In this lesson students explore some basic separation techniques and use these to separate a given mixture.
Show the students an image of shells on a beach and ask the students how they would collect the shells in the picture.
Explain that this is a very simple way of separating components of a mixture and is called ‘hand picking’.
Ask the students to suggest other examples of where hand picking could be used as a separating technique.
Shells on a beach
Source: © Ria Novosti/ Science Photo Library.
- Explain to students that because most substances occur naturally as mixtures, humans have devised many different ways to separate them. Many simple separation techniques, including hand picking, have been used for centuries by different cultures. Describe threshing and winnowing and show images of farmers threshing and rice winnowing.
- Brainstorm other ways in which mixtures can be separated and record these on the board. Ask students to group similar ways together and record in their science journals.
- Ask the students how they would separate cooked rice and water. Identify this as sieving and check if it was one of the ways of separation identified by the students. Check for other examples of sieving.
- Explain to the students that they will be given a mixture of dried beans, rice and flour and they are to conduct an investigation to separate the components using some of the techniques they have learned about.
Teacher note: For details on the preparation for this investigation see Background information (PDF, 908 KB).
- Divide the students into groups. Distribute the worksheet Separating a mixture of beans, rice and flour (Word, 391 KB) and samples of the mixture to each group. Display the equipment available. Discuss how the students could perform the separation and identify what equipment they would need from what is available.
- Have students complete numbers 1–3 on their worksheet and have them checked off before conducting the separation.
- Allow students to conduct the separation and complete the worksheet.
Discuss the conclusion and the effectiveness of techniques used in the investigation. Identify any improvements that could be made to the method to produce a more effective separation.