Solute: the substance that makes up the minority of the solution (substance that dissolves in a solvent). E.g salt (solute) dissolves in water (solvent)
Solvent: the substance that makes up the majority of the solution (the substance that dissolves the solute). E.g water (solvent) dissolves salt (solute).
Note: water is a universal solvent. “Universal” is used here because water can dissolve more substances than any other liquids.
Solution: is the mixture of the solute and the solvent (liquid and soluble solid).
Suspension: Liquid and insoluble solid.
Graphical summary of filtration, distillation, evaporation and chromatography.
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Syllabus
4.1 Separating Mixtures
At the end of the lesson, pupils should be able to:
- Explain how the constituents of a mixture can be separated based on their properties using magnetic attraction.
Magnet attracts only magnetic materials (iron, nickel, cobalt, steel) à I Need Complete Silence. Non-magnetic materials (plastic, leather, gold, silver)
- Apply magnetic separation as a physical method for separating magnetic materials from a mixture in everyday life and industries.
Industry –> salvaging iron and steel at junkyard
Everyday life –> Food processing : remove metal pieces that may accidentally get into the food products.
- Explain how the constituents of a mixture can be separated based on their properties using filtration.
Filtration is used for insoluble solid from liquid in a liquid-solid mixture.
NOTE: filtration is not used to separate the components of a solution, as the solute is soluble in the solvent and other liquids. The solution would be able to pass through the pores in the filter.
- Apply filtration as a physical method for separating mixtures based on particle size in everyday life and industries.
Everyday life –> coffee makers, our nostrils and kidneys.
Industry –> water treatment. Filtration is a cost-saving technique for producing potable water.
- Explain how the constituents of a mixture can be separated based on their properties using evaporation.
Evaporation is used to separate dissolved solids from a solid-liquid mixture.
NOTE: evaporation takes place all the time. Heating only serves to speed up the evaporation process and not to initiate it.
- Apply evaporation as a physical method to obtain impure residual solid from a solute-solvent mixture (solution) in everyday life and industries.
Industry –> Obtain salt from seawater.
Everyday life –> drying of wet clothes on bamboo pole.
- Explain how the constituents of a mixture can be separated based on their properties using distillation.
Distillation is used to separate a pure liquid from a solid-liquid or liquid-liquid mixture.
TWO main processes involved: vaporization (liquid state changes to gaseous state) & condensation (gaseous state changes to liquid state).
Vaporization is seen in boiling and evaporation.
- Apply distillation as a physical method to obtain a pure liquid from a suspension or solution.
Application: treatment of seawater to obtain potable water (a.k.a desalination)
*Desalination is a high-cost process of obtain potable water as fuel is needed to heat up the mixture to its boiling temperature.
- Explain how the constituents of a mixture can be separated based on their properties using paper chromatography.
Chromatography is used to separate small amount of substances from mixtures based on the different solubilities of the components in a particular solvent.
NOTE:
- Different substances must be soluble in the same solvent or else it will not work.
- Filtration and distillation usually required larger amount of the mixture compared to chromatography.
- Apply paper chromatography as a physical method to separated mixtures in industries.
Industry –> identify food colouring/ identify the dyes used in ink.
- Interpret chromatograms visually (without calculating Rf values)
Look at the position of the spots as different dyes in the mixture travel at different rates (based on the solubility, more soluble –> travel faster) along the paper.
- Carry out physical separation in sequence to separate mixtures with a variety of physical properties.
Farmer Sam/Filtration Investigation
4.2 Obtaining drinking water from non–portable water
At the end of the lesson, pupils should be able to:
- Describe some physical methods to obtain drinking water from non-portable sources.
Describe: requires students to state in words (using diagrams where appropriate) the main points in logical sequence.