why do things float in the dead sea
Late night talk show host David Letterman has a long running segment entitled БWill it Float? Б where an object presented and Letterman and his on-air staff debate and then guess whether it will float in a tank of water. If the tank happened to be filled with salt water, more of the objects Letterman used would have, in fact, floated. Adding salt to water changes the physical forces that water exerts on objects, making them float, a concept that you can demonstrate in your own home. Buoyancy is the upward force that a fluid exerts on an object. When an object is dropped into a fluid, the force of gravity pulls the object down towards the Earth. The magnitude of that force depends on the mass of the object. The fluid pushes back up on the object and the magnitude of the force is dependent on the mass of the displaced fluid. If the mass of the object is less than the mass of the displaced fluid, the object will float.
Buoyancy is influenced by the density of the object and the density of the fluid, that is the mass and volume of the object and the fluid it displaces. Adding salt increases the density of water. As the salt dissolves in the water, the ions fit into the spaces between the water molecules, similar to marbles filling the spaces if you poured them into a bucket full of tennis balls. The mass of the saltwater is much higher and the volume only slightly greater, so the saltwater is more dense than freshwater. If the same volume of water is displaced by an object, the weight of saltwater displaced is greater and thus the force of buoyancy is proportionally greater. The Dead Sea, in Israel, is a fun place to experience the buoyancy effects of saltwater first hand. The Dead Sea is a dead end; it is the lowest point on Earth and the end of the Jordan River. The river carries salt into the sea and the evaporating water concentrates it.
The salt concentration in the Dead Sea is 300 parts per thousand, by contrast, ocean water is 35 parts per thousand. The high salinity means that swimmers float easily and a popular tourist activity is to recline effortlessly on top of the water while reading a newspaper or magazine. You donБt need to travel to Israel to explore why salt makes things float, you can do a science project. All you need is a peeled hard-boiled egg, a jar of warm water and salt. Place the egg in the jar of water. It will sink to the bottom. Take the egg back out and stir in as much salt as will dissolve in the water. Try to place the egg in the jar again and this time, the salt has increased the density of the water enough to float the egg.
When you think of the activities that tourists usually do in Israel - exploring historic ruins, visiting religious sites, enjoying water sports or nightlife - bowling doesn't exactly come to mind.
But if you had access to a 14-lb. bowling ball when traveling through the Holy Land, wouldn't you try to see if it floats in the Dead Sea? That's just what I did on a recent trip to Israel. Armed with a bright pink 14-lb. bowling ball (pink for good contrast against earth tones), I experimented at different bodies of water around the country until I arrived at the Dead Sea - a popular attraction for its unique geological characteristics. Not only is it the lowest point on earth (over 1,380 ft below sea level), but it's also one of the iest, with the salinity of the water at about 31% - that's about 8 times saltier than ocean water. And because of this high concentration of natural salt, the density of Dead Sea water is almost 24% higher than regular water, which means that many things that don't normally float actually become buoyant - but does that include a 14-lb. bowling ball? Find out:
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