bubbles, or lots of bubbles.

I only put one in each one so that I can compare.

Oh, can you see that there are more bubbles in the second one than in the first one? That one's reacted even faster.

That is a really fast reaction.

Can you see how the bubbles are rising? Some, lots, many, vigorous.

Now I'm going to convert this into my table.

Write the amount of bubbles that we found for each solution under where it says result in your table.

You should be able to see that these two reactions are producing many more bubbles than the first two.

What can we conclude about the amount of vinegar in our solution and the effect on the reactivity? When there was more vinegar, the reaction was more vigorous.

So our conclusion would be that the more vinegar in the solution, the more vigorous the reaction.

Wow! Thanks, Miss Couves.

That was so interesting.

I loved watching your experiment.

Hi everybody, my name's Miss Simkin, and I've just come along to the end of your lesson to help Miss Couves and you to answer some conclusion questions about the experiment that you've just watched or taken part in.

So here are your questions.

Can you write the answers in full sentences to these questions on your piece of paper that you have? Question one, is this a chemical reaction? How do you know? So what are the signs that it might be a chemical reaction? Question two, what happens to the reactivity as you increase the amount of vinegar? And number three, can you write a word equation for the reaction? Hint, the product, what's produced, the gas in the bubbles, is carbon dioxide.

Can you pause the video and have a go at answering those conclusion questions for me now? Great, let's mark our work.

If you have a different coloured pencil, you can mark with that.

Tick if you got the answer right.

And if you need to make any corrections, that's okay.

Just do it in your different colour.

So number one, you might have written an answer like this.

This is an example of a chemical reaction, as a new product was formed, carbon dioxide.

We saw bubbles of carbon dioxide in our investigation.

If you wrote something similar to that, you can tick it.

Maybe you need to add some more in and be more specific that the bubbles that you saw were carbon dioxide.

If you need to do that, you can edit your answer with your different coloured pencil now.

Question two.

As we increased the amount of vinegar, the more bubbles there were.

This means that the vinegar solution was more reactive.

So if you wrote an answer about the vinegar getting more reactive as the experiment went on, or it being more reactive when you added more vinegar, then you can give yourself a tick.

That's the key point there.

And then the last question.

Here's your word equation.

Vinegar + sodium bicarbonate, an arrow to show the product, carbon dioxide.

Well done if you got that correct.

Great, that's the end of your lesson today.

Miss Couves and I are really proud of how hard you've worked.

Have a great rest of your day, everybody.