DENSITY

Density: By definition: How heavy something is compared to its size In math: d=m/V m=mass V=volume Example: The density of gold is 19.3 g/mL this means that every 1 mL of gold weighs 19.3 grams.

What is volume? Volume: the amount of space an object occupies. Formula: Cube = l·w·h Sphere = 4/3πr3 Cylinder = πr2 * h How could you determine the volume of an irregular object? Water displacement

Calculating Volume Try this one… Q: What is the volume of the cube? V = 288 in3 Make sure to correctly label your answer!

Things you should know: Density of water: 1 g/mL An object will float in water if the density is less than 1 g/mL (ie d=.97 g/mL) An object will sink in water if the density is greater than 1 g/mL (ie d=1.1 g/mL)

Try this one If this cube has a mass of 36 grams, what is the density of the cube? Will the cube float? 4 cm 3 cm 6 cm Volume = 4cm * 6cm * 3cm = 72 cm3 Density = 36 grams / 72 cm3 = 0.5 g/cm3 Yes, it will float.

A baseball has a mass of 146 grams. If it has a radius of 3 A baseball has a mass of 146 grams. If it has a radius of 3.5 cm, what is density of a baseball? Will a baseball float? First calculate the volume. V = 4/3π(3.5cm)3 = 180cm3 Density = 0.81g/cm3 IT FLOATS

What about the density of a cylinder? If the cylinder shown has a mass of 18 grams, what is its density? Volume = 100.5 cm3 Density = 0.18 g/cm3 2 cm 8 cm

What about with an irregular object? A rock has a mass of 260 grams. In order to determine its volume it is dropped into a graduated cylinder. The water level changes from 40 mL to 120 mL. What is the density of the rock? Density = 260g / 80mL = 3.25 g/mL Will it float?

Q: What is the density of the Earth in g/mL? Mass: 5.98×1024 kg Volume: 1.08×1024 L 5.98×1024 kg 1000 g = 5.98×1027 g 1 kg 1.08×1024 L 1000 mL = 1.08×1027 mL 1 L A: 5.98×1027 g/ 1.08×1027 mL ≈ 5.5 g/mL

Try this one… Q: A block of aluminum occupies a volume of 15.0 mL and weighs 40.5 g. What is its density? d= 40.5g/15mL A: d= 2.7 g/mL

More Practice Q: What is the weight of the ethyl alcohol that exactly fills a 200.0 mL container? The density of ethyl alcohol is 0.789 g/mL. Use density as a conversion factor in dimensional analysis A: g=158 grams 200.0 mL 0.789 g 1 mL

Use dimensional analysis A chunk of aluminum displaces 4 Liters of water. If the density of aluminum is 2.70 grams/mL, what is the mass in kilograms of the sample? 4 L 1000 mL 2.70 g 1 kg = 10.8 kg 1 L 1 mL 1000 g

One More Q: A piece of metal has a density of 12.6 kg/L. If you have 25 mL of this metal, how many grams is it? 25 mL 1 L 12.6 kg 1000 g 1000 mL 1 L 1 kg A: 315 grams

THE END Yay for density…