Properties of Fluids Viscosity SCI 8: Fluids Unit

1. Properties of Fluids ViscositySCI 8: Fluids Unit • Curriculum Outcomes Addressed • - Design an experiment to test the viscosity of various common fluids and identify the major variables (208-6)- Compare the viscosity of various liquids (307-6) • - Describe factors that can modify the viscosity of a liquid (307-7) • - Use a temperature-measuring technology effectively and accurately for collecting data in temperature-viscosity investigations (209-3) • - Demonstrate a knowledge of WHMIS standards by demonstrating the correct methods of disposal of various oils, for example (209-7) • - Identify and relate personal activities and potential applications to fluid dynamics (109-10, 112-7, 210-12)

2. We will study the following properties of fluids: • Density • Buoyancy (Floating and Sinking) • Displacement (Archimedes’ Principle) • Viscosity • Pressure (Pascal’s Principle)

3. Key Terms • Viscosity: “ A fluid’s resistance to flow.” • Viscous: “Having a thick, sticky consistency between solid and liquid; having a high viscosity.”

4. What is Viscosity? • Viscosity is the physical property of a fluid that limits its ability to flow • Viscosity only applies to fluids (liquids and gases) because solids do not flow. • The higher a fluid’s viscosity, the slower it flows. • The lower a fluid’s viscosity, the easier/faster it flows. In this example, viscosity increases from left to right (left has lowest viscosity, right has highest viscosity)

5. What Causes Viscosity? • A fluid’s viscosity depends on its internal friction or strength of particle bonds. • If the bonds between a fluid’s particles are strong, then viscosity is high, which means there is high resistance to flow, and the fluid does not flow easily (flows slowly). • If the bonds between particles are weak, then viscosity is low, which means there is low resistance to flow, and the fluid flows easily (flows quickly)

6. Practice Questions • If a fluid flows very slowly, what can you say about its viscosity? Is this fluid viscous or not viscous? 2) If a fluid flows very easily/fast, what can you say about its viscosity? Is this fluid viscous or not viscous?

7. Practice Questions - ANSWERS • If a fluid flows very slowly, what can you say about about its viscosity? Is this fluid viscous or not viscous? A fluid that flows slowly has a high viscosity. We would say that this fluid is viscous. 2) If a fluid flows very easily/fast, what can you say about its viscosity? Is this fluid viscous or not viscous?A fluid that flows easily/fast has a low viscosity. We would say that this fluid is not viscous.

8. Practice Questions 3) Name three liquids that have a high viscosity. 1. 2. 3. 4) Name three liquids that have a low viscosity. 1. 2. 3.

9. Practice Questions - ANSWERS 3) Name three liquids that have a high viscosity. 1. Molasses 2. Maple Syrup 3. Motor Oil 4) Name three liquids that have a low viscosity. 1. Water 2. Vegetable Oil 3. Pop

10. Order of Viscosity • Order the following liquids from least to most viscous (at room temperature): • Molasses • Honey • Water • Window Putty • Maple Syrup • Anti-Freeze • Blood • Shortening • Peanut Butter • Ketchup • Motor Oil

11. Order of Viscosity - ANSWER • Order the following liquids from least to most viscous • Centipoise: The unit of dynamic viscosity in the centimetre gram second system (how many cms 1 gram of a fluid flows per second)

12. The Pitch Drop Experiment:The Highest Viscosity in the World http://www.smp.uq.edu.au/content/pitch-drop-experiment

13. Viscosity and Temperature • How might the viscosity of a fluid be affected by temperature? Make a two-sentence prediction by filling in the blanks below. As temperature increases, viscosity ________________. As temperature decreases, viscosity _______________.