the syrup molecules in water, so that finally the water concentration is the same in all the glass.
This “diffusion” phenomenon is important in gherkins production: when the plant samples are put first
into salt, their water molecules move so that they go out of the plant tissue, and dissolve salt. This
process is called osmosis.
For example, if a strong coffee is added to a glass of water, the large number of water molecules in
the water will redistribute themselves evenly in the coffee, and the resulting solution will be an evenly
distributed mixture of coffee and water….or a much weaker coffee!
Solubility in water
Molecules are often classified by how they interact with water. Molecules that like to interact with water
are called “hydrophilic”, or water-loving. These molecules like to interact with water because, like
water, they are charged, so are attracted to the water molecules and can form links with them. This is
what occurs when a substance “dissolves”. For example, when salt is added to water, it will dissolve.
Salt is made of Na+ ions and Cl- ions held together, and in the presence of water, these ions will
separate and be attracted to and form bonds with the water molecules. Because the salt has been
split into individual Na+ and Cl- ions, it is no longer visible to the naked eye because the separated
ions are too small. However, if the mixture is heated to evaporate all the water, only the Na+ and Clions
will be left, which will then be free to rejoin with each other to form the original salt.
The boiling point of water can be changed if substances added to it, depending on the relative boiling
point of the added substances. For example, water will boil at a slightly higher temperature if salt is
present because salt has a much higher boiling point than water. The more salt contained in the water,
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the higher the boiling point of the solution. However, if alcohol, which has a boiling point lower than
that of pure water, is added to water, it will decrease the boiling point of the final mixture.