Matter

For instance, if we take a cup of water and leave it in the sun, the cup will become warmer and gain heat energy. This causes the molecules in the water to move faster. If they move fast enough, they will leave the surface of the cup and enter the air - this is called evaporation.

On the other hand, if we place the same cup of water in the freezer, the cup will become colder and lose heat energy. As a result, the water molecules will move slower. If they move slowly enough, they may stop moving position and just shake in a spot. When the water molecules are no longer sliding past each other, then you have a solid.

Solid

molecules shake (vibrate) in one spot

Like watching a movie at the theatre, while needing to urgently go for a pee

Liquid

Molecules shuffle - they slide past each other but always stay near each other

Like when the movie finishes and everyone shuffles towards the doors

Gas

Molecules zoom - they fly fast past and away from each other

Like once you are out of the cinema and everyone runs to the various toilets throughout the mall

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Energy and Atoms

The movement of atoms determines if something is a solid, liquid or gas.

This movement also causes state changes and expansion and contraction

Lets start with a low energy (cold) solid.

We will just look at 3 molecules in a solid

Solid

They are next to each other, and shaking a little bit. They are attracted to each other, but also repulsed, this causes the shaking. Kinda like going to the movies with an attractive (hot) person, who has really, really bad body odor. You want to sit next to them, but not really at the same time. This causes you to shuffle back and forth in your seat.

As we add heat to it they start to shake more. Imagine, you in the seat next to the attractive person, however their b-o is getting worse as it is getting hotter, so you shuffle more and more in your seat.

As they shake more, the space between them increases (The atoms themselves never change size) . Because the space between them increases, the matter starts to occupy more space. This is expansion of a solid.

As we keep adding heat, they shake so much that eventually one overcomes the power of attraction and starts to shuffle freely around. Although it will stay near the other molecules. This is Melting.

Put another way, imagine that the b-o is now so bad that you have to hop out of your seat and you start to walk around, however you want to see the end of the movie, and the person is still attractive, just too smelly to sit next to.

As we keep adding heat energy, the other two molecules will eventually shake to the point that they just start shuffling instead. The solid has fully melted and we now have a liquid

Liquid

As we keep adding heat, the atoms shuffle past each other faster, and faster. The hotter the liquid, the faster atoms will move past each other (diffusion is faster when hot).

As the atoms get more heat energy, they move faster and faster (increase in kinetic energy. Heat energy transforms into Kinetic energy).

As they move faster and faster, the space between the molecules gets bigger and bigger - just like when you are playing football- you can walk as a team, but if you start to run, then the team spreads out.

The molecules are still attracted to each other, but move quickly past each other instead of lingering. Its as if the attractive person has farted. You still want to chat, but you walk away and then walk back to see if the smell has gone, it hasn't, so you walk away again.

As the space between the molecules increases, the matter expands - this is how a thermometer works.

If we keep adding heat, some of the atoms will shuffle past each other so fast, that the ones at the top of the liquid will zoom off into the air - this is Evaporation

If we keep heating the liquid all of the atoms will gain sufficient energy to move fast enough to become a gas.

Please note - the atoms are still the same size. Their size never changes. The space between the atoms increases (when heat is added, because they are moving more) or decreases (when heat is removed, because they are moving less)

Gas

Now our atoms are in the gas state. They zoom all over the place, and have no attraction for each other. This is like you and the attractive person. You have realized that they smell, and will always be smelly, so you run away.

If they are in a container, or in a balloon, they will smash against the walls of the container or balloon and bounce off. This creates the pressure which keeps a balloon inflated.

The hotter it gets, the faster the gas atoms will move. Leave the balloon in the sun and the balloon will expand as the walls of the balloon are hit harder by faster moving atoms.

If the gas is in a container, then the faster movement will increase the pressure in the container as the atoms are hitting the walls faster and harder.

This knowledge is super important:

All of Chemistry is about the movement of atoms and how they interact with each other

Interactive animations and videos

Have a play with the 'states of matter' interactive animations. See if you can cause the lid to explode off the top of the container. What different things can you do to cause it, and how does that translate to real life situations?

Watch the videos - they will help to clarify and consolidate your knowledge around this.

‪States of Matter‬

Expansion and Contraction

Atoms always stay the same size

But matter can expand and contract

But how?

As atoms gain more energy, they move more

This increased movement increases the space between the atoms

This causes the matter to Expand

As atoms lose energy, they move slower

This slower movement reduces the space between the atoms

This causes the matter to Contract

More heat energy = more kinetic energy = more space = expansion of matter

Less heat energy = less kinetic energy = less space = contraction of matter

State Changes

Add Heat Energy

Increased Movement

Remove Heat Energy

Reduced Movement

Add Heat Energy

The application of Heat Energy causes Atoms to move more.

If the atoms move enough, then they can change state!

Melting

If we start with a Solid, and add heat energy, the solid will melt into a Liquid

Evaporation

If we keep take the Liquid, and add heat energy, the liquid will evaporate and become a gas

Remove Heat Energy

This process can be reversed by removing heat energy

Condensation

If we take a Gas and remove heat energy, the gas will condense into a Liquid

Solidification

If we take the Liquid and remove heat energy, the liquid will solidify (freeze) into a Solid

Sublimation and Deposition

Sublimation

Sometimes, when you add heat to a Solid it becomes a Gas, skipping the liquid phase (phase and state mean the same thing and can be used interchangeably).

When a substance moves straight from a Solid to a Gas, this is called Sublimation.

In other words:

Sublimation is: Solid, add heat, Gas

Substances that do this include Iodine as well as Dry Ice (Carbon Dioxide)

Deposition

The substances that undergo Sublimation, also undergo Reverse Sublimation

Take Iodine, or Carbon Dioxide, remove heat, and they will Deposit on the cold surface. This process of depositing on the cold surface is called deposition

Deposition or Reverse sublimation is: Gas, remove heat, Solid

Evaporation vs Boiling

Evaporation and Boiling are very similar - the transition of a liquid to a gas

The difference is that Evaporation occurs at the Top of a Liquid and Boiling is Inside the liquid

Also, Boiling is Fast, Evaporation is Slow

Evaporation

With Evaporation, the molecules in the liquid are moving around, bumping each other. Sometimes some of the molecules are moving fast enough that when they bump the molecules on the top of the liquid, those molecules get pushed out of the liquid into the air, they are now gas molecules.

This bumping is why puddles can evaporate without boiling

This bumping is also why puddles can slowly evaporate even when it is cold

This bumping is also why puddles evaporate faster on hot days than on cold days

Boiling

With Boiling, the molecules are gaining heat energy at or near the bottom of the container. This means that the atoms near the bottom have enough energy to loose their attraction tot he other atoms, and start to fly about, but they are still surrounded by liquid molecules, so a bubble is formed. It looks kind of like a fight breaking out in a mosh-pit

Because there are fewer atoms per cubic millimeter in the bubble, than there is in the surrounding liquid, the bubble is less dense than the liquid, and so it rises up

Distillation

Adding energy then removing energy

Evaporation then Condensation

Distillation:

Take your mixture

Heat liquid so that evaporation occurs
Cool the vapor in so that condensation occurs

The condensate will be pure

Distillation uses two of the state changes: Evaporation and Condensation

Distillation is used if there is a mixture of substances in the liquid and you are wanting to separate them.

Like our wine experiment. Water boils at 100 degrees Celsius, whilst Ethanol boils at 78 degrees Celsius.

So, if you heat the wine, at around 78 degrees Celsius, the bubbles that form are NOT water, but are ethanol! As the ethanol molecules have enough kinetic energy to overcome their attraction to each other and become a gas

The ethanol evaporates, but then hits the cold glass test tube. When this happens the ethanol condenses on the sides of the test tube, then the droplets of ethanol slide down to the bottom of the test tube where it is collected.

To prove we had collected ethanol we set fire to it

Distillation at the Beach

You can use the Distillation to get fresh water from sea water too!

All you need is something to cover the hole - plastic sheeting is best

And something to collect the fresh water in

Then boom - fresh water from sea water using the power of distillation!

How could you do it?

Diffusion

Diffusion is the movement of atoms or molecules of one type through a collection of other atoms.

Because this movement means that atoms are moving past each other, it can only occur in Liquids, and Gases

Diffusion is the movement of particles from an area of high concentration to an area of low concentration until equilibrium occurs - then, on average, there is the same number of each type of molecule throughout the solution.

This movement occurs randomly and happens faster if there is more heat energy, which makes the atoms move faster.

Try the interactive below by clicking on it.

‪Diffusion‬

Student Diffusion in the Gym

Imagine your class are sitting in the gym. This is a area of high concentration of students. The empty spaces have no concentration.

Then I say spread yourselves out across the gym.

If we took a drone photo of the gym 10 seconds after I gave the instructions - some students would have already moved to the furthest reaches of the gym, but these guys are the lowest in number, so that is a low concentration. There is also a group of students talking in the middle, who have yet to follow instructions, this is the area of high concentration. Everyone, else is slowly moving out, but as only 10 seconds have past, they are still near, but not at, the middle so they represent an area of medium concentration.

This represents a concentration gradient (like a hill), high where the most students are, medium, where some are, and low, where there are very few.

If we then film the following 15 seconds, we will see that the students move from the area of high concentration, to the area of low concentration. (as a gradient (hill), this means they are moving down the gradient).

It we took another drone photo of the gym 60 seconds after the instructions, then we will see that all the students are randomly distributed and freely moving throughout the gym, and there are no areas of high or low concentration, rather we have equilibrium.

Diffusion in a Liquid

If you place a drop of food coloring into a glass of water, eventually the entire glass is colored evenly with that dye. Use the model below to observe how the food coloring diffuses throughout the water.

Below is a model showing pure water. Try placing a drop of food coloring by clicking somewhere in the container. Observe how the dye diffuses. Click on the snapshot button and describe the diffusion process

Diffusion in a Gas

Diffusion is the net movement of particles from areas of high concentration (number of particles per unit area) to low concentration.

This happens in gases as well as in liquids.

Imagine you are watching a movie with your friends. Then you fart. Is everyone going to smell it?

Below is a model of diffusion in a gas. The blue molecules are the

It is because of diffusion, that the person sitting nearest the person that farted, will smell it first. It is also the reason that the fart is weaker, the further away you are.

Below is a model of diffusion in a gas.

The Blue dots are the smelly sulfide molecules released in a Fart. The other dots are the air, with the white being oxygen and the green as nitrogen

Click the Run arrow at the bottom of the model to observe the diffusion of the Fart in the room low temperature.

Reset the model by clicking the Reset button and increase the temperature by moving the temperature slider up. Click the Run arrow at the bottom of the model to observe the diffusion of the fart across the room at a higher temperature.

Dissolving

When you mix a spoon of sugar into a glass of water, it disappears and the water becomes sweet

This mixing of a solid with a liquid is called dissolving

For this the molecules of the solid become surrounded by, and float in, the liquid

Solution = Solvent + Solute

When you dissolve a solid in a liquid, you get a new thing... a solution

So, when you mix Salt with Water, you get a solution ... Salty water!

Likewise

Coffee powder with water = black coffee

The Solid, or Coffee, is called a Solute

The water is the Solvent

And the mixture is called a Solution

A Solute that dissolves in a Solvent makes a Solution

If the Solute dissolves then it is Soluble and makes a Solution

If the Solute does not dissolve then it is Insoluble and no solution is created

(e.g. sand that blows into your glass of water at the beach)

The way I remember it is that Vodka is a Solvent

If you drive your ute after drinking Vodka you might end up in a lake (the solution to drink driving)

Solute = ute = solid

Solvent = vodka = liquid

Ute + Vodka = Crash into lake

Solute + Solvent = Solution

Dilute ... Concentrated ... Saturated

When making coffee, you can use different amounts of coffee powder in your cup of hot water.

If you use only half a spoonful, the coffee will be very weak. If you use four spoonfuls, the coffee will be very strong. You can even use so much coffee powder that it stops dissolving, and it creates a saturated solution.

This happens when each coffee molecule is surrounded by water molecules, and there are no free water molecules left to dissolve any more coffee.

The saturated solution can't dissolve any more solute. You might have heard the word "saturated" used to describe people walking in the rain. If they are damp, it means it just rained a little bit on them. If they are wet, it means it rained enough to soak their clothes. If they say they are saturated, it means it rained on them for so long that their clothes are completely soaked.

Mixtures

Matter

Pure Substance

Pure Substance: Element

Gold

If I buy a Gold gangsta chain to wear to school, I want it to be pure gold. This would be a pure substance. The only atoms it would contain is ... gold. Gold is on the periodic table, so it is an element. It cannot be broken chemically. So, my

Gold is a pure substance and it is an element.

Pure Substance: Compound

Water

I take a glass of water. Water has nothing else in it. Water is a Pure Substance. If I zoom into the water, I will see that each molecule is H2O; that is, it has 2 Hydrogen atoms and 1 Oxygen atom. H2O is a compound.

A compound can be broken into parts chemically.

If you run an electrical current through water, the H2O will break apart, with the Hydrogens gathering around the negative electrode, and the oxygens gathering around the positive electrode. Hydrogen is a pure element as is Oxygen

Water is a pure substance and it is a compound

Mixture

Heterogeneous Mixture: Suspension

Flour water

If I take my cup, and add some Flour to it, it is a mixture

I can stir the flour in the cup. It might look uniform; however, if I look very closely, I will see the bits of flour floating in the water. The flour is suspended in the water, floating around in it. If I leave the cup overnight, I will find that all the flour will settle to the bottom of the cup. This is a suspension because the flour can float and be suspended in the water!

Also, if you look at the flour water under a magnifying glass, you will see bits of flour and clear area with no flour - because it is not the same everywhere, it is called Heterogenous.

So Flour water is a heterogeneous mixture and it is a suspension

Heterogeneous Mixture: Colloid

Milk

Milk is an interesting one, if you look at it it looks all the same everywhere, so it is appears homogenous. However, if you look at it under a strong microscope, you will see that it is actually small white balls of fat and protein floating in water. So it is actually Heterogenous.

If you leave it sit overnight, the fat and protein will not sink to the bottom. They are too small. The particles are smaller than the particles in a suspension so the effect of gravity is unable to pull them past all the water molecules, so they can not sink to the bottom.

The molecule sizes are halfway between the Solution and Suspension.

Milk is a Colloid

Milk is a Heterogeneous Mixture and is a Colloid

Homogeneous Mixture: Solution

Salt water

If I take my cup of water, and add some salt to it, it is no longer a pure substance. Rather it is a mixture.

If I stir the water and it all dissolves and disappears, then I have a Solution. The reason it disappears is because the molecules are so small. If the molecules are so small that you cannot see them, even with a microscope then it is a solution.

So Salt water is a mixture and it is a solution

Food colouring

If I take my cup of water and add some food colouring, it is no longer a pure substance, again it is a mixture.

Once the food colouring as diffused to all parts of the cup of water, then the colour is the same everywhere. If I take take 2 drops from the cup, one drop in an eye dropper from the top of the cup, and on from the bottom, and I look at the drops, the will be the same colour. Things that are the same are said to be Homogeneous. 'homo' means the same. 'hetero' means different.

So food colouring in water is a homogenous mixture

If we look at the food colouring under a microscope, we can not see the molecules that give the food colouring its colour - because they are too small even for a microscope. So, they food colouring in water is a Solution!

So food colouring in water is a homogeneous mixture

In fact, Coca Cola is also a Solution!!

Separating Mixtures

You can use a range of methods to separate mixtures, these include: Decanting, Sieving, Filtering, Distillation, Magnetic Separation, Chromatography and Centrifuging.

Decant

This is when you pour off the liquid, but leave the solids in the container
- Effective for separating heavy visible solids from the liquid
  - e.g pebbles when panning for gold
  - Who cant? De cant!

Sieving

This is when you pour the liquid and the solids into a porous receptacle, the liquid passes through the small pores, but the solid is trapped - thus separating the liquid and the solid
- Effective for separating solids that can be seen with the eye
  - e.g vegetables from hot water when boiling your vegetables

Filtering

The filter has microscopic pores, the liquid will pass through, but the solids will be trapped
- Effective for separating solids that can be seen with a magnifying glass
- Can separate suspensions
  - e.g coffee grounds when grinding coffee - but the smaller coffee particles will move through the filter paper

5. Centrifuging

Spinning the sample in a very fast circle, increases the 'gravity' imposed on the substance, causes solids in the sample to move to the bottom of the sample
Effective for separating solids that can be seen with a microscope
Can separate colloids
- e.g separating blood cells from the water (plasma) in our blood

Distillation

This is when you evaporate the liquid away from the solid, the liquid's vapor then hits a cold surface and then condenses back into a liquid
Effective for separating solids that can-not be seen, including solids that can-not be seen with a magnifying glass and solids that can-not be seen with a microscope
Effective for separating solids that have fully dissolved in the liquid
Can separate Solutions
- e.g separating salt from water

5. Chromatography

separates Solutes in a Solution according to the size of the solutes
e.g used in DNA analysis (Gel electrophoresis)

6. Magnetic Separation

using a magnet to remove magnetic elements from a mixture
- E.g separating Iron from sand - used at Glenbrook Steel Mill at Waiuku

Energy and Atoms causing observed phenomena and explained by our Scientists

Science TimeThis is Daniel, David, and Wilson's science channel.

The Amazing Life Of_ Science

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