what is a substance, a mixture;
which safety rules should be followed in the school chemical laboratory;
what do the terms physical properties and chemical properties mean and how the properties of the substance can be tested;
according to what criteria the mixtures are classified.
plan and carry out separation of homogeneous mixtures into components (eg water and rock salt, ethanol and ink, potassium nitrate and water)
Homogeneous mixtures
Recall what homogeneous mixtures are. How can you characterize these?
Recall known methods of separating homogeneous mixtures and then present them in the form of a mind map.
How to separate the mixtures?
Homogeneous mixtures can be separated by:
evaporationevaporation – heating up the liquid mixture and the solid dissolved in it to evaporate the liquid; this process is used in the preparation of jam, while in countries with a warm climate it is the effect of evaporation of sea water and the formation of rock salt deposits;
R10I0QdPNDkr1 crystallizationcrystallization – this technique allows the separation of solid crystals from the solution;
distillationdistillation – a method of separating multi‑component liquid mixtures that differ in boiling point; it involves moving into steam and then condensing it;
RJ9a8pLQp3rea chromatographychromatography – a method for separating or testing the composition of mixtures of chemical compounds; uses the differences in the speed of movement of the components of the mixture - e.g. different dyes on the strip of tissue immersed in the liquid (vinegar, spirit, acetone);
Before you watch the movie „Separating the mixture of sodium chloride and water”, write down the research question and hypotheses. Please note what properties of the mixture ingredients were used when separating them. After the screening, note down your observations and conclusions.
How to separate a homogeneous mixture? How to choose the right way to separate mixtures?
water,
rock salt,
evaporating dish,
tripod with a ceramic grid,
glass rod,
burner,
safety glasses.
Add rock salt to a beaker with water and mix it using glass rod.
Transfer the resulting mixture to the evaporating dish (alternatively into a piece of metal plate or a thicker aluminium foil, holding it with pliers).
Light the burner or heater and, under the supervision of an adult, heat it until the water evaporates.
How do you get a mixture of water and potassium nitrate? How to separate a homogeneous mixture? How to choose the right way to separate mixtures?
water,
potassium nitrate,
lighter / matches,
tube,
paw and test tube stand,
teaspoon,
torch,
beaker,
goggles.
In a test tube to give 2 cm Indeks górny 33 of water and pour 1 teaspoon of potassium nitrate.
Cover the tube with the contents in the flame of the burner.
If the saltpetre dissolved, add half a teaspoon and continue heating to dissolve it.
Place the tube in a beaker with cold water.
Watch the changes taking place.
Summary
The mixtures can be separated using various techniques.
Separation methods depend on the type of mixture and use the properties of its components.
The methods for separating homogeneous mixtures include: solvent evaporation (eg water), distillation, crystallization, chromatography.
The methods of separation of inhomogeneous mixtures include: sedimentation, decanting, filtration, mechanical separation, separation by means of a separator.
Some techniques should be used when separating some mixtures. When separating the mixture of rock salt and chalk, we should successively: dissolve the mixture in water (rock salt will dissolve), filter (chalk will remain on the filter), evaporate the filtrate (rock salt will remain).
Keywords
mixture, homogeneous mixture, methods of separation of mixtures, evaporation, distillation, crystallization, chromatography
Glossary
destylacja – metoda rozdzielania wieloskładnikowych mieszanin ciekłych różniących się temperaturą wrzenia; polega na przeprowadzeniu w stan pary, a następnie jej skropleniu składników
krystalizacja – polega na wydzieleniu się substancji stałej w postaci kryształów wskutek np. obniżenia temperatury mieszaniny utworzonej przez rozpuszczenie maksymalnej ilości ciała stałego w cieczy
odparowanie – polega na ogrzewaniu ciekłej mieszaniny w celu odparowania cieczy
chromatografia – metoda służąca do rozdzielania lub badania składu mieszanin związków chemicznych; wykorzystuje różnice szybkości przemieszczania się składników mieszaniny – np.: różnych barwników po pasku bibuły zanurzonym w cieczy (ocet, spirytus, aceton)