Fast Fact:
The crankshaft of an Indy car engine turns at astounding speeds- up to 14,500 revolutions per minute!
Objective:
The students will explore the effect of temperature change on the viscosity of different kinds of oil.
In the Film:
At the engine test center, engineers run the motor at high revolutions. You can see the exhaust manifolds turn red from the hot gases being expelled from the engine. Indy car engines must run at extremely high temperatures. Since heat affects the viscosity of liquids, it is crucial to choose the right oil for an Indy car. Oil is important because it is the only protection the motor has against the friction caused by the metal parts moving against each other.
Background:
Viscosity is the ability of a fluid to resist the forces that make it flow. High-viscosity fluids, such as molasses, do not flow readily; low-viscosity fluids, such as water, flow easily. When viscosity is optimum, the cars moving parts work with each other without direct contact by sliding against the oil. The oil flow is such that it does not impede the movement nor reduce the efficiency of the engine, but at the same time it does not allow the parts to come into direct contact with each other.
If the viscosity is too high, the oil flow does not allow the moving parts to move freely enough, therefore reducing engine efficiency. If the viscosity is too low, the oil flows too easily and the engines parts rub against one another, causing friction and engine wear. This reduces the efficiency and life of the motor.
Materials:
Chick peas or other small seeds, four tall, clear glass jars (750 mL to 1L), 10W30 motor oil, 10W40 motor oil, vegetable oil, baby oil, oven mitts, a stopwatch.
To Do:
Fill each bottle with one of the oils to a height one centimeter below the mouth of the jar. Drop a chick pea into one of the oils and time how long it takes to reach the bottom.
Repeat four times. Record the times. Repeat this procedure for each oil. Place the jars in a freezer for one hour, then do the same as before, recording the results. Place the jars in an oven at 125ÞC (250ÞF) for 30 minutes. Observing all safety protocols, remove the jars of hot oil from the oven using the oven mitts and repeat the same procedure, recording the results.
Have the students compare their results and discuss the viscosity of the different liquids at each temperature. Ask them to determine which oils would be better suited for a race car and which would be best for a car during the cold winter months.
Whats Going On?
Baby oil has the lowest viscosity and 10W40 motor oil has the highest. All the oils lose viscosity when heated. When they become cold they all gain viscosity. Heat reduces the viscosity by decreasing the friction between the layers of molecules in the oils, allowing them to flow more easily. Cold does the opposite.
Taking It Further:
1. Ask the students to think about what parts of the car would be harmed by reducing the friction, for example, the brakes. Also, have them explore how heat affects other parts, such as the joints and tires.
2. Have the students consider using a lubricant on the race cars they designed in Activity 1.