Hello there.

My name is Mr. Wilshire.

In this lesson, we're going to be looking at growing yeast, and this is our do and review stage.

Let's jump into the lesson.

Our outcome for this lesson is to carry out and evaluate an investigation to find out about food sources for microorganisms. There are different keywords that will come up throughout the lesson.

I'm going to say them, and I'd like you to repeat them.

The first one is yeast.

The second one is carbon dioxide.

Great.

Next up, fermentation.

Now, conclusion.

And finally, evaluation.

Here are some of the definitions for the different keywords.

You may have come across some of these words before, and so you may know what they mean.

But if you're not too sure, you can pause the video here and continue when you're feeling a bit more confident with them.

Let's dive straight into the lesson then.

The first part of our lesson is called "Investigating food sources for yeast." Now, yeast is a type of fungus which releases carbon dioxide gas when it consumes food.

This is called fermentation.

Fermentation is really useful for baking because the carbon dioxide bubbles that are produced cause bread dough to rise.

You can see in the picture there a picture of some bread dough that is rising.

Now, Lucas here planned a fair test.

His investigation was to answer this question: Which food source is the best for yeast? You can see a picture of his investigation there.

It says that he's going to add some different food sources, salt, sugar, flour, and oil, to bottles with some warm water and yeast.

Remember that yeast needs to be warm in order to start fermenting.

Then he's gonna add a balloon to the top of each one to see how much carbon dioxide is produced in each one.

So all that carbon dioxide bubbles are going to bubbling away at the bottom of the bottle, and it's going to rise to the surface and hopefully inflate the balloon.

In a fair test investigation, scientists must control different variables carefully to make sure that their results show the effect of just one variable.

It's no good doing an investigation when you don't have any control over some of the variables.

So apart from the one variable that's being investigated, all others are kept the same.

Lucas says, "The variable that I will change is the type of food source." So that means he's going to have the same amount of yeast, the same amount of water, the same type of bottles, and he's got to make sure that he puts those bottles in the same places, or otherwise he might get different results and we don't know what the true answers are.

So let's stop and think at this point in our lesson.

Which of these variables that could affect the production of carbon dioxide by yeast does Lucas need to keep the same across his inquiry? Is it the amount of yeast, the temperature of the water, the type of food source, or the amount of food? Pause the video here, and continue when you've had your discussion.

The answer here, well, there's three different answers.

It's the amount of yeast, the temperature of the water, and the amount of food.

All of those things need to keep the same, or otherwise he's going to get different results.

The type of food source is the one thing that's going to be different each time.

Lucas needs a way to record the results of his inquiry.

There's Lucas again, look.

He's going to observe his balloons after 10, 20, and 30 minutes to see how much carbon dioxide has been produced in each bottle.

That's a good amount of time, isn't it? There's 10-minute intervals in the times that he's going to be checking.

Now, he's also going to measure the height of the froth, which are the bubbles at the top of the mixture in each bottle.

So, have a think here.

What type of diagram would be useful for recording these results? Pause the video, and discuss this question.

Restart when you're ready.

So, I wonder what kind of diagrams you came up with.

There's lots of different type of diagram that you could have chosen.

Some of them are colourful, some of them are large, but the main important thing is that they need to be useful to read the results.

Lucas decides to draw a table in this case, a table to record his results.

One heading at the top there says food.

Then he's got observation after 10 minutes, then 20 minutes, then 30 minutes.

So each column is showing a different time.

Then each row is showing a different food source.

This is going to allow him to quickly record his observations in a really organised way.

He's going to be able to work quite systematically here, isn't he? He's going to be able to record each thing after each step he takes.

Let's pause and think again.

Why has Jacob made a table to record his results? He really could have chosen any type of table here to record his results, but why specifically a table? Is it just because his teacher told him to? Not sure.

Have a discussion, and restart the video when you're ready.

Let's look at the answers.

Well, it's because he wants to be able to record his results quickly and clearly.

The answer to A, because his teacher told him to, isn't quite right here, is it? And C, because he wanted it to look attractive, that's not right either.

It doesn't matter how good it looks.

What matters is that he's able to get the results quickly, clearly, and he's able to understand it.

So, here's the first task for this lesson.

The first part here of this task says to create a table for recording your results.

Make sure that you include some space for any observations that you're planning to make.

That's a good point.

You need to take lots of notes when you're doing different observations and different investigations because you might not remember them later.

The second part of this task is to set up and carry out a fair test investigation to find which food source is the best for yeast.

You can use your own investigation plan here or the one that Lucas has done.

Remember, you need to control all of the variables so that only the one you are investigating changes.

So let's take a look at some different ways you could do the investigation.

Step one here says to add a sticky label to name each bottle.

That's a good idea.

Now we know what food source is going to go in each individual bottle.

The second part there says to add 150 millilitres of warm water to each bottle using a funnel.

Of course, if we don't use a funnel, it might spill out over the edges, and then we won't know how much is inside.

Step three says to add two teaspoons of yeast to each bottle using a funnel.

Same rules apply there.

And step four, add one teaspoon of each of the different food sources to the correctly labelled bottle, flour, sugar, salt, and vegetable oil.

But your investigation might be slightly different.

Use a clean funnel for each food source.

That's really important as well.

We don't want to cross-contaminate the different types of food, do we? Step five, give the bottles a gentle swirl to mix the ingredients together.

Then step six, you've got to add a balloon to each of the bottle and leave them together in a warm place.

There was a really good reason, wasn't there? Oh, yes, yeast needs to be warm in order to start fermentation.

Step seven says to make observations of each bottle after 10, 20, and 30 minutes.

Well, those are the different steps for your investigation.

I'd like you to pause the video here and continue once you've had a go.

Best of luck.

Right, let's dive into some answers then.

It said to set up and carry out a fair test investigation into which food source is the best for yeast.

You can see there in these pictures, after 10 minutes, after 20 minutes, and then after 30 minutes.

I wonder if you can see what I can see here.

Yeah, I think there's one very clear winner that created the most carbon dioxide.

Lucas says, "Here are my results.

Are they similar to yours?" Well, I wonder because we didn't actually write down the exact temperature that the room was.

Lucas's room might have been slightly warmer or colder than yours, so there may be some discrepancies there in the results that you get.

Here is Lucas's table.

You can see there that the salt, there was no change to the balloon at the beginning, then not much change, and still no change at the end, but there was some difference to the froth.

Sugar, the balloon inflated a very small amount after 10 minutes.

Then after 20 minutes, the balloon was standing upright, and then after 30 minutes, the balloon was more inflated and taller than before.

With the flour, there wasn't much change to the balloon at all, but there was a little bit of froth that started to build.

Then the vegetable oil, there was no change to the balloon at all, and no froth.

Hmm, so the vegetable oil didn't really seem like the best kind of thing to use in this situation.

So hopefully, looking at those different answers there, you've got some pretty good results that you can compare with, and you can start to make some of your own decisions and wrap up your investigation.

Was there a clear food source that created more carbon dioxide there? So which of the food sources is going to be best for the yeast? Let's dive in to the next part of our lesson, "Making conclusions." Now, when they've completed an investigation, scientists look at their results and make a conclusion based on what they found.

In their conclusion, they try to answer the investigation question by saying what happened and what this shows.

There's no point doing an investigation unless you're going to prove something or go through the answers.

Our investigation question was: Which food source is best for yeast? Remember, in the last section, I challenged you just to have a little think about the things that you'd seen in your investigation.

So, we're going to go through that question now and decide for ourselves what food source is the best.

Now, what can Lucas conclude from his results here? Here's Lucas again, and he says, "My conclusion is that the pink balloon inflated the most." Yeah, that is a good conclusion, isn't it? It definitely inflated the most, but it's not very scientific as an answer, is it? Has Lucas answered his inquiry question here? Have a discussion, and restart the video when you're ready.

I wonder what kind of discussions you had and if you were able to make some conclusions of your own.

Lucas hasn't really answered the question here, has he? Yes, the balloon is inflated the most, but what does that tell us? What does the balloon actually inflating more actually tell us about this answer? Izzy here had some results that were quite different.

"None of my balloons inflated," she said.

"My inquiry went all wrong, and I don't think I can make a conclusion from my results." Hmm, let's have a look there.

Salt there, there was no change.

Sugar, there was no change.

Flour, there was no change.

And vegetable oil, there was no change.

But there was a little bit of froth in each.

One of them had more froth than the other.

Do you agree in this situation? Discuss with someone nearby.

Restart when you're ready.

Well, I wonder what you discussed.

I wonder if you agreed with Izzy here that she wasn't able to make any conclusion at all.

So Izzy's inquiry didn't exactly work out how she thought it would and not like some of the other people in the class.

She couldn't make any observations of balloons growing, but she can still use the results here to make some sort of conclusion.

There were, just like I said, different amounts of froth in each bottle.

That shows that some sort of fermentation took place, more in some and less than in others.

Maybe in Izzy's experiment, the balloon wasn't quite tied on correctly.

And this is why it's a good idea to have lots of different investigations of the same thing happening at the same time, just in case a silly mistake like that happens and you don't attach the balloon in the correct way.

Let's stop and think then.

Which of these are included in a conclusion? Have a read of those statements, and restart the video when you've made your decision.

So the statements that are correct here are an explanation of what happened during an inquiry and an answer to the investigation question.

That's why Lucas's wasn't quite right.

He just said, "The balloon is inflated." You don't need to include equipment, and you don't need to include instructions.

You would have done that before.

So, here's the next task in our lesson.

Use your results here to write a conclusion about your investigation.

Remember to explain what happened, and try to answer the investigation question based on your findings.

Don't worry here if some of your investigation findings were different to someone else's.

Look at your own investigation and decide, what does it tell you? Lucas says, "Which food source is the best for yeast?" That was the question.

So have a look at your answers here and decide, how does it tell you? Pause the video here, and continue when you've done that.

So, you had to use your own results here.

Lucas says that this is his conclusion.

He wonders if it's similar to yours.

You might have written a little bit less but maybe included a bit more detail.

"In my investigation," says Lucas, "three of the food sources had froth at the top of the mixture, salt, sugar, and flour.

I think this means that yeast was able to feed on these three food sources because the froth is evidence that carbon dioxide was produced.

The balloons for the flour and sugar also inflated, which gives me further evidence of fermentation." Oh yes, the gas was able to rise in the bottle, wasn't it? "The sugar had the most froth and the largest balloon by a long way, so I can conclude that the sugar was the best food source for yeast.

Nothing seemed to happen to the bottle containing vegetable oil.

I think that this means that yeast doesn't feed on vegetable oil, and so no fermentation took place in that bottle." That's a really good conclusion there.

He's summarised everything that's happened, even the one that didn't seem to work.

Remember, when you are doing your own science experiments, the failures can often lead to a really good success story, so it's always a good idea to write about the failures as well and decide why those things failed.

Let's move on to the next part of our lesson.

The final part is called, "Evaluating investigations." So, Izzy and Lucas's investigations went quite differently.

We didn't really get a chance to look at Izzy's results properly before.

They were both able to make a conclusion that sugar was the best food source for yeast out of all the ones that they tested using all the evidence that they gathered.

You can see there on the left-hand side, there's Izzy's sugar result, and on the right is Lucas's sugar result.

One of them is definitely more inflated than the other.

Scientists will need to evaluate their investigations to help them decide how reliable their results are.

When they're evaluating an inquiry, they will need to think about: Were they able to successfully control all the variables? Did anything go wrong that could have affected their results? Was there anything they could have done better? And did they gather enough data to answer the inquiry question? So those four things are really important, aren't they? The scientists will need to think, if something did go wrong, was it because they weren't able to control a variable in some sort of way? Well, I think in Izzy's case, the balloon either had a hole in it or maybe it wasn't connected properly.

But it's still important to write down what you noticed.

Lucas and Izzy are evaluating their investigations, another really important part of an investigation process.

Izzy says, "I think my group did a good job for controlling all the variables.

We were able to make sure the amounts of food, water, and yeast were all the same, and the temperature of the water was the same." Lucas says, "Well, my group didn't manage to get all the bottles set up at exactly the same time.

This means that some of them had longer to ferment than others.

This could have affected my results." So, in your investigations, did you manage to control all your variables? Have a quick discussion.

If you didn't, decide what you think went wrong and why.

Pause the video here.

Restart when you're ready.

So, I wonder then, from those discussions, was there anything else that you could have done better when carrying out your investigation? Hopefully you've had a good chance to discuss there and decide.

Well, Izzy says, "I don't think we had properly secured our balloons onto our bottles." That's what I thought had happened as well.

"Maybe we could have checked that they were on tightly or added some sticky tape to be sure." Lucas says, "Maybe we could have invited more people into our group so we could start all of our bottles fermenting at exactly the same time." Well, yeah, four bottles, four people, each filling things up at the same time, is going to make sure that everything is done in the right order and at the same time.

Did you gather enough data to answer the question: Which is the best food source for yeast? Have a quick discussion here.

Were you able to answer this question? Have a discussion.

Restart the video when you're ready.

Well, I wonder if your discussions were similar to Lucas and Izzy here.

Lucas says, "We were able to see which was the best food source out of the ones that we tested.

We could get an even better answer to our question if we tested even more different types of food source." Hmm.

Izzy says, "Even though my balloons didn't inflate, I was able to gather some data because I measured the froth on top of each mixture." So both of the children there have had a really good think about their investigations and their experiments and had a really good think if they really were able to answer the question.

Even though something went wrong, they know what went wrong and what results would help answer anyway.

Let's pause and think.

Which of these things should scientists think about when they're evaluating their inquiries? Pause the video, read the statements, and continue when you're ready.

The answer here is B and D, how well they controlled the variables and whether their results give them enough information to answer their investigation question.

How quickly they were able to set it up and how much mess they made, that's not really something we needed to evaluate, unless, of course, we needed to keep things tidy all the time.

So, the final task for our lesson is to evaluate your investigation with your group.

You need to think about four things here.

Were you able to successfully control the variables? Did anything go wrong that could have affected your results? And was there anything you could have done better? Did you gather enough data to answer the investigation question? Pause the video, have some discussions about this, and then write up your own conclusion about this task.

Pause the video, and continue when you've done that.

Excellent, your answer might look a little something like this.

We used water from different taps, hot and cold, for our bottles.

This could have affected our results, so we didn't manage to control the temperature of the water very well.

We made sure that we used the same amount of yeast, water, and food sources, so we controlled our other variables well.

We could have used water from the same jug instead, and this would have meant that the temperature of each bottle was the same.

We were only able to test four food sources for yeast.

I didn't think this is enough to say which is the best food source for yeast out of all possible food sources, but we know which is the best out of these four.

Well, you could have an experiment that goes on for days using every type of food source, couldn't you? So, yeah, I think they know out of those four, they've got a good result, but it doesn't give the answer for every type of food source in the world, does it? Let's summarise our learning then.

Yeast is a type of fungus that consumes sugar and releases carbon dioxide.

This is called fermentation.

Fermentation can then be observed over time and recorded in a table so it's clear and easy to read.

Scientists carry out their fair test investigations to see the effect of changing one variable while keeping all the others the same.

And after carrying out an inquiry, scientists make a conclusion by using their results to try and answer their original investigation question.

They also evaluate their investigation by thinking about how well it went and how reliable their results are.

Sometimes, the best kind of answers that you'll get will be out of things that go wrong.

Without something going wrong, you won't be able to get it better next time.

As long as you keep learning from your mistakes and you keep on improving, you'll be able to get better and better results.

I hope that you've enjoyed this investigation and really looking into some of your results and evaluating how well you did so you can do better next time.

I've been Mr. Wilshire.

Thank you very much for listening.