Why are the bubbles in fizzy drink so small? The ones I blow are much bigger - Alison, aged seven, Aberdeen, UK

Thank you for your question, Alison! First of all, we have to know where the bubbles in the fizzy drink come from. This happens because they have a gas called carbon dioxide dissolved in them.

The gas and the liquid (and everything else) are made up of tiny bits of stuff called molecules. When the gas dissolves in the liquid, the molecules mix together really well so that the gas gets trapped without there being any bubbles.

The amount of gas you can dissolve into the liquid depends on how much pressure it is under. When the pressure is high, it is like there is a lot of weight pushing the gas into the liquid, so lots of it can dissolve. To make a fizzy drink, carbon dioxide is bubbled through liquid at a pressure that is five times greater than the normal pressure we live at.

We would feel the same amount of pressure if we swam to the bottom of a swimming pool that was 50 metres deep (50 metres is about eight giraffes standing on top of each other).

Curious Kids is a series by The Conversation, which gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.com. We won’t be able to answer every question, but we’ll do our very best.

This is how so much gas is trapped. A can of fizzy drink has enough gas dissolved in it to blow up a small balloon.

When you open a bottle or can of fizzy drink, the pressure on the liquid suddenly gets smaller. The drink can trap much less carbon dioxide at this pressure, so the extra gas stops being dissolved and forms bubbles.

Watch the bubbles

To learn more we will need to run some experiments. Pour some fizzy drink into a glass (ask a grown-up first). Look at how the bubbles start where the liquid touches the glass – at the bottom and sides, but not in the middle of the drink.

To make a new bubble, the molecules in the carbon dioxide and the drink move around and get organised to make a surface between them. Less new surface needs to be made if the bubble starts against the edge of the glass. This uses less energy and means new bubbles usually start here.

This is also why small bubbles tend to stick to the glass. More gas will join the small bubble, as it takes less energy to escape into a bubble to make it bigger than make a new one.

Eventually, the bubble gets big enough that it will float to the top of the drink. This happens when the bubble is still smaller than a grain of sand.

When you blow through a straw to make bubbles, the same forces are acting on the bubbles as before. But the bubble is stuck to the straw all round the edge of the hole. This means that you can’t make bubbles that are smaller than the hole in your straw.

This is why they are larger than the bubbles that form on their own in a drink. Try to find a thinner straw to see how small a bubble you can make.

Bubbling volcanoes

You might be surprised to learn that now that you know how bubbles form in a fizzy drink, you also know why volcanoes erupt. If you dug down deep under a volcano, you’d find hot, liquid rock called magma. This has gases dissolved in it.

As the magma rises to the surface, the pressure goes down. It can hold less gas and so bubbles form in it, just like in your fizzy drink. The bubbles make the magma more buoyant, like a hot-air balloon. This pushes it upwards, causing an eruption.

We know that magma usually has lots of small crystals in it. Do they affect the bubbles?

Time for one final experiment: pour some salt into your fizzy drink and watch what happens. You should see lots of bubbles forming all at once because the salt crystals have lots of surfaces for the bubbles to form on. You’ve just made your own volcanic eruption!

Children can have their own questions answered by experts – just send them in to Curious Kids, along with the child’s first name, age and town or city. You can:

• email curiouskids@theconversation.com
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Here are some more Curious Kids articles, written by academic experts:

• Why do some animals have two different coloured eyes? – George, aged ten, Hethersett, UK.

• How long has gravity existed? - Aine, aged 13, Edinburgh, UK.

• Does the sky protect the Earth and if yes, then how? – Saskia, aged eight, Estonia.

Ed Llewellin, Professor, Durham University and Elena Patyukova, Postdoctoral research associate, Durham University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

This is an article from Curious Kids, a series for children of all ages. The Conversation is asking young people to send in questions they’d like an expert to answer. All questions are welcome: find out how to enter at the bottom.

Why do things look smaller when further away and bigger when closer to me? – Elena, age ten, Haywards Heath, UK

The easiest way to understand this is by thinking about something called your field of view. This is how much you can see, without turning your head. When things are closer to you, they take up more of your field of view, so they seem bigger. When they’re further away, they take up less of your field of view, and so seem smaller.

One way to measure our field of view is to use an angle. An angle is a measure of how much something turns, and it’s measured in degrees. Zero degrees means there is no turn at all, while 360 degrees means a full turn.

So if you spin yourself all the way around, you have turned 360 degrees. If you spin yourself half way around, so that you’re facing the opposite direction, you’ve turned 180 degrees.

Vertically (that means up and down) our field of view is about 150 degrees. How big things appear to us has to do with how much of our field of view they take up.

If you look at a building from a long way away, you can easily see the whole building from top to bottom. So the angle between the line from your eye to the top of the building, and the line from your eye to the bottom of the building, is quite small.

The further away the object is, the smaller this angle will be. So, the subject appears small, because it takes up less of your field of view.

But as you get closer to the building, it will take up more and more of your field of view, as the angle between the line from your eye to the top of the building, and the line from your eye to the bottom of the building, grows larger.

When you get right up close to the building, you may not even be able to see the top without tipping your head backwards. The angle between the line from you to the bottom of the building, and the line from you to the top is bigger than 150 degrees. The building will take up your whole field of view – and then some!

Scientists know that things are always better with experiments, so here’s one for you to try. You’ll need a smart phone with a camera, a big empty space (like a football field) and two friends or grown ups to help you.

One person stands far away, at the other end of the field. Another person stands much closer to the photographer, and holds out their hand. Now, the photographer might have to move around a little bit and give everyone directions, but as soon as everything is in line – click!

You should have a picture that looks something like this.

Of course, one person isn’t really that much smaller than the other – you’re actually just playing a trick, using everything you’ve just learned.

The camera is very much like your eye, so you know that the person who is closer to the camera will take up more of its “field of view”, appearing bigger, while the person who is further away will take up less of its “field of view”, appearing smaller.

Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:

* Email your question to curiouskids@theconversation.com
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Please tell us your name, age and which town or city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question, but we will do our best.

More Curious Kids articles, written by academic experts:

• How do you know that we aren’t in virtual reality right now? – Erin, 13, Strathfield, Australia

• If the universe is like a giant brain, then where’s its body? – Aine, age 12, Edinburgh, UK

• How does our heart beat? – Aarav, age nine, Mumbai, India

David Franklin, Associate Head of Education, University of Portsmouth

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How do batteries work? – Dominick, aged seven, Indiana, US.

A battery is a device that can make electricity, with the reaction of certain chemicals. Lots of different chemicals can be used in batteries – it depends how the battery is made, or what you’re using it for.

The rechargeable batteries used in smartphones or electric cars are called “lithium ion batteries”. But it’s really rare to see them, because they don’t normally need to be replaced and are hidden away safely inside.

You’re much more likely to see alkaline batteries, which are used in things like clocks, torches, remote controls and lots of other objects around the house. Strictly speaking, they should be called “alkaline cells”, since a battery is a number of cells connected together.

Curious Kids is a series by The Conversation, which gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.com. We won’t be able to answer every question, but we’ll do our very best.

Making electricity

Inside the metal case of the alkaline cell there are three main chemicals: zinc, manganese dioxide and potassium hydroxide.

It might sound complicated, but the way the cell works to make electricity is actually pretty simple: a chemical reaction takes place, which moves tiny, negatively-charged particles called “electrons” around to create an electric current.

When the cell is connected to a circuit – like a light bulb, for example – the zinc inside reacts with the manganese dioxide and loses electrons.

The electrons are collected by a metal rod inside the cell, which allows them to flow from the bottom of the cell (the negative terminal), through the wires to the bulb (making it light up) and then back into the top of the cell (the positive terminal).

This reaction produces around 1.5 volts of electricity. Because not many devices can work on 1.5 volts, very often two or four cells are used together to give more power. So four cells connected together (end to end) would give six volts.

When most of the zinc has reacted with the manganese dioxide, we say the cell is “flat”, which means it can’t make any more electricity. Because the chemical reaction that takes place in alkaline cells cannot easily be reversed, it means that the cell can’t be recharged.

But remember, most cells and batteries can be recycled, so make sure you get rid of them carefully.

Reversing the reaction

All types of cells and batteries have a similar type of chemical reaction taking place to produce the electricity.

But in some types of cell or battery, the chemicals are different, and the reaction can be reversed. This way, the cells can be recharged – just like the lithium ion batteries in cars or smartphones.

It used to be much cheaper to make non-rechargeable cells, like alkaline cells, so they were used very widely.

But now that people have recognised how bad for the environment it is to just throw away non-rechargeable cells, and since rechargeable cells are getting cheaper, we’ll probably use non-rechargeable cells less and less in the future.

Children can have their own questions answered by experts – just send them in to Curious Kids, along with the child’s first name, age and town or city. You can:

• email curiouskids@theconversation.com
• tweet us @ConversationUK with #curiouskids
• DM us on Instagram @theconversationdotcom

Here are some more Curious Kids articles, written by academic experts:

• When fish get thirsty do they drink sea water? – Torben, aged nine, Sussex, UK.

• Why do some animals have two different coloured eyes? – George, aged ten, Hethersett, UK.

• How high could I jump on the moon? – Miles, aged five, London, UK.

Roger Clarke, Honorary Visiting Senior Research Fellow, University of Bradford

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Curious Kids is a series for children of all ages, where The Conversation asks experts to answer questions from kids. All questions are welcome: find out how to enter at the bottom of this article.

Where did the first seed come from? – Alice, age six, Beverley, UK

Hi Alice. This is a clever question. As I’m sure you know, plants use seeds to spread their young and make new plants. But plants haven’t always used seeds to do this. Seeds came together bit-by-bit over a really long time, as plants evolved.

To understand how this happened, you need to know that all living things change slowly over time, to get better at surviving in their environment – this process is called evolution.

Here’s how it works: when a living thing has a feature which works well, it will be able to live longer and have more young. These young will probably have similar features, thanks to their parents.

Plants started using seeds to spread their young somewhere between 385m and 365m years ago. Before seeds existed, plants had other ways of doing this.

Back then, most plants used spores. Some plants today, such as algae, mosses and ferns, still do. You might have spotted the tiny brownish dots on the underside of fern leaves – these are spores.

Spores are different from seeds in a few ways. A spore is made of just one part – a single cell – while a seed contains many cells, each with different jobs to do.

Another difference is that spores only have one parent plant, while seeds have two.

This means that, after a seed starts sprouting, it can grow into a plant, just like its parents.

But spores have to work a bit harder: once they’ve travelled away from their parent plant, they grow into a little green plate of cells, which scientists call a “gametophyte”. Then, two gametophytes must join together, before they can grow into a plant.

It’s easier for gametophytes to join together when its wet – and that’s why plants that use spores usually need to grow in wet places.

For example, horsetails are a very ancient type of plant, which like to grow along lakes, rivers and ponds: they have very strange spores with four “legs” which help them to move and travel further away.

The first seed

Scientists believe that an extinct seed fern, called Elksinia polymorpha, was the first plant to use seeds.

This plant had cup-like features, called “cupules”, that would protect the developing seed. These cupules grew along the plant’s branches.

Today, plants with seeds do things a little differently. There are two main types: “angiosperms” and “gymnosperms”.

Angiosperms are flowering plants – their seeds develop inside of fruit, like apples, tomatoes or even rose hips or holly berries.

Gymnosperms, such as pine trees, grow their seeds inside a hard cone.

The upside of seeds

Seeds have evolved because they are better at helping plants to survive than spores are. For example, seeds contain a food source to help the new plant grow.

They also have a hard coat, which helps them to live longer in different conditions: this means plants with seeds can life in lots of different places, from hot, dry deserts to cool, rainy places.

Seeds are so good at helping plants to spread their young that most plant species on Earth today use seeds.

Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question – along with your name, age and town or city where you live – to curiouskids@theconversation.com. Send as many questions as you want! We won’t be able to answer every question, but we’ll do our best.

More Curious Kids articles, written by academic experts:

• Why do spiders have hairy legs? - Audrey, age five, Melbourne, Australia

• Why do we have different seasons at specific times of the year? – Shrey, age nine, Mumbai, India

• How is water made? – Clara, age eight, Canberra, Australia

Marjorie Lundgren, Lecturer in Environmental Physiology, Lancaster University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to CuriousKidsUS@theconversation.com.

Why do people get headaches? – Evie V., age 10, Corpus Christi, Texas

Whether sharp and stabbing or dull and throbbing, a headache can ruin your day. But your brain doesn’t actually feel pain. So what is going on when it feels like your head is in a vise or about to explode?

I am a child neurologist – that is, a doctor who specializes in diseases of the brain in kids. Most of my patients are kids and adolescents who are struggling with headaches.

Head pain is complicated, and there is still a lot to learn about what causes it and how it can be treated. But researchers know there are a few key players that take part in generating pain.

What are headaches?

Nerves communicate information like pain through electrical signals between the body and the brain.

While the brain itself doesn’t have any nerve sensors to feel pain, blood vessels in the head and structures that protect and surround the brain do sense pain. When these tissues detect injury or damage, they release chemicals that trigger transmission of electrical signals through nerves to tell the brain the head is hurting.

The brain will also use nerves to signal the body to respond to pain with symptoms like feeling tired, teary eyes, runny nose, upset stomach and discomfort in bright or loud environments. It’s not clear why humans evolved to feel these symptoms, but some scientists theorize that this can lead to healthier lifestyle choices to decrease the chance of future headache attacks.

What causes headaches?

Often, headaches are a sign that the body is under some kind of stress. That stress triggers chemical and physical changes to the nerves and blood vessels around your brain, head and neck that can cause headaches.

Many types of stresses can cause headaches, including an infection, allergies, hormone changes during puberty and menstrual cycles, not getting enough sleep, not drinking enough water, skipping meals or drinking too much caffeine or alcohol. Sometimes, headaches happen with emotional stress, like feeling anxious or depressed. Even pressure in your sinuses due to changes in the weather can cause your head to hurt.

One in 11 kids have had a type of severe headache called a migraine. They feel like a pulsing and pounding pain in your head and come with other symptoms, including nausea or being sensitive to lights and sounds. During a migraine, it can be hard to do everyday activities because they can make the pain worse. It is also very common to feel unwell or irritable before the head pain starts and after the pain is gone.

Migraines occur when the nerves and other structures used in signaling and interpreting pain aren’t working properly, leading to pain and discomfort from stimulation that wouldn’t normally provoke this. There are many environmental and genetic factors that contribute to this dysfunction. Some people are born with a higher risk of developing migraines. Most people with migraines have someone in their family who also experiences them.

What can treat and prevent headaches?

Identifying what type of headache you’re experiencing is crucial to making sure it is treated properly. Because migraines can be severe, they’re the type of headache that most often leads to doctor’s visits for both kids and adults.

There are several ways to reduce your chances of having headaches, such as drinking plenty of water and limiting caffeine. Eating, sleeping and exercising regularly are other ways you can help prevent headaches.

While painkillers like ibuprofen are often enough to relieve a headache, prescription medications are sometimes necessary to make head pain more bearable. Some medications can also help control or prevent headache episodes. Physical therapy to exercise the body or behavioral therapy to work on the mind can also help you manage headache pain. There are even electronic devices to treat headaches by stimulating different parts of the nervous system.

It is important to talk with a doctor about headaches, especially if it’s a new problem or you experience a change in how they usually feel. Sometimes, brain imaging or blood tests are needed to rule out another health issue.

Recognizing a headache problem early will help your doctor get started on helping you figure out the best way to treat it.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Katherine Cobb-Pitstick, Assistant Professor of Child Neurology, University of Pittsburgh

This article is republished from The Conversation under a Creative Commons license. Read the original article.