Explaining velocity

Imagine 3 moving things

1) sports car

2) bunny running after a carrot dangling on the sports car

3) human, running after his runaway bunny

One thing that probably jumps out at you after you visualise this scene, is that all 3 things are travelling at different speed.

speed = velocity

velocity is about HOW FAST something is.

Sports car = VERY FAST velocity

Rabbit = FAST velocity

human = SLOW velocity

Scientists go one step further with knowing the velocity of something, because it can tell you about the amount of kinetic energy of the object!

If the bunny is 0.1Kg heavy, and is running at a speed of 1m/s

it has kinetic energy of 0.05 Joules

What scientists also know from Newton’s first law, is that if the bunny is running on a frictionless surface,

that kinetic energy of 0.05 joules allows the bunny to RUN FOREVER at the speed of 1m/s without stopping or without giving it a choice to stop either.

Taking about no choice of stopping, if you are a spacecraft sent out to to explore Neptune or Jupiter or something, there is a chance that you just keep going and going outwards into space after you pass by Jupiter because you cannot stop at all…

Velocity = speed + direction!

the bunny with 0.05J of energy and the spacecraft will keep going in the SAME DIRECTION, provided nothing happens to the bunny or spacecraft…

 

 

Metals and non-metals

Metals and non-metals are like guys and girls… they both behaves on totally both side of a spectrum!

Metals like to give up their outermost electrons.

Non-metals, on the other hand, like to take in more electrons to fill up their outermost shell!

You might be able to imagine that metals behave one way with other metals, and that non-metals behave in one way with each other but when both of them meet…

metals_non_metals

the reason is all so that everyone is happy and whether metal or non-metal, all can achieve a stable electronic configuration!

Notes on metallic bonds

When metal particles and other metal particles come together, they form metallic bonds.

In metallic bonding, every metal atoms give up their valence shell electrons.

The beauty of metallic bonding is that the metal atom can happily give up his valence electrons and be happily stable, and the presence of other metal atoms also doing the same thing allows all of them to do so.

and  and these valence electrons become the free electrons that help metals conduct electricity and heat…

 

Gene amplication logic

Oh dear,  a fire breaks out!

In a room full of people (aka proteins), only 1 protein is responsible for saving the fire. So this protein takes a bucket of water, and rushes to put out the fire.

Or imagine another scenario

The protein responsible for putting out the fire contacts a few people in the room that are sleeping fire wardens… each fire warden contacts a few sleeping firefighters… the whole room of inactive people suddenly wakes up into action! The original protein simply needs to do one little thing… which is to activate the wardens, and each warden in turn does one small thing, to activate the firefighters… and finally the vast numbers of activated firefighters fights the fire!

Explaining Diffusion

Hi! 🙂

Diffusion is really about one thing actually… 

which is… that

particles move about randomly!

ImageTo give you an example… you and your friend walked into a party

Imagenow, if both of you moved randomly, after a while, you will definitely spread out!

Spreading out takes time! But start out with particles next to each other, they will be further apart after a while by random movement, and eventually fully spaced apart!

Image

 

Here is another example

Image

Now think about the following experiment

Image

 

you see the brown colour of bromine gas spreading to the top after the air in the two cylinders are allowed to mix!

Image

 

Do you know why the colour of bromine becomes lighter after it has spreaded out?

The reason is because bromine has become LESS CONCENTRATED! 🙂

Next we will look at another example… 

which is the very striking purple compound called Potassium Permanganate

Put crystals of Potassium Permanganate at the base of a conical flask and add water… you will see

Image

The reason why this has happened is because

Image

 

Again, take note that the concentration of Potassium Permanganate particles actually decreased as it spreads out into the liquid! 🙂

Acid

Hi I am freshly squeezed from a lemon! I am lemonade

Do I

taste sour? Yes!

Conduct electricity? Yes!

react with metals, bases, and carbonates? Yes!

Image

The baking soda (a base) and the lemon juice (an acid) combine to release Carbon Dioxide gas. The liquid soap turns the bubbles into a foam that often erupts right out of the glass.

Image

So I am lemon juice, and I am ACIDIC!

An acid can do all 3 things mentioned above!

Image

An acid has pH less than 7!

Rain, wine et-cetera et-cetera all contain different acids! Rain’s acidity comes from dissolved carbon dioxide, while wine’s acidity comes from fermented grapes!

They all have pH below 7, so what is pH?

Image

pH measures the concentration of hydrogen ions in something!

What are hydrogen ions?

First let us see what all acids have in common!

Image

They all have H in them!

When in water, the H splits apart from the acid to become H+ ions! They left their electrons behind with their acid pal to form a negatively charged ion.

Image

Why do you need water to be present to have H+ ions?

Because water has the ability to attract the H from the acid to split from the acid!

Image

the hydronium (H3O+) here is the same as H+!

H+ ions are the big deal that makes acids who they are!

hydrogen_ion

If you are an acid, you will react with metals, and other stuff… and that is all because your H+ ions are attacking those guys!!!

reactions_of_hydrogen_ion

H+ makes an acid incredibly powerful

A really powerful acid releases all the H immediately to form lots and lots of H+ ions when it dissolves in water.

strong_acid

Whereas a weak acid does not release all of its H to form H+ ions, it may hold on to its H! 🙂

weak acid

Compare the 2 pictures above, can you see that there are more H+ ions per unit volume for strong acids compared to weak acids?

This means that strong acids have a higher concentration of H+ ions than weak acids.

Recall that pH measures amount of H+?

pH

Can you see that a strong acid contains a really large amount of H+ ions?

This explains why chemists need to take precautions when working with strong acids!

source:

http://www.sciencebob.com/blog/?tag=lemon-juice

Explaining how osmosis occurs

Osmosis is the movement of water molecules from a region of higher concentration to lower concentration… (not forgetting the partially permeable membrane) But what on earth does it means? 🙂

Isn’t water just another compound? Why is it so special that there is a term called osmosis to describe how it moves?

It is actually quite simple to understand and you will find out that water is not really that special after all!

1st thing to note:

Large quantities of water molecules constantly move across membranes by random movement!

For example, it has been estimated that an amount of water equivalent to roughly 250 times the volume of the cell diffuses across the red blood cell membrane every second; the cell doesn’t lose or gain water because equal amounts go in and out.

2nd thing to take note of

Water molecules can dissolve other substances.

dissolve_saltYou put a cube of salt into a cup of water and the cube of salt rapidly disappears!

 

 

 

salt_dissolve

The reason is because the water molecules attract the salt particles out of the cube…

solution

 

 

 

 

 

and distribute the salt particles all around the liquid

That is why light can pass through the gaps and we cannot see our salt particles anymore!

 

 

3rd thing to take note of

Water molecules are locked with their solute particles because of the attraction towards the solute particles.

water_solvent

Take note of the cluster of water molecules that are binded to the solute! The other water molecules are free!

 

 

osmosis

Take note of the water molecules that are also binded to the sodium ions!  Take note of there is a lot more FREE water molecules on the left than on the right

 

 

 

 

4th thing to take note:

You must have a partially permeable membrane to block solute particles from going over to the other side

permeable_membrane

Now finally,

we can go into the idea that it is the free water molecules moving randomly that causes this phenomenon called osmosis

osmosis1

Notice that the volume on both sides of the membrane is the same

There is a lot more FREE water molecules on the right

So there is a higher concentration of FREE water molecules on the right compared to the left

Therefore by random movement alone, more water molecules will find themselves on the left side!

osmosis2

Same thing for this picture!

 

 

 

 

 

 

osmosis3

Last but not least, see if you understand this picture below

osmosis4

You will definitely encounter pictures of some visking tubing etc having higher water levels on one side than the other…

the reason is because osmosis balances out the number of FREE water molecules on both sides. But one side has more solute particles and binded water molecules to them so the water level is higher!

Hope you have gained a better understanding of osmosis! 🙂

source:

http://arbl.cvmbs.colostate.edu/hbooks/cmb/cells/pmemb/osmosis.html

http://serendip.brynmawr.edu/sci_edu/waldron/pdf/OsmosisProtocol.pdf