Unit 3 - Forces, Fluids, and Density Big Ideas All fluids demonstrate the property of viscosity, or the internal friction that causes a fluid to resist flowing. Density is another important property of fluids. Fluids exert a buoyant force on objects that causes some objects to float. Understanding the properties of fluids helps in the design and construction of useful devices.
What is a fluid? Write a definition of what a fluid is What are 2 examples of fluids? Part 1 - Oobleck - Is It A Fluid? Materials : 1. cornstarch 2. water 3. 2 1L glass containers 4. spoon Note: Oobleck is 1 part water to 1.5-2 parts cornstarch Part 2 - Carbon Dioxide - Is It A Fluid? Materials : 1. balloon with Co 2 - pop bottle, baking soda, vinegar, spoon and balloon 2. lighter 3. candle 4. 1L glass beaker Conclusion : Do you think oobleck and carbon dioxide are fluids? What is a fluid? * A fluid is any gas or liquid that flows, can be poured, and takes the shape of its container *
Big Idea 1.0 - All fluids demonstrate the property of viscosity, or the internal friction that causes a fluid to resist flowing. What is Matter? If something has mass and takes up space, then it is composed of matter Examples: you, dog, plant, pencil, snow, atom Particle Theory of Matter All matter is made of tiny particles (atoms) Different substances are made of different particles The particles of matter are always moving and vibrating Particles move differently in solids, liquids, gases and plasma (the 4 States of Matter ) Note : there are actually more than 4 but it is very confusing so we will just worry about the 4 above! States of Matter Adding heat makes particles move more and vibrate more. As a result, the state of matter may change Pulse Glass Demonstration
Viscosity is a property of fluids it is a fluid's internal resistance or friction that keeps it from flowing The Bubble Test Question : Do all fluids have the same viscosity? Observations: Time for Bubble Test Fluid (50 ml) Test #1 (seconds) Test #2 (seconds) Test #3 (seconds) Average Time (seconds) #1 Water 1.5 #2 Dish Soap 8 #3 Shampoo 90 #4 Corn Syrup 130 #5 Vegetable Oil 2 Conclusion : 1. What were we trying to learn? 2. Explain how we tested it? 3. What were the results? 4. What do these findings mean? *Different fluids (liquids) have different viscosities. Some fluids are thicker and resist movement...these fluids have a high viscosity*
The Effect of Temperature on Viscosity Question : Is the viscosity of oil affected by a change in temperature? Hypothesis : What do you think will happen in this experiment? Observations: Ramp Method of Testing Viscosity Oil Grade At Room Temperature (23 ) Below Room Temperature (-18 ) Above Room Temperature (100 ) 0W 20 28.58 seconds 51.76 seconds 9.01 seconds 5W 20 39.95 seconds 65.67 seconds 7.78 seconds 5W 30 51.32 seconds 92.12 seconds 9.12 seconds 10W 30 55.61 seconds 88.13 seconds 7.81 seconds Conclusion: 1. Which grade of oil would you recommend for summer driving? Why? 2. Which grade of oil would you recommend for winter driving? Why? 3. How does temperature affect the viscosity of oil? *The temperature affects the viscosity of all fluids (liquids). As the temperature decreases fluids the viscosity increases. As the temperature increases the viscosity decreases* How does car engine oil work?
Big Idea 2.0 - Density is another important property of fluids. Weight, Mass, and Volume Key Terms : Weight It is the measure of the force of gravity on an object It is measured in Newtons (N) Weight = mass x gravity Earth gravity is 9.807 m/s 2 Moon s gravity is 1.633 m/s 2 Jupiter s gravity is 24.92 m/s 2 OK Go - Upside Down & Inside Out Mass The amount of matter that is in the object It is measured in kilograms (kg) Volume It is the measure of how much space it takes up It is measured in millilitres (ml) Density Is the amount of matter or number of particles in a given volume It is measured in grams per millilitre cubed (g/ml 3 ) The Mass vs Weight Song Is It mass or weight - Using a bathroom scale in an elevator Bathroom Scale - Mass or Weight? http://scienceline.ucsb.edu/getkey.php?key=432
Note : Remember that cm 3 = ml for volume units
Egg...Water...Salt...Density? Question: What can an egg, water and salt teach about density? Alternative investigation: Salty Science : Scientific American Observations: Answer the following questions in complete sentences. Do not write the questions. 1. What happens when you put a raw egg into water? 2. When the egg is on the bottom of the beaker, what is more dense, the water or the egg? 3. When salt is added to the water, what will happen? 4. In which container do you think the egg will float? 5. You know the density of three objects. Object #1 Density = 2.25 g/ml Object #2 Density = 0.91 g/ml Object #3 Density = 1.20 g/ml Which one(s) will sink and which one will float? 6. What does it mean if the egg sits suspended in the mixture, neither at the top nor the bottom? How Taking A Bath Led To Archimedes Principle The Real Story Behind Archimedes Eureka! TED-Ed Lesson
How Dense? Question : What is the density of unknown substances? Name: Class: Hypothesis: Predict the densities of the substances. List them from most to least dense. (answer on a separate piece of paper) Observations : 1 2 3 4 5 6 7 Substance Mass of Substance (g) Measured Volume of Substance Used (ml or cm 3 ) *see note below Initial Volume of Water in Cylinder (ml) Volume in Cylinder After Substance Added (ml) Displaced Volume (ml) **see note below Density of Substance (g/ml) ***see note below Aluminum (Al) Iron (Fe) Brass (Bu) Copper (Cu) Acrylic Nylon PVC Oak Pine Poplar * To calculate Measured Volume length x width x height ** To calculate Displaced Volume Column 5 minus Column 4 *** To calculate Density Column 2 divided by Column Column 6
Conclusion : 1. List the substances from the most dense to the least dense. 2. Assume you have two substances with the same volume. How do different masses affect density? 3. Assume you have two substances with the same mass. How would different volumes affect density? Layer Liquid Density Tower
Density and Temperature What happens to the density of fluids when temperature increases or decreases? What does the Particle Theory of Matter say about increases or decreases in temperature? if you increase temperature, particles in matter begin to vibrate more and it changes states (solid to liquid to gas)...the space between particles begin to increase if you decrease temperature, particles in matter vibrate less and the space between particles decrease As the temperature of a fluid increases the density of the fluid decreases. As the temperature decreases the density increases. Rise Lantern Festival Experiment Effects of Temperature on Density Water Density Note: Water is an exception to the above rule water is most dense at 4 (1 g/ml) the density of ice is 0.92 g/ml swimming in a lake ice fishing TedEd - Why Does Ice Float in Water?
Big Idea 3.0 - Fluids exert a buoyant force on objects that cause some objects to float. Buoyancy and Forces Force - is a pull or push that tends to cause an object to move or change its motion Gravitational force - is the force on the object that pulls it down toward the Earth. It is measured in newton (N) Buoyant force - is the force that acts upward, opposite gravitational force of the floating object * For an object to float, the downward force of gravity must be equal to the upward force of the object s buoyant force. Archimedes Principle the buoyant force acting on an object equals the weight or gravitational force of the fluid displaced by the object Bouyancy Quiz Bouyancy Answer
The Rule of Buoyancy Boat Building Read p.223 +
Building A Tin Foil Boat Question : How many washers can your tin foil boat hold? Name: Grade: Procedures : Form your boat from the tin foil provided Place the washers in one at a time. Be care! Observations : Sketch the final design of your boat. Include a side and top view. Conclusion : If you were to complete another tin foil boat, what design features would you include?
Cardboard Boat Challenge What do you need to complete for the Cardboard Boat Challenge? Blueprint of your boat - make sure you include the following on the blueprint... 2 pages of grid paper - 4 x 8 and 4 x 4 all the measurements Team Name Names of all the members of your group Scale 1:3 Scale model of your boat made of construction paper or cardboard Decide - measuring tape or metre stick? I will need to see your blueprint and boat on TBA
Predicting Buoyancy Question: What factors affect whether an object will remain suspended in water or sink? Hypothesis : What do you think will happen? Observations : Mass (g) Density (g/ml) Sink or Float? Coke 385.4 1.086 Diet Coke 364.2 1.026 Tonic Water 381.4 1.074 Orange Crush 384 1.082 Conclusions : 1. Did each pop can have the same buoyancy? 2. Why do the differences exist among the types of pop? Video - The Beaker Ball Balance Problem 3.6 Check Your Progress p.234 Complete # 2, 3, 4, 5 & 6
Big Idea 4.0 - Understanding the properties of fluids helps in the design and construction of useful devices.
Hydraulic and Pneumatic Devices Hydraulic Devices use water or some other liquid in motion Pneumatic devices use air or other gases These devices place fluid under PRESSURE. Pressure is the amount of force applied to a particular area (or force per unit area) the force is measured in newtons (N)
the size of an area being pushed or pulled in measured in square meters (m 2 ) The pressure also causes fluids to compress. COMPRESSIBILITY is the property of fluids where they become more compact when squeezed. Gases have very large spaces between particles. When pressure is exerted on a gas, those spaces become smaller, resulting in a decreased volume. Liquids have smaller spaces between particles. When pressure exerted on a liquid, its volume cannot be decreased, meaning that it is not compressible Pascal s Law when pressure is applied to a contained liquid, that pressure and force are transmitted without losing any force and in all directions throughout the liquid
A mechanical advantage is created because the input force of A (4,000 N) is larger than the output force of B (64,000 N)
Example : In a hydraulic system that has a 30cc follower and a 10cc driver, the force in the driver is pushing against 10cc while the follower it is pushing against 30cc. Since the follower is 3 times as large, the increase in force from the driver to the follower is 3 times which means a MA of 3. If the volume of the follower was 50 times more than that of the driver you get 50 times as much force and a MA of 50.
Hydraulic or Pneumatic Bridge Challenge Name: Group Members: Challenge Situation : The city of Newtonville requires a new bridge to be built across the Pascal River. The Pascal River is a very busy river that has many boats and barges that carry goods to and from the city. As a result, the new bridge needs to be a MOVEABLE bridge. Your job is to design and then create a model of this bridge. Your bridge must allow vehicles to pass over it and boats to pass under it. Project Criteria : It must be operated by using a hydraulic or pneumatic device It must be made out of the materials provided or materials approved by Mr. Leschyshyn The bridge must be free standing and long enough to span the width of the river The bridge must be moveable and allow one boat to pass beneath it The bridge must be strong enough to hold two trucks for 1 minute Materials: 2 syringes tubing popsicle sticks other teacher approved materials
S.P.I.C.E S - Statement of Problem: P - Possible Solutions: (Sketch 3 numbered sketches) *Complete your sketches on 3 separate pieces of paper* I - Investigate the 3 possible solutions and choose one. Our choice is sketch number We selected it because: C - Construct: Explain the steps that you will take to construct your prototype: E - Evaluate: To be completed when your prototype is completed The good things (strengths) of this model are: If I were to do this again, I would improve or change the following things about my model:
Student Evaluation - Hydraulic Bridge Competition Name: Group Members: Evaluation : (1 to 4) Evaluate each member of your group (including yourself). Give them a mark from 1 to 4. Include a one sentence explanation on why you are giving them that mark. Best Designed Bridge Whose bridge was the best designed? Explain the reason for your choice.
Preparing for the Test 1. Complete the Unit Review ( page 264) #2, 4, 5, 8, 9, 11, 13, 14, 15, 16, 17, 19 2. Review your notes ( and the notes that I will post online ) 3. Review the Study Guide 4. Define the Key Terms 5. Ask questions!