Investigating Factors Affecting the Solubility of an Unknown Powder in Water
Aim: To investigate the effect of temperature on an unknown powder's
solubility.
Prediction: As the temperature increases so will the solubility of the
powder. I think that the temperature and solubility will be directly
proportional - so that at temperature doubles so will the solubility
of the powder.
Hypothesis: I think this because my scientific theory says that:
Molecular solids, like sugar, and ionic solids, salts, both dissolve
in water. However, they both dissolve in different ways. The
intermolecular forces holding molecules of sugar together are quite
weak so when sugar is placed in water these bonds are broken and
individual molecules are released into solution. It takes energy to
break bonds between the molecules and it also takes energy to break
the hydrogen bonds in water. These hydrogen bonds have to be disrupted
in order to insert a sugar molecule into the substance. The energy
needed for this is produced by the forming of bonds between slightly
polar sucrose molecules and polar water molecules. This process works
so well between sugar and water that up to 800g of sugar can dissolve
in one litre of water.
The positive and negative ions in ionic solids, or salts, are held
together by the strong force of attraction between particles with
opposite charges. When a salt dissolves in water the ions are released
and become associated with the polar solvent molecules. Salts separate
from their ions when they dissolve in water.
There are several factors that affect solubility between different
compounds. These are:
* Temperature- If the solution process absorbs energy, endothermic,
then the solubility will be increased if there is a temperature
increase. If the solution
releases energy, exothermic, then solubility will decrease.
* Molecular Size- If the size or weight of the individual molecules is
large then
solubility will be low because larger molecules are difficult to
surround with solvent molecules.
* Polarity- Generally only polar solute molecules will dissolve in