The Effect of Different Salt Concentrations on Osmosis

Topics: Semipermeable membrane, Osmosis, Water Pages: 4 (1194 words) Published: March 7, 2011
The effect of salt concentrations on the mass of the pear cubes ‘Pyrus’ after being soaked in water

Aim:
The effect of salt concentrations on the mass of the pear ‘Pyrus’ pieces shaped as cubes of 1cm. Background:
Osmosis is the net movement of water molecules through a semi-permeable membrane from an area of higher water potential to an area of lower water potential. Water makes up to 70-90% of living cells and cell membranes are partially permeable membranes. Dissolved substances attract a ‘cloud’ of polar water molecules around them. The cloud is held by weak chemical bonds that include hydrogen bonds. Water molecules cannot move freely. Organic substances such as sugars, amino acids, polypeptides, and proteins, as well as inorganic ions like Na+, K+, Cl-, and NO3-, all have this affect on the water molecules around them. The stronger the solution (that is, the more solute it contains per volume of water), the larger is the number of water molecules that are slowed up and held. So, in a very concentrated solution, very many more of the water molecules have restricted movements than in a dilute solution. On the other hand, in pure water all the water molecules are free to move about randomly, and so on. Hypothesis:

Null Hypothesis: There is no effect of the different concentrations of salt on the mass of the pear pieces sizes. Alternate Hypothesis: There is an effect of the different concentrations of salt on the mass of the pear pieces sizes. Variables:

Independent variable: The different salt concentrations (2%, 5%, 10%, 15%, 20% and 50%), that would affect the mass of the pear pieces (by osmosis). Dependent variable: The mass, surface area and volume measured after being soaked in the different salt concentration for 5 minutes. Controlled variables:

* Volume of water with the different concentrations (solutions) should be the same. * Size of the pear pieces groups should have the same surface area and volume. * Mass of the pre soaked pear...
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