DensityA physical property of matter

I can apply an equation to determine the density of a substance based on its mass and volume.

0807.9.7 Apply the relationship between mass and volume to determine the density of a substance.

What is density?

Density is a comparison of how much matter there is in a certain amount of space or volume.

Density is a physical property of all materials and all phases of matter (solid, liquid, gas, plasma).

Density is determined by how closely packed particles are in a specific volume.

Which one is more dense?

Demonstration: People in a square

How about this: Which square is more dense?

Which one is more dense?

Now which one is more dense?

Density

Density is the mass per unit volume of an object.

Density is used to identify and classify substances (gold Vs pyrite, salt water Vs fresh water, steel Vs. aluminum, solid Vs. liquid)

I love Density

I Love Density

Density =

Density =

Density formula

Density = Mass m

Volume v

 

Units g/ml, g/cm3, g/cc

Remember 1 ml = 1 cm3 = 1 cc

ALWAYS REMEMBER

UNITS

Let’s try a density problem together

Get your density practice worksheet and let’s calculate the density of the regular Coke and the Diet Coke.

Use the bottom of the sheet to work the rest of the problems. Frank has a paper clip. It has a mass of 9g and a volume of 3cm3. What is its density?

Frank also has an eraser. It has a mass of 3g, and a volume of 1cm3. What is its density?

Now, try these on your own.

Al’Licia has a watch. It has a mass of 4g and a volume of 2cm3. What is the density of the watch?

Mia has a wallet. It has a mass of 15g and a volume of 5cm3. What is the density of the wallet?

Density Practice problems

What is the density of a 42 g rectangular solid with sides that measure 2 cm, 3 cm and 1.5 cm?

 

What is the density of a 24 g rock that has a volume of 8 ml?

Liquid Layers

If you pour together liquids that don’t mix and have different densities, they will form liquid layers.

The liquid with the highest density will be on the bottom.

The liquid with the lowest density will be on the top.

Liquid Layers

Check out this picture from your book. Which layer has the highest density?

Which layer has the lowest density?

Imagine that the liquids have the following densities: 10g/cm3. 3g/cm3.6g/cm3. 5g/cm3.

Which number would go with which layer?

Liquid Layers – Try with your neighbor

Which liquid has the highest density?

Which liquid has the lowest density?

Which liquid has the middle density?

Liquid Layers – Try on your own!

Imagine that the liquids on the right have the following densities:15g/cm3 10g/cm3

3g/cm3 9g/cm3

7g/cm3 12g/cm3

Match the colors to the correct densities.

3g/cm3

7g/cm3

9g/cm3

10g/cm3

12g/cm3

15g/cm3

Float or Sink

The density of water is 1 g/ml

Anything with a density less than one will float in water. If there are numbers to the left of the decimal it will sink!

So why do ships float ?

The density of steel is 7.8 g/cm3

The density of waters 1 g/cm3

Think of a steel ship as a can that is empty and watertight. The majority of its space is taken up by nothing more than air which has a specific gravity of about 0.00129. So if a make a ship that is like a can, empty inside and watertight it floats. Its volume sufficient that it causes its specific gravity to remain below 1.0 even after adding the weight of its contents.

The steel ship will remain afloat as long as its density remains below that of water. The problem is that if water is allowed to enter the ship it would sink. Ships made of steel have to be sealed so water can not get in and increase its density.

Steel can float only because of the way it is shaped, the space it takes up, and the seal that keeps its watertight. The ability of steel to float is the ability of people to shape metal and solve problems by examining outcomes.

Review

What is the formula for density?What happens if you pour together liquids

that have different densities?Will the liquid on the top have the highest

or lowest density?Will the liquid on the bottom have the

highest or lowest density?

Super Scientist Questions of the DayJake has a book, a ruler, and a balance.

How can Jake find the density of the book with the tools he has?

75 ml of a liquid has a mass of 50 g. Find its density. Will this liquid sink or float in water? Explain.

 An object of mass 55.4 g is dropped in 40 ml

of water. The water level rises to 46 ml. What is the density of the object?