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This is NOT DESTINY…. DENSITY!!! 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! 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! 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=vxd Write these down in your notes!! Density Triangle 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) 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) 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 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!! 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!!! 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! 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 Temperature An increase in temperature causes a DECREASE in density!! This is because volume increases when heat is applied Pressure An increase in pressure causes an INCREASE in density!! This is because as pressure increases on something, its volume decreases! 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) 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