DENSITY Density = MASS Volume

MASS –How heavy an object is. –Quantity of matter observed in an object. –Measured in kg, g, or mg –WE FEEL MASS (Atoms).

VOLUME –The size of an object. –The amount of space occupied by an object. –Measured in L, ml, cm 3. -WE SEE VOLUME!! (3-D).

EXAMPLE An object has a mass of 20 grams and a volume of 10 milliliters. What is the density of this object?

Density =20 grams 10 mL Density = 2 g/mL

**The density of a substance is always the same, no matter how large or small the sample is**

Water---1 g/mL, 1 g/cm 3 Iron g/cm 3 Lead g/cm 3 Gold g/cm 3

Why do some objects float in water? Why does a hot air balloon rise? Why are the oceans (Hydrosphere) always below the air (Atmosphere)? The solid earth, crust (lithosphere) is the most dense part of earth.

To change Mass of an object: Cut the object in ½, you will have two pieces each with ½ the mass and ½ the volume of the original. –This does not change density (½ the mass & ½ the volume…Check the density formula)! Add more atoms to the object, you will also be increasing the volume. –Same MASS per VOLUME as before (check it out)! Density stays the same!

Ways to change volume of an object: Change the temperature of an object. Compress the object (ex, Aluminum cube). –This does change density (same mass, more or less volume). Cut an object into different pieces. –Does not change density (Cut object in ½ you have two pieces each with ½ the mass and ½ the volume of the original.

The only way to CHANGE DENSITY is to cause a change in VOLUME without changing MASS. This can only happen through a TEMPERATURE CHANGE and/or a PHASE CHANGE.

PERCENT ERROR Compares a measurement with the accepted value. –Copy formula here from reference tables 1.Subtract 2.Divide 3.Then multiply