1. Respiration continued Part 2

18. Fluids Pg. 66 in textbook Can you give some examples of fluids that you know and see everyday?

19. Fluids Fluid: is a substance that has the capacity to flow and assume the form of the container into which it has been poured Ex: a liquid can be a fluid AND a gas can be a fluid!!! (the air we breathe assumes the shape of the nasal passages, trachea…) All liquids such as water, milk, saliva are fluids

20. Fluids All gases such as oxygen, helium, air are fluids Can you explain this with the particle model? draw it out in your notes and explain your drawing

21. Fluids particle model The particles in a liquid (water) are close together and held by forces of attraction relatively weak So, the particles can slide over each other and take the form of any container The particles of a gas (air) are much farther apart and are bound together by weak forces of attraction

22. Pg. 67 Particle model Fig 3.3 and 3.4 demonstrate the particle model Take a look at the space between the particles in each state (S, L, G) Does your drawing look like these? If NOT, adjust them!!

23. Determining if a substance is a fluid It can sometimes be difficult to determine is a substance is a fluid or not Here are some particular cases Some substances are mixtures in a liquid or gaseous phase that contains solid particles. Since these substances are still capable of flowing they are considered fluids Other substances like gels or pastes are harder to identify… what do you think?

24. Fluids If they can flow and take on the form of their containers, they are FLUIDS! If a solid exists in tiny pieces, like sand, and can flow, is it a Fluid? NO! sand does not flow continually like a liquid, and it does not naturally assume the shape of the container (it really forms a pile instead of a flat surface)

25. Compressible fluids Pg 68 Is a fluid whose volume can change (gases are compressible fluids) Describe what is happening in Fig 3.8

26. Incompressible fluids pg 69 A fluid whose volume cannot be varied (liquids are incompressible fluids) Explain Fig 3.9 What are some compressible and incompressible fluids in the body?

27. Pressure Def: the force exerted by particles when the collide with a constricting surface What happens in your lungs when you hold your breath?

28. Pressure exerted by fluids pg 73 The pressure exerted by fluids is equal in all directions since the particles are in constant motion…what about incompressible… Think about when you dive deep into a pool …what happens? Ears block and that is from the pressure exerted by the water Incompressible fluids (water) the force exerted comes from the mass of the fluid above the object

29. Pressure exerted by incompressible fluids The total quantity of fluid is not important Ex at a depth of 1 meter, we feel the same pressure in a pool as we do a lake! The more fluid above an object, the greater force exerted by the fluid and the greater pressure Fig 3.17 3.18

30. Density of fluids The denser the fluid the greater the pressure If you dove into a pool of mercury the pressure would be more since mercury has a higher density than water (13.55) Summary: pressure exerted by an object by incompressible fluid depends on: – Depth of object in fluid – Density of fluid

31. Pressure exerted by compressible fluid Particles of compressible fluid (gas) move randomly in all directions, if meet an obstacle they change direction With each collision the fluid particles exert a force on the obstacle The sum of these forces that create the pressure from a compressible fluid

32. Compressible fluid Pressure Depends on: – # of collisions (the more colllisions = more pressure) Factors that increase collision: – # of particles (the more particles = the more collisions) – Temperature (speed of particle increase with temp. increase) – Volume of Fluid (explained on next slide) How can fluids move around the body with pressure?

33. Volume and Pressure (at a constant temperature) when the volume of a compressible fluid decreases => they move closer together => less space to move around => increase collisions => INCREASE IN PRESSURE What happens when Volume increases?