Does it sink or float?

Did you know that seawater contains many dissolved substances and these add mass to the water producing a greater mass per unit volume, or density, than that of pure water?

Our campers discovered the relationship between the density of a fluid, weight of an object, and buoyancy is critical in understanding the ocean, because density has a direct influence on the way seawater and objects in seawater behave. They learned that an object can both sink and float depending on its relative density to the surrounding fluid. There are two main factors that make ocean water more or less dense: the temperature and the salinity. Less dense water floats on top of more dense water.

Essential Questions: 

• Why do some objects float in water and others don’t?
  
• Why do some objects behave differently in salt water than in fresh water?
  
• If we can’t detect density with any of our five senses, how do we know it exists?
  
• What is density a measurement of?
  
• Why does a ship float in the water and a paper clip sinks?
  
• Are fish “floating” when they are in the water, even though they are submerged?