Sticky Viscosity

Learning Objectives

In this activity students will study the concepts of viscosity through testing how easily a marble can flow through several liquids under the influence of gravity. Students will determine which material is higher in viscosity by comparing how fast a marble flows through one material compared to another.

Associated Curriculum Topic

Fluids

Materials

• baby oil
• vegetable oil
• honey
• motor oil
• corn syrup
• molasses
• ketchup
• an empty water bottle for each material
• magnetic marbles or ball bearings
• bar magnets

Introduction/Motivation

Fluids are essential to many industrial processes and form the basis of hydraulic and pneumatic devices. Any substance that flows is considered to be a fluid. This includes such things as water, shampoo, sunscreen, and honey. Even gases, such as air, can be classified as fluids. Viscosity is an important property that is usually associated with a fluid. Viscosity is in an indication of how “thick” or “sticky” a liquid is or how resistive a liquid is to flowing: different materials can have different viscosities. In this activity students will study the concepts of viscosity through testing how easily a marble can flow through several liquids under the influence of gravity. Students will determine which material is higher in viscosity by comparing how fast a marble flows through one material compared to another.

Procedure

Pre-activity:

• Place each of the liquids into each of the labeled water bottles.
• Have students guess which material will have a higher viscosity compared to another.

Activity:

• When the students are ready to start the activity, one student should drop a marble into each of the water bottles, while the other watches to see which marble hits the bottom of the bottle first. The student dropping the marbles should ensure that they are dropping the marbles at the same time and from the same height.
• Students should record which marble hit the bottom of the bottle first.
• Using the bar magnet, attract the marble to the side of the bottle and pull it back out of the bottle. Students should complete the race several times to ensure consistency.
• Once the students have reached a consistent result, they should trade one or both of their bottles with another group in the room, along with the marbles to avoid cross-contamination.
• Repeat the races with the next set of liquids and record these results.
• Repeat the races until each group has tested all the different liquids provided.

Investigating Questions

• What does it suggest if the marble hits the bottom of the bottle first?
• Which material is the most viscous? Which material is the least viscous?
• Why might someone want to have a more viscous material?
• What might happen to the viscosity of a liquid if you heat it?
• What might happen to the viscosity of a liquid if you cool it?