### Effect of temperature on viscosity

 Difficulty: Advanced 7 Cost (\$): 30 Time required: < 1 day 1 hour to prepare, 2 hours for the science project experiment Availability of materials: Readily available Easily found Required Skills: None Safety concerns: Basic safety requirements

### Abstract

This science fair project was conducted to find out how the temperature of a fluid affects its viscosity. The testing was done by measuring the viscosity of water, milk and corn oil using a measurement cup at different temperatures.

### Hypothesis

Water has the lowest viscosity and the fastest rate of flow followed by milk, while corn oil has the highest viscosity.

### Background

Viscosity

Viscosity is the measurement of resistance by a fluid to deformations caused by tensile stress and shear stress. It is commonly referred to as the thickness of a fluid. A thick fluid will have higher viscosity and a thin fluid will have lower viscosity. Viscosity also refers to internal resistance experienced by the fluid before it can flow.

The presence of viscosity in a fluid is caused by internal friction in a substance. Both fluids and gasses are made up of adjacent layers. When external pressure is applied to a fluid, the friction that occurs between layers will determine the type of response and flow that will happen. The measurement of fluidity is the opposite of viscosity where the lack of fluid resistance is measured.

The viscosity of a fluid will be affected by its temperature. By increasing the temperature of a fluid, the viscosity is reduced. An example is butter, which is solid at room temperature. When heated, it will melt and the viscosity is lowered. Similarly, cooking oil will become thicker with a higher viscosity when kept in a refrigerator.

### Scientific Terms

Viscosity, tensile stress, shear stress, friction, fluidity

### Materials

The materials required for this science fair project:
- 2 metal cups
- 1 electric drill  with small sized drill bits
- 1 bottle of tap water
- 1 bottle of milk
- 1 bottle of corn oil
- 1 hot plate
- 1 thermometer
- 1 stopwatch
- An assistant

### Procedure

1. For this experiment, the independent variable is the type of fluid used (water, milk and corn oil) and temperature. The dependent variable is the viscosity of the fluid. This is determined by using a measuring cup and a stopwatch to measure the flow rate. The constants (control variables) are the size of the hole in the cup and the volume of the cup.

2.  An electric drill is used to make a small hole at the bottom of one of the two metal cups.

3. The water is kept at 20°C. The assistant will hold the cup with the hole over the 2nd cup with one  finger covering the small hole at the bottom of the cup. The finger should be placed over the hole on the exterior of the cup. The cup is then filled with water . After the cup is filled,  have a  stopwatch ready.  Simultaneously, the assistant  removes the finger from the hole and the stopwatch  is started.  Water from the upper cup will fall into the lower cup through the hole. The time taken for the cup to  empty, is recorded.

4.  Procedure 3 is repeated 5 times and the average time is calculated by totaling the 5 measurements and dividing by 5. The results are recorded in the table given below.

5.  Procedures 3 and 4 are repeated by bringing the temperature of the water to 30°C, 40°C and 50°C using the hot plate.

6.  Procedures 3, 4 and 5 are repeated using milk and corn oil.

### Observation

It  was observed that water had the fastest rate of flow and the corn oil had the slowest.  The flow rate of water, milk and corn oil increased as the temperature increased.

 Adhesive material Viscosity and flow rate of water, milk and corn oil at different temperatures (seconds) 20°C 30°C 40°C 50°C Water 15 12 10 9 Milk 19 15 12 10 Corn oil 97 65 47 35

The graph below represents the results of our science fair project:

### Conclusion

The hypothesis that  water  has the lowest viscosity and the fastest rate of flow, followed by milk   while corn oil  has the highest viscosity, is proven to be true.

The understanding of viscosity and fluid dynamics is very important when transporting fluids like water, crude oil or natural gas through pipes over long distances. Changing climates and different temperatures will affect the viscosity and rate of flow of the fluid. Additional sensors and pumps are normally placed along the pipes to keep the rate of water flow constant.

### Also consider

Try to repeat the science fair project using different fluids like honey, ethanol and engine oil.

The science project experiment can also be repeated using a larger hole in the cup, and observing if that makes any difference.

### References

Viscosity - http://en.wikipedia.org/wiki/Viscosity

Specific gravity and viscosity of liquids - http://www.csgnetwork.com/sgvisc.html

What is viscosity? - http://www.wisegeek.com/what-is-viscosity.htm