Separation Techniques-A Quick Look (Part 2)

As said in my previous post, here are the topics I'll be covering. 

1. Filtration
2. Chromatography
3. Evaporation (to Dryness)
4. Distillation and Fractional Distillation
5. Crystallisation (as mentioned in previous post) 
6. Magnetisation 
7. Sublimation
8. Separation of immisicible liquids 

Now, I'll be talking about Sublimation! Sublimation is a process in which a solid substance gains heat and turns into a gas substance, bypassing the liquid state. Examples of substances that sublime include Iodine and Dry Ice (Solid Carbon Dioxide) 

Taken from: http://commons.wikimedia.org/wiki/File:Dry_Ice_Sublimation_2.jpg

Next, there is separation of immisicible liquids. They are basically liquids that don't mix with each other. To separate them, we use a separation funnel. The liquid with the higher density will remain at the bottom of the funnel while the liquid with the lower density will float on top. Take an example, water and oil. Oil has lower density, so it will float on top of the water, so when separating the two liquids, the water will flow out and into a beaker, whereas the oil will be left in the funnel. 

That's all for now, hope you've learnt a bit more! ^-^ 

Separation Techniques-A Quick Look (Part 1)

Another post for the day! (: It'll be about Separation Techniques, and I'll just cover a few different techniques. 

When separating solutions/chemicals etc, there are many ways of doing it. I will list them out, and highlight those I will be covering. 

1. Filtration
2. Chromatography
3. Evaporation (to Dryness)
4. Distillation and Fractional Distillation
5. Crystallisation (as mentioned in previous post) 
6. Magnetisation 
7. Sublimation
8. Separation of immisicible liquids 

Let's start with filtration. Filtration helps us separate (solid and insoluble) substances from liquid. An example would be trying to take out sand from water. 

The principle behind this is that undissolved solid particles are too big to pass through the filter paper, and they are left behind on the filter paper. Another name for the particles left behind is residue. The liquid that flows out and is collected is known as filtrate. 

In real life, we use filtration at the water treatment plant, where we remove solid waste from water.

Next, evaporation (to dryness). This procedure is used to recover a solute from a solution. In this process, we heat the solution up, causing the solvent to gain heat and evaporate, leaving the solute behind. However, this method is not suitable for solutes that can be decomposed by heating, such as sugar. Despite getting the solute back rather quickly, this process has a flaw. Soluble impurities will also be left behind, together with our solute. 

Lastly for this post, I'll be covering Magnetisation. As we can infer from the name, it involves us using a magnet to separate the substances/solids. Magnetic substances are separated from non-magnetic substances by using a magnet, since magnetic substances will be attracted to the magnet. Example, when we are trying to separate a mixture of sulfur from iron fillings. This method is useful in real life, where we use strong magnets to lift cars from the scrap metal pile at junkyards. 

This post has come to an end, the other two techniques will be mentioned in my next post, which should come about tomorrow! Have a great Labour Day holiday!! (: 

The Periodic Table-Atomic Number, Mass Number and Relative Atomic Mass

Hey everyone! This is rather late (the topic as in), because we actually learnt about it in February but I realised I never wrote anything on it! D: So here is a bit of information now... 

Also, the nucleon number/mass number can be derived by adding up the number of protons and the number of neutrons together. Let's take the element Silver as an example. It has a 47 protons, and 61 neutrons, which means it has a nucleon number/mass number of 108. The various values can be taken/derived from the Periodic Table. The image below will show you how to get the different values. 

However, during the exam, the periodic table will be given to you, and the atomic mass will be a whole number, so you do not need to worry but getting a weird number! One more thing, the atomic mass is the nucleon number/mass number!

(Credits to: http://kaffee.50webs.com/Science/activities/Chem/Activity.Atomic.Structure.1a.html for the photo!) 

We also learnt about isotopes. What are isotopes, you ask? Isotopes are atoms of the same element, but they have different number of neutrons. The average atomic mass of an element is calculated based on the average mass of all the isotopes available. 

That's all for now! (: Hope you learnt more!

Physical and Chemical Changes

I haven't updated this blog in a while so... Here's a post on what we did on 27th March! It's on Physical and Chemical Changes. It's mainly to help us differentiate between them (: 

Here is the first experiment we had that day. More specifically, it was a teacher demonstration.

Basically, iodine crystals were placed in a round-bottomed flask, which was then gently heated. When the crystals were heated, they sublimed to form purple gas. Later, the flask was cooled and the purple fumes were deposited on the side, forming a solid again. 

Then, we did another experiment, this time we did it by ourselves. We were made to heat two different substances, the first one is Sodium Chloride, the second one was Copper (II) Carbonate. When heated, the Sodium Chloride melted into liquid, whereas the Copper (II) Carbonate turned into the colour black upon heating. After leaving them to cool down for a while, the Sodium Chloride solidified, whereas there was no observable change for the Copper (II) Carbonate, meaning it still looked black after cooling. 

                                         













We then realised that the formal change was a physical change, because the substance went through a change of state, from solid to liquid, and then liquid to solid. Likewise, the Iodine crystals also went through a change of state, sublimation (solid to gas), thus it is a physical change too. However, the latter change is a chemical change, because the change is irreversible, which means that the Copper (II) Carbonate cannot be changed back to its original green colour. When the Copper (II) Carbonate was heated, a chemical reaction took place. The following word equation will show what happens when it is heated:
Copper (II) Carbonate --> Copper (II) Oxide + Carbon Dioxide
Since another substance is produced after heating the Copper (II) Carbonate, we can see that the latter change is a chemical change.

From this lesson and experiment, I learnt what makes up a physical change and what makes up a chemical change. A physical change is the change of state, and it is a reversible process. However, a new substance is produced during a chemical change, and the process is irreversible.