Let’s talk about Density What’s more dense…a bowling ball or a volley ball that is equal in size? The bowling ball of course! But why? Because it has more mass squeezed in the small amount of space! *Density is… a physical property that describes how much matter is packed in a given space (volume). *Do you remember what the density of water is from 7th grade? 1 g/cm3

Let’s Talk About Density… It is measured by taking the mass per volume ratio. In other words divide the mass by the volume. *Density = Mass Volume

Remember… Mass = how much matter is in an object. Volume = how much space an object takes up. What’s weight then? Weight is how much gravity is pulling on an objects mass!

DENSITY Let’s talk about units for a minute… For mass: kg, g, mg For volume: cm3, L, mL Why is cm cubed (to the 3rd power)? Because cm3 = length x width x height 1cm3 = 1ml or… For Density: g or g or kg or mg or kg ml cm3 L cm3 cc cc = cubic centimeter

This is how we will solve ALL our problems!!! So this is… DUFAS and… This is how we will solve ALL our problems!!!

How DUFAS works… All problems will be worth 5 points. You will get 1 point for every DUFAS step. So…correct answers are only worth 1 point!

DUFAS D is for Data (Write down all the important Data in the problem) U is for Units (Write down all the units in the problem) F is for Formula (set up the correct formula) A is for Arrange the formula (re-arrange it if you have to and plug in numbers) S is for Solve the problem

DATA: Copy this Example: Ashley’s 2.4 cm3 ear ring has a density of 19.3 g/cm3. What is it’s mass? What is the important Data in this question? V = 2.4 cm3 D = 19.3 g/cm3 What are we looking to solve for here? m = ? g

UNITS: Example: Ashley’s 2.4 cm3 ear ring has a density of 19.3 g/cm3. What is it’s mass? Write down all the CORRECT UNITS in this problem!!! V = cm3 D = g/cm3 m = ? g

FORMULA: Example: Ashley’s 2.4 cm3 ear ring has a density of 19.3 g/cm3. What is it’s mass? You must write the formula for EVERY problem. *The Power Triangle will help you to do this! Draw a triangle like this one!

How to use the Power Triangle m v What is the formula for Density? = So how do we set up the power triangle? So what is the formula for volume? *What about mass? D x V m D m D v

Arrange: Example: Ashley’s 2.4 cm3 ear ring has a density of 19.3 g/cm3. What is it’s mass? New Formula is M=D x V D= 19.3 g/cm3 V= 2.4 cm3 m=(19.3 g/cm3) x (2.4 cm3)

Solve: Now you need to substitute the data into the arranged formula to SOLVE. m = D * V m =(19.3 g/cm3)*(2.4 cm3) V = 2.4 cm3 D = 19.3 g/cm3 m = ? g m = 46.32 g What happened to the cm3? They canceled each other out!

*Recognizing Units Copy down all 10 examples and determine if they are density, mass or volume? 43 g/cm3 800 kg 456 cm3 77 mg/cc 762 ml 67 mg 31 g/liter 212 g 100 cc 67 mg/ml Density Mass Volume 10. Density

*Lets Practice using DUFAS! 1.) A 42.6 g gold ring has a density of 19.3 g/cm3. How much space is it taking up? 2.) A 257.8 cm3 man has a density of 11 kg/cm3. What is his mass? 3.) What is the density of a 52.1 cm3 block of ice that has a mass of 47.93 g?

Practice Answers 1.) m = 42.6 g D = m d = 19.3 g/cm3 v v = ? cm3 v = m v = 42.6 g = 2.20 cm3 D 19.3 g/cm3

Practice Answers 2.) m = ? kg D = m d = 11 kg/cm3 v v = 257.8 cm3 m= v*D m = 257.8 cm3 * 11 kg/cm3 = 2835.8 kg

Practice Answers 3.) m = 47.93 g D = m d = ? g/cm3 v v = 52.1 cm3

No it is not pure gold. It’s less dense than gold. Density 101 1. A gold-colored ring has a mass of 18.9 grams and a volume of 1.12 ml. Is the ring pure gold? (The density of pure gold is 19.3 g/ml.) D= M/V Density= 16.87 g/ml No it is not pure gold. It’s less dense than gold.

Density 101 2. What volume would a 0.871 gram sample of air occupy if the density of air is 1.29 g/liter? V= M/D .675 liters

Yes, pumice will float on water b/c it is less dense. Density 101 3. Pumice is volcanic rock that contains many trapped air bubbles. A 225 gram sample occupied 236.6 ml. What is the density of pumice? .950 g/ml 3a. What’s the density of water? 1 g/cm3 3b. Will pumice float on water? Yes, pumice will float on water b/c it is less dense.

Density 101 4. A cup of sugar has a volume of 237 ml. What is the mass of the cup of sugar if the density is 1.59 g/ml? M= D x V M= 376.83 g

Density 101 5. Which has a greater mass, 1 liter of water or 1 liter of gasoline? The density of water is 1.00 g/mL and gasoline’s density is approximately 0.68 g/mL. M= D * V Water = 1 g/mL * 1000 mL = 1000 g Gas = 1000 mL * 0.68 g/mL = 680 g WATER!

Density 101 6. From their density values, decide whether each of the following substances will sink or float when placed in sea water, which has a density of 1.025 g/mL. Gasoline 0.66 g/mL = float Mercury 13.6 g/mL = sink Asphalt 1.2 g/mL = Cork 0.26 g/mL =

Density 101 7. A sample of lead is found to have a mass of 32.6 g. A graduated cylinder contains 2.8 mL of water. After the lead sample is added to the cylinder the water level reads 5.7 mL. Calcualte the density of the lead sample. 5.7 mL – 2.8 mL = 2.9 mL = Volume D= M/V 32.6 g/ 2.9 mL = 11.24 g/mL

The Density Column Lab

Using Density to Predict Position *If we put a solid into a liquid, and the solid is more dense than the liquid it will *If the liquid is more dense then the solid will *The same thing goes for all liquids. The least dense floats on top of more dense. sink Float

Question… If the lead weight is dropped into the beaker of water… will it sink or float? d= 11.4 g/ml What will happen if it is dropped into the mercury? mercury d = 13.5 g/ml water d = 1.0 g/ml

Alcohol 0.80 g/ml Veg. Oil 0.90 g/ml Water 1.00 g/ml ALL solids have the same volume of 15.6 ml Masses: pine = 5.4g acrylic = 17.3g steel = 128.5g wax = 9.8g pvc = 13.7g Calculate the densities of these five substances and place them where they would sink to in the density column. Take two places past the decimal. Alcohol 0.80 g/ml Veg. Oil 0.90 g/ml Water 1.00 g/ml Corn Syrup 1.20 g/ml Draw the column with the densities

ALL solids have the same volume of 15.6 ml Masses: pine = 5.4g acrylic = 17.3g steel = 128.5g wax = 9.8g pvc = 13.7g .34 g/ml .62 g/ml Alcohol 0.8 g/ml .87 g/ml Veg. Oil 0.9 g/ml Water 1.0 g/ml 1.1 g/ml Corn Syrup 1.2 g/ml 8.23 g/ml