2 D=m/v D = density, What Is Density? Density is how heavy something is for its size.Density is mass divided by volume orD=m/v D = density,M = massV = volume
3 Another Way of Looking at It. You will often hear density referred to as “mass per unit volume.”Let’s break this down:Mass = how much matter the object has.Per = means divided byUnit volume = how much space it takes up
4 Take the mass and divide by its volume! So… When you hear mass per unit volume, you should think…Take the mass anddivide by its volume!
5 What Are the Units of Density? Mass units would includeGrams for very small objects orKilograms for larger objectsVolume units would includeCubic centimeters for small objects orCubic meters for large objectsMilliliters for small amounts of liquidsLiters for larger amounts of liquidLets stick to grams and cubic centimeters for now.
6 How to State Density Units massYou have grams forYou have cubic centimeters forThese are not the same units, they don’t cancel so you have to include both units in your answervolume
7 How to State Density Units The units of density are:Grams/Cubic Centimeter org/cm3
8 length multiplied by width multiplied by height or Why Cubic Centimeters?Remember that volume islength multiplied by width multiplied by height orl X w X hIn each case, the distance is in cm and since you are multiplying it three times, you get cubic centimeters.
9 Now, How About an Example? l=10 cmh=5 cmw=2 cmMass= 100 gramsUse the information provided to calculate the density of the object
10 What Did You Get? If you got 1g/cm3, you are correct! Lets see how this works:V=l x w x hV=10 cm X 5 cm X 2 cmV=100cm3Mass = 100 g (given)D=m/vD=100 g/100cm3=1g/cm3
11 A Word About Irregularly Shaped Objects. If you are given an irregularly shaped object and told to find the density, you might have a problem.If the length, width, and height of the object are not uniform (the same), you cannot use l X w X h to determine volume.
12 A Word About Irregularly Shaped Objects. To determine the volume of an irregularly shaped object, start with a graduated cylinder of water filled about half fullRecord the volume of water in the cylinderDrop in the irregularly shaped objectRecord the volume of water in the cylinder with the object in itSubtract the original volume from the second volume to determine the volume of the object
13 A Word About Irregularly Shaped Objects. You are measuring the amount of water displaced by the object which is equal to the volume of that objectThis is called:VolumeBy Displacement
14 g/cm3 Liquids Milliliters Or liters So far we have been talking mostly about solids. Solids have densities that can be easily expressed inLiquids tend to be measured inThis is not a problem because you can convert milliliters or liters into grams per cubic centimeter.g/cm3MillilitersOr liters
15 LiquidsYou can also weigh a liquid to determine its mass. Now we are going to use the word massing for weighing to avoid confusionTo do this, measure your cylinder in grams and record its empty massAdd your liquidNow mass the cylinder againSubtract the mass of just the cylinder and you have the mass of your liquid
16 Can you guess what kind of solid would sink in water? Sink or Float?Solids can float or sink in a liquid.Can you guess what kind of solid would sink in water?
17 Answer:Any solid will sink in water if it has a density greater than the density of water.Water has a density ofAny solid with a density greater than 1g/cm3 will sink in water!1g/cm3