0:00:05 > 0:00:08# If you've got a question and you don't know where to go
0:00:08 > 0:00:11# Ask Nina for some help Cos she's got a science show
0:00:11 > 0:00:15# She makes sense of her senses While helping all her fans
0:00:15 > 0:00:17# By doing her experiments with potions and with bangs
0:00:17 > 0:00:19- # Touch your tongue - Tongue!
0:00:19 > 0:00:20- # Fingers - Fingers!
0:00:20 > 0:00:23- # Eyes.- Eyes! - Ears.- Ears!- Nose.- Nose!
0:00:23 > 0:00:26# Nina and the Neurons find out what you need to know
0:00:26 > 0:00:29# Nina and the Neurons find out what you need to know
0:00:29 > 0:00:32# Luke, he helps us with our eyes and Felix with our touch
0:00:32 > 0:00:35# Ollie sniffs out smells And Belle, she hears so much
0:00:35 > 0:00:38# Bud is Ollie's brother He helps us with our taste
0:00:38 > 0:00:41# They're Nina's little Neurons And they're coming to your place!
0:00:41 > 0:00:43- # Touch your tongue - Tongue!
0:00:43 > 0:00:44- # Fingers - Fingers!
0:00:44 > 0:00:48- # Eyes.- Eyes! - Ears.- Ears!- Nose.- Nose!
0:00:48 > 0:00:50# Nina and the Neurons find out what you need to know
0:00:50 > 0:00:53# Nina and the Neurons find out what you need to know
0:00:53 > 0:00:54# Oh yeah! #
0:00:55 > 0:00:57Ooh...
0:00:57 > 0:00:59Oh, hello!
0:00:59 > 0:01:03I'm seeing how big my eyes look through a magnifying glass.
0:01:03 > 0:01:06What do you think? Pretty EYE-mazing!
0:01:06 > 0:01:07Woooo...
0:01:07 > 0:01:10BLEEPING
0:01:10 > 0:01:14I hear a beep, I see a flash, I wonder what they're going to ask.
0:01:15 > 0:01:17BOTH: Hi, Nina!
0:01:17 > 0:01:18Hi, guys.
0:01:18 > 0:01:23We've got a question for you. Why do onions sometimes make us cry?
0:01:23 > 0:01:26That's a great question. Why do onions sometimes make us cry?
0:01:26 > 0:01:28So why don't you come down to the lab
0:01:28 > 0:01:30and we'll do some experiments to investigate?
0:01:30 > 0:01:35- See you soon, Nina. Bye!- Bye!
0:01:35 > 0:01:37I'm going to need some help to answer this one
0:01:37 > 0:01:39and I know just who to ask.
0:01:39 > 0:01:41OK, Neurons. Time to get to work.
0:01:57 > 0:02:00- ALL:- Neurons at the ready, Nina!
0:02:00 > 0:02:05OK, today's question is, "Why do onions sometimes make us cry?"
0:02:05 > 0:02:09Now, which neuron do you think would be most useful in helping us find the answer?
0:02:09 > 0:02:11- Me!- Me!- Me!
0:02:11 > 0:02:14Will it be fabulous Felix?
0:02:14 > 0:02:18I can help so very much, if you need the sense of touch.
0:02:18 > 0:02:20Will it be beautiful Belle?
0:02:20 > 0:02:22I send messages to brain from ear.
0:02:22 > 0:02:25If there's a sound, I'll help you hear.
0:02:25 > 0:02:26Will it be lovely Luke?
0:02:26 > 0:02:28For looking and seeing, day or night,
0:02:28 > 0:02:31I'll help you with your sense of sight.
0:02:31 > 0:02:33Will it be...awesome Ollie?
0:02:33 > 0:02:35If it's pongy or whiffy but you can't tell,
0:02:35 > 0:02:37my messages help your sense of smell.
0:02:37 > 0:02:39Or will it be baby Bud?
0:02:39 > 0:02:41Sour, salty, bitter or sweet,
0:02:41 > 0:02:44I'm your taste buddy whenever you eat.
0:02:47 > 0:02:51It's Luke!
0:02:51 > 0:02:57Go, Luke! Go, Luke! Go, Luke!
0:02:57 > 0:02:59Cool, Nina.
0:02:59 > 0:03:02I'll be looking out to help you.
0:03:02 > 0:03:06Today's question is, "Why do onions sometimes make us cry?"
0:03:06 > 0:03:11Because we cry with our eyes, Luke, our sight neuron, will help us.
0:03:11 > 0:03:16Right, I need to get the lab ready before the experimenters arrive.
0:03:16 > 0:03:20Matthew likes gardening. His friend, Tia, loves horses.
0:03:20 > 0:03:24But they both want to find out more about nippy onions.
0:03:24 > 0:03:27So today, for one day only, Matthew and Tia become...
0:03:27 > 0:03:29the experimenters!
0:03:31 > 0:03:34- Hi, guys. - Hi, Nina.
0:03:34 > 0:03:35Welcome to my lab.
0:03:35 > 0:03:39Your question is, "Why do onions sometimes make us cry?"
0:03:39 > 0:03:42- Which is a really good question. - SHE CRIES
0:03:42 > 0:03:44why do you want to know?
0:03:44 > 0:03:48Because sometimes, when my mum chops the onions, it makes me cry.
0:03:48 > 0:03:51Yes, sometimes when I'm chopping onions,
0:03:51 > 0:03:53it makes my eyes feel a bit nippy too.
0:03:53 > 0:03:57So I think we need to investigate to find out more.
0:03:57 > 0:03:59And for our first experiment, we're going to use our senses!
0:03:59 > 0:04:03Woo-woo! A senses experiment!
0:04:03 > 0:04:04We're ready, Nina.
0:04:04 > 0:04:06So here we have some onions.
0:04:06 > 0:04:10So let's have a feel of an onion and see if it makes us cry.
0:04:10 > 0:04:12OK, have a good feel.
0:04:15 > 0:04:18- Any tears yet?- No.
0:04:18 > 0:04:20No. Maybe we should sniff the onion,
0:04:20 > 0:04:24because onions sometimes smell quite strong. OK? Here we go.
0:04:25 > 0:04:29That's strange. Onions are normally very whiffy,
0:04:29 > 0:04:31but I can't smell much at all.
0:04:31 > 0:04:33Can you smell anything?
0:04:33 > 0:04:35- No.- No.
0:04:35 > 0:04:37And we're not crying, either.
0:04:37 > 0:04:40I think you need to chop them up, Nina.
0:04:40 > 0:04:43Oh, Matthew - I think you might be onto something there.
0:04:43 > 0:04:47OK, I'll try and chop this one up.
0:04:47 > 0:04:51Now, remember, you should never try this yourself at home.
0:04:51 > 0:04:53Knives can be very sharp.
0:05:02 > 0:05:03Oh, dear.
0:05:03 > 0:05:06I'm definitely starting to cry now.
0:05:06 > 0:05:10Yes, the tears are starting to flow. Ooh.
0:05:10 > 0:05:14Ooh. What about you guys? Do your eyes feel a bit nippy, a bit runny?
0:05:14 > 0:05:15A little bit.
0:05:15 > 0:05:21So, onions only make us cry when we chop them up.
0:05:21 > 0:05:22But you guys are quite far away.
0:05:22 > 0:05:26So how can they still make us cry when they're not even near our eyes?
0:05:26 > 0:05:32I think we need to have a really close look at some onions.
0:05:32 > 0:05:37This is a microscope. It makes small things look much bigger
0:05:37 > 0:05:39and helps us see them better.
0:05:39 > 0:05:43This is what a piece of onion looks like to us normally,
0:05:43 > 0:05:46and this is what it looks like underneath the microscope.
0:05:46 > 0:05:50An onion is made up of lots of tiny pockets of onion juice.
0:05:50 > 0:05:52These pockets are called cells.
0:05:52 > 0:05:56Can you see the cells under the microscope? What do they look like?
0:05:56 > 0:06:00- They look like some wonky sausages. - Wonky sausages!
0:06:00 > 0:06:02You're right, actually.
0:06:02 > 0:06:04Well, who'd have thought it?
0:06:04 > 0:06:07There's so much more to an onion than meets the eye.
0:06:07 > 0:06:10Imagine this is the onion cell we've been looking at
0:06:10 > 0:06:12under the microscope.
0:06:12 > 0:06:15So let's see what happens if we cut into it.
0:06:15 > 0:06:17I'm going to be using a knife but remember,
0:06:17 > 0:06:18you should never touch sharp knives.
0:06:18 > 0:06:22Safety goggles on! Woo-hoo!
0:06:22 > 0:06:25OK, here we go.
0:06:25 > 0:06:27Three, two, one!
0:06:29 > 0:06:31NINA LAUGHS
0:06:31 > 0:06:35So, when we cut into an onion cell, it breaks open
0:06:35 > 0:06:38and the onion juice inside squirts up into the air.
0:06:38 > 0:06:43When you cut the real one, I didn't see any juice squirt in the air.
0:06:43 > 0:06:46Ooh, that's right, Tia. I wonder why not.
0:06:46 > 0:06:51Oh, I think we need to take a trip to somewhere really warm.
0:06:53 > 0:06:59Oh, goody! I love this bit. I wonder where Nina is taking us?
0:06:59 > 0:07:05Nina said we were going on a trip to somewhere warm.
0:07:05 > 0:07:07Maybe we're taking a little holiday.
0:07:15 > 0:07:17Have you guessed why we're here yet?
0:07:17 > 0:07:19That thing looks like a giant onion!
0:07:19 > 0:07:23It does, a bit, Tia, but it's actually a great big greenhouse
0:07:23 > 0:07:27called a biome, and it's where we're headed to now. Let's go.
0:07:38 > 0:07:41Whoo! I told you it'd be warm, didn't I?
0:07:41 > 0:07:44- Yeah, it's really warm in here.- Yeah.
0:07:44 > 0:07:46They have to keep this place really warm,
0:07:46 > 0:07:49because all these plants only grow in warm countries.
0:07:49 > 0:07:52Let's explore!
0:08:04 > 0:08:08Wow, it's just like the jungle! Watch out for the lions, Nina!
0:08:10 > 0:08:13I don't think there are any lions in here, Bud.
0:08:13 > 0:08:15Oh, but I can hear something.
0:08:15 > 0:08:17Oh, there's a funny hissing noise.
0:08:17 > 0:08:21I told you! Maybe it's a jungle snake!
0:08:21 > 0:08:24- HISS - Can you hear that hissing noise?
0:08:24 > 0:08:27- Yes.- Yes. I think it is coming from that black thing over there.
0:08:27 > 0:08:28I think you're right.
0:08:28 > 0:08:32The hissing noise is coming from that black pole.
0:08:32 > 0:08:33That's called a mister,
0:08:33 > 0:08:37and it does a very important job for the plants all around it.
0:08:37 > 0:08:41As well as heat, these plants need water to live and grow.
0:08:41 > 0:08:45So the mister sprays out lots of tiny drops of water
0:08:45 > 0:08:47into the air around the plants.
0:08:47 > 0:08:50The droplets are so tiny that it's very hard to see them,
0:08:50 > 0:08:53and this is the same with the onion juice.
0:08:53 > 0:08:56It's being sprayed into the air when we chop the onion
0:08:56 > 0:08:58and travels up to our eyes,
0:08:58 > 0:09:02but the droplets of juice are so tiny that we can't even see them.
0:09:02 > 0:09:05But why does onion juice make us cry, Nina?
0:09:05 > 0:09:08Ooh. I think we need to get out of the jungle
0:09:08 > 0:09:12and go back to the lab. It's time for one final experiment. Let's go!
0:09:14 > 0:09:18So, your question was, "Why do onions sometimes make us cry?"
0:09:18 > 0:09:20So far we've found out that an onion is made up
0:09:20 > 0:09:24of lots of tiny pockets, or cells, full of onion juice,
0:09:24 > 0:09:27and when we cut into an onion, these cells break open
0:09:27 > 0:09:32and the onion juice squirts into the air, in very fine droplets
0:09:32 > 0:09:34that are really hard to see.
0:09:34 > 0:09:36But we still don't know why onions make us cry.
0:09:36 > 0:09:38So let's get experimenting!
0:09:38 > 0:09:41OK, guys, we've all got our safety goggles on,
0:09:41 > 0:09:44and this is because we're going to be using onion juice,
0:09:44 > 0:09:46and it's a bit stingy.
0:09:46 > 0:09:51So, in front of you on your clamp stands you have two test tubes.
0:09:51 > 0:09:54In one of the test tubes we have onion juice
0:09:54 > 0:09:56and in the other test tube is something else,
0:09:56 > 0:10:02which looks clear, and these beakers contain a special liquid.
0:10:02 > 0:10:06You need to put ten drops of this liquid into each test tube.
0:10:06 > 0:10:07Off you go.
0:10:09 > 0:10:10Lovely.
0:10:16 > 0:10:19Excellent, guys. Now, give them a good stir.
0:10:25 > 0:10:28The onion juice has turned pink!
0:10:28 > 0:10:30The onion juice has turned pink
0:10:30 > 0:10:33because it's what we scientists call an acid.
0:10:33 > 0:10:37Some acids are very strong and would be dangerous to eat
0:10:37 > 0:10:41but some acids are quite weak. Onion juice is a weak acid,
0:10:41 > 0:10:44and so is lemon juice, and vinegar.
0:10:44 > 0:10:48They're safe to eat but they'd be a bit stingy in your eyes.
0:10:48 > 0:10:53- What's happened to the clear liquid? - It has gone gold.
0:10:53 > 0:10:55That's right - the clear liquids have turned a goldy yellow
0:10:55 > 0:10:58and that tells us that they're not acids.
0:10:58 > 0:11:02Matthew, can you pour your yellow liquid into the pink onion juice?
0:11:02 > 0:11:04You can use the funnel to help you.
0:11:04 > 0:11:06Very good.
0:11:08 > 0:11:09So what's happened?
0:11:09 > 0:11:11It's still pink.
0:11:11 > 0:11:14That right, and that's because you just had water
0:11:14 > 0:11:17and the water hasn't changed the onion juice at all.
0:11:17 > 0:11:21It's still stingy and pink. So it's still an acid.
0:11:21 > 0:11:23Tia, can you now pour your yellow liquid
0:11:23 > 0:11:25into the pink onion juice?
0:11:29 > 0:11:31It's turned yellow!
0:11:31 > 0:11:34It did turn yellow, Luke, and that's because
0:11:34 > 0:11:38the liquid that you added, Tia, had something special in it
0:11:38 > 0:11:42that changed the onion juice and stopped it from being a stingy acid.
0:11:42 > 0:11:46That's why it's not pink any more. This is what happens in our eyes.
0:11:46 > 0:11:49Our tears have something special in them too,
0:11:49 > 0:11:52which stops the onion juice from being stingy.
0:11:52 > 0:11:56Nina And The Neurons!
0:11:56 > 0:12:00Your question was, "Why do onions sometimes make us cry?"
0:12:00 > 0:12:01I think we've answered it.
0:12:01 > 0:12:05We saw that onions are made up of lots of tiny pockets, or cells,
0:12:05 > 0:12:07full of onion juice.
0:12:07 > 0:12:10And when we cut an onion, the cells break
0:12:10 > 0:12:15and the onion juice squirts into the air, even though we can't see it.
0:12:15 > 0:12:17The onion juice is a bit stingy but our clever eyes
0:12:17 > 0:12:23make tears, which stop it from being so stingy and wash the juice away.
0:12:23 > 0:12:25And that's why onions make us cry.
0:12:25 > 0:12:27Here are some tissues to take home with you
0:12:27 > 0:12:30for the next time someone's chopping onions.
0:12:30 > 0:12:35- Thanks, Nina. Bye!- Bye!
0:12:36 > 0:12:40If you want to know more about the science that's all around us,
0:12:40 > 0:12:43go to the Nina section on the CBeebies website. Have fun!
0:12:43 > 0:12:47- Lab coat on, Nina? - Lab coat on, Ollie.
0:12:47 > 0:12:51- Safety gloves on, Nina? - Safety gloves on, Felix.
0:12:51 > 0:12:55- And don't forget your goggles, Nina. - Goggles are on, Luke.
0:12:55 > 0:12:57I think we're ready!
0:12:59 > 0:13:02- # We do experiments in the lab - In the lab
0:13:02 > 0:13:04# Shooby-dooby, in the lab
0:13:04 > 0:13:08- # Bubbling experiments in the lab - In the lab!
0:13:08 > 0:13:10# Go, Nina, in the lab
0:13:10 > 0:13:13# Hissing and popping Steam and smoke
0:13:13 > 0:13:16# We need protection Don't we, folks?
0:13:16 > 0:13:21# We always put our safety first
0:13:21 > 0:13:23# Shooby-dooby-dooby-dooby
0:13:23 > 0:13:26- # We do experiments in the lab - In the lab!
0:13:26 > 0:13:27# Go, Nina! #
0:13:27 > 0:13:30Ah, it's been such a great day, man.
0:13:30 > 0:13:34Looking at that onion under the microscope was amazing.
0:13:34 > 0:13:39It's been a marvellous day, feeling the onion juice spraying everywhere.
0:13:39 > 0:13:41Oh, I've had a brilliant day.
0:13:41 > 0:13:45Hearing the hiss of the misters, that was ace!
0:13:45 > 0:13:48I've had a fabby day!
0:13:48 > 0:13:51The tears stop the stingy onions!
0:13:51 > 0:13:54Our day has been bursting with sensational experiments.
0:13:54 > 0:13:57I hope you've enjoyed it. See you soon. Bye!
0:13:57 > 0:13:58ALL: Bye!