A physical change is a change in which no new substances are formed. Physical changes affect the form of a chemical substance, but not its chemical composition. Mixtures can be separated into their parts by physical methods, such as spinning in a centrifuge. but can not usually be used to separate compounds into chemical elements or simpler compounds.
Most physical changes are reversible. Examples: changes of shape, changes of states, passing electricity through a copper wire. Some physical changes are melting, freezing, boiling.
An ionic bond is the bonding between a non-metal and a metal, that occurs when charged atoms (ions) attract. This happens after a metal atom loses one or more of its electrons to the nonmetal atom. This makes the bond stronger and harder to break.
When this happens, the metal becomes a positive cation, and the non-metal becomes a negative anion. This occurs, for example, when sodium and chlorine join to form common salt, NaCl.
In other words, an ionic bond is the electrostatic force of attraction between two oppositely charged ions. The positive ion is called cation, and the negative ion is the anion.
Features of ionic bonds
- Three dimensional structure called an ionic lattice.
- Soluble in water.
- They are compounds formed from metals and non-metals.
- In a solid state they do not conduct electricity. However, in a liquid state or when dissolved in water, they will conduct electricity well because the ions are free to move.
- They contrast to the characteristics of a covalent bond.
- Sometimes if they do not have a spare electron to create a complete shell one will act as two and spin in a figure of eight around both atoms.
Solubility is the ability of a substance (the solute), to mix into a liquid (the solvent).
It measures the highest amount of substance mixed into a liquid solvent while they are both at equal amounts. When the two mix together it is called a saturated solution. Certain substances can mix into any amount of a liquid solvent. An example of this is ethanol in water. This process is better described as “miscible” (the ability to mix with one another). Solubility does not depend on the size, in fact even the large particles will eventually all dissolve.
Watch the animation of salt dissolving into water.
Watch the animation of sugar dissolving into sugar.