2 DENSITYPbPbBoth of the above blocks consist of pure lead (Pb)
3 PbPbWHICH BLOCK HAS THE GREATER DENSITY?IF YOU ANSWERED, “THEY HAVE THE SAME DENSITY.”YOU ARE CORRECT!!!WHY?
4 WHY?1. Both of the above blocks consist of pure lead (Pb)2. Density is a ratio of Mass to Volume (D=M/V).Let’s do some calculations to explore this.
5 Let’s take measurements of each block. Small block:mass: glinear measurements:2.00cm x 3.00cm x 4.00cmLarge Block:mass: glinear measurements:4.00cm x 5.00cm x 6.00cm
6 Let’s calculate the volume of each block. Small block:mass: gVolume Calculations:2.00cm x 3.00cm x 4.00cm =24.0 cm3Large Block:mass: gVolume Calculationss:4.00cm x 5.00cm x 6.00cm = cm3
7 Now let’s calculate the density of each. Small block:mass: gVolume: 24.0 cm3DENSITY=M/Vg = 11.3 g24.0cm cm3Large Block:mass: gVolume: 120cm3DENSITY=M/V1360.8g = 11.3g120cm cm3
8 Small block:mass: gVolume: 24 cm3272.16g = 11.3 g =DENSITY24.0cm cm3Large Block:mass: gVolume: 120cm31360.8g = 11.3g = DENSITY120cm cm3Note: the mass to volume ratios (DENSITIES) are the same.
9 Density as a Conversion Factor Note: The units of density are in a ratio form, so density can be used as a conversion factor to change mass to volume or volume to mass.Let’s explore this.
10 Problem: Determine the mass of a 1.00 L sample of Pb. (The density of Pb is 11.3 g/cm3, 1 L = 1000mL =1000 cm3Solution:1. What are the units of what we are looking for?__________________ = g (mass units = grams)2. What do we have?1.00 L______________ = g3. Now convert L into g using density1.00 L = g1000 mL1L11.3 gmL11300
11 Problem: Determine the volume of a 1.00 lb (454 g) sample of Pb. (The density of Pb is 11.3 g/cm3)Solution:1. What are the units of what we are looking for?__________________ = cm3 (volume units)2. What do we have?1.00 lb______________ = cm33. Now convert lb into cm3 using density1.00 lb = cm3454 g1.00 lbcm311.3 g40.1740.2 cm3
12 Let’s compare the two solutions. 1.00 L mL g = g1 L mL1.00 lb g cm = cm31.00 lb gCompare how density was used in the two solutions.
13 Now work with someone next to you to solve this problem. Problem: A rock having a mass of g was placed in a graduated cylinder containing water with an initial reading of 23.0 mL. The water level rose to a reading of 48.5 mL. Calculate the density of the rock.Volume = =25.5 mLDensity = g = 5.34 g = 5.34 g25.5 mL mL cm3
14 Cooking oil has a density of approximately 0.952 g/mL. a. Determine the mass of 550 mL of cooking oil.550 mL= g523.6520 gb. Determine the volume of 870 g of cooking oil.870 g= mL913.9910 mL
15 Densities of Some Common Materials Substance Density g/cm3 water (25oC)ice (0oC)GoldLeadsand ??Does density change with temperature?