Real-life applications - Density and Volume

1 8/20/13 6:43 PMReal- life applications - Density and VolumePage 1 of 6 #bPhoto by: thieuryDensity and Volume - Real-life applicationsLike3 people like this. Sign Up to see what your friends EASURING V OLUMEWhat about the Volume of a solidthat is irregular in shape? Someirregularly shaped objects, such asa scooter, which consistsprimarily of one round wheel anda number of oblong shapes, canbe measured by separating theminto regular shapes. Calculus maybe employed with more complexproblems to obtain the Volume ofan irregular shape but the most basic method is simply to immerse the object in water.

2 Thisprocedure involves measuring the Volume of the water before and after immersion, andcalculating the difference. Of course, the object being measured cannot be water-soluble; if it is,its Volume must be measured in a non-water-based liquid such as liquid volumes is easy, given the fact that liquids have no definite shape, and will SearchPowered by JRankScience Clarified Real-life Chemistry Vol 3 - Physics Vol 1 Density and VolumeeLearning Masters of Science from A&M Commerce Apply Now for October 2013 Start!

3 Science Clarified8/20/13 6:43 PMReal- life applications - Density and VolumePage 2 of 6 #bsimply take the shape of the container in which they are placed. Gasesare similar to liquids in the sense that they expand to fit theircontainer; however, measurement of gas Volume is a more involvedprocess than that used to measure either liquids or solids, becausegases are highly responsive to changes in temperature and the temperature of water is raised from its freezing point to itsboiling point (32 to 212 F or 0 to 100 C), its Volume will increase byonly 2%.

4 If its pressure is doubled from 1 atm (defined as normal airpressure at sea level pounds-per-square-inch or 10 5 Pa)to 2 atm, Volume will decrease by only , if air were heated from 32 to 212 F, its Volume would increaseby 37%; and if its pressure were doubled from 1 atm to 2, its volumewould decrease by 50%. Not only do gases respond dramatically tochanges in temperature and pressure, but also, gas molecules tend tobe non-attractive toward one another that is, they do not tend tostick together.

5 Hence, the concept of " Volume " involving gas isessentially meaningless, unless its temperature and pressure UOYANCY : V OLUME AND D ENSITYC onsider again the description above, of an object with irregularshape whose Volume is measured by immersion in water. This is notthe only interesting use of water and solids when dealing with Volume and Density . Particularlyintriguing is the concept of buoyancy expressed in archimedes 's than twenty-two centuries ago, the Greek mathematician, physicist, and inventorArchimedes (c.)

6 287-212 ) received orders from the king of his hometown Syracuse, a Greekcolony in Sicily to weigh the gold in the royal crown. According to legend, it was while bathingthat archimedes discovered the principle that is today named after him. He was so excited,legend maintains, that he jumped out of his bath and ran naked through the streets of Syracuseshouting "Eureka!" (I have found it).What archimedes had discovered was, in short, the reason why ships float: because the buoyant,or lifting, force of an object immersed in fluid is equal to the weight of the fluid displaced by the8/20/13 6:43 PMReal- life applications - Density and VolumePage 3 of 6 # A STEEL SHIP FLOATS ON most ships are made of steel, and therefore, it is even harder to understand why an aircraftcarrier weighing many thousands of tons can float.

7 After all, steel has a weight Density (thepreferred method for measuring Density according to the British system of measures) of 480pounds per cubic foot, and a Density of 7,800 kilograms-per-cubic-meter. By contrast, sea waterhas a weight Density of 64 pounds per cubic foot, and a Density of 1,030 difference in Density should mean that the carrier would sink like a stone and indeed itwould, if all the steel in it were hammered flat. As it is, the hull of the carrier (or indeed of anysea-worthy ship) is designed to displace or move a quantity of water whose weight is greater thanthat of the vessel itself.

8 The weight of the displaced water that is, its mass multiplied by thedownward acceleration due to gravity is equal to the buoyant force that the ocean exerts on theship. If the ship weighs less than the water it displaces, it will float; but if it weighs more, it another way, when the ship is placed in the water, it displaces a certain quantity of waterwhose weight can be expressed in terms of Vdg Volume multiplied by Density multiplied by thedownward acceleration due to gravity. The Density of sea water is a known figure, as is g (32 ft m/sec 2 ); thus the only variable for the water displaced is its the buoyant force on the ship, g will of course be the same, and the value of V will be thesame as for the water.

9 In order for the ship to float, then, its Density must be much less than thatof the water it has displaced. This can be achieved by designing the ship in order to maximizedisplacement. The steel is spread over as large an area as possible, and the curved hull, whenseen in cross section, contains a relatively large area of open space. Obviously, the Density of thisspace is much less than that of water; thus, the average Density of the ship is greatly reduced,which enables it to OMPARING D ENSITIESAs noted several times, the densities of numerous materials are known quantities, and can beeasily compared.

10 Some examples of Density , all expressed in terms of kilograms per cubic meter,are:8/20/13 6:43 PMReal- life applications - Density and VolumePage 4 of 6 #bHydrogen: kg/m 3 Air: kg/m 3 Oak: 720 kg/m 3 Ethyl alcohol: 790 kg/m 3 Ice: 920 kg/m 3 Pure water: 1,000 kg/m 3 Concrete: 2,300 kg/m 3 Iron and steel: 7,800 kg/m 3 Lead: 11,000 kg/m 3 Gold: 19,000 kg/m 3 Note that pure water (as opposed to sea water, which is 3% denser) has a Density of 1,000kilograms per cubic meter, or 1 gram per cubic centimeter.