25ml graduated. dish soap 100ml graduated cylinders. cylinders. Metric ruler with mm divisions. digital scale

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1 You are challenged to get your film canister to float while filled with the most weight you can. The film canisters will not be capped, so if they go under water at all, they will sink. You want to get the most weight you can in your film canister WITHOUT any practice trials or placing the canisters in the water at all. Using any of the following materials: 250ml beakers 25ml graduated dish soap 100ml graduated cylinders paper towels cylinders Water displacement tins Pipets 50ml graduated cylinders Metric ruler with mm divisions Sand digital scale Your canister will have a certain number of BBs to start with and you will add sand to your desired level Helpful information: Density of water = 1.00g/cm 3 Dish soap will make the surface tension of water less.

2 Density Challenge Period: Name: Physical Science Date: 1. What is the conceptual definition of density (the definition you can use to conceptually understand density)? How much stuff (matter) is packed into a certain space. 2. What makes some objects float while others sink? Explain! Objects float on fluids that are more dense than themselves, and sink in fluids that are less dense than themselves. When floating the buoyant force is equal to the weight of the object.

3 3. Explain why something that is very heavy like the ferry floats, but something that is very light, like a penny, sinks. The Ferry is filled with air, people, etc, besides the metal so on average there isn t as much stuff packed into the space as there is with the solid-metal penny 4. Explain why the ferry does NOT sink lower in the water when fully filled, or float higher when cars off load (some people think it does, but if it did, the boarding ramp would get steeper as cars and people got on and flatter as cars and people got off). The ferry has ballast tanks that it can put water into or take water out of. The ferry takes in water to replace the air that was in the tanks while offloading, or pumps water out to get rid of extra mass as mass is loaded on. 5. Explain why in cold climates, large lakes rarely freeze over in the winter at the center, but do often freeze over at the edges. As the top layer of water cools down it contracts (water is most dense at about 4ºC), so it sinks to the bottom. This keeps happening until ALL the water under top layer (from the surface down to bottom of the lake) is cooled to 4ºC, 6. What is the density of an object with a mass of 20g and a volume of 15 ml? Show your work, let your units be your key to solving! Density has units of g/ml, so we must divide g by ml or 20g/15ml = 1.33 g/ml or 1 g/ml with 1 sig fig.

4 7. The ferry MV Tacoma is listed as being 6,184 long-tons (1 long-ton = 1,016.05kg) when loaded. Approximately, 21.1% of the Ferry s overall volume is below the water line. Seawater has an average density of 1.027g/ml. a. Calculate the volume of seawater that is displaced by the ferry. Show your work using unit canceling. Since the mass of the water displaced and the mass of the object are equal for a floating object (Archimedes principle) the weight of the water displaced is also 6,184 long tons. So we can convert 6,184 long tons kg g ml for the seawater. 6,184 long tons 1,016.05kg 1 1 long ton 1000g 1kg 1 ml 1.027g = 6,283,253,200 ml = 6,118,065,433ml = 6,118,000,000ml (4 sig figs) 6.118x10 9 ml b. Calculate the overall volume of the entire ferry (treat the ferry as a solid object, so you don t have to take any air, people, seats, etc. into account). Show your work. V Ferryunderwater = 21.1% of V FerryTotal 6,118,065,433ml = 0.211xV FerryTotal V FerryTotal = 6,118,065,433ml x10 10 ml = 28,995,570,773.9ml = 29,000,000,000ml c. Calculate the average density of the ferry (treat the ferry as a solid object with all mass evenly distributed, in that way the density everywhere in the ferry is equal). Show your work using unit canceling. units of density = g, so divide g by ml. From part a, mass is ml 6,283,253,200 g 28,995,570,773. ml = g = 0.217g (3 sig fig) ml ml

5 8. An object has a mass of 650.2g and a density of 1.45g/ml, what is the object s volume? Show your work using unit canceling method g 1 1ml 1.45g = 448ml 9. An object has a volume of 20.2ml and a density of 2.4g/ml, what is the object s mass? Show your work using unit canceling method. 20.2ml 1 2.4g 1ml = 48g

6 10. For your experiment you ll have to measure the volume and mass of the canister. What is smallest division shown and to what can you estimate the precision for of each of the devices you chose to use? Explain how you know for each. The digital scales have precisions that are just the last digit shown on the scale. So, depending on what scale you used the precision was either to the nearest 0.1 or the nearest 0.01g. The analog graduated cylinders or rulers, depending on how you measured the volume, can be estimated to1/10 th of the smallest division shown, which are: Device Smallest division shown Estimated to 25ml graduated cylinder 0.5ml 0.05ml 50ml graduated cylinder 1ml 0.1ml 100ml graduated cylinder 1ml 0.1ml 250ml beaker 25ml 2.5ml 50ml beaker 10ml 1ml Metric ruler with mm shown 1mm 0.1mm or 0.01cm 11. How will you ensure validity of your measurements? Why will that ensure validity? Have each lab partner measure the volume and masses to make sure the measurements are accurate. If all partners get very similar results, take the average, or if results are off by much, then redo at least one trial. That way, our data will be shown to be reliable and hence valid.

7 12. What volume do you need to have at or below the fluid surface? Show your work or describe your process. If doing water displacement: fill the displacement tin with water and wait until the no more water comes out, breaking the surface tension with an object as it comes out of the spout. When ready, submerge the object just to the level assigned and collect and measure the fluid displaced. If doing calculations: Diameter of film canister is 3.09cm, so the radius is 1.545cm. The volume would then be: π r 2 h = 3.14 (1.545cm) 2 h = cm 2 h group depth submerged (cm) as close as your measuring device can get to volume submerged

8 13. What is the mass of the ethanol that needs to be displaced? Show your work using unit cancelling cm g 1cm 3 = 15.38g 14. What is the mass that your canister, BBs and sand needs to be? Explain. Since the canister is floating, the buoyant force upwards must cancel the downwards gravitational force (the weight of the canister and all contents), otherwise the canister would sink lower or float higher instead of staying at same depth. Archimedes Principle says that the weight of the fluid displaced is equal in size to the buoyant force, which we already said equals the weight of the floating object, so the whole canister and contents must have a mass equal to the mass of the ethanol displaced, so 15.38g 15. What is the overall volume of the canister? Explain or show work? The height of the canister is 4.91cm, so 3.14 (1.545cm) cm = 36.82cm What overall density of canister do you need? Show your work or explain g/36.82ml = g/ml 17. What is the initial mass of the film canister? 3.95g 18. What is the mass needed just for the BBs? Show your work =11.43g 19. How many BBs did you have to add to your canister to achieve your desired mass? 32

9 20. What is the approximate mass of 1 BB? Show your work with unit cancelling (start with 1BB). 1BB g 32BB = 0.357g 21. What final mass of the sand, canister, and BBs did your achieve? 15.37g 22. Did your canister float: Yes. How high above the water line is the top 1 mm of your canister? 23. What are some sources of error in this experiment? At least 2 sources of error: Measuring the volume of just the plastic Not measuring full volume displaced Not taring out the scales before putting things on them, etc.

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