Lesson video

Hello again, my name is Miss Couves.

I am really excited about our lesson today.

In today's lesson, we are going to be looking at chemical changes.

Chemical changes are really important to scientists.

We use them for all sorts of things; from keeping us warm, to designing new medications.

Scientists that study chemical reactions are called chemists.

Today, we are going to be chemists and study some chemical reactions.

In today's lesson, we will begin by recapping our previous knowledge.

We will then find out what a chemical reaction is, look at some examples and then find out how scientists represent chemical changes using a word equation.

For this 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.

Press play when you're ready to start.

Let's start by recapping our knowledge.

Can you remember the properties of solids, liquids and gases? Pause the video now and complete the table.

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

Pause the video to tick and fix your answers.

Solids cannot be compressed, do not flow and cannot change their shape.

Liquids cannot be compressed, but they can flow and they take the shape of the bottom of their container.

Gases can be compressed and they can flow and they fill the shape of their container.

Pause the video to complete the diagram in your notes.

Press play when you're ready to continue.

Particles in solids are touching and in ordered rows.

In liquids, they are touching and arranged randomly.

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

What happens as you increase the temperature? As you increase the temperature, particles have more energy.

Which state change involves a solid becoming a liquid? Melting involves a solid becoming a liquid.

Which state changed involves a liquid becoming a solid? Freezing involves a liquid becoming a solid.

Which state change involves a liquid becoming a gas? Boiling involves a liquid becoming a gas.

Which state change involves a gas becoming a liquid? The state change that involves a gas becoming a liquid is called condensing.

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

We have three examples: ice cream melting, paper tearing and glass smashing.

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 pail to lots of tiny shots, but the type of substance doesn't change, it is still floss.

Now we are going to learn about chemical changes.

Chemical changes are sometimes called reactions.

My turn reactions, your turn.

A chemical reaction is a change that forms a new substance.

My turn a chemical reaction is a reaction.

A chemical reaction is a change that forms a new substance.

Your turn.

Right.

I'm going to show you an example of a chemical reaction.

For this, I'm going to need my lab coat.

This is an experiment that you shouldn't try at home.

The experiment that I'm going to do is burning paper.

Here I have a piece of paper.

I'm going to light my paper using a match.

When I light the paper, I want you to look really carefully at what happened while the paper burns.

Can you see the paper burning? What's happening to the paper while it burns? Can you see the block solid that's being produced? That's called ash.

The paper has turned black and some small white fragments have been produced.

They're called ash.

The paper is no longer the same substance.

When I burn the paper, it turned into two gases, water and carbon dioxide and ash.

Because burning produces new substances, it's a chemical change.

Let's look at some other examples.

Other examples of chemical changes are: a match burning, a cake baking and a bike rusting.

Why is it bike rusting an example of a chemical change? A bike rusting is an example of a chemical change because a new substance is formed.

Pause the video and write down three examples of chemical reactions.

Press play once you're ready to continue.

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

For example, a match burning, a cake baking and a bike rusting.

Let's look at some examples.

For these examples, you need to decide whether it is an example of a chemical change.

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

So in all of these examples, we're looking for whether a new substance is formed.

Is this a chemical reaction? Toasting bread.

What particles are present at the start? What particles are present at the end? Has a new substance been formed? Toasting bread is an example of a chemical reaction because a new substance is formed.

What about this? Is this a chemical reaction? A bonfire burning.

What particles are present at the start? What particles are present at the end? Has a new substance been formed? What do you think? Is this an example of a chemical reaction? A bonfire burning is an example of a chemical reaction because a new substance has been formed.

Is this a chemical reaction? Mixing sand iron filings.

What particles are present at the start? What particles are present at the end? Has a new substance been formed? What do you think? Mixing sand and iron filings is not an example of a chemical change because a new substance has not been formed.

The mixture can be easily separated to get the iron and sand back.

Can you remember how to separate sand and iron filings? You can separate sand and iron filings using a magnet because iron is magnetic and sand is not.

Is this a chemical reaction? Burning metals like lithium in fireworks.

What particles are present at the start? What particles are present at the end? Has a new substance been formed? What do you think? Burning metals in fireworks is an example of a chemical change because a new substance is formed.

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

Scientists use word equations to represent changes that occur in chemical reactions.

Reactants are the substances at the beginning.

Products are the substances at the end.

When we read a word equation, when we get to arrow, we say the word produces because we are saying that a chemical change has taken place.

So I would read my word equation as reactants produce products.

What goes on the left-hand side of the arrow? The reactants go on the left-hand side of the arrow.

What are the reactants? The reactants are the substances present at the beginning of a reaction.

What goes on the right-hand side of the arrow? The products go on the right-hand side of the arrow.

What are the products? Products are the substances formed in a reaction.

Let's think of an example.

In this chemical change, cookie mixture is producing a cookie.

What is the reactant? In this example, the reactant is the cookie mix.

Where does the reactant go in a word equation? The reactant goes on the left-hand side of the arrow.

What is the product in this chemical reaction? The product and its chemical reaction is the cookie, 'cause it is formed in the reaction.

Where does the product go in the word equation? The product goes on the right-hand side of the arrow.

What are these word equations describing? I'm going to read them to you, then you can pause the video to describe the word equations using a sentence.

Number one, cake mixture produces cooked cake.

Two, bread produces toast.

Three, explosive powder produces firework ash.

Four, iron plus oxygen produces iron oxide, which is also called rust.

Use this sentence starter to help you describe the word equations.

The word equation describes the chemical reaction that takes place when? Pause the video to describe all four word equations.

Press play when you're ready to continue.

For number one, the word equation describes the chemical reaction that takes place when a cake mixture is cooked to produce cooked cake.

Number two, the word equation describes the chemical reaction that takes place when bread produces toast.

Number three, the word equation describes the chemical reaction that takes place when explosive powder produces firework ash.

Number four, the word equation describes the chemical reaction that takes place when iron and oxygen produce iron oxide.

Write the word equation for the following.

I'm going to read all four examples to you.

Then you can pause the video to write the word equations.

Number one, cookie dough reacts to produce cooked cookies.

Number two, a bike reacts an air to form rust.

Three, a match reacts with oxygen to produce carbon dioxide and water.

Number four, carbon and oxygen react to produce carbon dioxide.

Remember the reactants go on the left-hand side of the arrow and then products go on the right-hand side of the arrow.

Pause the video and write four word equations.

Press play when you're ready to continue.

Number one, cookie dough produces cooked cookies.

Number two, bike plus air produces rust.

Number three, match plus oxygen produces carbon dioxide and water.

Number four, carbon plus oxygen produces carbon dioxide.

Well done for all your hard work today, you have been an excellent chemist.

We've looked at chemical reactions and how scientists represent them using word equations.

And you've written your own word equations.

Remember to do the quiz to show everything that you've learned in today's lesson.

See you next time.