This document discusses chemical changes that occur in aqueous solutions. It explains that water is a polar solvent that is able to dissolve many ionic and polar compounds. When ionic salts dissolve in water, their ions dissociate from each other. Acids also ionize when dissolving in water, representing a chemical change. The solubility of different compounds, such as salts, in water depends on factors like the identity of the ions and whether they form strong ionic bonds. Precipitation reactions can occur when two soluble salts are mixed and one of the resulting salts is insoluble.

1. CHEMICAL CHANGE
Reactions in aqueous solution

2. Ions in aqueous solution
■ Many reactions in industrial processes and in living systems take place in aqueous
solution.
■ Water is a very good solvent and therefore many substances can dissolve in it.
■ The microscopic structure of water makes it possible to dissolve other substances.

3. Polarity of water
■ The water molecule is polar.That is it has a slightly positive end and a slightly negative
end.
■ The atoms in a water molecule are held together strongly by covalent bonds to form
an angular molecule.
■ Oxygen attracts electrons to itself.
• It becomes slightly negatively charged.
• Hydrogen becomes slightly positively charged.

4. Polarity of water
■ The shape of the water molecule is important for its polarity.
■ Polarity is a difference in charges on molecules.
■ Water molecules are dipole ( they have two poles).
■ The negative and positive charges are equal, so they cancel each other and the overall
charge on a water molecule is zero.

5. Dissolution process
■ When ionic salts dissolve in water, their ions dissociate from each other.
■ This can be represented by ionic equation:

6. Dissolution processes
■ Acids are important group of covalent compounds that dissolve in water.
■ When acids dissolve in water, they ionise.
■ The new product form and so the process is a chemical change

7. Solubility in water
■ Ionic compounds are made of positive and negative ions that are tightly packed in a
crystal lattice.
■ Strong ionic bonds consists of electrostatic forces and hold the ions in position in the
solid phase.
■ Solubility is defined as the amount of a given substance that can be dissolved in a
certain amount of solvent.
■ Dissolving is a process of a solid ionic crystal breaking into its ions.

8. Solubility
Substances fall into three main categories of solubility
1. Generally, a substance is considered “soluble” if it dissolves into solution completely.
2. “Sparingly (or slightly) soluble” substances are partially soluble. A limited amount of
substance dissolves.
3. “Insoluble” substances do not dissolve at all (or a very tiny amount dissolves.)

9. Solubility of salts
■ Salts are ionic compounds that are made up of metals and none metals.
■ Salts can be soluble, sparingly soluble, and insoluble, depending on the identity of the
cation and anion.

10. Electrolytes
■ Liquids that can conduct an electric current are called electrolytes.

11. Precipitation reactions
Precipitation reactions happen when:
Two soluble salts are mixed
An exchange reaction occurs
And one of the salts formed is insoluble
• This insoluble substance is called a precipitate.

12. Reference
■ Itutor (2013) Solutions & solubility. Retrieved September 1, 2018, from
https://www.slideshare.net/itutor/solution-solubility
■ Janetra (2007) 9 Aqueous solutions. Retrieved 01 September 2018, from
https://www.slideshare.net/janetra/9-aqueous-solutions
■ Lauralici (2007) Solutions. Retrieved 01 September 2018, from
https://www.slideshare.net/lauralici/solutions