DENSITY!!!

1. This is NOT DESTINY…. DENSITY!!!

2. What the heck is Density anyway? • Density is the amount of matter (mass) contained within a given amount of space (volume) • There is a formula for this, on the front page of the ESRT! What is this formula? Look at your ESRT!! • Hurry up!

3. Density Formula • Density = Mass (grams) / Volume (cubic cm or mL) • D = m/v • Remember…NO NAKED NUMBERS! • ALWAYS include units and remember to round to the nearest 10ths • 4 is not an answer for density • 4.0 g/cc is an answer!

4. Formula Manipulations • You WILL NEED to manipulate this formula in order to solve for Volume and Mass • If you manipulate this equation, you will get the following *(USE THE DENSITY TRIANGLE!!) • V = m/d • M = v x d • Write these down in your notes!!

5. Density Triangle

6. Determining the Mass • Mass is the amount of matter contained within a given object • It can be measured using an electronic balance or scale • The proper units to measure MASS in is grams (g)

7. Determining Volume • Volume is the amount of space an object occupies • It can be measured by either by using a ruler to obtain the LENGTH, WIDTH, AND HEIGHT of a rectangular/square object or by using water displacement • The proper units for volume is cubic centimeters (cc) or milliliters (mL)

8. Volume of rectangular/square objects L=?, W=?, H=? • V= L x W x H • V = ? cc • What if this block’s mass is 320 g? What’s its density? • D = m/v • d = 320g / ? cc • D = ? g/cc

9. Volume of Irregular Objects • Volumes of irregular objects must be determined by water displacement • We use a graduated cylinder for this! Let’s see how to do this!!

10. Water Displacement in 3 steps • 1) Place a certain amount of water into the graduated cylinder (20mL in this example) • 2) Place the object into the water CAREFULLY, and record the new water level (it changed to 23mL in this example) • 3) Now, subtract your old volume from the new volume: 23mL – 20mL = 3mL • So the volume of this object is 3mL!!!

11. Volume of a liquid?? • This is MAD easy, yo! • Just pour the liquid into t graduated cylinder and READ! • So, what’s the volume of the water in the graduated cylinder on the left? • That’s right : 20mL!

12. Size and Shape • Size and shape of an object have NO EFFECT on density • But size and shape DO have an effect on mass and volume! • Check out this example • Sample 1: m = 20g and V = 10cc • D = m/v • D= 20g / 10cc • D = 2.0 g/cc • Sample 2: m = 40g and V=20cc • D = m/v • D = 40g / 20cc • D = 2.0 g/cc

13. Temperature • An increase in temperature causes a DECREASE in density!! • This is because volume increases when heat is applied

14. Pressure • An increase in pressure causes an INCREASE in density!! • This is because as pressure increases on something, its volume decreases!

15. Earth • In Earth, more dense materials tend to sink toward the core • Less dense materials tend to rise to the surface • Earth’s inner core is MOST dense • The Outer Atmosphere is LEAST dense (due to VERY light gases there)

16. Some other interesting tidbits… • EVERYTHING on this planet is most dense in its SOLID phase…well, almost everything • WATER is the only exception • Water is most dense in its LIQUID phase • Water is most dense at 4 degrees C • Pure water has a density of 1.0 g/cc • When putting objects in water, less dense objects will float, more dense will sink, and equal density objects will float right in the middle