Physical Properties & Physical Properties & DensityDensity

Physical PropertiesPhysical Properties

How would you describe someone or How would you describe someone or something?something?

The weight, height, length, eye The weight, height, length, eye color, hair color, etc. would be good color, hair color, etc. would be good items to use to describe someone.items to use to describe someone.

It is easy to identify chemicals, It is easy to identify chemicals, compounds and elements based on their compounds and elements based on their physical properties also.physical properties also.

These include color, odor, and state These include color, odor, and state of matter to name a few.of matter to name a few.

DensityDensity

Another physical property Another physical property that can be used is that can be used is density.density.

Density is a measure of the Density is a measure of the relationship between mass relationship between mass and the volume it occupies.and the volume it occupies.

Think of it like using Think of it like using weight and height.weight and height.

Density UnitsDensity Units

Density can be defined as Density can be defined as the unit mass per unit the unit mass per unit volume.volume.

Density = Mass/VolumeDensity = Mass/Volume Density is recorded as Density is recorded as g/ml.g/ml. Mass is measured in g.Mass is measured in g. Volume is measured in ml.Volume is measured in ml.

Density CalculationsDensity Calculations To perform a density calculation:To perform a density calculation:

Determine if it is a density problem. The Determine if it is a density problem. The problem should include statements for mass problem should include statements for mass and volume and density. and volume and density.

Read the word problem.Read the word problem. You will need to calculate one of the You will need to calculate one of the three terms but the other two should be three terms but the other two should be given (# unit).given (# unit).

Write down the mathematical formula for Write down the mathematical formula for density. density.

Plug in the given. Plug in the given. Convert to the correct units if necessary.Convert to the correct units if necessary. Solve the problemSolve the problem

Let’s look at some examplesLet’s look at some examples

DensityDensity

What is the density of 5 g of tin What is the density of 5 g of tin that has a volume of 1.2 ml?that has a volume of 1.2 ml?

Density, = Mass, / Volume,Density, = Mass, / Volume, g/ml = g / g/ml = g / ml ml

? g/ml = 5 g / ? g/ml = 5 g / 1.2 ml 1.2 ml

4.2 g/ml4.2 g/ml

DensityDensity

What is the volume of 5 g of tin What is the volume of 5 g of tin that has a density of 4.6 g/ml?that has a density of 4.6 g/ml?

Density, = Mass, / Density, = Mass, / Volume,Volume,

g/ml = g / g/ml = g / ml ml

4.2 g/ml = 5 g / X 4.2 g/ml = 5 g / X mlml

DensityDensity

4.6 g/ml = 5 g / X ml4.6 g/ml = 5 g / X ml

• Get the unknown by itself.

1. Multiply both sides by X ml to cancel it off the bottom.

4.6 g/ml * X ml = ( 5 g / X ml) * 4.6 g/ml * X ml = ( 5 g / X ml) * X mlX ml

4.6 g/ml * X ml = 5 g4.6 g/ml * X ml = 5 g

DensityDensity

• Get the unknown by itself.

2. Divide both sides by 4.6 g/ml to finish getting the unknown alone.

4.6 g/ml * X ml = 5 g4.6 g/ml * X ml = 5 g

(4.6 g/ml * X ml)/ 4.6 g/ml = 5 g / 4.6 (4.6 g/ml * X ml)/ 4.6 g/ml = 5 g / 4.6 g/ml g/ml

DensityDensity

X ml = 5 g / 4.6 g/ml X ml = 5 g / 4.6 g/ml

If at this time while doing other problems, if the units don’t match, you are wrong and need to restart the problem

X ml = 1.2 ml X ml = 1.2 ml

Grams cancel out and you are left with ml.

Try the math.

Buoyancy and DensityBuoyancy and Density One factor that density controls is One factor that density controls is floating and sinking. floating and sinking.

Objects float and sink because of Objects float and sink because of their density.their density.

Compounds that are MORE dense than Compounds that are MORE dense than water sinkwater sink

Compounds that are LESS dense than Compounds that are LESS dense than water floatwater float

The density of water is 1.0 g/ml.The density of water is 1.0 g/ml. The density of cork is 0.34 g/ml.The density of cork is 0.34 g/ml. The density of lead is 13.9 g/ml.The density of lead is 13.9 g/ml.

Does metal float or sink in water? Does metal float or sink in water? Sink.Sink. Look at lead.Look at lead. What is the density of lead?What is the density of lead? Is it less or more dense than Is it less or more dense than water?water?

MoreMore Compounds that are more dense than Compounds that are more dense than water sink.water sink.

Name some other items that will Name some other items that will sink in water.sink in water.

Buoyancy and DensityBuoyancy and Density

Buoyancy and DensityBuoyancy and Density Does cork float in water? Does cork float in water? Yes.Yes. Look at cork.Look at cork. What is the density of cork?What is the density of cork? Is it less or more than water?Is it less or more than water? Compounds that are less dense Compounds that are less dense than water float.than water float.

Name some other items that will Name some other items that will float in water.float in water.