 # Density. What exactly is Density? Is a quantitative physical property Is a quantitative physical property It is the same for any sample of a particle.

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Density

What exactly is Density? Is a quantitative physical property Is a quantitative physical property It is the same for any sample of a particle substance in solid or liquid form It is the same for any sample of a particle substance in solid or liquid form How much mass is crowded into a given space How much mass is crowded into a given space Appendix D in your text has a list of densities for some substances (page 564) Appendix D in your text has a list of densities for some substances (page 564) Remember that units are important!!! Remember that units are important!!!

Density vs. Heaviness We need to remember that just because something is heavier does not mean that it is denser!!!! We need to remember that just because something is heavier does not mean that it is denser!!!! Example: Example: Although lead is much more dense than iron, if you have a larger sample of iron than lead it will probably be heavier. Although lead is much more dense than iron, if you have a larger sample of iron than lead it will probably be heavier. Heaviness deals with weight while density deals with both mass AND volume! Heaviness deals with weight while density deals with both mass AND volume!

Density – The Mathematical Formula But we can also use this formula to find the volume of a substance if we know the mass and the density AND we can find the mass of a substance if we know the volume and density! But we can also use this formula to find the volume of a substance if we know the mass and the density AND we can find the mass of a substance if we know the volume and density!

Formulas Density = mass/volume = g/cm 3 Density = mass/volume = g/cm 3 Volume = mass/density = cm 3 Volume = mass/density = cm 3 Mass = density x volume = g Mass = density x volume = g

Example: A chunk of silver has a volume of 2.00 and a mass of 21.0 A chunk of silver has a volume of 2.00 and a mass of 21.0 What is the density of silver? What is the density of silver? Given: volume and mass Required: Density Analysis: D = m/V Solution: D = 21.0g / 2.00 cm 3 = 10.5 g/cm3 Paraphrase: The density of silver is 10.5 g/cm 3

Example: A softball has a mass of 360 and a volume of 270 A softball has a mass of 360 and a volume of 270 Find it’s density. Find it’s density. Given: Mass and Volume Required: Density Analysis: D = m/V Solution: D = 360/270 Paraphrase: The density of the softball is 1.3 g/cm 3.

Example: The density of nickel is 8.9 The density of nickel is 8.9 What is the volume of 500 of nickel? What is the volume of 500 of nickel? Given: Density (8.9) and Mass (500) Required: Volume Analysis: V = m/D Solution: V = 500/8.9 = 56.1 cm 3 Paraphrase: The volume of nickel is 56.1 cm 3

Example: What is the mass, in grams, of a What is the mass, in grams, of a 1.0 block of iron? 1.0 block of iron? First thing we need to do is find the density of iron which happens to be on page 166 of our text and it is 7.9 First thing we need to do is find the density of iron which happens to be on page 166 of our text and it is 7.9 Given: Volume and Density Required: Mass Analysis: M = density * volume Solution: M = 7.86 * 1.0 Paraphrase: The mass of a 1.0 cm 3 block of iron would be 7.86 g/cm 3

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