Density

1
Density

• Intro to the Ocean and Atmosphere

2
Objectives

• To how to calculate density
• To predict how high density molecules will move
• To predict how low density molecules will move
• What factors can change density?

3
Take a guessWhich is more dense?

• Wood or water
• Ice or steam
• Cold water or hot water
• Metal or clay
• Hot air or cold air
• Freshwater or salt water
• Pepsi or Coke Zero

4
Density Vocabulary

• Density compares the mass of an object to the
  amount of space it takes up
• Mass how heavy the molecules are in an object
• Volume the amount of space an object takes up
• Density Current vertical (up/down) current
  caused by density
• Salinity the amount of salt in a solution
• Evaporation liquid turning into a gas
• Composition what something is made of, the
  number of molecules inside

5
What is density?

• Density compares the mass of an object to the
  amount of space it takes up
• Mass how heavy the molecules
• Density of pure water is usually 1.0 g/cm3

Less dense less molecules in a specific space,
tends to rise
More dense more molecules in a specific space,
tends to sink
6
Do Gases, Solids, and Liquids have the same
density?
7
Why does hot air rise?

• As molecules heat up, they move faster and spread
  out
• If the molecules spread out, what happens to
  density?
• Less density, because the same molecules take up
  more space
• Consequence hot air will rise (like in a hot air
  balloons)

8
Why does cold water sink?

• Cold water molecules move more slowly and get
  closer together
• Same mass taking up less volume more dense
• Cold water sinks to the bottoms

9
How does composition affect density?

• Pure water, with no other molecules in it, is
  rare. Drinking water and the water in the ocean
  have many different types of molecules dissolved
  in it.
• What is dissolved in the ocean water?
• Salts like NaCl, gases like carbon dioxide (CO2)
  and oxygen (O2), and other things
• Which is more dense, pure water or ocean water?

Ocean water is more dense. It has more things
dissolved in it. It has a larger mass to take up
the same space. The more stuff that is dissolved
in the ocean, the more dense it is.
10
How do you calculate density?

• Ex1 If a cube has a mass of 25g but still has
  only a 5cm3 volume, what is its density?

• Ex2 If a cube has a mass of 50 grams and a
  volume of 5 cm3, what is its density?

Ex3 Which is more dense, the cube from ex1, or
the cube from ex2?
11
Why should I care about density?

• Hot water rising and cold water sinking will
  explain
• GLOBAL OCEAN CURRENTS
• Hot air rising and cold air sinking will explain
• GLOBAL WIND PATTERNS
• The interaction of rising and cooling air and
  water will explain
• GLOBAL CLIMACTIC CHANGES

12
On your climate map, label the oceans.
13
SoWhich is more dense?

• Wood or water
• Ice or steam
• Cold water or hot water
• Metal or clay
• Hot air or cold air
• Freshwater or salt water
• Pepsi or Coke Zero