YR 8 Topic 3: Separation of Mixtures

topic 2: Separating mixtures

Explain the importance of proper water sanitation

Diarrhoea kills 4,000 children every day around the world. In Africa, it is the leading killer of children under 5 years old, causing more deaths than AIDS, malaria and measles combined. But there are very simple solutions to this problem - clean drinking water, hygienic toilets and effective hand washing.

Providing people in developing countries with access to clean drinking water, effective sanitation and education on the importance of good hygiene practice are some of the most cost effective ways of achieving real results in health. It helps them beat poverty and can help to prevent around 2.4 million unnecessary deaths every year.

Recall mixtures and solutions

Mixtures are absolutely everywhere you look. If they are mixed up, their properties in physical terms would remain the same. An example of this is salad. If you mix the lettuce, tomatoes and cucumbers, you yield the same physical properties. You can still sort which item is which as well.

In a solution, the mixture of substances involves dissolving the substances into a new form of solution. An example is tea. To make a tea, milk and sugar is dissolved in tea, and one cannot separate the milk or sugar in the tea again.

Explain the differences between solute and solvent

A solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent. A common example is a solid, such as salt or sugar, dissolved in water, a liquid.

As a rule of thumb, there is usually more solvent than solute. Be patient with the next sentence as we put it all together. The amount of solute that can be dissolved by the solvent is defined as solubility

Outline why water is a good solvent

Water is called the universal solvent because more substances dissolve in water than in any other chemical. This has to do with the polarity of each water molecule. The hydrogen

side of each water (H2O) molecule carries a slight positive electric charge, while the oxygen side carries a slight negative electric charge. This helps water dissociate ionic compounds into their positive and negative ions. The positive part of an ionic compound is attracted to the oxygen side of water while the negative portion of the compound is attracted to the hydrogen side of water.

Explain the factors that affect solubility

Solubility is defined as the upper limit of solute that can be dissolved in a given amount of solvent at equilibrium. There are many factors that influence solubility and the factors

1) The polarity of the substance and the polarity of the solvent (like dissolves).

2) The temperature of the solvent (for solids, the higher the temperature of the solvent, the higher the solubility -- sugar in hot tea dissolves more easily than in iced tea -- but often for gases, the solubility goes down at higher temperature -- and why soda goes flat when its warm).

3) The size of the particles and whether or not you stir the solution will help speed up the dissolving process, but it will not change the total amount that can be dissolved (whereas #1 and #2 do affect the total amount dissolved)

Describe how filtering works

Explain saturated solution

Describe how salt can be obtained from seawater or from mines

Explain how to purify water

Compare different solvents

Recognise the nature of hazards associated with solvents

Discuss distillation in terms of changes of state

Describe how mixtures of dissolved solids can be separated

Key Terms:

solvent
particle
solute
filter
distillation
solution
vapour

water
partical model
alloy
filtrate
acetone
condense
Liebig condenser
desalination

pure solution
white spirit
separation
distillate
boiling point
chromatograms
sanitation

temperature
salt
crystal
solvents
mixture
evaporate
salinity

dissolve
solubility
soluble
insoluble
residue
distillation flask
extracting
chromotography

Class Assignments:

Solubility
Partical Theory worksheet
Extracting Salt from Mixture practical
What Substances Dissolve In Water practical
Mysterious M&Ms practical
Sweet Tooth worksheet.
Rock Candy practical
Saturation practical
Solubility Graph
Temperature Effect on Solubility practical
Making Pure Salts practical
Salty Sea Water practical
Super Solvents practical
Solutions Revision Poster

Distillation
Distillation worksheet
Labelling the Liebig Condenser
Distillation of ink practical

Chromatography
Forensic Evidence
Separating Colours practical

Useful Links:

Water
Water Sanitation WHO
Solubility
Click here for an interactive activity to see how caves are formed.
Check out this fun dissolving activity
Click here to check out an interesting animation on solubility
Click here to try the Particle Model interactive activity
Mining for Salts
BBC Bitesize Particle Model
Inquiry In Action from ACS Dissolving
Solubility Virtual Lab animation

Distillation
Chem4Kids review on States of Matter
Distillation
Distillation animation from RSC
School Science.com Discover petroleum distillation animation
What Happens to The Salinity of Seawater When It Freezes?
Desalination process

Chromatography
Chromatography from Buzzle
Kids.Net.Au encyclopedia on Chromatography
BBC Bitesize Separating Mixtures
Chromatography animation
Pearson Lab Bench chromatography animation

Video Clips:

Dihydrogen monoxide (better know as water) is the key to nearly everything. It falls from the sky, makes up 60% of our bodies, and just about every chemical process related to life takes place with it or in it. Without it, none of the chemical reactions that keep us alive would happen - none of the reactions that sustain any life form on earth would happen - and the majority of inorganic chemical reactions that shape the surface of the earth would not happen either.

Lack of access to water and sanitation and poor hygiene is one of the principal causes of death and disease worldwide. It also leads to loss of productivity and forms a major barrier to development.

Globally, 2.5 billion people do not have access to basic sanitation facilities and as a result, the lives of billions of people are adversely affected. Sanitation receives only 12 per cent of the total pool of global aid funding for water and sanitation. While nearly 800 million people still lack decent water, reallocating funds more evenly makes sense given the larger needs in sanitation.