Mass vs. Weight Mass = amount of matter in an object Weight = attraction between matter The moon is much smaller than the earth. As a result, the force of gravity on the moon is only about one sixth as strong as gravity on earth. Gravity is what holds us down on the earth's (or moon's) surface. If you were to weigh yourself on a scale here on earth and then could take that same scale to the moon and weigh yourself there, the weight read on the moon would be 1/6 your earth weight. So, If you weighed 100 pounds on earth, you would weigh only about 16 pounds on the moon.

D= Density Density = mass / Volume Physical property of a substance Aids in identification of a substance DENSITY you BREAK MY HEART D=

The Formula M D = V Density = Mass Or Volume Units: Mass — g or kg Volume — cm3 or ml Density — g/cm3 or g/ml g/l When determining density you always reduce it to the mass in one cm3. This allows you to compare substances of different sizes (volumes) 1 ml is 1 gram because the density of water is 1g/ml at 4C. 1 cm3 is 1ml solids & liquids gases

Matter separates according to their densities

Finding Densities Mass Cube Cylinder Liquid Irregular solid Use a balance l x w x h = s3 V = ¶r2h graduate Water displacement

IMPORTANT!!! Let’s try it … When working with formulas you must: 1. write the formula out 2. substitute the known 3. cancel where you can 4. identify the answer with the variable you are solving for Let’s try it …

Using the Density Formula Plug and Chug D = M V & Ex: 27.2 g of liquid occupies 2.00 cm3. What is the density of the liquid? D = 27.2 g Or 13.6 g 1 cm3 = 13.6 g/cm3 2.00 cm3 *when determining density you are always reducing the mass to one cm3. This allows for comparison of different volumes.

Plug and Chug D = M V & A cylinder of aluminum (Al) has a density of 2.70 g/cm3. If its mass is 15.0 g, find its volume. 2.70 g/cm3 = V 15.0 g 2.70 g/cm3 * V = 15.0 g V = (15.0 g) 2.70 g/cm3 V = 5.56 cm3

Plug and Chug D = M V Air has a density of 0.0013 g/cm3. Calculate the mass of a 200. cm3 sample. 200. cm3 M 0.0013 g = /cm3 M = (200. cm3) (.0013 g/cm3) & M = .26 g

Using the density formula V Solve for Mass…. Multiply both sides by V V x D = M x V V Solve for Volume…. Multiply both sides by V V x D = M x V V V’s cancel out… V’s cancel out… M = V x D Divide both sides by D and cancel D M = V x D V = M D

M D V A little trick… Solve for V? Cover up V Get M/D!!! Solve for D? Cover up D. Get M/V!!! Solve for M? Cover up M. Get V * D !!

Practice A certain object has a mass of 22 g. If its density is 12 g/ml, what is its volume? 2. A certain metal has a density of 21 g/ml. Calculate the mass of a 5 ml sample. 3. If you know that 21 grams of a liquid occupies 10 ml, what is the liquid’s density? & 1.83 ml 105 g 2.1 g/ml

Ice floats! Conclusion: The volume of ice must be greater than the same mass of liquid water. Why does the volume increase?  Molecular basis for the Volume Increase of Ice: The normal pattern for most compounds is that as the temperature of the liquid increases, the density decreases as the molecules spread out from each other. As the temperature decreases, the density increases as the molecules become more closely packed. This pattern does not hold true for ice as the exact opposite occurs.In liquid water each molecule is hydrogen bonded to approximately 3.4 other water molecules. In ice each each molecule is hydrogen bonded to 4 other molecules.

Law of Conservation of Matter and Energy Matter and Energy can not be created and destroyed by ordinary chemical means No change in quantity! Can only change form! The total amount of matter and energy in the universe is a fixed amount