# Donna (7) asks “Where do clouds come from?”

Donna, many thanks for the question. Before trying to answer it I thought I would ask my team a question.

Donna, what do you think about the puddles question? Think about how you would answer it and then go to my answer to a previous question.

Now to your question. Firstly I have created a little animation to show how the puddle disappear. You have to imagine that the shapes are water particles (molecules is the proper word). In the puddle they are all moving around. Most of them like being with the other particles BUT some are just moving around a little bit too fast and manage to escape from the puddle. When the Sun begins to warm the puddle it makes more water particles move around faster and more escape. This goes on until the puddle disappears.

The water particles are very small and are are lifted by the air up into the sky. High above the ground the air is quite cold so the water particles ‘slow down’. When they are moving ever so slowly if they meet another water particle they join up with each other and form droplets of water. This is how a cloud begins to form.

At home look at the steam from a kettle, BE VERY CAREFUL AND CONSULT AN ADULT.  At the exit of the kettle spout you can see nothing, BUT just above this the hot water particles begin to cool down and slow down and reform clouds of water.

(revised 21/4/17)

# “Why can heavy things float”? ask Aiden (10)

Aiden, great question,a difficult answer. I hope that you have investigated which things float and which things sink. You should be able to look around you and say ‘That floats’ and ‘That sinks”. Think about this – when something sinks it seems to be breaking the surface of the water. What is it breaking? I pass this back to my team.

The attractive forces between water molecules are called intermolecular forces. Look at this post to find out more.  When the much bigger metal boat hits the water, because of it’s design (spread out) there are lots more water particles that push on the boat and keep it floating.  Squash the boat up into a small lump of metal  and drop it into the water. What do you think will happen? Let me know what you think by leaving a comment in the ‘Leave a Reply’ box below.

# Mattheiu (Yr 4) asked “If sound can’t travel through vacuums, why are they so loud?”

This is an excellent question. We are told that sound travels through the air to us by the vibrations of the air molecules between speaker and listener. But how does is get to us from a very distant speaker? Or through a vacuum? The magic formula is that one form of energy can be converted to another form of energy, as my team have explained.

If we can convert one form of energy to another then why not convert sound, which is moving air and therefore kinetic energy (the energy of movement) to electrical energy that can be passed down a wire or through a vacuum as an electromagnetic wave to a listener a long way away. When it is received the reverse conversion process can take place where the electrical energy can be converted back to kinetic energy, via electromagnetics and loudspeakers and not forget ears and brain.  Then by controlling the input to the conversion process we can control the loudness. Magic but real.

# Science Master Special – atoms, molecules, intra and inter molecular forces, heat energy and kinetic movement

There is a bit of everything in the title. Maybe the basis of everything as we know it up to now.

• Atoms are the foundation of our understanding of matter (all the stuff around us).
• Molecules are the the building blocks that are constructed from atoms to build the stuff around us.
• The forces between atoms that make up the molecule are called intramolecular forces.
• The forces between the molecules that the atoms make are are the intermolecular forces.
• The study of molecular kinetics is the study of the movement of particles and the movement is usually associated with applied heat. Heat energy and movement are strongly linked. Heat something and it moves faster.

For a more detailed look at the structure of atoms look at this Science Master Special

Any questions?

# Jamie asked a question – “Why does water sometimes boil at different temperatures?”

I must apoligise to Jamie because he specifically asked about the water in Yellowstone River boiling at 106 0 C.  Why does it do that? Does water boil at a higher or lower temperature in other situations? I asked my friends about this.

Jamie, the properties of water does depend on it’s intermolecular structure. If it didn’t have these intermolecular forces (called hydrogen bonds) the water would likely be a gas at room temperature. Life on Earth would therefore be impossible or maybe very different.

Ok, water is as it is now, so why can it’s boiling point change? The main reason is the environment in which it is trying to boil, not the water. Boiling is linked to the process of the water molecules getting enough energy from the heat source to make it move so fast that the intermolecular forces can be broken and it can escape from the water into it’s environment.

BUT

If the environment is changed this can affect the boiling point. Make the environment thicker(more dense) and the water molecules have greater difficulty in escaping making the boiling point go up, in the kitchen a pressure cooker prevents the faster water molecules from escaping.  Make the environment thinner (go up a mountain, where the air is ‘thinner’) and you make it easier for the water molecules to escape so the boiling point goes down.

HOWEVER

There is another way to affect the intermolecular forces of the water molecules. Introduce something into the water that increases the intermolecular bonding. Introducing salt NaCl, which gives Na+ and Cl ions in water. These make it more difficult for the water molecules to become gaseous molecules so the boiling point go up.

There are other posts that could help you…..On intermolecular forces and a game you could play and adapt.

# Isabelli (10) asked a follow up question on- Why are things absorbed and how does temperature affect water?

Isabelli, a couple of interrelated interesting questions. I asked my team to prepare the scene …be back later.

First a little experiment. Put a small amount of water into a saucepan and place it on a heat source (parental permission required) carefully observe what happens (observation is an incredibly important science skill). Make notes of what you see. when the water is obviously boiling switch off the heat source and leave the water to cool down. Avoid moving it. Now repeat the experiment, again making notes on your observations. Are there any differences?

Look at the water molecules in the diagrams above. Water is a dipolar liquid. That means that there is an uneven charge distribution in each molecule. It has a negative ‘end’ and a positive ‘end’. This gives it the capability of making the Oxygen molecules (which are not normally dipolar) dipolar and subsequently creates an attractive force between the water and Oxygen molecule (bit like two magnets). The Oxygen molecules like this arrangement and are held within the water structure.

But …. if you heat up the water the water molecules begin to move about faster so the tentative attraction between the water molecule and the oxygen molecule breaks and it escapes from the water. Can this explain what you observed when you heated the water?

# Why is the sky blue in the day and black in the night? asks Lamar (12)

Lamar – a brilliant question. I will ask my friends to think about it.

Lamar. I hope that you have had the opportunity of passing ‘white light’ through a prism and see the fantastic ‘spectrum’ of coloured light that results. If not then try ‘creating’ white light by using torches and  coloured cellophane (blue, red, green) on each torch and shining them at a white piece of cardboard. Let me know what happens.

Things then get a little difficult. You have to think of the Sun’s white light reaching the atmosphere of the Earth. The two major components of the atmosphere are nitrogen and oxygen. The structure of the molecules of these two components makes them very receptive to the blue part of the white light from the Sun. The air molecules absorb this blue part and then re-emit it in all directions. This is a process called ‘scattering’. Thus the blue sky. The rest of the (white minus some blue) sunlight passes onwards.

At night the Sun is shining on another part of the Earth, so no white light is falling on your part of the Earth. No light ….blackness.

Lamar . An interesting question, a complex answer. Feel free to ask another question.

# Science Master Special – the Bernoulli effect (Flying)

Blowing through two pieces of paper results in the two pieces of paper coming together. The same can be done with two balloons. Hold two inflated balloons in front of your mouth and blow between them. You will be surprised.

The question is why does this happen? Bernoulli in 1782 looked at a similar phenomena using water and blood. He discovered that when blood  moved faster it applied less pressure on it’s surroundings. I have tried to illustrate this phenomena in the form of an animated GIF (there are some great free animated GIF builders online)

As I have said before the air is FULL of particles/molecules which are so small you cannot see them. BUT you feel them all the time. Try running holding a great sheet of cardboard in front of you, feel the wind blowing on you. Air molecules are constantly banging into you and everything around you. This is normally called ‘air pressure’. It’s the push of air on you and the two pieces of paper that you might be holding in front of your mouth.

Bernoulli in his work found that if you increase the speed of the, already moving , molecules they hit things around them less frequently and therefore less push means less pressure. I have tried to illustrate this in the animation above.

In an aeroplane as it moves through the air that goes over the top of the wing speeds up compared to the air underneath the wing. Look at a cross section of the shape of a wing. The push of the air on the bottom of the wing is therefore greater than the push of the air on top of the wing. Thus lift.

# Apply asked “If the pressure on the surface of a gas is increased. What will happen to the inter particle force?

A fascinating question. I asked my friends to look at this and they came up with a couple of definitions which might dictate the way I try to answer this question.

Your question seems to be directed at intermolecular forces between similar particles/molecules

In a past question I talked about the way water molecules are attracted to each other by things called ‘hydrogen bonds’. This aids the formation of liquid water at very high temperature and low pressures. The molecules ‘like’ being close together. Another molecule is that of carbon dioxide – these are not attracted to each other so strongly. To attract each other they need to be ‘pushed’ much closer together, only then will they form a liquid. For some molecules like butane you need really high pushes because the attraction between the molecules is so small. For some other molecules there is no force of attraction, this can almost be described as repulsion. The gases, Helium, Nitrogen and Hydrogen  are only liquefied under immense pressure (push) and low temperature (low temperature slow the individual molecules down) conditions.

# Floating clouds a further answer for Tate

Air might be invisible but it is there. It is invisible stuff  but seems to have a lot of push . Scientists have found out that it consists mainly of nitrogen and oxygen particles moving around in the the space between you and everywhere else. The space also contains carbon dioxide and a few other particles (we call the particles molecules).

This is a possible image of a sample of air consisting just of oxygen(blue) and nitrogen molecules (orange)

Why are they moving? Because they have energy. It make them move. You would move if you were given lots of energy. Remove the energy – reduce the temperature to -200 degrees centigrade and the particles would stop moving.

Is there water in the air around us?

Experiment – Put a saucer of water on a window ledge and watch for a day. What happens? Where has the water gone?

Maybe some of the water has escaped into the air that surrounds it. If this has happened we describe this as water turning into water vapour. The liquid water has turned into a gaseous water.

The water particles or water vapour molecules (blue and red particles)  are being pushed around by the air particles which keep them ‘floating’.

How much water is in the air that is floating around us?

Experiment. Fill a beaker with crushed ice, cover the top with cling film and observe what happens.

Think about what has happened. Why did the water leave the air?

Another important observation that you need to make is what happens to hot air?

Experiment. Create a paper spiral and hang it over a source of heat. You could try a ‘hot water bottle’

DO NOT USE A FLAME – IT WOULD BE VERY DANGEROUS

What happens? Does anything happen?

Thoughts

If hot air rises then the water particles that are ‘trapped’ in the hot air will rise as well. The air gets cooler as it rises. The water vapour becomes very small water droplets. Small enough to still be ‘trapped’ by the energetic moving air molecules. A floating cloud is formed.