SNC 2DO LESSON PLANS

Ontario Curriculum objectives: U=understanding concepts (U1-U7) D=developing skills  (D1-D6) R=relating science (R1-R5)

Text: Science 10, Nelson

weather – environmental conditions that are encountered day to day
climate – set of environmental conditions and patterns over many years

weather dynamics – study of motion of water/air that causes weather patterns

eg. Bernoulli’s principle –if the speed of fluid is high then the pressure is low
                                        -if the speed of fluid is low then the pressure is high
   -movement generally occurs from high to low pressure

Demonstrations of Bernoulli's Principle
blow over paper – blowing creates low pressure over paper, which rises towards the low pressure area

blow into open bag – blown air enters the bag, making it low pressure. surrounding high pressure air enters bag.

blow between cans – low pressure area between cans, so cans move together

blow  ball in funnel – low pressure in funnel pulls ball towards funnel, not out

Weather Terms
Longitude – lines running from north to south pole – 0^o is Greenwich, England

Latitude – lines running parallel, from east to west

    Some important latitudes:

    Tropic of Cancer is 23.5^o N of equator
    -northern most point to have vertical rays of sunlight (on June 21)
    -southern equivalent is the Tropic of Capricorn (23.5^o S of equator)

    Arctic Circle is 66.5^o N of equator
    -southern most point to have a full day of darkness (on December 21)
    -southern equivalent is the Antarctic circle (66.5^o S of equator)
 
    Mid-latitudes are regions found between the circles and the tropics (most Canadians live mid latitude)

heat –kinetic energy of particles of matter (thermal energy)

-heat moves from through one substance, or from one substance to another, by direct contact
 (from hotter substance to cooler substance)
 eg. a spoon becomes hot when placed in hot coffee
-conduction does not occur if there is no temperature difference.
-substances that are good at conducting heat by conduction are called “conductors” (eg. metals)
-solids can conduct heat better than liquids or gases
-“insulators” are poor conductors of heat (eg. plastic, wood)

KMT (kinetic molecular theory) to explain heat transfer by conduction:
 -remember that molecules move faster when heated.
 -if brought in contact with cooler slower moving molecules, they hit them, transferring kinetic energy
 (heat will now increase in the cooler object as it's molecules speed up)
-solids will conduct quicker as the molecules are close together, and don’t have to move as far to influence the others
-“thermal conductivity” is a measure of how well a substance conducts (high in conductors, low in insulators)

-heat is transferred through a fluid from a region of high temperature to a region of low temperature by the movement of the fluid itself.
 (does not occur in solids since they do not flow)

KMT (kinetic molecular theory) to explain heat transfer by convection:
 -hot molecules in fluid move quickly, and spread out. As these molecules spread out, they become less dense.
  The fluid with less density rises in the denser fluid. This fluid rises and loses heat to the denser cool fluid.
  As the hot fluid cools, it becomes more dense and drops back down again.
  This is a “Convection Current”. (eg. water, air are able to flow in convection currents)

Albedo: amount of reflection an object gives off
 -black soil absorbs more light/reflects less light...low albedo
 -white snow absorbs less light/reflects more light...high albedo

Heat sink –absorbs and holds more energy than other matter

Heat capacity – how much heat is required to increase temperature

 -the higher the heat capacity, the better the heat sink
   metals are poor heat sinks as they lose energy quickly,
   water is good heat sink as heat spreads quickly by convection, absorbing much heat

Convection refers to vertical heat transfer in fluids
Advection is the same type of heat transfer if it occurs horizontally

-radiation is transfer of energy in waves, and does not require a medium (material to move through)
-heat transfer by radiation can therefore occur in space
-the electromagnetic spectrum consists of large waves (radio, micro, infrared), visible light (ROYGBIV),
 and small waves with much energy (UV,X rays, gamma rays)
-these waves are converted into heat as molecules absorb the energy and move faster

-the atmosphere is the thin blanket of air/moisture around earth
-atmosphere is most dense at sea level
-atmosphere consists of 78% N₂, 21% O₂, and other gases in small amounts (argon, CO₂, H₂O)
(other spheres... lithosphere –area covered by earth/rock
                          hydrosphere –area covered by water
                          biosphere –area covered by living things)

Atmosphere is wider at equator as high temperature results in warmer air expanding (this is narrowest and denser at the poles)

Levels within the atmosphere distinguished by altitude/elevation (height above sea level (km)

TROPOSPHERE (0-12 km over earth) contains most ,moisture responsible for weather systems
-temperature decreases from 20^oC to –50^oC with altitude
-highest (16 km) at equator, smallest (8 km) at poles for an average of 12 km

TROPOPAUSE –thin boundary over the Troposphere, with no temperature drop with altitude increase
-ozone increases with altitude, trapping UV light and increasing temperature

STRATOSPHERE (12 km –50 km over earth) dry layer with high ozone concentration
 -as height increases, ozone traps more UV, so temperature increases to 10^oC

MESOSPHERE (50 km-80 km over earth) contains low density gases, cooler (-75^oC)

THERMOSPHERE (80 km-500 km over earth) low density gases, but moving quickly so the temperature is high (30^o)
-X-rays trapped here, and so heat increases
-ions are made by the sunlight and produce Northern, Southern lights

EXOSPHERE (500 km-up) thin outer layer
-space
-few particles spread out, mostly hydrogen

Temperature gradient –change in temperature (can be gradual or sudden)
 -in the troposphere  the temperature drops 6^oC per 1000 m
 -there is a less consistent gradient at higher levels

Prevailing winds are characteristic winds that affect large areas
These winds are generally named after the direction from which they originate

-coriolis effect is an apparent change in direction of a moving object due to a rotating system
 eg. the earth, as viewed from the north pole, is moving counterclockwise
-a wind moving from one side of the earth towards the north pole will therefore appear to bend to the right
 because of the counterclockwise rotation of the earth
-this results in northerly winds moving EAST (to the right) and southerly winds moving WEST (to the left)
-viewed from the southern hemisphere, the effect is reversed as the earth appears to move in a clockwise direction.

Do worksheet on prevailing winds.

PREVAILING WINDS IN THE NORTHERN HEMISPHERE

Northeast Trade Winds (blow south and west from 30^o to equator)
 -hot air in equator rises (less dense) pulling cooler, denser air from 30^o N
 -a convection current is created this way, resulting in a Southern wind
 -Coriolis effect produces the easterly direction

Mid Latitude Westerlies (blow north and east from 30^o to 60^o)
 -some air descending at 30^o from convection currents creating Northwest
  trade winds moves north towards low pressure region at 60^o
 -at 60^o, warm southern winds meet cooler polar winds and rise as they are
  less dense. This results low pressure (less air).
 -a convection current results with a Northern wind, moving west because of Coriolis effect

Polar Easterlies (blow south and west from pole to 60^o)
 -pole has very dense atmosphere, and air moves south to lower pressure
 -at 60^o this air is less dense, and encounters warm southern air. Some rises.
 -a convection current results with a Southern wind, moving east because of Coriolis effect

Jet Stream (blow east at 30^o and 60^o)
 -air in middle of convection currents (in middle of troposphere) has air above it creating pressure.
 -when cold northern air meets warm southern air, the warmer air has higher pressure
 -this pressure difference between the fronts is greater at higher altitudes
 -high pressure warm air moves north towards the cooler low pressure air where these fronts meet

-this northern wind moves easterly at these gaps because of Coriolis effect and creates the "jet stream"

Do lab on Sunlight and Seasons

-additional causes of ocean currents:

Heat Capacity:
-warm air holds more water, and cool air stores less.
-the oceans act like “heat sinks”, and take a long time to heat up and a long time to cool down.

Salt in Oceans:
-as water evaporates, the concentration of salt in water near the surface increases
-the dense surface water drops down to be replaced by less salty water from lower in the ocean.

-heat capacity results in June 21 being followed by the hottest days, as the water (and warm air) take some time to heat up.
-the coolest days follow Dec. 21 as water and air take some time to cool down.

-warm wet air in warm currents that hit Brazil on the east coast result in rain.

-cool dry air in cool currents that hit Peru result in desert conditions on coast.

-warm gulf stream air warms Sweden but not northern Canada (does not move that way),
-this results in frozen Canadian harbors freeze, while those in Sweden do not freeze.

Current around Antarctica goes all the way around the world unstopped.

Hydrosphere is the 70% of earth covered in water
  -of that, 97.5% is salt water
  -of the 2.5% is fresh water, 87.3% is frozen, 12.3% is underground and 0.4% is on the surface
  -of the 0.4%, 90% is in lakes, 9% is in the atmosphere and 1% is in rivers

 -review water cycle from ecology unit

 -clouds form when warm air, carrying vaporized water, rises as it is less dense.
 -this rising results in cooling of the water and it recondenses form droplets
 -when 1000’s of droplets join a raindrop is formed and gravity pulls it down

Clouds form as:
Convective clouds: warm moist air absorbs energy from heated surfaces
   -this less dense air rises and cools as the particles lose energy and the pressure decreases
    (low pressure = low temp.)
   -as the rising air cools the water recondenses and forms clouds

Frontal clouds: a warm front hits a cold front, and warm air rises over the top
   -as the warm air rises cooling occurs with energy loss and less pressure
   -as the rising air cools the water recondenses and forms clouds

Orographic clouds: warm moist air hits a mountain, and moves up
   -as the warm air rises cooling occurs with energy loss and less pressure
   -as the rising air cools the water recondenses and forms clouds

 Fog (low lying clouds): on clear nights heat is lost from the earth and the ground level cools
   -air on ground level cools and water recondenses to form clouds/fog
   -on shorelines warm ocean air collides with the cool land
   -as ocean air cools the water recondenses and forms clouds/fog

 Cumulus clouds: billowing rounded clouds
   -grow vertically
   -indicate unstable weather (warm air hitting cool air)
 Stratus clouds: flattened layered clouds
   -grow horizontally
   -indicate stable weather (warm air going over cool air)
 
prefixes and suffixes:   -alto: mid level clouds (prefix)
                                     -cirrus: high level clouds (prefix)
                                     -nimbus: rain holding clouds (suffix)

-weather Systems are a set of temperature, wind, pressure and moisture that moves as a unit over a period of days
-these move with prevailing winds (west to east in our area)

-from the North:
Northwest -cold polar air comes from North Pacific, bringing wet stormy weather as it rises
                  to form orographic clouds on Rockies
North        -cold dry air comes from poles with little evaporation
Northeast  -cool wet air masses from Atlantic

-from the South:
Southeast -warm, wet air from the Gulf of Mexico
South        -warm, dry air from deserts, with little evaporation
Southwest -warm, wet air masses

Trends: Cold from North
             Warm from South
             Dry in center
             Wet at coasts

These masses collide at mid-latitudes, producing a low pressure region

Low Pressure Regions are usually stormy, cloudy skies
-a cold front (air mass shown with blue line and triangles) hits a warm front (air mass shown with red line and circles)
-a stationary front results, as the two fronts stop movement

Do practice sheet

Answer video questions on weather systems

Thermal –solar energy (radiation) heats land
  -this heat warms the air near the ground which moves up (expands, less dense)
  -this thermal updraft increases as the sun rises, drops in afternoon as the sun falls
  -in extreme cases, thunderstorm forms because of a thermal

Sea Breezes –thermals occur on land near the water at START of day (land heats quicker than water)
 -convection current results as thermal rises over land, pulling cool air from over the water
 -warm air moves over the water and cools, dropping down

Land Breezes –large body of water cools slower than land at END of day
 -convection current results as thermal rises over water, pulling cool air form the over land
 -warm air moves over land and cools, dropping down

Lake Effect Snow –forms in winter on east end of lake
 -water is warmer than land in winter (acts as a heat sink)
 -moist warm air rises over water, reaches cool shore and recondenses as snow
  (on east side because of  of the lake because of prevailing winds)

Cumulonimbus Clouds result in the formation of:
water droplets                               or             ice crystals
water droplets fall as DRIZZLE      or             ice joins to form DRY SNOW
join to form RAIN                          or             hits warm air and forms WET SNOW
at 0^o is FREEZING RAIN                 or             hits warm, then cold air to form SLEET
                                                     or             hits warmer air to form RAIN

Dew –ground is cool as heat is lost at night.
         This results in ground level condensation of water vapour in the air called dew

Frost –sublimation of water vapour at ground level when temperature is freezing
Hail – cumulonimbus clouds have ice crystals moving up and down in updrafts, resulting in up to 20 layers of ice

Do work on precipitation

Absolute Humidity
-water vapour in the atmosphere (highest when cloud formation occurs)
-this is potentially higher in warmer weather

Relative Humidity
-amount of water in air as a percentage of the maximum level (cloud formation)

eg. what is the concentration of water in the air if it is 20^o C
     (maximum = 15 g water/kg air) and there is 50% humidity?
      Answer = 7.5 g water/kg air  (half the maximum)

Saturated air results in cloud/fog formation
Less water evaporates when it is more humid (water is already in air), and so
it becomes harder to cool down in humid weather (less sweat evaporates)

Relative humidity is measured with a psychrometer. This consists of a wet
and a dry thermometer. As water evaporates from the wet thermometer, the
thermometer cools relative to the dry thermometer. The more evaporation,
the more it cools, and the less humid it is. The difference in temperatures
is used on the chart on page 560 to find the relative humidity.

demonstrate use of psychrometer

Do work on humidity

Distribute other teachers copy of tests on biology and chemistry

In class exam: 10% of mark