SRP- Lamina Shawkat
Effects of salt on the surface tension of water
Introduction
What is surface tension? Surface tension is a phenomenon in which the surface of a liquid acts like a thin elastic sheet when it comes in contact with an external force, such as a gas like the air. This physical property allows the surface of a liquid to “resist” the pressure of the external force by reducing its interaction with the force.
What causes this layer to form upon water? atoms that make up water molecules are always at an unequal charge distribution causing a push and pull effect on their shared electrons. Oxygen has a stronger attraction to the shared electrons when compared to hydrogen. Thus, the electrons are mostly closer to the oxygen atom. The unequal sharing of electrons causes water to have both positive and negative poles, making it polar. This polarity causes water molecules to be attracted to each other, as the positively charged atom in water molecules is always hydrogen, the types of bonds they form are called hydrogen bonds. Hydrogen bonds are weak and last a small short time (fraction of a second). But it takes a lot of energy to overcome the combined bonds (four bonds possible per molecule) this explains the skin that is formed on top of water (surface tension).
What I would like to understand throughout my experimentation are the affects upon water’s surface tension when the salinity levels of water are changed.
Aim
To understand if different amounts of salt (NaCl) added to water effects it’s surface tension.
Hypothesis
If salt is added to water, then it will increase surface tension.
Equipment
1. 4 Beakers
2. Tweezers
3. Roll of aluminium foil
4. Pen
5. Scissors
6. Masking tape
7. Grains of rice
8. Salt
9. Distilled water
10. ½ tbsp measure
How I will insure validity and reliability within the experiment
The experiment only uses quantitative results and is repeated multiple times, the averages are used as the final data. This along with keeping all variables other than the independent and dependant controlled. Allowing for a valid and reliable experiment and results (data).
Risk assessment
Risk
Injury
Prevention method/ steps if injury takes place
Glass ware breaking
Cuts from glass
Be careful around glass, however if you have been injured seek medical attention and clean up the glass thoroughly.
Method
Step 1: collect all required equipment
Step 2: label 3 beakers with the amount of salt they will contain starting from ½ tbsp going up to 1 ½ tbsp at ½ tbsp intervals. Label the remaining beaker control as it shall have no salt in it allowing for comparison to take place later.
Step 3: mix in the amount of salt according to each label making sure to leave the control free of salt.
Step 4: take your foil and draw four 2cm by 2cm squares, then cut them out.
Step 5: place 1 square per beaker making sure it is sitting on top of the waters skin (surface)
Step 6: using your tweezers start placing rice grains on the one of your aluminium f...
