Weather Unit

1
Weather Unit

• Investigation I Locating Matter

Lesson 1 Weather or Not
Lesson 2 Raindrops Keep Falling . . .
Lesson 3 Having a Melt Down
Lesson 4 Its Sublime
Lesson 5 Water World
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Weather Unit Investigation I

• Lesson 1
• Weather or Not

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ChemCatalyst

• Below are a picture and weather report of a
  hurricane off the coast of Florida in the United
  States.

(cont.)
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• (cont.)
• FORECAST FOR THE MIAMI AREA The tenth depression
  of the season in the Atlantic has become
  Hurricane Jan. The center of Jan is southeast of
  Florida. The maximum sustained winds are near 120
  miles per hour. The estimated minimum central
  pressure is 28.5 inches. Skies over Miami are
  mostly cloudy. The temperature is 35?C / 95?F
  with 90 humidity.

(cont.)
5

• (cont.)
• Jan is expected to drop as much as 10 inches of
  rain in the southern part of Florida with rising
  temperature and humidity.
• What are hurricanes and what do you think causes
  them?
• What is weather? What causes weather?
• How do meteorologists predict things like
  hurricanes?

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The Big Question

• What causes water to cycle or move around on
  the planet?

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You will be able to

• Explain what causes rain on the planet Earth.

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Activity

• Purpose In this activity you will heat and cool
  water in a flask with a balloon attached. Your
  observations will help you determine what makes
  the water cycle.

(cont.)
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(cont.)

• Materials (for each team of two students)
• 250 mL Erlenmeyer flask
• 25 mL graduated cylinder
• Medium sized party balloon
• 5 mL of water
• Hot plate
• Oven mitt
• Bucket or large beaker with ice and water

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Making Sense

• Based on this experiment, explain what causes
  water to cycle around the planet?

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• Notes
• Evaporation is the changing of a substance from
  the liquid phase to the gas phase. Condensation
  is the changing of a substance from the gas phase
  to the liquid phase.
• Gas, liquid, and solid are three different phases
  of matter. A phase change refers to the
  conversion of a liquid to a gas or a solid, or
  vice versa.
• A physical change is one in which the form or
  temperature of a substance is changed without
  changing its chemical make-up.

(cont.)
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Notes (cont.)

• Humidity is a measure of the amount of water
  vapor (or gaseous water) in the air.

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Check-In

• Answer the following question
• Using what you learned today about the movement
  of water, explain what causes rain on the planet
  Earth.

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Wrap-Up

• Weather is an interaction between the sun (a heat
  source), the water on the planet, the Earths
  surface, and the Earths atmosphere.
• Water moves around through phase changes.
• Phase changes affect the volume of substances.

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Weather Unit Investigation I

• Lesson 2
• Raindrops Keep
• Falling . . .

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ChemCatalyst

• Annual rainfall in the United States

(cont.)
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• (cont.)
• How much rain fell where you live?
• How is rainfall measured?
• What type of instrument or container is used to
  measure rainfall?

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The Big Question

• How do meteorologists keep track of rainfall?

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You will be able to

• Relate volume of water to rainfall amount.

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Activity

• Purpose This lesson introduces you to precision
  in measurement and allows you to explore
  measuring rainfall in inches and milliliters.

(cont.)
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(cont.)

• Materials (per team of 2 students)
• 25 mL graduated cylinder
• 100 mL beaker
• 12 inch ruler
• Water bottles (use plastic pipettes or droppers
  if you do not have water bottles)

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Making Sense

• Meteorologists can keep track of the amount of
  rainfall by measuring either the volume or the
  height of rainfall in a rain gauge.
• If the amount of rainfall increases, do both the
  volume and height of water in the rain gauge keep
  track of this increase? Explain your thinking.

(cont.)
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• (cont.)
• What does the precision of measuring height and
  volume depend on? Is there a difference in the
  precision of measuring height or volume? Explain
  your thinking.

(cont.)
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(cont.)
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Notes

• Significant figures are the numbers one can read
  off of an instrument or piece of equipment, plus
  one more estimated number. The glassware or
  instrument being used in a measurement determines
  how many significant figures can be recorded.

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Significant Figures
Notes (cont.)
(cont.)
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Measuring Rainfall Data
Notes (cont.)
(cont.)
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• Notes (cont.)
• Two quantities are proportional if a graph of the
  two variables results in a straight line that
  passes through the origin (0, 0).

(cont.)
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Notes (cont.)
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Check-In

• Answer the following question
• Suppose you find that 1.0 inch of rainfall in a
  graduated cylinder has a volume of 4.0 mL. What
  volume would you measure for 2.0 inches of
  rainfall?
• A) 4 mL B) 4.0 mL C) 4.00 mL D) 8 mL
  E) 8.0 mL F) 8.00 mL
• Explain your thinking.

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Wrap-Up

• Precision differences in measurements are a
  result of the glassware or instrument that is
  used.
• Significant figures are defined as all of the
  numbers that can be read directly from an
  instrument, plus one estimated number.

(cont.)
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• (cont.)
• The volume of water in a cylindrical container is
  directly proportional to the height of the water.
  
• Graphs of two variables that are proportional
  always lead to a straight line through the origin.

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Weather Unit Investigation I

• Lesson 3
• Having a Melt Down

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ChemCatalyst

• Meteorologists measure the snowpack in the
  mountains to predict the amount of water that
  will fill the lakes and reservoirs. Do you think
  that 3 milliliters of snow is the same as 3
  milliliters of rain? Explain your reasoning.

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The Big Question

• How can you convert from volume of snowfall to
  volume of liquid water?

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You will be able to

• Understand the relationship between density, mass
  and volume.

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Notes

• The density of a substance is the slope of the
  line for a graph of mass vs. volume.
• Density Mass/Volume

(cont.)
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Notes (cont.)

• The slope of a line is the change in y divided by
  the change in x.
• For a line that goes through the origin (0, 0),
  the slope is simply any value of y divided by the
  corresponding value of x.

(cont.)
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Slope Density
Notes (cont.)
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Activity

• Purpose This activity allows you to relate
  volume of snowfall with volume of rainfall by
  using the density of snowfall and rainfall.

(cont.)
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(cont.)

• Materials (for each team of four students)
• 25 mL graduated cylinder
• Scale
• Water bottle (small dropper or plastic pipette if
  water bottles are not available)

(cont.)
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(cont.)
Mass of the graduated cylinder empty ______
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Making Sense

• Explain how you can relate volume of snow to
  volume of rain.

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(cont.)
(cont.)
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(cont.)

• m1 / V1 slope m2 / V2

(cont.)
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(cont.)

• Example Problem I
• Imagine you have a box that is 5.0 mL in volume.
  What mass of ice will just fit this box?

(cont.)
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(cont.)

• Example Problem II
• You have 20 grams of snow with a density of 0.50
  g/mL. What volume does this snow occupy (how many
  milliliters)?

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(cont.)

• Example Problem III
• If you have 100 mL of snow, what volume of water
  do you have? (You must first find out what mass
  of snow you have and then convert that to volume
  of water.)

(cont.)
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(cont.)
50
(cont.)
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Check-In

• You have equal masses of snow and rain. Which has
  a greater volume? Explain your thinking.
• What is the mass of 14 mL of rainwater?

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Wrap-Up

• Density is a measure of the mass of a substance
  per unit of volume.
• If the ratio between two quantities is constant
  then a graph of these two quantities will be a
  line that passes through the origin.

(cont.)
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(cont.)

• Water can have different densities depending on
  whether it is snow, ice or liquid (rain).
• When a substance changes phase (from solid to
  liquid to gas) it changes density.

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Weather Unit Investigation I

• Lesson 4
• Its Sublime

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ChemCatalyst

• Describe the differences between the two.
• Why do you think one is called dry ice?

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The Big Question

• How different are the densities of a solid and a
  gas of the same substance?

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You will be able to

• Understand the change in density as a substance
  goes from a solid to a gas.

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Activity

• Materials
• 5-20 grams of dry ice per team of students
• Styrofoam cooler or ice chest
• Scale
• Medium plastic garbage bagsfive-gallon size
• Twist tie

(cont.)
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(cont.)

• 2 Oven mitts
• Five gallon bucket or other cylindrical
  receptacle (Note 5 gallons 19 liters)

(cont.)
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(cont.)
Copy this table into your notebook.
Note This table is different than the one in
your book.
(cont.)
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• Safety Note Use gloves dry ice can cause
  frostbite.

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Making Sense

• If you sublime 1 mL of CO2 (s), what volume will
  the gas occupy?
• How many times larger than the volume of the
  solid carbon dioxide is the volume of the carbon
  dioxide gas?

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(cont.)
(cont.)
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(cont.)
Solid CO2 Gas Model A Gas Model B Gas
Model C
Which model is correct?
(cont.)
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(cont.)

• How do we find the volume of the solid?
• D m/V or V m/D
• We know m g (from our data table)
• D 1.56 g/mL (from graph)
• So do the math . . .

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Sample Data
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Wrap-Up

• Sublimation occurs when a substance goes directly
  from a solid phase to a gas phase (or vice
  versa).
• The density of a gas is about 1/1000 the density
  of the same solid.

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Weather Unit Investigation I

• Lesson 5
• Water World

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ChemCatalyst

• Suppose a quantity of rainwater occupies a volume
  of 1 mL.
• What volume do you think the rainwater occupies
  as water vapor? Explain your thinking.
• When water changes phase what other changes take
  place? Name at least three changes.

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The Big Question

• How are volume, density, and phase of water
  related to weather?

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You will be able to

• Explain the increase in volume as 1 mL of water
  goes from a liquid to a gas.

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Activity
Purpose The purpose of this lesson is to explore
how phase changes are related to volume changes,
density changes, and the water cycle in general.
Part I Comparing densities Densities of various
substances have been labeled in the Density
Landscape handout.
(cont.)
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(cont.)
(cont.)
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(cont.)
Part II Average rainfall A map of average
rainfall in the United States (in inches/yr) is
shown below.
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Making Sense

• How are volume, density, and phase of water
  related to the weather?

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Phase Change
Notes

• Drives the water cycle and weather
• Results in changes in volume and density

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Check-In

• As water moves around the water cycle, its volume
  changes.
• If rainwater occupies a volume of 1 mL, what
  volume will it occupy when it forms water vapor?
• What is the main reason for the increase in
  volume during this phase change?

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Wrap-Up

• The density of a substance in the solid phase is
  nearly the same as its density in the liquid
  phase.
• The density of a substance in the gaseous phase
  will be much lower than its densities in the
  liquid and solid phases. Gases are about 1000
  times less dense than liquids and solids.

(cont.)
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(cont.)

• The density of a substance has a great deal to do
  with where that substance can be found on the
  planet in relationship to other substances.