Density is a property of a substance, unless

1
Density is a property of a substance, unless

• If you have a giant boulder with a density of 5
  g/cm3, and you break off a chip, it will have a
  density of 5g/cm3.
• We say density is a property of a substance. In
  this example, the volume would change, but the
  mass would change proportionally, causing the
  density to remain the same.

• BUT, if you change the temperature or pressure on
  the substance, density changes.
• As temperature , volume , density
• So the hot air balloon floats!
• As pressure , volume , density

2
DENSITY OF WATER

• Water has a density of 1 g/ml it is the
  standard.
• However, water has an unusual property.
• Most materials are densest in the solid phase.

• Water is densest at 3.980C
• Since water freezes at 00C, it is liquid at
  3.980C!
• Water is at its densest when it is in the
  liquid state

• Thus, ice (solid water) floats. The most dense
  water sinks to the bottom, providing a safe
  environment for aquatic life

3
Changes Slow Vs. Sudden

• Changes can occur suddenly, or slowly.
• The factor that changes is known as the VARIABLE
• More than one variable can cause a change to
  occur in nature!
• Slow changes happen over thousands of years, even
  millions of years
• Examples Glaciation, erosion, plate tectonics,
  pollution, evolution.
• Sudden changes happen in seconds, or minutes.
• Examples Mud slides, meteors, earth quakes,
  tornadoes.

4
Changes and Graphs

• Changes are often best observed by graphing them.
• The rate of change, how quickly it occurs can be
  determined from the graph.
• Rate of Change
• Rate of Change Change in value/time
• Miles per hour is a good example of rate of
  change.

5
Graphs, what they tell us

• Graphs can tell us whether two variables are
  directly, indirectly related, if they cause a
  repeating pattern, or do not effect each other at
  all.
• Memorize the Chart On the next slide!

6
Types of Graphs
7
CYCLIC CHANGE

• Cyclic change repeats a pattern at definite time
  intervals.
• Notice that the height of the peaks is not
  consistent, just the timing of them.
• Cyclic changes are important because they are
  predictable.

8
Cyclic Change

• Some changes that occur on Earth are cyclic-they
  occur over and over again at regular intervals.
• List two changes that occur on a regular basis
  and can be considered cyclic, and two changes
  that are not cyclic.
• Some examples of cyclic change include
• The tides, phases of the moon, Earth's rotation
  on its axis, Earths revolution around the sun,
  El Nino, and Sun spot cycles.
• Some examples of NON-cyclic change include
• Changes in population, changes in climate due to
  man made influences.

9
Energy and Change

• A body that gives off energy is called an ENERGY
  SOURCE.
• A body that absorbs energy is called an ENERGY
  SINK.
• The boundary between sink and source is called an
  interface.
• Interfaces are surfaces forming a common boundary
  between adjacent regions, bodies, substances, or
  phases where energy is transferred.

10
Energy Flow

• Energy is not stagnate, it moves and flows
  between bodies and systems at the interface
  between them.
• Energy usually flows from areas of high energy
  towards areas of low energy.
• A good example of this is when you open the door
  on a cold winters day, the heat flows out the
  door towards the cold, sometimes you can see the
  wave of heat.

11
Dynamic Equilibrium

• Equilibrium is a balance between forces, and
  dynamic equilibrium is a balance between changes.
  
• For example, the water flowing into the sink
  would equal the water flowing out of the sink
  there is change, but it is balanced.
• When the natural balance (equilibrium) of the
  environment is disrupted the system has been
  polluted. Pollution can be natural, or man-made.
• Man Made CO2 emissions
• Natural Volcanic Eruptions