Presentation Transcript

1. Science 8

   Unit 2- Fluids
2. Big Ideas Fluids are an important component of many systems. Fluids have different properties that determine how they can be used. Fluids are essential to life.
3. Overall Expectations 1. analyse how the properties of fluids are used in various technologies, and assess the impact of these technologies on society and the environment; 2. investigate the properties of fluids; 3. demonstrate an understanding of the properties and uses of fluids.
4. What are “fluids”? If you had to come up with a definition of “a fluid”, what would it be?
5. Fluids Fluids are materials that have no fixed shape and that are free-flowing (take the shape of their container) BOTH liquids and gases are fluids How does the scientific definition change your idea of what fluids are?
6. Lesson 1- Fluids in the body The majority of your body is made up of fluids We have all been hearing for years that we are mostly made up of water (% differs depending on who you talk to) Other than water, what other fluids do we have in our bodies?
7. Fluids in our bodies
8. Fluid Systems in the body Our body has several systems within that help us function every day. Fluids are integral to several of these systems: 1. Circulatory System 2. Respiratory System 3 .Urinary System
9. Circulatory System Moves blood through our body Blood carries oxygen, co2, nutrients, hormones, etc. Works with the respiratory system to create the cardiovascular system The heart pumps to send blood away from the heart to the body through arteries (with oxygen in it) and to the lungs (to receive oxygen) Veins return “used” blood to the heart to start the process again
10. Respiratory System The system that brings air into our bodies We take in air, use oxygen, and breathe out (mostly) carbon dioxide Once the air is in our bodies, the respiratory system works with the circulatory system to get the oxygen to our cells We inhale through our nose/mouth, the air travels down the trachea (windpipe), into the bronchial tubes and into the lungs At the end of the bronchioles there are tiny sacs called alveoli, which absorb the oxygen into your blood (then the circulatory system takes over) Our bodies produce carbon dioxide as waste which travels through the respiratory system in the opposite order The diaphragm helps in breathing by contracting/pulling down during inhalation and relaxing during exhalation
11. Urinary System Also known as the renal system, this system rids the body of waste, regulates blood pressure, chemicals in the blood, etc. The kidneys filter waste from the blood and create urine If your kidneys don’t filter waste from the blood properly, a dialysis machine can clean your blood for you The bladder then stores the urine until it is ready to exit the body
12. Questions for your notes Is air a fluid? Explain why or why not. Name three fluids that you need in order to live. What do kidneys do? What treatment is needed if kidney’s don’t work properly? Choose a body fluid. Why is that fluid important to your body? What do you think would happen to your body without that fluid?
13. Lesson 2- Characteristics of Fluids Last class, we learned a definition for fluids. Who remembers what it is?
14. Fluids….. Fluids are materials that have no fixed shape and that are free-flowing Liquids and gases are both fluids, but that does not mean they are the same. Each state has its own set of properties- some that are shared amongst both liquids and gases, some that are different between the two
15. Shape As we discussed earlier, neither liquids or gases have a definite shape; both take the shape of the container they are in. Even though you cannot see the gas inside these containers, the have taken their container’s shape like the liquids- trust me 
16. Volume Liquids have a definite volume If you have 2 L of water, it doesn’t matter what container you put it in, the volume will be 2 L if you took the 2 L of coke in the bottle, and poured it into the 50 L garbage can, it would barely cover the bottom, but there will still be 2 L of coke Gases do not have a definite volume Think about perfume- If you spray a tiny bit from a bottle (a liquid), it evaporates, becomes a gas, and fills the whole room All gases will fill whatever container (or room) they occupy
17. Why the difference? The particle theory helps explain the similarities and differences between states of matter (solids, liquids, and gases) Particle theory of matter All matter is made of particles All particles have empty spaces between them Particles are constantly moving in random directions Particles move faster and spread further apart when they are heated Particles are attracted to one another
18. Solids Particles in solids have a strong connection to one another and have less space between them. So, when they move, they only vibrate. They do not slide past one another which is why solids have a definite shape AND volume (and why solids are not fluids
19. Liquids In liquids, the particles are not as strongly attracted. Therefore, there is more space between them. The connection is strong enough to hold liquids together, so they have a definite volume BUT the connection is weak enough to allow the particles to slide around more freely, which is why liquids do not have a definite shape
20. Gases In gases, particles are really far apart because they have a weak force of attraction Gas particles go wherever they please (within their containers) which is why they do not have a definite shape or volume
21. For your notes….. Fill out the chart below to show the differences between solids, liquids and gases
22. Flow All fluids have the ability to flow This is a characteristic of fluids This happens because the particles inside liquids and gases are not strongly attracted to one another to stay put; they can move around (think about what happens when you like a boy or girl. If you really like them, you stay put. But, if your attraction fades, you might start to wonder other places)
23. Examples of how fluids flow Where does oil flow? Where does air flow? Where does water flow? If you fill a container full of sand, poke a hole in the top, and tip it over, the sand will “flow”, right? Does that mean that sand is a fluid?
24. WRONG!!! The sand isn’t actually flowing All the individual grains of sand are moving through the hole (thanks to gravity) but each gain is keeping it’s shape Air, water, and oil particles can flow freely
25. Types of Flow 1. Laminar Smooth and regular “uninterrupted” Less energy required 2. Turbulent Choppy and irregular Something interrupts Requires more energy and moves slower
26. Rapids The water flow shown here is an example of turbulent flow What has interrupted the flow of this water? Is this good or bad?
27. Good Turbulent flow of water is actually great for the environment! It adds oxygen to the water that living things need to survive Its also a lot of fun for white water rafters and kayakers
28. Fluids flowing in our bodies Do we want laminar or turbulent flow of blood in our circulatory system? Why?
29. Laminar Free-flowing blood is definitely needed in our veins and arteries to get our blood where it needs to go quickly If plaque builds up in our arteries, it can lead to blockages that create turbulence and can cause blood clots, heart attacks, and strokes!
30. Different types of flow Golf balls have tiny dimples on them that are designed to create turbulent flow of air. Why?
31. For your notes….. What are the two main characteristics of fluids? What are the 5 parts of the particle theory of matter? Why can’t solids flow? Why isn’t salt considered a fluid? What are the two types of flow? (with examples) Why are airplane wings designed for laminar flow, not turbulent flow?
32. Lesson 3- Viscosity Some fluids flow very quickly while other flow slowly. Give an example of each………
33. Fast vs. Slow Molasses flows very slowly Water flows quite quickly Why don’t they both flow the same?
34. Flow rate We can determine how fast (or slow) fluids move by measuring the volume that a fluid moves past a point in a certain amount of time (like a racer crossing the finish line) For example, if it takes you 10 seconds to fill up your 5 L Brita container from the tap, the flow rate is : 5 L/ 10 s = 0.5 L/s If you turn your tap on full blast, it will fill faster Than if you decrease your water flow **What else might affect flow rate?
35. Factors affecting flow rate The size of the opening The force pushing on the fluid The surface the fluid is flowing over The type of fluid Viscosity
36. Viscosity The substance’s viscosity also affects flow rate Viscosity is the substances thickness or resistance to flow Generally, the thicker the fluid, the slower it flows Think about table syrup- does it flow faster when you leave it on the counter or keep it in the fridge? Why?
37. Factors affecting viscosity 1. Cohesion How strongly the particles in the fluid are attracted to one another The stronger the attraction, the slower the flow Weaker attraction = faster flow 2. Adhesion How strongly the particles are attracted to the particles of another substance (often the particles of the container) This is why rivers flow more quickly in the middle than at the edges
38. Viscosity in Nature The viscosity of magma can affect the type of volcanic eruption that happens and even how the volcano is formed Magma that is less viscous (flows faster) leads to more eruptions because gas can escape through it easier These types of eruptions are less violent and lead to lava flows that create gentle sloping sides to volcanos More viscous (slower flowing) magma leads to less eruptions because gas is trapped However, when the explosions happen, they are more violent because of the pressure that builds up Lava shoots into the sky and volcanos with steeper slopes are formed (because the lava moves faster)
39. http://www.youtube.com/watch?v=cn0mIj0_4ws Non-Newtonian Fluids Not all fluids act the same (as I am sure you have already realized) BUT….would you believe me if I told you that there are fluids out there than can stop bullets and support your weight?? http://www.youtube.com/watch?v=3zoTKXXNQIU http://www.youtube.com/watch?v=bLiNHqwgWaQ
40. For your notes… (Viscosity) It takes Jimmy 5 minutes to fill a 2 L bottle of molasses. Calculate the flow rate of the molasses in L/min. What are the 5 factors that affect flow rate? What are the two factors that affect viscosity? How does viscosity affect volcano formation? Name one non-Newtonian fluid and describe how it is different than “regular fluids Fill out the cart below to show your understanding of cohesion vs. adhesion
41. Viscosity Experiment Next class, we will test the viscosity of different fluids Let’s brainstorm different liquids that you would like to test…..
42. Viscosity Experiment Materials needed: cardboard, plastic sheet, spoon, various liquids….. Procedure: We will time how long it takes each liquid to travel down the cardboard (or plastic sheet) from start to finish Fill out the prediction sheet then compare our predictions to our results
43. Lesson 4- Density Density is the measure of the amount of matter per unit volume of a substance Every substance has a density that can be calculated/measured Think about two completely different substances; We would need a lot more Styrofoam to make 1 kg than we would need to make 1 kg of rocks. This is because rocks have a higher density than Styrofoam.
44. Density depends on two things The mass of the particles (how much matter is in a substance) How tightly packed the particles are The more tightly packet the particles, the more dense the substance is
45. Thinking back Last lesson, we looked at the spaces between particles in each state of matter Because particles in solids are closest together, solids are usually more dense than liquids, and gases (least dense)
46. Calculating Density Not all fluids (liquids or gases) have the same density. Think about oil and vinegar salad dressing. The two parts don’t mix together even when we shake them. This is (at least partially) because vinegar is more dense. Oil will settle on top (because it is less dense) To calculate the density of a substance, you divide an the mass by the volume. D = m/v or ρ = m/v (ρ is the Greek letter “rho”) The density of solids and liquids are commonly expressed in g/mL or g/cm³ Gases; kg/m³ Why do you think we measure gases in kg but solids and liquids in g?
47. Densities of common gases **Density can be affected by temperature and pressure Several common substances have their density measured at NTP (normal temperature and pressure) 20ºC STP (standard temperature and pressure) 0ºC Since helium is less dense than air, balloons filled with helium float
48. Densities of common liquids Many substances are liquids under “normal conditions”(e.g., room temperature) Other substances require different conditions to appear in their liquid state (see Oxygen)
49. The world’s Densest liquid At room temperature, (21ºC), Mercury is the world’s most dense liquid (13600 kg/m³) Also know as quicksilver, is the only metal that is liquid at room temperature
50. The special properties of water Water is one of the few substances that actually becomes less dense as it changes from a liquid to a solid (1.0 kg/L vs. 0.92 kg/L) This is why ice floats to the top of your drink
51. The Dead Sea A salt lake in the Middle East (bordering Jordan, Israel, and Palestine) It is one of the world’s saltiest bodies of water Density = 1.24 kg/L Regular salt water is approx. 1.03 kg/L Approx. density of a human is 1.01 kg/L Since humans are less dense than the water of the Dead Sea, you can “float” in it
52. Density Simulation file:///C:/DOCUME~1/athompso/LOCALS~1/Temp/phet-density/density_en.html
53. Density Demonstration We are now going to use graduated cylinders, water, salt, and food colouringto make this happen. Anyone know how?
54. Rainbow water demonstration
55. For your notes…. (Density) 1. Density- the measure of the amount of per of a substance 2. The two factors that affect density 3. How do you calculate density? 4. Why do ice cubes float in a glass of water? 5. Complete the “Solve Density Problems” worksheet (p.173-174 of text for a copy, if you lost yours)
56. Lesson 5- Buoyancy Last lesson, we learned all about density (the amount of matter per unit volume of a substance) Density helps determine whether substances sink or float, but it is not the only factor A screw made of steel will easily sink in water but steel boats that weight thousands of tons (and carry much more weight) float in water. WHY?
57. Buoyancy The upward force that a fluid exerts on an object that opposes the weight of an object An object’s buoyancy determines whether it will sink or float
58. Factors affecting Buoyancy 1. Weight of the object 2. Fluid displaced by the object 3. shape of the object 4. Density of the object
59. Fluid Displacement When we put anything in a fluid (think water), the fluid is displaced (or moved) Weight of displaced fluid = upward buoyant force Objects float when they displace an amount of water that is greater than (or equal to) its own weight Sinking occurs when the amount of water displaced is less than its own weight
60. Shape The shape of an object affects the amount of fluid it displaces Think about a diver vs. a belly flopper; Divers (good ones, anyway) enter the water by displacing very little The other guy? Not so much
61. The screw vs. the ship The screw is tiny and displaces very little water The buoyant force acting on the screw is very small, cannot support the weight of the screw It sinks Cargo ships are large and have a hollow shell They displace a great deal of water The buoyant force acting on the ship is large, so it supports the weight of the ship It floats
62. Density The density of the fluid is also a factor in buoyancy The denser the fluid, the more buoyancy force, the easier objects float think back to the Dead Sea example) Do you think a ship will float more easily in the Atlantic Ocean or in Lake Ontario? Why?
63. Plimsoll Line Engineers need to understand buoyancy to design ships. Most ships have a plimsoll line painted on them to show how high (or low) the ship will float in different water types The notches on the left are freshwater, salt water on the right
64. Buoyancy Test http://www.planetseed.com/files/flash/science/lab/liquids/buoy_exp/en/buoyancy.html
65. For your notes…..Buoyancy Definition of Buoyancy 4 factors that affect buoyancy “Check your Understanding” questions from page 177 and “Will it Sink of Will it Float?” activity on page 178
66. Lesson 6- Pneumatics and Hydraulics Pneumatics- systems that use compressed fluids (specifically air or other gases) to work Hydraulics- systems that used compressed fluids (specifically liquids) to do work
67. Examples of Pneumatic systems Air brakes Some exercise machines Pressure gauges Balloons Air pumps Air tubes for mail
68. Examples of Hydraulic systems Car lifts Water pump Combustion engine in a car
69. Parts of a fluid system Pump- forces fluids through the system Conductor- carries fluid through the system Valve- keeps fluids moving in the right direction at the right time or stops it at the right time) Pressure Gauge- measures pressure in the system
70. For your notes…..Fluids under pressure Define “compression” Explain the difference between Pneumatics and Hydraulics (and provide examples of each) Identify each of the 4 main parts of a fluid system and the job of each THINGS NOT COVERED IN CLASS (USE YOUR BOOKS) Define pressure and give the formula for it (p. 189) Pascal’s law (p. 191) The effect of pressure, volume, and temperature on fluids (p. 195) Valves (2 examples where they help systems- circulatory system and engines)- (p. 200-202)