1. DENSITY… Will it sink or float??

2. Why do some things float… … and other things sink?

3. NOT because it is lighter than the liquid… Some things float… Two men on a tree trunk… definitely not lighter than water

4. NOT because it is heavier than the liquid… And, some things sink… A small marble is not heavier than a beaker of water but it will still sink

5. The MASS AND the VOLUME!! So, density depends on… That’s why the wood (and men) don’t sink!!

6. volume = the amount of space an object takes up Some vocabulary background… Mass = the amount of stuff that an object has

7. That is why a heavy metal ship can float on water… Density = ratio of mass to the volume. even though the mass is big, the volume is big too!! Ratio means that density depends on both the mass AND the volume.

8. But, how do you calculate the density??? Density =mass volume

9. Sample problem What is the density of 50.0 g of a solid which occupies a volume of 6.4 mL? the mass = the volume= 50. 0 g 6.4 mL Density = mass volume D = 50.0 g / 6.4 mL D = 7.8 g / mL the equation=> the unknown= density