SWBAT explain buoyancy and calculate density to

determine buoyancy.

Catalyst1) A whole snickers bar has a mass of 2.14 g and

a volume of 2 cm3. What is its density? Show ALL of your work.

2) If you break it in half, what will its density be? How do you know?

Catalyst

3) If you break it in half again (so that you now have ¼ of the original snickers bar), what will its density be? Why?

Catalyst

BUOYANCY –

Upward force that keeps

things afloat

GRAVITY

BUOYANCY

Objects that FLOAT are LESS dense than the liquid they are

placed into. They are BUOYANT

Objects that SINK are MORE dense than the liquid they are

placed into. They are NOT BUOYANT.

What is the density of water?

Which is buoyant in water, Coke or Diet Coke? Why?

Comparison of: Regular Coke Diet Coke V = 355 cm3 V = 355 cm3

Water = 355 g Water = 355 g Sugar = 39 g Sugar = 0 g

Nutra Sweet = 0 g Nutra Sweet = 0.1 g Total Mass = 394 g Total Mass = 355.1 g

Which is buoyant in water, Coke or Diet Coke? Why?

D Density of Coke Density of Diet Coke

It will ____________________ in water. It will ____________________ in water.

It is not _____________________. It is _____________________.

Which is buoyant in water, Coke or Diet Coke? Why?

D Density of Coke Density of Diet Coke

It will ____________________ in water. It will ____________________ in water.

It is not _____________________. It is _____________________.

Step 1: Write your formulaD = M V

Which is buoyant in water, Coke or Diet Coke? Why?

D Density of Coke Density of Diet Coke

It will ____________________ in water. It will ____________________ in water.

It is not _____________________. It is _____________________.

Step 2: Plug your givens into the formula

D = M V

D = 394 g 355 cm3

Which is buoyant in water, Coke or Diet Coke? Why?

D Density of Coke Density of Diet Coke

It will ____________________ in water. It will ____________________ in water.

It is not _____________________. It is _____________________.

Step 3: Solve

D = M V

D = 394 g 355 cm3

D = 1. 1098859155 g/cm3

Which is buoyant in water, Coke or Diet Coke? Why?

D Density of Coke Density of Diet Coke

It will ____________________ in water. It will ____________________ in water.

It is not _____________________. It is _____________________.

Step 4: Round to the nearest tenth’s place.

D = M V

D = 394 g 355 cm3

D = 1. 1098859155 g/cm3

D = 1.1 g/cm3

Which is buoyant in water, Coke or Diet Coke? Why?

D Density of Coke Density of Diet Coke

It will ____________________ in water. It will ____________________ in water.

It is not _____________________. It is _____________________.

Step 5: Will it sink of float? Is it buoyant?

D = M V

D = 394 g 355 cm3

D = 1. 1098859155 g/cm3

D = 1.1 g/cm3

SINK

BUOYANT

In the box below, fill in the density, then write whether the object will sink or float, and finally whether or not it is buoyant.

Silent, independent work. You may use a calculator.

Remember…

Density of water = 1 g/cm3

Density of object < 1 g/cm3 Float

Density of object > 1 g/cm3 Sink

In this assignment I explained step by step how to calculate density and determine if something is buoyant. I performed a demonstration for my students where I put a can of diet coke and a can of regular coke into a bin of water and the students saw that the regular coke sank to the bottom and the diet coke floated at the top. Students figured out why this occurred and we had a discussion about how the extra sugar in the regular coke increased the mass, which increased the density, which caused it to sink.