WARM UP (for NOTES) 1. Which is more dense, water or wood? How do you know? 2. Which is more dense, 1 pound of lead or 100 pounds of lead? Density is an intrinsic property of a material Wood, if it sinks in water. Water, if the wood floats. *Less dense things float on top of more dense things SAME! because… 1

Density: m V d = ratio of mass to volume If you have lots of mass, but little volume (very dense) Have Lead, Carbon, etc of same volume to pass around. If little mass, but lots of volume (not dense)

A NOTE ON DISPLACEMENT A submerged object displaces a volume of liquid equal to the volume of the object. One milliliter (1 mL) of water has a volume of 1 cubic centimeter (1cm3) Example: I put a metal cylinder in 20. mL of water (initial) and the water rises to 25 mL Volume of Cylinder = Final Volume of Water – Initial Volume of Water 25. mL – 20. mL = 5 mL = 5 cm3

Density depends only on the substance, not the size of the sample. 1 piece Aluminum d = 2.70 g/cm3 2 equal pieces Aluminum d = ??? g/cm3 1 ton of lead of 1 lb of lead is same density, both sink same with balsa wood, both float d = 2.70 g/cm3

m d = V d = 42.7 g 4.8 cm3 d = 8.9 g/cm3 Calculating Density A copper block has a mass of 42.7 g. What is the density of copper? m V H = 1.9 cm d = W = 1.1 cm L = 2.3 cm V = L x W x H d = 42.7 g 4.8 cm3 V = (2.3)(1.1)(1.9) d = 8.9 g/cm3 V = 4.8 cm3

Calculating with Density A cup of sugar has a volume of 100. mL, and a density of 1.59 g/mL. What is the mass of the sugar? m V 1.59 = m . 100. d = (1.59)(100.) = m m = 159. g 6

m d = V 17.5 = 425 V V = 425 17.5 V = 24.3 mL Calculating with Density What is the volume of 425 g of a solution with a density of 17.5 g/cm3 ? 17.5 = 425 V m V d = V = 425 17.5 V = 24.3 mL 7