Is slime a solid or a liquid? asks Taya (11)

In development.

Hello Taya, many thanks for your question.  Slime is a fascinating substance and the best way of producing it is to mix a substance called Borax, with a substance like PVA with some water. There are other ways to do it but this is the traditional way. Is slime a liquid or solid?  How do we measure how ‘liquid’ something is. We use a measure of the way a liquid pours, or if you drop something (a small metal ball) into it …how quickly it falls through it. This property of liquids is called it’s viscosity. Like most scales of measurement there are usually two extremes  and something in the middle can have a little bit of both of the properties of a solid and a liquid – the slimes.

The Viscosity Scale was established by Newton in (would you believe it 1770 -almost 250 years ago). Slimes are registered as a Non-Newtonian fluids .

Why Borax and PVA? PVA is a substance called a polymer. A polymer is a long molecular particle of repeating units. Polymers usually quite happily slide over each other (not very viscous). Add borax and it’s molecules attach themselves to the PVA polymers and stop the easy sliding. Thus a slime is produced.

Uncertain about things in this answer. Please ask more. You can also look at this previous answer to a similar question.

If pressure on a gas is increased what will happen inter-particle force?” asks Prince (13)

Prince.  An initial answer.

You have to think of how you are going to increase the pressure of a gas.

I can think of two methods …..imagine the gas in a Coke tin. The gas particles are rapidly moving around, bouncing of each other and the sides of the container. We can increase the pressure by

(1) decreasing the volume of the coke can ….the particles therefore will hit the sides more often (increasing pressure) or (2) increasing the amount of gas in the can which again increases the number of gas particles that hit the side of the can, again increasing pressure.

In both these cases the intermolecular forces are quite small. Most gas particles are fairly inert , they have intermolecular forces but they are slight. Water H2O and NH3; (ammonia) are probably exceptional.

HOWEVER as you increase the pressure further the gas molecules have less room to move and they get closer to each other …the intermolecular forces increase UNTIL they are so strong (because there are so many molecules in the small space) that the gas becomes a LIQUID. This is helped if you reduce the temperature at the same time (molecular movement is temperature dependant).

 

 

 

 

Science Master

Liam (10) asks “Why does warm air go up?”

 

Thanks team. You are quite right we have to start at the beginning to really understand why warm air goes up. Let’s start by looking at what is air?

Air is a mixture of small gas particles (called molecules) of nitrogen, oxygen, carbon dioxide and some other gases. The image below could be a picture of what it would look like, if you could see it. What do you notice about it?

The red molecules are the oxygen, the blue the nitrogen and the others water and carbon dioxide. Imagine them moving around (I am trying to make an animation). Because they are moving they have energy.

If we heat the air, we are giving the molecules in it more energy. This makes them move faster and they move further apart.

The ‘thicker’ cold air surrounding the warm air drops into the space under the warm air and doing so pushes up the warm air which rises.

You can see this happening in a beaker of heated water.

Mason (7) asks “Why is water wet?”

Thanks team. Let us start with a investigation. Let us look at the way water interacts with different materials.

 

Let us now look at the properties of water drops. Firstly let me define ‘cohesion’ and ‘adhesion’. The term ‘hesion’ means  … to stick. Cohesion is is the attraction and sticking together of the same things while adhesion is the attraction and sticking together of different things.

Look at the image of the water drop below. Each water particle is attracted to the other water particles around it , this is cohesion. Now add a different surface and the water particles are attracted to that rather than each other, this is adhesion. When adhesion occurs we get the spreading of the water drop and wetting,  providing the adhesive forces are greater than the cohesive forces.

So what about your investigation? Is there any evidence of cohesion or adhesion?

Here is a thought. it has been suggested that water is ‘wet’ because you can feel it’s wetness.

Maybe another little experiment.

You could let me know by clicking on the ‘Reply’ box below.

Pete (10) asks “What is the pitch of a sound?”

Thank you team.  Lets first look at the motion of the particles. You suggest that the motion of the particles is in the form of waves. I think that is quite difficult to imagine but I think I have an example that will help illustrate this type of motion. Look at what happens when you drop a pebble in a pond. The pebble, when it hits the water, it creates  one vibration.

 

 

 

In this image the sound is produced by the piston creating the waves. Notice the wavelength, that is important. If we can manipulate the piston, make it go slower or faster  we can change the wavelength. Changing the wavelength is changing the pitch, think about that.  How does the sound change?

Try blowing over, or tapping, some bottles.

 

Pitch and Frequency ..Test your hearing a little bit more …….

In the video below you can see and hear how the pitch of the sound and the wavelength change together.  We measure wavelength in units called Hertz. 1 Hertz is one cycle per second. In the image above imagine that it takes one second to get from the flute to the ear. Then there are 8 cycles in the top sound is so frequency is 8 hertz and there are 3 cycles in the bottom sound so the  wavelength is 3 Hertz.

You can now test your hearing.    Take Care….make sure you have control of the volume.

 

 

Thanks to
Orion Lawlor, for the water ripples video, Published on 9 Jan 2011
Earmaster at https://www.earmaster.com/music-theory-online/
The ISVR from the Institute of Sound and Vibration Research, University of Southampton.
The Sound Video, unknown but thanks.

Ellie (12) asks “What are the damages of hurricanes?”

Great question Ellie. I was going to ask my team to tackle this, however for some reason the question was left unanswered so to apologize I think I will try to answer it myself.

How is a hurricane created?

Air is made up of tiny molecules. When molecules are heated, they move faster. As they move faster they become become spaced farther apart, which makes the air less dense – meaning that there are fewer molecules in a given volume. This also means that the air has a lower overall pressure – pressure is the push of the gas on it’s surroundings. In comparison, cold air is made of more tightly packed molecules, and so it is denser and has relatively higher pressure.

The warmer, lower pressure air begins to move upwards and therefore it creates space below it which is filled by the colder higher pressure air. The warmer air ‘floats’ on the colder air. It also carries with it water vapour – water that has evaporated and contains lots of energy. A wind begins to be created. The hotter the air near the surface of the sea, the lower the pressure and the faster the rise.

As this warm air gets higher it begins to cool and also the water vapour that would have risen with it begins to turn back to water. A cloud begins to form. The energy of the condensing water vapour is given to the cloud.

The cloud of colder air and water vapour begins to move in circles (because the Earth is rotating). It meets other storm clouds. The hurricane is forming and is being fed by the warm air close to the warm sea.

What are the damages of the hurricane?

The strong winds of a hurricane can push water up and onto land. This water can cause major flooding and damage to homes, cars, and boats. Heavy Rains – Hurricanes can cause heavy rains that flood places inland and away from the center of the storm.

This video will help explain the formation of the hurricane.

 

 

 

“How do compounds and elements work together?” asks Candice (13)

Thanks for that information team. It does illustrate the relationship between elements and compounds and the way in which they work together. To understand this a little more you will have to know  more about the structure of  the atoms which make up the elements. All of the atoms of the 118 elements have a different number of protons in their nucleus and this dictates the way in which they behave in the formation of compound.

Below is a drawing of an atom of the element Lithium with the electrons, protons and neutrons.

I hope this gives you some answers to your question. If not please comment or ask another question.

PS  You and your friends might be interested in the crossword puzzle background. Its all about atoms, elements and compounds. You can download the crossword and the answers from the link below.

Crossword.
(Anyone reading this post who wants to ask a question or make a comment please feel free to do so)

Hello (13) asks “How do tectonic plates work and influence earthquakes?”

Quite right my friend it’s all about convection. Warm water, air, oil, or any liquid/gas stuff  will move upwards (rise) when it is heated. Why. Think about it.

Lets think of an experiment (this is a science blog) where we can test this idea and then move on to the question that Hello asked.

The experiment

You will need a beaker of water, some pencil lead, 3  A batteries, two leads with attached crocodile clips and some food colouring and a dropper

Connect the pencil lead to the batteries using the leads. As the electricity passes through the pencil lead, the pencil lead will heat up. Drop the attached lead into the water. Look carefully at the water, what is happening. If you put a small screen behind the beaker of water and shine a torch on the water you will be able to get a better view of what is happening to the water.

OR

Drop a small amount of food colouring into the water.

Hopefully what you will see are convection currents that have been created by the water close to the lead  warming up and beginning to rise. The next question is WHY.

Warning. Do not use mains electricity. It could be very dangerous and kill you.

Why does the water rise?

When the water particles(molecules) come into close contact with the heated pencil lead they gain kinetic energy (see Science Master Special Energy), they move faster. The water molecules spread out so that in any given space there are less water molecules (less dense). This means that gravity comes into action and the colder water can begin to move into the space where the warm water was. The warmer water ‘floats’ on top of the cold water. The cold water then gets warm and and more cold water moves in and the original warm water floats up higher in the beaker. As the warm water rises it gets colder and more dense and eventually will join the column of cold water that is moving (by gravity) downwards toward the hot pencil lead. Wow…..I hope you can see the picture

The movement of the tectonic plates is caused by convection currents and it is this movement that can cause earthquakes. Hopefully when you watch the excellent video below you will see the links.

Hello. If you would like to question anything, please make a comment or ask another question.

 

 


(Anyone reading this post who wants to ask a question or make a comment please feel free to do so)

Billie and Zali (10) asked “How does the activator form slime?”

Sorry team.  You have provided some good background material. The important thing about making SLIME is that all the ingredients in it’s making (The Activator, the PVA and water)  have something in common, lots of O-H chemical bonds. It is these that make the SLIME a reality. Look at the diagram of a PVA molecule and count the number of O-H bonds. Remember this is a Polymer so the image below is just one bit of a much bigger molecule of PVA.

So what is it about the O-H bonds that make them so important.

Look at the following short video ….

It’s all due to Hydrogen bonding. Everything is attracted to everything else by the Hydrogen bond environment that is introduced when you put all of the ingredients together. SLIME becomes the reality.

 

Think about it. Make a comment or if you don’t understand a complicated bit then please- Ask another Question
(Anyone reading this post who wants to ask a question or make a comment please feel free to do so)

(revised 13/9/17 – PVA is polyvinyl acetate not polyvinyl alcohol, Diagram of PVA included and last paragraph revised)

How does the wind manage to topple things like wheely bins over? With the bins being big objects how is this possible? asks Imran (10)

 

A useful place to start Imran would be to look at the way in which wind is can exert a very strong force. Wind is created by the Sun warming up the ground around us and the air. Sorry team, I don’t think the wind does much pulling.

Air is made up of tiny molecules. When molecules are heated, they move faster. As they move faster they become become spaced farther apart, which makes the air less dense (meaning that there are fewer molecules in a given volume). This also means that the air has a lower overall pressure (pressure is the push of the gas on it’s surroundings. In comparison, cold air is made of more tightly packed molecules, and so it is denser and has relatively higher pressure.

The warmer, lower pressure air begins to move upwards and therefore it creates space below it which is filled by the colder higher pressure air. A wind is created. The hotter the air near the surface of the Earth the lower the pressure and the faster the rise. The 2017 hurricanes were caused by the hot sea and hot temperatures near the surface.

Can you measure how much push (force) is needed to push over a wheely bin?  Let’s first make our own push-pull measurer. You will need an elastic band, cotton reel, a couple of drawing pins, some sellotape and a paper clip to make your own measurer.

You can use it directly to measure pushes and pulls just by seeing how far the cotton reel moves up the dowel rod. It would however be better if we calibrated the rod in some way. In the images below the rod has been calibrated in Newtons (theses are the units of force). To do this a 500 gramme mass was attached to the hook. It is known that a 500g mass will exert a force (pull) of 1/2 Newton. So when the mass is attached, the elastic band will stretch, and the dowel rod will be pulled down. The distance on the rod between the ‘no’ force point and the 500g point is therefore equivalent to half a Newton.

It is estimated that an 80 mph wind would have a push of about 400 Newtons per square metre and be able to move a car. A breeze 5 mph might have a push of between 5-10N per square metre. You could try your meter on a sheet of cardboard in a strong breeze and see what you get.

Imran your question was very interesting to answer and you might have some difficulty in understanding some of the stuff above. If that is the case and also for anybody else reading this PLEASE ask another question or make a Comment.