← Integrated Science / 2 Mixtures, Elements and Compounds
2.1 Mixtures
Integrated Science · Grade 7 · 18 lessons in the design
What this covers
- Homogeneous mixtures: solid-solid, solid-liquid, liquid-liquid and gas-gas
- Heterogeneous mixtures, for classification
- Solute, solvent and solution
- Separation of homogeneous mixtures: evaporation, crystallisation, simple distillation, fractional distillation, sublimation, solvent extraction and chromatography
- Applications of methods of separating mixtures in real life
What you will be able to do
- separate homogeneous mixtures using appropriate methods
- outline applications of separating homogeneous mixtures in day-to-day life
- appreciate the use of different methods of separating mixtures in day-to-day life
Key questions
“How is the separation of mixtures important in day-to-day life?”
Lessons
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What a mixture is
40 min · 1 practice tasks · quizA mixture is two or more substances together. Each keeps its properties. Pure is one substance only.
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Homogeneous and heterogeneous mixtures
40 min · 1 practice tasks · quizHomogeneous looks the same throughout. Heterogeneous still shows its parts. Classify before you separate.
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Solid-solid and solid-liquid mixtures
40 min · 1 practice tasks · quizHomogeneous solid-solid examples are alloys. Solid-liquid examples are solutions such as salt water.
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Liquid-liquid and gas-gas mixtures
40 min · 1 practice tasks · quizMiscible liquids make homogeneous liquid-liquid mixtures. Air is the everyday gas-gas mixture. Oil and water do not mix.
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Solute, solvent and solution
40 min · 1 practice tasks · quizSolute dissolves, solvent does the dissolving, solution is the uniform mixture. Water is the usual school solvent.
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Why we separate mixtures
40 min · 1 practice tasks · quizWe separate to get a useful part: salt, water, fuel, medicine, clean grain. The method follows a property.
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Evaporation
40 min · 1 practice tasks · quizHeat or sun removes the solvent; the solid solute remains. Use when you want the salt, not the water.
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Crystallisation
40 min · 1 practice tasks · quizConcentrate, then cool so crystals grow. Different from boiling a solution to a dry crust.
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Simple distillation
40 min · 1 practice tasks · quizBoil the solvent, condense the vapour, collect the liquid. Salt stays in the flask. Use when you want the water.
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Fractional distillation
40 min · 1 practice tasks · quizMiscible liquids with different boiling points separate in a taller column. Petrol, kerosene and diesel come from crude oil this way.
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Sublimation
40 min · 1 practice tasks · quizSome solids turn to gas and back to solid, skipping the liquid. That separates iodine or ammonium chloride from sand.
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Solvent extraction
40 min · 1 practice tasks · quizA second liquid pulls out the solute. Kitchen cousins: tea, coffee, groundnut oil. Shake, wait, take the layer you need.
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Paper chromatography
40 min · 1 practice tasks · quizColoured substances travel at different speeds on paper. Split black ink or leaf pigment. Keep the spot above the solvent.
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Matching method to mixture
40 min · 1 practice tasks · quizChoose evaporation, crystallisation, distillation, fractional distillation, sublimation, extraction or chromatography from the need and the property.
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Kitchen and home applications
40 min · 1 practice tasks · quizChai, drying food, salt crusts, oils and inks: name the Grade 7 method in ordinary Kenyan homes.
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Farm and cereal applications
40 min · 1 practice tasks · quizCereals are often heterogeneous: winnow and sieve. Farm salt and sugar solutions still use evaporation and crystallisation.
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Industry, water and fuel applications
40 min · 1 practice tasks · quizMagadi brine, distilled water for clinics, and refinery fuels: the same methods at Kenyan scale.
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Sharing tasks and appreciating separation
40 min · 1 practice tasks · quizUnity, peer mentoring and safe waste close the sub-strand. Separation is a daily-life skill worth practising together.