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Grade 6 Chem L4
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Separating Mixtures
Separating Mixtures
What type of mixture do you think will be more challenging to separate and why?
Why do we want to
separate mixtures?
Separation Processes
Mixtures can be separated due to differences in component properties.
Example: Magnetism, density, particle size,
etc.
Mixtures range from those that can
be easily seen with the naked eye, to
those that seem to be pure substances.
As mixtures range, so do the methods
used for separating them.
Hand Separation
Picking Apart
- Used when you can easily see the different pieces (Heterogenous Mixtures)
- Works well for small quantities of mixtures
- Too time-consuming and laborous for large quantaties
Filtration
- Uses a device that allows smaller particles to pass through but holds back larger particles
- Removes solid pieces of matter from a liquid or gas
- Liquid that passes through is called the filtrate
- Solid material held back is called the residue
What are some examples of filters used in our everyday lives?
Density Separation
Mechanical mixtures are made of matter with varying densities.
Some substances may float or sink in certain liquids and can thus be seperated.
Magnetism
Magnetism can be used to seperate components in mechanical mixtures if one of the substances is magnetic.
Distillation
Another common separation process is called distillation. Distillation uses boiling to separate mixtures of liquid solutions. It takes into account that different substances in the mixture will have different boiling points.
For example, if you heat salt water the water in the solution will boil before the salt. The water will then evaporate leaving the salt behind. If the steam from the water is collected it will turn back into liquid as it cools. This cooled water will be pure water without any salt.
Distillation
Indigenous Knowledge
First Peoples use of separation and extraction methods
- Eulachon oil
- Extraction of medicines from plants
- Extracting dyes from plants
Eulachon Oil
Eulachon oil is separated by putting the fish in what's called a stink box, where the blood drains into cedar boughs laid on the bottom. The eulachon ferment for several days until their eyes turn red before they're moved to another box for cooking at a precise temperature that releases the grease.
Extracting Medicine
Medicine is all around us. For centuries, Indigenous peoples found all of the medicine they needed on the land, using plants to treat a variety of ailments and conditions. Plants were, and still are, an important component of indigenous medicine.
Indigenous peoples have identified over 400 different species of plants (as well as lichens, fungi and algae) with medicinal applications.
Extraction Methods
All different parts of plants — roots and underground parts, bark, leaves, buds, flowers, fruits, and sap or pitch — have had recognized medicinal uses, and there are many different modes of preparing and applying them.
Preparation methods:
- Paste: Fresh plant parts are crushed to obtain a paste used externally or internally.
- Poltice: Plant parts are crushed to obtain a soft moist mass generally used externally to treat swellings, pain, inflamed or infected body parts.
- Juice: Obtained by squeezing or crushing plant parts and filtering through cloth. Sometimes requires addition of freshwater or other liquid for dilution.
- Powder: Obtained by crushing dried plant parts.
- Chewing: Fresh plant parts are chewed without prior transformation.
- Infusion: Plant parts are plunged in either hot or cold water for several minutes. If hot water is used infusion is taken as a tea. More than one plant species can be used in conjunction.
- Decoction: Plant parts are boiled in water for several minutes and the extract is used. More than one plant species can be used in conjunction.
Extracting Dyes From Plants
Natural plant dyes have been around for hundreds of years, and have been very helpful to many First Nations communities in Canada with dyeing clothing. There are dyes for each different colour made from a variety of trees, flowers, barks, leaves, and berries.
Separation
Homework
1) Why are homogenous mixtures generally more challenging to separate than heterogeneous mixtures?
2) What are some reasons why people would want to separate mixtures?
3) Provide an example of a mixture that can be separated using the following methods:
- Hand Separation - Filtration - Density Separation - Magnetism - Distillation
4) What is a centrifuge and what is it commonly used to separate?
5) What are some historical and current First Peoples use of separation and extraction methods?
6) In a paragraph or two, compare and contrast the separation methods used in science labs today versus the methods used by First Peoples. Discuss similarities and differences and include examples where needed.