Hello, my name's Mrs. Hart and I'm going to be guiding you through this lesson today.

I can't wait to get started and do some learning with you, so let's go.

Welcome to today's lesson from the unit, materials.

Today's lesson is called, The Effect of Adding Salt to Ice Plan.

And by the end of today's lesson, you're going to be able to plan an investigation into the effect of adding salt to ice.

Perhaps this is something you haven't tried before, but don't worry, I'm here to help and we're going to have a great time.

Here are the key words for today's lesson.

You might know some of these words already or perhaps they're new, but don't worry, I'll explain them as we go through the learning.

Our key words today are rock salt, grit, melt, comparative test and variable.

Our lesson today is in two parts.

The first part is called rock salt, and the second part of our lesson is called, Planning to investigate melting ice.

But we're going to start with our first part of the lesson now, rock salt.

Sofia and Lucas are on their way to school and they pass an unusual yellow object on the corner of a main road.

And here's a photo of that unusual yellow object.

And Sofia says, "I think it's a bin to put rubbish in." What do you think? Pause the video now and talk to your partner.

What is this unusual yellow object? Is Sofia right? And come back when you've had a chance to discuss this.

The object is a type of box or bin, but it is not used for waste.

It contains rock salt, also known as road salt or grit.

Rock salt is the name that we give to salt before it's processed.

We often call rock salt grit, because it looks a brown colour and it's a bit like gravel.

So you might see the word grit through this lesson referring to rock salt.

Rock salt is often stored in a public grit bin and used to help melt ice on roads and pavements.

So perhaps you've seen one of these bins near to you.

Perhaps there's one near to your school, or even on your school grounds.

It might say salt or grit on the bin and it will contain rock salt, which we can use to melt ice on roads and pavements to make them safer to drive or to walk on.

Rock salt is also used in gritting lorries, where there is a risk of ice or snow on the roads.

You might have seen these driving around in wintertime.

Their main purpose is to spread grit on the roads to prevent the formation of ice and to improve friction for vehicle wheels.

This makes it safer for us to travel around in cars when the weather is snowy or icy.

Most councils place yellow grit bins around their towns so that if a gritter cannot clear your road, you can safely do so yourself.

Lucas says, "Can I take rock salt from a grit bin to melt ice around my house?" What do you think? Lucas' brother replies, "You cannot take grit from grit bins if you're using it on private property such as driveways." So you can use the grit from a grit bin to clear your road, but you can't use it for your own private property, like driveways or paths outside your house.

Here's our first check for understanding.

Where is rock salt often stored? Is it A, in a salt shaker, B, in a public grit bin, or C, in a fridge? Pause the video now and come back when you have your answer.

What did you decide? Where is rock salt often stored? In a public grit bin.

Those unusual yellow objects that we saw at the beginning of this lesson, that's where you'll find rock salt.

A second check for understanding now.

True or false? Rock salt is used to add flavour to food.

Pause the video now and come back when you've thought of your answer.

How did you get on? Well, this is false.

But why? Again, pause the video and perhaps talk to a partner next to you about why this is false.

Rock salt is not used to add flavour to food.

Let's find out, shall we? This is false because rock salt is often used to help to melt the ice on roads and pavements.

Where does rock salt come from? Lucas says, 'I heard that salt comes from the sea, so perhaps that is where rock salt is from." Sofia says, "Maybe rock salt is cut from rocks in mountains and that's why we call it rock salt." What do you think? Pause the video now and talk to your partner.

Where do you think that rock salt comes from? Most rock salt comes from underground salt mines and here we can see an image of an underground salt mine.

It is extracted through traditional mining methods such as drilling and blasting, or by solution mining, where water is pumped underground to dissolve the salt.

Then it is brought to the surface and evaporated to leave the salt behind.

Did you say something like this? Perhaps you already knew that rock salt comes from underground salt mines.

Sofia asks, "Does rock salt go straight from the salt mine to the grit bin?" And in this image we can see a large piece of rock salt.

What do you think? After being extracted, rock salt usually undergoes processing to remove impurities and sometimes to crush it into smaller, more manageable pieces.

Then it's transported and stored in grit bins for use.

Here's our next check for understanding.

What happens to rock salt after it's been extracted.

A, it is processed and crushed.

B, it is frozen, C, it is added to food, or D, it is transported to grit bins.

Let's see if you can remember what you've learned so far in this lesson.

Pause the video now and come back when you've worked out your answer.

So what happens to rock salt after it's been extracted in those underground salt mines? Well, hopefully you said it is processed and crushed and it is transported to grit bins.

Well done if you got that right.

Now we're onto our first task.

For this task, you're going to need to take a baking tray and fill it with a layer of water.

Put this in the freezer overnight.

Make sure you put it in horizontally so none of the water comes out of the baking tray.

Then when you've left this overnight in the freezer, the next day you need to take a small sample of rock salt from the grit bin in your school grounds.

You're then going to sprinkle the rock salt onto the ice and your task is going to be to observe and record what happens to the ice around the rock salt over time.

You could do this by taking photographs or by drawing.

It's up to you.

So this is your first task.

I hope you enjoy it.

So how did you get on with this task? The first part of the task was to observe and record what happens when you put rock salt onto ice.

So perhaps you took some photographs.

Here's our photograph.

After 10 minutes I observed that the ice surrounding the rock salt had melted.

Did you see something like this? After 15 minutes I observed that most of the ice on the tray had melted to water in the liquid state.

You can see in this image how the amount of water has increased between 10 and 15 minutes after the rock salt was added.

Did you see something similar? Perhaps you drew what you observed.

Sofia says, "When I put the rock salt onto the ice, the ice started to melt around the rock salt within 10 minutes.

After 15 minutes, I observed that almost all of the ice melted into liquid water.

And here's Sofia's recording of what she observed.

Did you observe something similar? How long did you have to wait for the rock salt to melt the ice? Here's the second part of today's lesson.

This part is called, Planning to investigate melting ice.

Izzy says, "I think it is really fascinating how rock salt is used to melt ice." Jun replies, "I wonder if it has to be rock salt that is used? Can the table salt that is used to flavour food also be used to melt ice?" What do you think? Pause the video now and have a talk with a partner.

Does it have to be rock salt that we use to melt ice? Come back when you've had a chance to discuss this.

Well, Izzy's mum says, "Last winter we did not have any rock salt, so I sprinkled table salt on our icy pathway and it was very efficient at melting ice." This is an interesting observation from Izzy's mum.

Perhaps we can use different types of salt to melt ice.

Scientists plan investigations to make comparisons and find answers to questions.

Izzy says, "I would like to plan my own investigation to find out which salt is best for melting ice." When ice is melted, it goes from the solid state of ice to the liquid state of water.

Jun says, "Our question is, which type of salt melts ice the fastest, rock salt or table salt? Izzy says, "I'll make a plan so that we know what equipment we will need and what we will do." Jun says, "I think the easiest way for us to compare rock salt and table salt is to sprinkle the same mass of each type of salt over some ice cubes and use a stopwatch to time how long the ice cubes take to melt.

Here's our next check for understanding.

Who do you agree with? Alex says, "Scientists plan investigations to make comparisons and answer questions." Aisha says, "Scientists plan investigations to practise using different equipment." Laura says, "Scientists plan investigations to work only in laboratories with other scientists." Pause the video now and have a chat with your partner.

Who do you agree with? So who did you agree with in the end? It was Alex who was correct.

Scientists plan investigations to make comparisons and answer questions.

They might use different equipment as part of that, but they don't tend to plan investigations in order to practise using equipment.

Scientists' investigations can take place in many different locations.

It doesn't just have to be in a laboratory.

It could be indoors or outdoors depending on what they're investigating.

So well done if you said Alex.

Izzy says, "We will need to think about the different variables in this investigation." Variables is a word you may have heard before and these are the things that can be changed, measured, or kept the same.

Jun says, "The only variable that we will change is the type of salt.

The name or type of salt cannot be counted or measured, so our investigation will be a comparative test.

In a comparative test, the thing that is being changed has different labels.

In this case it's either rock salt or table salt.

When we carry out our investigation, we could put some ice cubes into two funnels and place each funnel on top of a measuring cylinder or a beaker.

And here's a diagram of what Izzy is suggesting.

You can see the funnel inside the beaker and then four ice cubes have been placed inside each of the funnels.

Next, we will add each salt to the ice cubes and use a stopwatch to time for 10 minutes.

After 10 minutes, we will measure and compare how much ice has melted into each beaker.

And you can see here Jun has added different types of salt to the diagram.

We will put the rock salt onto the ice cubes in one of the beakers and the table salt onto the ice cubes in the other beaker.

Control variables need to be kept the same throughout an investigation.

What are the control variables in this comparative test investigation? Pause the video here and have a talk with your partner.

What are the things that we are going to keep the same in this investigation? What are our control variables? Well, here are some examples of the control variables from this investigation.

We're going to keep the amount of ice the same, the location of the ice the same, the amount of salt must be the same in each beaker and the size of the funnel should be the same.

Did you say these things or perhaps you thought of something different? Jun says, "It will be difficult to keep each ice cube exactly the same size, but we will try to control this variable as much as we can.

That's good advice Jun, thank you.

Now we have our next check for understanding.

True or false? All variables must be kept the same in a comparative test.

Is this true or false? Pause the video now and discuss your answer and then come back when you're ready.

How did you get on? What did you decide? This is false, but why is it false? Again, pause the video now and talk to a partner about how we know this statement is false.

Come back when you're ready.

So how did you get on? We know that variables can be changed, measured, or kept the same in a comparative test and well done if that's what you said or perhaps you said it in a similar way.

Great work.

Now we're onto our second task.

I would like you to write a plan to investigate this question.

Which type of salt melts ice the fastest: rock salt or table salt? Include what you will do and what equipment you will need.

Remember to include what variable you will change, what variable you will observe or measure, and what variables you will control, keep the same.

You might like to use some of the ideas that you've seen in this lesson.

Perhaps you have a different idea for how you'd like to investigate this question.

Don't forget to include all of this information in your plan.

How did you get on? How did you find writing the plan? Did you remember all of those things that we've discussed? Well, here's an example of what you may have written.

Yours might look similar or a little bit different to this.

Equipment, so we're going to use 12 ice cubes, two cups, some rock salt, some table salt.

We're going to need two stopwatches and some digital scales.

I've drawn a diagram to show how we're going to do this experiment.

And you can see we have two cups and in each cup I've put six ice cubes and then the different types of salt will go into each cup.

Does your investigation look like this? Is it similar? Perhaps there are some things that's different.

And this is how I'm going to do the experiment.

One, measure 30 grammes of each type of salt using the digital scales.

Two, put six ice cubes into each cup.

Three, add 30 grammes of rock salt to one cup and 30 grammes of table salt to the other cup.

Four, start the stopwatch to record the time it takes for the ice in each cup to melt.

When I do this experiment, I'm going to try and do it in a very timely fashion, which means that once I've put the ice cubes into the cup and they're out of the freezer, I'm going to act as quickly as possible to put the rock salt and the table salt into the cups, 'cause I know that if I leave those ice cubes in the room, they're going to start to melt.

It's important once you've taken the ice cubes out of the freezer to work quickly to set up this investigation.

Is your plan similar or different to this one? Perhaps you're going to use the measuring beakers and funnels like we saw in the lesson.

Perhaps you thought of something completely different.

Well, I hope you've written a great plan, because you're going to have the opportunity to use it if you'd like to in a different lesson.

Here's what we've learned today.

Rock salt is often stored in a public grit bin and used to melt ice on roads and pavements.

And you might have seen this in the area where you live or go to school if you've seen these large yellow bins by the side of main roads.

After being extracted, rock salt usually undergoes processing and crushing before it is transported to grit bins.

Scientists plan investigations to make comparisons and answer questions.

And you've had the chance to do that today as well.

Variables can be changed, measured, or kept the same in a comparative test and in your test today, you've got some variables that you have changed, but you've also got control variables, those variables that you're going to keep the same.

Well, I hope you enjoyed planning this investigation today and I can't wait to see you soon.

Well done for all your hard work and I'll see you again.

Bye.