Lesson video

Hello, my name is Miss Couves.

I am so excited to be teaching you science today.

We have learnt so much in our lessons about chemical and physical changes.

Today, we are going to be looking at what happens when we react metals with acids.

We are also going to look at what makes our results from experiments repeatable and reproducible.

Scientists want their results to be repeatable and reproducible as it means they can be more confident in the conclusions that they make.

Let's get started.

In today's lesson, we will be looking at what makes results repeatable.

Then we will look at what makes our results reproducible.

We will end by investigating the reactivity of metals and checking to see if our results are repeatable and reproducible and what conclusions we can make as a result.

In today's lesson, you will need an exercise book and a piece of paper, and a pencil.

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

Press play when you're ready to start.

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're touching and arranged randomly.

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

As you increase the temperature, particles have? More energy.

Let's recap on our knowledge of state changes.

Pause the video and write down the four state changes that we have learnt.

When a gas becomes a liquid, it's called? Evapo.

When a gas becomes a liquid, sorry about that, when a gas becomes a liquid, it's called condensing.

When a liquid becomes a solid, it's called? Freezing.

When a solid becomes a liquid, it's called? Melting.

And when a liquid becomes a gas, it's called? Boiling.

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

Why is paper tearing an example of a physical change? Paper tearing is an example of a physical change because the form of the paper has changed from a large sheet to many tiny pieces.

The type of substance hasn't changed.

It's still paper.

Pause the video and write down why ice cream melting and glass smashing is a type of physical change.

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

Can you remember three examples of chemical changes? Our three examples of chemical changes were wood burning, cakes baking, and a bike rusting.

Let's think about wood burning.

When wood burns, it produces carbon dioxide and water.

Two new substances have been produced so this is an example of 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 bike rusting is an example of a chemical change.

There are three things we might see if a reaction happens.

There are: bubbles forming, a colour change, and a temperature change.

When a bike rusts, what do we see happen? We see a colour change from the silver metal to a dull orange substance.

When metals react with acid, what do we see? When metals react with acid, we see bubbles forming, so we know chemical reaction has taken place.

The independent variable is the thing that you'd change.

The dependent variable is the thing that you measure.

And the control variables are the things you keep the same.

In an experiment, how many things can you change? In an experiment, you can only change one thing because you need to make sure your investigation is a fair test.

Now let's look at what makes results repeatable.

Results are repeatable if the same person gets the same results when they do the experiment again.

When are results repeatable? Results are repeatable if the same person gets the same results when they do the experiment again.

Pause the video and write down what makes results repeatable.

Press play when you're ready to continue.

We're going to look at whether these results are repeatable.

In this experiment, the scientist is investigating the conditions on a plant's growth.

Are these results showing the same pattern? In trial one and trial two, the results are very similar.

In trial three, the result for no water seems unusually high.

We call this result an anomaly.

Scientists ignore anomalies when looking at the pattern.

Because the results in the three trials, excluding the anomaly, showed the same pattern, these results are repeatable.

The same person has found the same thing when they repeated the experiment.

These trials show that a plant with water and sunlight grows more than a plant with no water and no sunlight.

What makes these results repeatable? These results are repeatable because the same person has found the same thing when they repeated the experiment.

Now let's look at what makes results reproducible.

Results are reproducible if a different person gets the same result when they do the experiment.

What makes a result reproducible? Results are reproducible if a different person gets the same result when they do the experiment again.

Pause the video and write down what makes results reproducible.

Press play when you're ready to continue.

Let's look at this results table.

Are these results reproducible? In this experiment, we can see that three different people have done the experiment.

Have they got a similar result? Person A and Person B seem to have very similar results, but Person C seems to be different.

It looks like Person A and Person B have reproducible results.

But because of Person C, we're not sure of the pattern.

What can we do to be absolutely sure? We could ask someone else to try the experiment and see what kind of results they get.

Now we're going to do our own investigation into metal reactivity.

In order to be able to draw a conclusion, we need our results to be repeatable and reproducible.

What does the word repeatable mean? Results are repeatable if the same person repeats the experiment and finds the same thing.

What makes results reproducible? Results are reproducible if a different person conducts the experiment and finds the same thing.

Pause the video to copy the results table into your notes.

Press play when you're ready to start.

I am going to do the experiment twice.

Why do you think I have decided to do the experiment twice? I've decided to do the experiment twice to check my results are repeatable.

I have also asked my friend Kirsty to complete the experiment.

Why do you think I have asked her to do the experiment too? I've asked her to do the experiment too to check that my results are reproducible.

Are you ready? This experiment is not an experiment that you can try at home.

You need to follow me and watch really carefully to see the results that I get.

We are doing an experiment to find out about the reactivity of three different metals: magnesium, copper, and nickel.

I'm going to react each of the metals with acid and record the amount of bubbles.

I am repeating my experiment twice to make sure my results are repeatable.

In order to make sure my experiment is a fair test, I am going to have some control variables.

I am going to put one piece of metal into each test tube, and then I'm going to add the same amount of acid.

I'm putting my magnesium into the first test tube.

Oh, might be tricky.

Oh, it might be easier with my, let's get to the bottom.

Okay! I'm going to add nickel to the second one.

Bit tricky to just get one piece on my spatula.

There we go.

Nickel is in the second one.

So I have magnesium in the first test tube and nickel in the second test tube.

Finally, I'm going to add copper to my third test tube.

Oh, that was much easier, wasn't it? I'm going to add the same amount of acid to each test tube.

And watch what happens.

Can you see that magnesium is producing lots of bubbles and it's reacting vigorously? Nickel is producing some bubbles but many less than magnesium.

Copper is producing no bubbles.

It is not reacting with magnesium.

It is not reacting with acid.

We need to try our experiment again.

You should have recorded the results for trial one in your table.

Magnesium produced lots of bubbles.

Nickel produced a few bubbles.

And copper produced no bubbles.

Okay, I've cleaned my test tubes so that we can have another go.

Remember, we are repeating the experiment so that we can check our results are repeatable.

I'm going to add one piece of metal to each test tube.

I'm going to put magnesium in the first test tube, nickel in the second test tube, and copper in the third test tube.

I'm going to add the same amount of acid to each test tube.

Then I'm going to observe and write down my results.

If I look carefully, I can see that copper is not reacting with acid.

Nickel is producing a few bubbles, but not very many.

Magnesium is reacting vigorously with acid.

Which of my metals was the most reactive in trial two? Magnesium was the most reactive in trial two.

Which was the most reactive in trial one? Magnesium was also the most reactive in trial one.

Do we think that our results are repeatable? Our results are repeatable.

We found the same thing in both trials.

Add Kirsty's results to your table.

Did Kirsty find the same thing that we did? Question one, which metal was the most reactive and how did you know? Question two, which metal was the least reactive and how did you know? Question three, were our results repeatable and how did you know? Question four, were our results reproducible and how did you know? Pause the video and answer the questions in full sentences.

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

Magnesium was the most reactive metal as it produced the most bubbles.

Copper was the least reactive metal as it produced the least bubbles.

Our results were repeatable as we found the same pattern in trial A and trial B.

Our results were reproducible because our results and Kirsty's results showed the same pattern.

Pause the video to tick and fix your answer.

Well done for all of the hard work that you've done in this unit.

If you'd like to, please ask your parent or carer to share your work on Instagram, Facebook, or Twitter by tagging @OakNational and #LearnwithOak.

I have really enjoyed teaching you science in this unit.

We have learnt so much about physical and chemical changes, and we've done some of our own investigations.

See you next time!.