3. In our study of fluids, we are going to investigate different properties. The first one is VISCOSITY! What is VISCOSITY?

4. VISCOSITY is a measure of the resistance that a fluid has to movement and flowing. It is also referred to as a fluid’s “thickness/thinness” or resistance to flow. Low viscosity = thin = low resistance to flow High viscosity = thick = high resistance to flow

5. Why does VISCOSITY matter? When a fluid is stationary, viscosity is not a concern. However, when a fluid is flowing, or when something is moving through a fluid, the property of viscosity is very important.

6. Can you guess the Viscosity?

7. 1. Strength of Attraction Between Particles 2. Temperature

8. Cohesion * Cohesion measures how strongly the particles in a fluid attract to one another * The stronger the attraction  the slower the liquid flows  high viscosity * The weaker the attraction  the faster the liquid flows  low viscosity * Example: The particles in honey have a strong attraction to each other so it has a high viscosity

9. Adhesion * Adhesion measures how strongly the particles of a fluid are attracted to the particles on another substance Example: Water flows more quickly at the center of a river than it does along the edges. The water particles are attracted to dirt, rocks, or sand and this slows the flow.

10. * http://www.planetseed.com/files/flash/scienc e/lab/liquids/visco_exp/en/viscosity.htm?widt h=620&height=500&popup=true http://www.planetseed.com/files/flash/scienc e/lab/liquids/visco_exp/en/viscosity.htm?widt h=620&height=500&popup=true

11. * Particles are in constant motion * As liquids are heated, the particles move faster and farther apart * The viscosity decreases because there is less attraction between particles * A liquids viscosity decreases as a fluid is heated and increases as the fluid is cooled.

12. * The effect of temperature on a gas is the opposite of a liquid * The particle theory states that the particles in a gas are far apart * When the temperature increases, the particles collide more  increasing viscosity * A gas’ viscosity increases as the fluid is heated and decreases as the fluid is cooled

13. How can we compare the VISCOSITY of different substances? Viscosity can only be discussed when it is compared to another substance. One way to measure the viscosity of a liquid quantitatively involves timing how long it takes the liquid to flow. This is referred to as: FLOW RATE

14. FLOW RATE can be defined as the time required for a specific fluid to move. FLOW RATE = -Example: millilitres per second(ml/s) FLOW RATE = - Example: centimetres per second (cm/s)

15. 1. A kitchen tap takes 4 seconds to fill up a 500 mL container of water. The flow rate is: 2. A spoonful of ketchup takes 25 seconds to travel 50 centimetres. The flow rate is:

16. * The higher the viscosity, the lower the flow rate * The lower the viscosity, the higher the flow rate