Surface tension of water
The materials required for this science fair project:
- 2 beakers
- 400ml distilled water
- A measurement cylinder
- 2 tablespoons of salt
- A cup of rice grains
- 2 pieces of aluminum foil measuring 1cm x 1cm each
- A refrigerator
- A hot plate
- A thermometer
- A hot plate
1. For this science fair project, the independent variable is the salinity of the water and its temperature – 15°C, 25°C, 35°C, 45°C and 55°C. The dependent variable is the weight exerted on the aluminum foil before it sinks. This is determined by gradually adding grains of rice on the surface of the aluminum foil. The constants (control variables) are the size of the aluminum foil, the size of the grains of rice and the room temperature.
2. The 2 beakers are labeled “pure water” and “salt water”. The beakers are each filled with 200ml of distilled water. In the beaker labeled “salt water” 2 tablespoons of salt are added and mixed into the water. The 2 beakers are placed in the refrigerator until the contents in the 2 cups reach 15°C. The beakers are taken out of the refrigerator and the required temperature confirmed using a thermometer.
3. The 1cm x 1cm piece of aluminum foil is made to float on the surface of the water in the beaker labeled “pure water”. The grains of rice are placed one at a time on the aluminum foil until the aluminum foil sinks into the water. The number of rice grains placed on the foil is recorded and the results shown in the table below.
4. Procedure 3 is repeated with the beaker labeled “salt water” and the results recorded in the table below.
5. The 2 beakers are brought to a room temperature of 25°C and Procedure 3 is repeated on these 2 beakers. The results recorded in the table below.
6. The 2 beakers are then placed on a hot plate and heated to temperatures 35°C, 45°C and 55°C. Procedures 3 and 4 are repeated at each required temperature level and the results recorded in the table below.