Focus question

What effect does temperature have on the viscosity of common liquids?

Essential materials

• Clear or light colored shampoo (at room temperature)
• Clear plastic bottle about 444 mL (15 oz) capacity or slightly larger, with tightly fitting cap [Note: Perhaps use two plastic bottles of inexpensive shampoo.]
• Stopwatch that measures to 0.1 or 0.01 seconds
• Glass marble small enough to fit through the mouth of the bottle
• Permanent marking pen
• Ruler
• Hot water (hot water from a faucet is OK)
• Basin large enough for bottle lying on its side to fit
• Cold water
• Ice cubes
• Paper towels
• Safety goggles
• Thermometer (optional)
• Chart like the one below to record your results

Main ideas and background information

• Viscosity is the property of a fluid that causes it to resist flowing. Thick liquids such as shampoo and corn syrup are more viscous than water.
• Temperature affects the viscosity of most common liquids. As the temperature increases, the liquid usually becomes thinner and it pours more readily. On the other hand, as the temperature decreases, the liquid usually becomes thicker and does not pour as readily.

Procedural tips

• Be sure to have students draw the lines all the way around the bottle. They will need to have their eyes level with each line when making their time measurements, and this will help them to do so. Note how the camera is positioned in the photographs for step #4 for the top and the bottom line.
• If students use a couple of bottles of inexpensive shampoo, they could uncap one bottle, drop in the marble, and then pour in shampoo from the other bottle to top it off, rather than using an empty bottle.
• For the most consistent results, students should let the marble drop from the top to the bottom of the bottle. If the marble begins inside the top, this will increase the likelihood that it will sink down the middle of the shampoo. If the marble sinks next to the wall of the bottle, the results will be inconsistent.
• Hot water from a faucet can usually heat the shampoo sufficiently. Make sure that the water bath covers as much of the shampoo bottle as possible. In the photograph for step #6, the hot water is not quite covering the bottle. However, by turning the bottle every few minutes, the shampoo is heated more evenly.
• Ice water cools the shampoo effectively. Make sure that there is unmelted ice in the water. Distribute the cold water evenly by gently moving the shampoo bottle around.

Discussion

1. How did increasing the temperature of the shampoo affect the time it took for the marble to sink through it? What happened when the temperature was cooler?
2. How did your data compare from one trial to the next at any given temperature? How might you explain any inconsistencies? [One source of inconsistency is related to the path of the marble as it drops. For example, we found that the speed of the marble is slower if it drops close to the side of the bottle. The most consistent results were when the marble dropped down the middle of the bottle. Another source of inconsistency might be the starting or stopping of the stopwatch. The timer must observe closely and use the same technique for each trial.]
3. Looking at your data, what do you think might happen if the temperature of the shampoo had been higher? What if it were cooled below the temperature of the ice water?
4. How might this activity be useful in your everyday life? [For example, students might heat honey or syrup so that it will pour more easily.]

Assessment

Are students able to describe the effect of temperature on the viscosity of most liquids? [Raising the temperature of a liquid generally decreases its viscosity, making it easier for objects to move through it.]

Extensions and further investigations

• If time permits, measure the sinking time of the marble in warm shampoo every five minutes as it cools down to room temperature. Plot this on a graph and discuss the results. Repeat for cold shampoo as it warms up to room temperature.
• Corn syrup is often used in classroom viscosity investigations because it is readily available and reasonably inexpensive. What other fluids might show similar results? Design an investigation to find out. [Think about comparatively thick fluid food materials such as vegetable oil, maple syrup, molasses, and the like.]
• What do you think would happen if you dropped a marble that weighed half as much as the one you used in this experiment? …twice as much? Design an investigation to test your predictions.
• Motor oil for automobiles often has a multiviscosity characteristic: the oil is designed to be thinner in winter and somewhat thicker in summer. An example is 10W-30 oil. This liquid behavior is opposite to that observed in this experiment. Why do you think this would be desirable for motor oil? [In winter, the colder temperature would make the oil more viscous. It would not flow easily to all parts of the engine to lubricate it. If the oil gets thinner or less viscous in colder temperatures, it will still be able to lubricate the engine effectively. Likewise, in summer, oil that is too thin would not be able to lubricate effectively. Petroleum engineers design motor oil so that it has the most effective viscosity for different operating conditions.]

Career connections

• Developing and manufacturing products such as
  • mineral oils and hydrocarbons
  • cosmetics and pharmaceuticals
  • foods (such as honey, beer, gelatin, etc.)
  • chemicals (such as polymers, solvents, resins, adhesives)
  • paints, varnishes, inks, lacquers
  • detergents
  • fuel (diesel oil, gas/petrol, paraffin)
  • automotive fluids, coolants
• Petroleum engineers developing multiviscosity products
• Paper industry (additives, pigments, emulsions)
• Maple syrup production

Correlations with Standards

United States: This activity correlates with portions of NSES Content Standard A, Science as Inquiry, and Content Standard G, History and Nature of Science, Grades 5-8 and 9-12, and with the following additional standards:

Grades 5-8
Standard B – Physical Science: B1, B2

Grades 9-12
Standard B – Physical Science: B2

Britain: This activity correlates with the English National Curriculum standard Sc1, Science Enquiry, and the following additional standards:

KS2, Sc3, 1a
KS2, Sc3, 13

Glossary/vocabulary

viscous
viscosity

Resource links

Geotechnical, Rock and Water Resources Library
Does hot water flow faster than cold water? Click and drag on the temperature control arrow to find out.

North American Maple Syrup Producers Manual
The important role of viscosity in producing and grading maple syrup. [The term degrees Brix refers generally to the percentage of dissolved sugar in a solution at a specified temperature, often taken to be 20 deg C.]

The Physics of Maple Syrup Making
The physics of making maple syrup, including viscosity.