Video: Food tests

﻿Hi everyone. And welcome to the Oak National Academy science videos. My name is Mr. Humphries and I'm really excited to be helping to guide you through your GCSE science. In this particular set of videos, we'll be looking at the organisation units. So seeing as this is a brand new unit, I'm introducing you to, I want us first to consider what careers, the information we're going to learn will relate to. We're going to be learning all about how the human body works. This information is really important in the field of food science. So food sciences ensure that food is safe and pleasant to eat. And there are even food scientists that make sure that chocolate has exactly the right melting point to melt in your mouth. How the body works is also really important in the field of exercise science, where coaches, personal trainers, and dieticians use their knowledge of the human body to ensure peak performance for athletes. So with that in mind let's get ready to start our lesson. All you're going to need for today's lesson is a pen and some paper. I'll give you the opportunity now to pause the video and get that equipment if you don't have it. Now take a moment to make sure that you're away from any distractions and your phone is on silent. Finally, if you can try and find a quiet place where you won't be disturbed throughout the lesson. So when you're ready, let's begin. Our lesson today is going to consist of three main areas. So firstly, we're going to have a look at the different food groups. Secondly, we're going to have a look at the food tests we can use to identify different foods. And then finally, we're going to have a look upon all of that into some longer answer exam questions. The food we eat can be broken down into three main groups: carbohydrate, protein, and fat. Our first food group is carbohydrates. These are found in bread and in pasta. These carbohydrates are needed for energy. Now these carbohydrates that we eat usually come in two forms. Our first form is starch and our second form is sugar. Our second food group is protein. So protein is usually found in meat and in beans and it's needed by our body for growth and repair. And our final food group is fat. The fats are usually found in cheese or oils. We need these fats for energy. Right then, let's check that we're all still on board. So after three, I want you to point out the correct answer on your screen. So fats are? Three, two, one. And well done. I'm sure you got the correct answer there which is fats are needed for energy. So pasta and bread are examples of food containing what? After three I want you to say the correct answer to your screen. Okay. So three, two, one. And well done if you got carbohydrates there. So pasta and bread are examples of foods that contain carbohydrates. And finally then what do we need protein for? So there's two things that we need something and something. So after three, tell your screen the correct answer. Three, two, one. Brilliant. So we need protein for growth and repair. So now we're all caught up. Let's put that into practise. So pause the video and complete the task using your pen and paper. How did you do? Pause the video and use the completed table to check your answers? We're now going to have a look at food tests. And the first one that we're going to look at is how we test our foods for the presence of starch. But before we do any food tests, we need to make sure that we are keeping safe. So whenever you're doing a food test, you need to make sure that you've got goggles on which will protect your eyes. So now we've got our safety specs on, We can start our test for the presence of starch. The chemical that we use to test for starch is called iodine. What we do, is we add a few drops of iodine to our food and if starch is present, the iodine will turn from orange to blue black. If starch is not present, then there will be no change. So quick check then. The chemical that we use to test for start is... Tell your scream the correct answer after three. Three, two, one. Brilliant Iodine. If starch is present iodine changes from... Three, two, one. Orange. Well done. To... Three, two, one. Blue black. So it's really important, whenever you're describing food tests to say the colour that it changes from and the colour that it changes to. If starch is not present, there will be... Three, two, one. No change. So no change is basically just a fancy scientific way of saying that the colour stays the same. But if you're writing an exam, make sure that you say no change. And now our safety precautions, what we're going to do to keep safe whilst we do this food test. So put in the correct answer. Three, two, one. Brilliant. We need to wear goggles. Now we're going to have a look at how we test our food for the presence of sugar. It's a food test. So before we begin, we're going to make sure that we're wearing goggles. The chemical that we use to test for the presence of sugar is called Benedict's solution. However, unlike iodine, you can't just add Benedict's to the food straight away. What we need to do is grind up the food using a pestle and mortar, and then add that ground up food to a test tube containing Benedict's. We'd then heat that test tube. If sugar is present, the Benedict's solution will change from blue to red. If sugar is not present, there will be no change. Right. Let's check if we've got our main points there. The reagent, which is another name for a chemical, which we use to test for sugar is called what? Point to the correct answer on your screen after three. Three, two, one. Brilliant. It's Benedict's solution. So if sugar is present, Benedict solution goes from... Three, two, one. Blue, to... Three, two, one. Red.Brilliant. It's important to note that if there's only a little bit of sugar present, Benedict's can go a greeny orangy colour. But if you're asked for the food test and the colour change, Benedict's goes from blue to red. And if sugar is not present there will be no change. Brilliant. And our safety precautions when we're working with Benedict's solution.. You're right. Wearing goggles. To test food for the presence of protein, you need to use a chemical or reagent called Biuret solution. Just like Benedict's you can't add it to your food straight away. So you need to grind up your food, using a mortar and pestle, and then you need to add that food to a test tube containing your Biuret solution. You then give that test tube a shake. If protein is present, Biuret solution will change from blue to purple. If protein isn't present, there will be no change. Right. Let's see if you're awake. The chemical we use to test for protein is Biuret solution. Brilliant. If protein is present... And if sugar is not present there will be... And our safe... To test food for the presence of protein. you need to use a chemical or reagent called Biuret solution. Just like Benedict's, you can't add it to your food straight away. So you need to grind up your food, using a mortar and pestle, and then you need to add that food to a test tube containing Biuret solution. You then give that test tube a shake. If protein is present, Biuret solution will change from blue to purple. If protein isn't present, there will be no change. Right. Let's see if you're awake. The chemical we use to test for protein is... Biuret solution. Brilliant. If protein is present, Buiret will change from blue to purple And if protein is not present there will be no change. Brilliant. So the final food test we need to look at is how we test our foods for the presence of fat. The chemical that we use to test for fat is ethanol and water. So we add our food to a test tube containing ethanol and water. And if fat is present, ethanol and water will change from clear and colourless to a cloudy white. If there is no fat present, there will be no change. So how are we doing then? The chemical we use to test for fat is ethanol and water. If fat is present ethanol and water will change from clear and colourless to cloudy white. And if there is no fat present there will be as always no change. Okay. Very quick summary of our food tests to test for starch we use iodine. If starch is present it in turns from orange to blue black. To test for sugar we used Benedict's solution. If sugar is present, Benedict's changes from blue to red. To test for protein we use Biuret solution. If protein is present, Biuret goes from blue to purple. And finally to test for fats, we use ethanol and water. If fats are present, ethanol and water will go from clear and colourless to cloudy white. Okay then, pause the video and complete the task using your pen and paper. Let's see how we did. Use the completed table to check your own answers. Okay, we now going to have a look at some long answer exam questions. To begin with, I'm going to talk you through how I would answer the following question. The question says, describe the method for testing for fat. To get the first mark, we need to talk about the chemical that we use. So to test for fat, we use ethanol and water. For the second mark, we need to say how we use this chemical. So for our second mark, we'll say we add the food to a test tube containing ethanol and water. For our third mark, we need to say what happens if fat is present. If fat is present, ethanol and water changes from clear and colourless to cloudy white. Remember you need to say from and to. For our fourth mark, we need to say what happens if fat is not present. So if that is not present, there will be no change. And for our fifth mark, we need to describe the safety precautions. So as a safety precaution, we should wear goggles. Let's have a look at a different question now. This time the question says, describe the method for testing for sugar. It's a different question, but the way that we answer it and the way that we structure our answer is going to be very similar. So again, for the first mark, we need to say what chemical or reagent we use. So to test for sugar, we use Benedict's solution. The second mark, we need to say how we use that chemical. We add the food to a test tube containing Benedict's. For our third mark, we need to describe what happens if sugar is present. If sugar is present Benedict's changes from blue to red. For our fourth mark, we need to say what happens if sugar is not present. If sugar is not present there will be no change. For our fifth mark, we need to describe our safety precautions. So as a safety precaution we should wear goggles. Okay then, let's have a go at putting that into practise. Pause the video and complete the task using your pen and paper. If you're struggling, there's some help coming up on the screen now. So let's see how we did. Pause the video and use the complete answers on the screen to check your own answers. So we've done really well and learned a lot of new information today. So let's just have a quick recap of what we learned. There are three main food groups: carbohydrates, proteins, and fats. Food tests can be used to test for the presence of different foods such as: starch, sugar, protein, and fat. Finally, we put all this together and had a look at some long answer exam questions. So that just about does it for today's lesson. Well done for completing this video. I'm certain that all your hard work will pay off when it comes to your exams. So just one more thing before you go, make sure you click the next button and complete the post lesson quiz. See you next time.

Exit Quiz: Food tests

Completed: Food tests

This lesson will look at the different food groups and how we can test for the presence of different foods.

Combined Science

Food tests

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Final Quiz

Lesson Complete