Convert Mass Convert 12 lb weight of bowling ball to g, showing unity factors 12.00 lb x 453.59237 g/lb = 5443 g Calculate and convert volumes V=4/3 π r 3 V = 4/3 * 3.1416 * (1/2 * 8.59 in) 3 = 4/3 * 3.1416 * 79.23 in 3 =331.9 in 3 Unity Factor: 2.54 cm = 1 in 331.9 in 3 x (2.54 cm / 1 in) 3 Note!!! 331.9 in 3 x 16.39cm 3 /in 3 = 5439 cm 3 Densities Will the bowling ball float in water? Demo [1] D = 5443 g / 5439 cm 3 Too close to call. See Errors in Measurement Lecture Demonstrations Mass vs. Weight What is the mass of hydrogen? Density of hydrogen at room temperature and 1 Atm = 0.082 g/L What is the volume in L, assuming same size as bowling ball? Unity Factors? 1 cm 3 = 1 mL = 10 -3 L (Note: 1 mL = 1 cm 3 = “1 cc”) V (L) = 5500 cm 3 x (1 L / 1000 cm 3 ) m (g) = V (L) * D (g/L) = 5.500 L x 0.082 g/cm 3 = 0.451 g Why does the Hydrogen balloon float? F = W = m g F = W = (0.451 g x 1 kg /1000g) * 9.8 m*s -2 = = 0. 0044 N Force Upward: (Archimedes) D of air = 1.2 g /L; Archimedes Principle: buoyancy = mass of air displaced (6.6 g) F = m g F = ( 6.6 g x 1 kg /1000g) * 9.8 m*s -2 = = 0. 065 N Net force = 0.065 N - 0.044 N upwards. References J. Chem. Educ., 2004, 81 (9), p 1309