2 What is Density? Density = Mass Volume Density is defined as mass per unit volume.Density = MassVolume
3 Density describes how matter is packed into space. Density is a derived unit. It is calculated from other measurements.
4 Density is a physical constant. A physical constant a physical property that can be described with a number and a unit.A physical constant is the same for all samples of a substance regardless of sample size or shape.
5 1 drop of pure water has the same density as 1 liter of pure water. Density does not change with sample size.
6 Physical ConstantsWe use physical properties such as density to identify substances.Some other physical constants include melting point, boiling point, heat capacity, heat of vaporization, and heat of fusion.
8 What are the units of density? The most common units of density are grams per cubic centimeter (g/cm3) or grams per milliliter (g/mL).By the way, 1 cm3 = 1 mL.
9 Density and PhaseFor most substances, the solid is the densest phase and the gas is the least dense.S L GWater is Weird! Water is at its densest at 4.0C, when it’s a liquid.L S G
10 The density of water is 1.0 g/mL (At 4.0°C). The relative density of any substance can be determined by adding it to water.If the substance floats, it’s density is less than the density of water:d < 1.0 g/mLIf the substance sinks, it’s density is greater than the density of water:d > 1.0 g/mL0.80 g/mL1.0 g/mL1.2 g/mLsource
12 Density of GasesBalloonx.movBalloony.movFlow of CO2
13 What is the density of …? Substance Density (g/cm3) water 1.00 seawater1.025ice.92aluminum2.70gasoline.70oil0.90lead11.30gold19.30white pine.50rubber1.10cork.24bone1.80iron7.90human fatmercury13.60helium
14 What is the density of some selected elements? source
16 What variables affect density? Temperature, TPressure, PLiquid or solid: Even large changes in P & T small changes in density.Gas: Even small changes in P & T large change in density.
17 How does Temperature affect Density? Most materials expand when they are heated.Mass stays the same (it’s constant), but volume increases. So the matter isn’t packed as tightly.Density must decrease. (Hot air balloons!)
18 When the material expands, the density decreases.
19 Temperatue & Density As T , liquid becomes less dense. Spheres sink. As T , liquid becomes more dense. Spheres rise.Source:
20 How does Pressure affect Density? If you the pressure on an object, the volume .If the volume , the matter must be packed more tightly & density must .
21 When you apply pressure to an object, the density increases!
22 Remember: Water is weird! Ice BombInsert V. 2, CCA
23 Density Problems Algebra-type problems. The density equation has 3 variables.In any given problem, you are given information about 2 of them and you solve for the 3rd.You might have to rearrange the equation.
24 Problem-solving Rubric Given: Identify the given info.Unknown: Identify the unknown.Equation: Identify the correct equation and rearrange it as necessary.Substitute: substitute numerical values in for the letters.Solve: Do the math!
25 You can’t ignore reciprocals! 1 can’t magically become V.V