Density PDF

Density  Density Density is the mass per unit of volume of a material. Units are g/mL or g/cm3 Different materials have different densities.  Density The equation for density is: How to use a Scientific Formula List the givens in the problem....

Density  Density Density is the mass per unit of volume of a material. Units are g/mL or g/cm3 Different materials have different densities.  Density The equation for density is: How to use a Scientific Formula List the givens in the problem. Write the quantity, value, and units. Write the formula Rearrange the formula to solve for the unknown Plug in your numbers Solve – don’t forget units!  Density Problems 1. A block of aluminum has a mass of 8.1g and a volume of 3 cm3. What is the density of aluminum? Givens: m = 8.1 g V = 3 cm3 D=?  Density Problems 1. A block of aluminum has a mass of 8.1g and a volume of 3 cm3. What is the density of aluminum? Givens: Formula: m = 8.1 g V = 3 cm3 D=?  Density Problems 1. A block of aluminum has a mass of 8.1g and a volume of 3 cm3. What is the density of aluminum?  Density Problems 2. Water has a density of 1 g/mL. What is the mass of 75 mL of water?  Density Problems 3. A piece of iron has a mass of 31.6g. The density of iron is 7.9g/mL. What is its volume?  Density Problems 4. A sealed 2500 mL flask is full to capacity with 35 g of a substance. Determine the density of the substance.  Density Problems 5. Diamonds have a density of 3.5 g/cm3. how big is a diamond that has a mass of 1.0 g? [Figure 1] The man in this cartoon is filling balloons with helium gas. What will happen if he lets go of the filled balloons? They will rise up into the air until they reach the ceiling. Do you know why? It’s because helium has less density than air. Defining Density Density is an important physical property of matter. It reflects how closely packed the particles of matter are. When particles are packed together more tightly, matter has greater density. Differences in density of matter explain many phenomena, not just why helium balloons rise. For example, differences in density of cool and warm ocean water explain why currents such as the Gulf Stream flow through the oceans. To better understand density, think about a bowling ball and volleyball, pictured in the Figure below. Imagine lifting each ball. The two balls are about the same size, but the bowling ball feels much heavier than the volleyball. That’s because the bowling ball is made of solid plastic, which contains a lot of tightly packed particles of matter. The volleyball, in contrast, is full of air, which contains fewer, more widely spaced particles of matter. In other words, the matter inside the bowling ball is denser than the matter inside the volleyball. [Figure 2] A bowling ball is denser than a volleyball. Although both balls are similar in size, the bowling ball feels much heavier than the volleyball. Q: If you ever went bowling, you may have noticed that some bowling balls feel heavier than others even though they are the same size. How can this be? A: Bowling balls that feel lighter are made of matter that is less dense. Calculating Density The density of matter is actually the amount of matter in a given space. The amount of matter is measured by its mass, and the space matter takes up is measured by its volume. Therefore, the density of matter can be calculated with this formula: Density=massvolume Assume, for example, that a book has a mass of 500 g and a volume of 1000 cm3. Then the density of the book is: Density=500 g1000 cm3=0.5 g/cm3 Q: What is the density of a liquid that has a volume of 30 mL and a mass of 300 g? A: The density of the liquid is: Density=300 g30 mL=10 g/mL Summary Density is an important physical property of matter. It reflects how closely packed the particles of matter are. The density of matter can be calculated by dividing its mass by its volume. Review What is density? Find the density of an object that has a mass of 5 kg and a volume of 50 cm3. Create a sketch that shows the particles of matter in two substances that differ in density. Label the sketch to show which substance has greater density.  SI CONVERSION FACTORS Length SI Unit: meter (m) 1 m = 1000 mm 1 meter = 1.0936 yd 5280 ft = 1 mi 1 m = 100 cm 1 meter = 3.28 ft 12 in = 1ft 1000 m = 1 km 2.54 cm = 1 in (exact) 3 ft = 1 yd 1 m = 1 x 106 µm 1 mile = 1.6 km 1 m = 1 x 1010angstrom 1 km = 0.62137 mi 1 m = 1 x 109 nm Mass SI Unit: kilogram (kg) 1 kg = 1000 g 1 kg = 2.2046 lb 16 oz = 1 lb 1 g = 1000 mg 453.59 g = 1 lb 2000 lb = 1 ton 1Metric ton = 1000 kg 1 g = 1 x 106 µg 1 g = 1 x 109 ng Volume SI Unit: cubic meter (m3) = kL 1 m3 = 1kL 1 L = 1.0567 qt 1 gal = 4 qt 1 dm3 = 1L 3.7854 L = 1 gal 1 qt = 2 pt 1 cm3 = 1 mL 1 pt = 2 cups 1 L = 1000 mL 1 cup = 8 oz 1 L = 1 x 106 µL 1 kL = 1000 L Time SI Unit: second (s) Temperature SI Unit: kelvin (K) 1 min = 60 sec 0 K = -273.15 oC 1 hr = 60 min K = oC + 273.15 1 day = 24 hr o C = 5/9(oF - 32) 1 yr = 365.25 day o F = 9/5(oC) + 32 Energy SI Unit: Joule (J) Pressure SI Unit: pascal (Pa) 1 J = 1 kg. m2/s2 1 atm = 101.325 kPa 1 cal = 4.184 J 1 atm = 760 mm Hg (or Torr) 1 J = 9.4781 x 10-4 btu 1 atm = 14.70 psi * btu = British Thermal Unit  Some Key Constants Gas Law Constant : R = 8.3145 J/K. mol Speed of Light: c = 2.9979 x 108 m/s Planck’s Constant: h = 6.626 x 10-34 J. s Avogadro’s number: N = 6.022 x 1023 atoms or molecules/ 1 mole Standard Temperature and Pressure (STP) = 273 K (0 oC) and 1 atm Mass of an electron: me = 9.109 x 10-31 kg Mass of a proton: mp = 1.673 x 10-27 kg Mass of a neutron: mn = 1.675 x 10-27 kg