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Density Problem - Where do I start?

Density Problem - Where do I start?. The density of water at 25°C is 0.997 g/cm 3 . What is the volume in liters of 7.00 lbs of water at 25°C? The temptation is to start with the density, since it’s the first number you come across.

justin-jenkins
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Density Problem - Where do I start?

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  1. Density Problem - Where do I start? The density of water at 25°C is 0.997 g/cm3. What is the volume in liters of 7.00 lbs of water at 25°C? The temptation is to start with the density, since it’s the first number you come across. Our answer should only contain a unit of volume (L), and it must be in the numerator. Density has units in the numerator AND denominator…and the volume is in the denominator (if you do not see that this is not good, PLEASE go get help in the math center!):

  2. Density Problem - pay attention to units! The density of water at 25°C is 0.997 g/cm3. What is the volume in liters of 7.00 lbs of water at 25°C? (1 lb = 453.6 g) Careful reading of the problem shows that you are given pounds and asked for liters: This is in dimensional analysis form and the answer will have 3 SFs: 3.18 L

  3. Density Problem - When do I start with the density? Find the density of 25.0 lbs of water at 100°C in lb/ft3 if its density at that temperature is 0.95838 g/mL. You are given the density in metric units and asked for the density in English units

  4. Density Problem - When do we start with the density? Find the density of 25.0 lbs of water at 100°C in lb/ft3 if its density at that temperature is 0.95838 g/mL. So you start with the density in g/mL: 59.83 lb/ft3to the correct number of SFs

  5. Density Problem - When do we start with the density? Find the density of 25.0 lbs of water at 100°C in lb/ft3 if its density at that temperature is 0.95838 g/mL. 59.83 lb/ft3to the correct number of SFs …what? Why not 3 SFs (because 25.0 lbs)? Or 1 SF (from 100°C)?

  6. Problems sometimes contain extra information Density is an intensive property. It does NOT depend on how much water is present. Its value does depend on temperature, but T is not used in the calculation and so does not affect SFs.

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