Natural Sciences and Technology Grade 6 Term 2: Matter and Materials Mixtures

Mixtures of Materials (2) Topic 2 Mixtures Mixtures of Materials (2) Gr 6 Natural Sciences and Technology – Term 2, Topic 2

What is a mixture? A mixture consists of at least two different materials mixed together. In some mixtures the different substances are still clearly visible after mixing. In others especially mixing of liquids it is difficult to see the original materials. Gr 6 Natural Sciences and Technology – Term 2, Topic 2

Mixtures Where the different substances can be clearly seen in a mixture then it is usually fairly easy to separate them by: hand sorting sieving (sifting) filtering settling decanting Gr 6 Natural Sciences and Technology – Term 2, Topic 2

Hand sorting This is when we can see the separate materials which are solids and separate them out easily by hand. Gr 6 Natural Sciences and Technology – Term 2, Topic 2

Sieving (sifting) With sieving (sifting) we use an instrument called a sieve to separate the substances. We separate solid particles in sieving because: the smaller particles will fall through the bottom of the sieve; and the larger particles will remain behind in the sieve. Gr 6 Natural Sciences and Technology – Term 2, Topic 2

Filtering In filtering we pour liquids through a filter and anything that has larger particles will stay behind. Examples of substances that will remain behind are: coffee grinds, sand, and oil. Gr 6 Natural Sciences and Technology – Term 2, Topic 2

Settling This is when we allow materials to stand for awhile so that they can separate by gravity. It is often used to separate oil from other liquids. It is also used to separate solids from liquids. Gr 6 Natural Sciences and Technology – Term 2, Topic 2

Decanting Decanting is a process that usually follows setting where you pour off one of the substances into another container. Gr 6 Natural Sciences and Technology – Term 2, Topic 2

Mixing solids The bigger the particles of materials are in the mixture the easier it is to separate them. e.g. rice and peas The smaller the particles of materials are in the mixture the more difficult it is to separate them. e.g. sand and sugar Gr 6 Natural Sciences and Technology – Term 2, Topic 2

Mixing solids & liquids When we mix solids and liquids together a lot can happen depending on: 1. the different quantities of each; 2. whether the solid is able to dissolve in the liquid; 3. the properties of each material. Gr 6 Natural Sciences and Technology – Term 2, Topic 2

Mixing liquids together When a mixture needs to be made, the person making the mixture must take the following into consideration: The quantities needed of each substance in the mixture. The properties of each substance to be added to the mixture. An anaesthetist needs to know the quantities and the properties of the chemicals being used in an operating theatre. Alfred Nobel needed to know the quantities and properties of the substances he mixed together to make dynamite. Gr 6 Natural Sciences and Technology – Term 2, Topic 2

In summary A mixture consists of two or more different types substances mixed together. Sometimes mixtures can be separated into the individual substances again. Some of the ways in which mixtures can be separated are: sieving, filtering, hand sorting, and settling and decanting. Gr 6 Natural Sciences and Technology – Term 2, Topic 2

Important information When a material forms a solution in another material, the process is called dissolving. Melting and dissolving are two different processes. Gr 6 Natural Sciences and Technology – Term 2, Topic 2