Properties of Fluids Viscosity SCI 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) • We will study the following properties of fluids: 1. Density 2. Buoyancy (Floating and Sinking) 3. Displacement (Archimedes’ Principle) 4. Viscosity 5. Pressure (Pascal’s Principle) Key Terms • Viscosity: “ A fluid’s resistance to flow.” • Viscous: “Having a thick, sticky consistency between solid and liquid; having a high viscosity.” 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) 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) Practice Questions 1) 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? Practice Questions - ANSWERS 1) 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. 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. 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 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 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) MATERIAL APPROXIMATE VISCOSITY (in centipoise) Water Blood Anti-Freeze Motor Oil or Maple Syrup Honey Molasses Ketchup Peanut Butter Shortening Window Putty 1 to 5 10 15 150 to 200 2,000 to 3,000 5,000 to 10,000 50,000 to 70,000 150,000 to 250,000 1,000,000 to 2,000,000 100,000,000 The Pitch Drop Experiment: The Highest Viscosity in the World http://www.smp.uq.edu.au/content/pitch-drop-experiment 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 _______________.