Colloids
To introduce colloidal solutions and familiarise students with filtering techniques.
ما يتعلمه الطلاب
الجانب العلمي وراء هذه التجربة
In the previous experiments the solutes were dispersed as molecules or ions throughout the solvent. It can happen that the solute does not dissolve completely but its molecules remain aggregated as small clusters; these solutions are called colloids and have different properties from true solutions.
Under certain conditions, it is possible to obtain colloids from a wide range of substances, such as metals, oxides and sulphides.
Some colloids, such as soaps, form micellar solutions where the solute exists as particles called micelles.
المعدات المستخدمة
- Test tubes — 1473.60
- Test tube rack — 1680.06
- Test tube holder — 5423.30
- Spatula — 5460.34
- Iron stand — 5404.52
- Universal clamp — 5416.20
- Right angle clamp — 5401.16
- Glass funnel — 1343.15
- Filter paper — 8340.08
المواد الكيميائية والمواد الكاشفة
- Sulphur — R:11-16 S:41
- Ethanol — R:11 S:7-16
ملاحظات السلامة
أسئلة للطلاب
- Describe the solution. What was it like before and after the addition of water?
- What happens to the solution after filtration? Why?
ما يمكن توقعه
<p>The sulphur dissolves in ethanol to give a clear, pale yellow solution. After adding water, the colloidal solution looks like a milky white solution.</p><p>The same results are obtained with milk that forms micelles with water molecules.</p><p>Filtration does not affect the solution because the sulphur particles are much smaller than the pores in the paper.</p>
التخلص
Dispose of liquids into the liquid wastes container.
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