Elements - Metals and Non-Metals

Elements and Pure Substances

Over the last couple of weeks, we have learned how to separate mixtures. We have been separating them into their pure substances.

Today, we learned what some of those pure substances are:

• elements
• compounds

Some elements exist as atoms, while some exist as molecules. The elements are all found on the Periodic Table, which has their special symbol.

Compounds are formed when different elements react. This means they join together chemically, forming bonds between the atoms. Compounds can be molecules (like some elements) or they can be ionic. We learn more about these in the next few years of Science and Chemistry...

Our task today was to classify all matter from what we have learned in the last few weeks and in today's lesson.

Chromatography

Chromatography is a method used to separate differently-coloured pigments.

We did an experiment to help us understand what chromatograhy really is and how it works. Thank you to Angus and Flynn for the results:

The Set Up (BEFORE)

The Results - the colours have separated (AFTER)

Separating Solutions - Evaporation and Distillation

First, we had to DESCRIBE Evaporation and Distillation:

For homework, we need to EVALUATE wen each method should be used:

Evaporation

Today, we learned about one way to separate solutions: evaporation.

We did an experiment (p36 in the Scipad) to help create a sequence to explain how evaporation works.

This was our apparatus. We have to DESCRIBE what happened
and EXPLAIN how this worked.

One of the groups' results - it is a solid now, not a solution!

Separating Suspensions

I was so impressed by Daniel's piece of writing that I felt it needed to be shared:

"Decantation is a very quick method for separating a mixture of a liquid and a heavier solid. This works by first letting the solid settle on the bottom of the beaker, and then you can pour the water off the top of the solid without disturbing it. The advantage of decantation is that it is very quick, but it is also rough and does not always work the way it is meant to. It cannot be used to separate a mixture of a liquid and a light solid, like sawdust and water. The particles of sawdust are suspended in the water. They are so light that they do not sink down to the bottom for a long time.

Filtering is a very good method used to separate solids from liquid. This method works by placing a sieve or micron paper over a container or beaker and pouring the mixture onto the filter. The filter separates the solid from the liquid and the liquid passes through without carrying the solid. For example with the sawdust experiment, the sawdust stayed on top of the filter paper while the water passed through. This is because the sawdust bits are too big to fit through the paper, but the water is not, so it passes right through.

A Centrifuge is a piece of equipment, usually driven by an electric motor, though some older models were spun by hand. The Centrifuge puts an object in rotation around a fixed axis, applying a force perpendicular to the axis. A Centrifuge is also used to separate the components of blood in blood banks. A Centrifuge is the most efficient type of filter, but it lacks portability and simple nature. You cannot just go out camping and take a centrifuge with you. First is requires a power source, and secondly it is too big to just chuck in your backpack.

In my personal opinion, I think that the paper filter is the best option. I think this because this method is easy to carry out, it can be carried out nearly anywhere, it does not require a power source to be performed, and it is also very efficient. Using a 1-micron paper filter you can remove harmful diseases from water is you are out tramping and avoid becoming severely ill. Although a paper filter is a very good option, it is not always the best. If you were cooking potatoes or pasta it would just be so much easier to apply decantation. Also if you are giving blood it is much quicker and easier to use a Centrifuge to separate the different parts of blood rather that using paper.

By Daniel Coulter

Solutions and Solubility

Today, we learned about solutions. If substances are soluble, they dissolve to make a solution. Some solutions have a lot of solute in them - we call these concentrated. Some have very little solute in them - we call these dilute.

How easily something dissolves is called its solubility. Some substances dissolve very easily (so have high solubility). Some are difficult to dissolve (so have low solubility).