Density and Buoyancy

The definition of Density

the amount of matter in a given space, or volume

The equation for finding density

D=M/V or Density = Mass/Volume

common units for density

g/cm3 or g/mL or kg/m3 or kg/L

Density of water

1 g/mL

Is density a physical or chemical property

physical property

definition of buoyant force

the upward force that fluids exert on all matter

Archimedes' Principle

the buoyant force on an object in fluid is an upward force equal to the weight of the fluid that the object takes the place of, or displaces

objects that float in water have a density

less than 1 g/mL

objects that sink in water have a density

greater than 1 g/mL

when an object's weight is greater than the buoyant force

the object will sink

when an object's weight is less than the buoyant force

the object will buoy up

when an object's weight is equal to the buoyant force

the object will float

Why do helium balloons float and balloons filled with carbon dioxide don't?

helium is less dense than air while carbon dioxide is more dense than air

How can a steel ship float when steel has a higher density than water?

the ship's hull is shaped so that the ship has a larger volume and therefore a smaller density

How do you make a submarine sink?

Fill the ballast tanks with water to increase the density of the submarine

How do you make a submarine rise?

Pump air into the ballast tanks to decrease the density of the submarine

Common units for liquid volume

mL or L

Common units for solid volume

cm3 or m3

Common units for mass

g or kg

how to find the volume of a cube

LxWxH

how to find the volume of an irregular solid

water displacement : H2O final vol - H20 initial vol

tool used to find mass

triple beam balance

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