A variety of people have studied weather over the years and added to our knowledge about the causes and effects of weather.
- Benjamin Franklin
- Thomas Jefferson
- Sir Francis Beaufort (1774-1857) British Admiral.
Carried a barometer up mount to see what altitude would do to pressure.
- Christoph Buys Ballot (1800) a Dutch Meteorologist who created the Buys Ballot's law
For students to conceptualize concepts related to weather, the water cycle, and how weather changes, it's necessary for them to have some background knowledge in temperature, thermometers, heat energy and air pressure. For example. Knowing air has mass and the mass of the Earths atmosphere exerts pressure (air pressure barometric pressure) or pushes on us and all objects from every direction. That pressure changes with altitude (1kg / cm2 or 15 pounds / square inch at sea level) and temperature.
Therefore, prior activities such as:
are necessary if students are to understand what causes weather and how it changes.
That doesn't mean younger students can't benefit with weather related experiences. They can when they make and record their weather observations and match them to drawings and photos of weather related pictures in books or other media.
Intermediate students are able to create weather instruments (engineering activities related to technology and science) to collect meteorological data and use it to look for weather patterns. Students may also research weather data on the internet and use the data to look for weather patterns.
Barometer or Thermometer?
- Volume of air and water change with temperature.
- Atmospheric pressure is created by the mass of the atmosphere.
- Temperature equipment can be constructed and calibrated to record temperature.
Coffee stirrer or very narrow straw, wide mouth jar, 14 inch balloon, heavy rubber bands, white glue, ruler.
Cut a piece of balloon large enough to stretch over the mouth of the jar and hold it in place securely with the rubber bands. Glue the stir to the center of the balloon.
- Is this instrument more sensitive to pressure or temperature?
- How might you calibrate it?
Straw, ruler, silicon or glue, food coloring, small glass soda bottle, screw cap with a hole the size of the straw, or modeling clay.
Put a straw through a hole in the cap, fill the bottle half way with water and food coloring, seal (silicon or glue) the straw in the cap so it will be in the water but not on the bottom and it will stay in place. (Or seal it in the same way only with modeling clay)
- Is this instrument more sensitive to pressure or temperature?
- How might you calibrate it?
Find the Dew point
- Dew point is the temperature F that water in the air will condense.
Metal can, water, ice, thermometer.
Fill a metal can about a third full of water at room temperature. Add one ice cube at a time and stir with a thermometer until the ice cube melts or there is condensation on the side of the can. When there is condensation on the side of the can the temperature of the water is the dew point.
To measure the dew point when the temperature is below freezing, use salt and record the temperature when there is frost on the can. If salt is used, handle the can with winter gloves as it may cause frost bite. Water vapor will condense directly into frost.
Measure Relative Humidity
- Air has the capacity to support water (moisture) and the amount of moisture varies by temperature.
- Humidity is the water vapor in the air.
- Absolute humidity is the actual amount of water in the air.
- Relative humidity is the ratio between the actual amount of water vapor (absolute humidity) at a certain temperature and the maximum amount of water vapor the air can hold at that temperature.
- Percent of relative humidity equals 100 times the amount of water vapor actually in the air divided by the maximum amount of water vapor the air at that temperature can hold.
Thermometers, shoe string or cheese cloth, small container for water reservoir. Relative humidity chart
Use one thermometer as usual. Arrange the second thermometer so one end of the shoestring, or other materials, covers the bulb of the thermometer and submerge the other end in a water reservoir so the bulb will stay continually wet. Use the device to find a wet and dry bulb temperature for the air you want to know the relative humidity. Use the chart to find the humidity.
Wind Vane and Anemometer
- Wind has speed and direction
- Wind direction is measured by a wind vane
- Wind speed is measured by an anemometer
- Beaufort Scale is a measurement system of wind speeds, in numbers from 0-17.
straws, pins, stapler, poster board
Two liter plastic bottles with tops cut off & ruler
Cut the top off the bottle, put about an inch of san or water into the bottom of the bottle to level the bottom of the container and add ballast so the bottle won't blow away. Invert the top and place in on the bottom, attach a ruler, calibrate, and set it out side away from obstructions.
Activity Water cycle.
Plastic soda bottle, sand or gravel (optional will retain heat longer), hot water, food coloring, aluminum foil or aluminum container, ice.
Take the plastic soda bottle and cut off the top. Mold the foil or aluminum container so that it fits around the top of the bottle and has a bowl shape on top of the bottle to hold four or more ice cubes. Place the sand or gravel into the bottle and pour enough very hot water into the bottle to cover the sand and gravel and have about 2 cm of water above the sand and gravel. Drop two drops of food coloring into the water. Put the aluminum bowl cap onto the soda bottle. Check the aluminum foil for leaks. Place the ice into the aluminum container. Watch the entire system and see what happens.
Activity Solar Energy and Weather
- The Sun transfers heat to the Earth.
- Seasons are caused by the tilt of the Earths axis (23.5 degrees)
- A variety of variables (water, land forms, vegetation, color, soil,) effect the suns transfer of energy (radiation creates different amounts of heat depending on the matter that absorbs it).
- Differences in the amount of heat energy and differences in the rate of transfer from different materials create convection currents.
- Convection currents create weather changes.
Graph or sketch the relative position of the sun rise or sunset for a period of time. How does the sun's position in the sky affect heat energy on Earth?
- Graph the solar energy for a period of time (local forecast or online).
- Graph the temperature for a period of time.
- Compare the solar energy graph to the temperature graph.
- What patterns do you notice?
Materials: Thermometer, plastic storage bags, three different colored sheets of paper
Fill each plastic bags with the same amount of water, place outside in sun with different colored sheets under each, record the temperature after ... hours
Place thermometers outside on different soils or kinds of vegetation and record the temperatures.
Place thermometers outside at different heights (6 inches below ground, surface, above surface) and record the temperatures. What variables affected the temperature?
Procedure Record the temperature at the bottom of a hill, at intervals up the hill, at the top, down the other side, and at the bottom of the other side.
Materials: Thermometer, plastic bags, and student made solar house.
- Put 1 liter of water, and a thermometer into a plastic bag.
- Seal the plastic bag and place it into the solar house.
- Place the solar house outside in the sun for 4-5 hours.
- Read the thermometers, compare, and discus.
Activity Relation of energy costs to temperature
There is a relationship to temperature and heating and cooling costs.
Source of monthly temperature averages, energy bills.
Graph the temperature averages for a series of months and the cost of energy to heat and cool a building.
Activity Climate is?
Temperature and precipitation are variables that effect climate.
Source of temperature averages and precipitation.
Make a climograph (a graph with monthly temperature and precipitation).
Activity How do temperatures change?
Temperature ranges vary consistently with the normal temperature.
Source for daily normal, high, and low temperatures.
Make a temperature scroll. Graph the normal temperature, observed highs, observed lows, and shade the area above and below different colors.
Activity Thermometers and the weather
- Position of a thermometer effects the temperature it records.
- Fact - Meteorologists from around the world have agreed to record temperatures from inside a white louvered building at a height of 4-5 feet (1.2-1.5 m) above the ground in a grassy area.
Collect information for the following question:
- Where is the thermometer on the bank or other places?
- How much of a diference does it make if thermometers are located at different places?
- Does it really make a difference?
Activity Land formations and weather
- A variety of variables (land formations, water masses, man made objects, plants, Earths rotation, pressure) affect wind.
- Friction from (land formations, water masses, person made objects, plants)
Safety concerns - Matches, candle, objects.
- Make sure students are aware of safety procedures necessary with candles.
- Try to blow out the candle with different objects between them.
- Diagram how the wind moves around the objects.
Activity Wind and land formations
Wind affects land formations on Earth.
Activity Wind and weather
- Earth's rotation (Corollas Force)
- High pressure air spirals out (Pressure, Corollas, and friction)
- Low pressure air spirals toward the center.
- Buys Ballot's law (Christoph Buys Ballot) With your back to the wind, turn 30 degrees to your right and the high pressure is to your right and the low pressure is to your left. (120 degrees from where originally facing).
Activity Weather fronts / cold and warm air
- Differences in temperature create winds.
- Isotherms are lines created by connecting places with equal temperatures.
- If you stand on an isotherm with the cold temperature to your left and warm temperatures to your right, the upper level winds would be blowing from your back to your front.
- Generally the closer the isotherm lines the greater the winds. Where the isotherms are the closest is generally where the jet stream is found.
- The jet streams usually carry the ground-level weather systems along with them.
Clear container (about 5 liters), hot water, cold water or ice, pepper, plastic bag.
Put the ice or cold water into the plastic bag and seal it. Fill the container with hot water, stir in some pepper until you have a fair distribution of pepper. Place the bag into it and observe the convection current.
Materials: Clear container (about 5 liters), hot water, and 100 ml of cold milk.
Put the hot water into the clear container. Slowly pour the milk down a narrow side of container. You should see a convection current know as a downburst.
Clouds shape and height of clouds determine the type of precipitation.
Camera, drawing materials to record clouds (white chalk & blue paper), media with pictures of cloud types identified
Take pictures or draw pictures of clouds and research the type. How high they are, what kind of moisture they contain, what kind of weather usually accompanies them.
Activity Clouds, how fast are they?
- Locate some cirrus clouds
- Select a starting point and stopping point so the cloud you are timing will travel half way across the sky.
- The distance from a person to the horizon varies depending on how far off the ground their eyes are and if there are mountains on the horizon. However, on the ocean a 6 foot tall person can see 3 miles. The equation to calculate this is: SquareRoot(height above surface / 0.5736) = distance to horizon
- Assume your eyes are 5.5 feet above the ground, then
- SquareRoot(5.5 / 0.5736) = 3 miles.
- The speed = 3 miles / time in hours
- Can you figure how fast clouds travel?
Water cycle, precipitation, and weather
- Change in pressure causes changes in weather.
- High pressure: winds clockwise, good weather,
- Low pressure: winds counterclockwise, means bad weather
- Water particles attract (adhesion) to other water particles.
- Air can support water vapor.
- The most water vapor air can support is about 4%.
- Water drops will grow (coales) when other drops collide.
- Dew point is the temperature at which condensation will occur.
- Warmer air can hold more water vapor than cold air.
- Precipitation can be of different sizes
- Precipitation (rain, drizzle, sleet, snow, hail, virga) is a result of the water cycle.
- Condensation, evaporation, transpiration, sublimation, deposition,
- A variety of variables affect the rate of evaporation (amount of heat, surface area, humidity, wind speed, air pressure) and condensation.
- Evaporation and condensation result in an energy transfer.
- The total amount of water on Earth is constant.
- Dew point, relative humidity, and temperature are related.
- Clouds form from water vapor.
- When air cools below its dew point water vapor condenses (into water (dew fog, clouds) or ice (frost)) on particles (dust, pollution, volcanic ash, smoke, salt spray) and forms clouds.
- Water vapor in clouds is so small that air can easily support it (like fog).
- When water vapor particles collide they coalesce and may eventually become heavy enough not to be supported.
- Rising air expands due to less pressure and transfers heat energy into motion and cools to its dew point temperature.
- Conduction, convection, and radiation transfer energy to form clouds.
- Looking for cloud shapes is called nephelococcygia, or "cloud cuckooland".
- Contrails are condensation trails from high aircraft. Created when moist warm air from the aircraft exhaust is quickly chilled.
Activity Foggy mirror
Put a mirror by your mouth and breathe.
What happens? Explain why.
Activity Sweaty glass
Ice, small glass or plastic container, lid, water.
- Put the ice and water into the glass or plastic container.
- From where did the moisture come?
- Inside the container?
- Put a lid on the container and repeat the experiment.
Activity Spray and drip
Water mister or spray bottle, water, plastic or glass surface.
Spray water on the surface, observe, repeat the process and see what happens.
Activity Rain drop fossils
Corn starch, cookie sheet, strainer, rain storm.
- Lightly sprinkle the cookie sheet with corn starch and place it in the rain for 5 seconds.
- Pour the cornstarch through a fine mesh strainer.
- Most of the starch will pass through the strainer and you will be left with raindrop fossils.
- These will be larger than the original raindrops. Why?
- Sort and count the rain drops.
- Record the rain event and save the raindrops in a carefully marked and sealed plastic bag.
- Repeat the process on other rainy days.
- Is there a relationship between the size and number of drops?
- The kind of rain and the number of drops?
- How much rain there was and the size of drops?
- Compute the area of the rain drop collector.
- How many raindrops fell per square inch in a minute? Per hour?
- How many would fall on a football field? City block? Square mile?
Activity Snow prints
Scotch tape, snow, construction paper.
- Collect snow flakes on the scotch tape.
- Answer the same kinds of questions for the rain fossils activity.
Alcohol, water, other liquids, cotton balls.
- Procedure Swab some liquid onto your skin.
- What happens?
- Which of the liquids cause your skin to feel the coolest?
- How does this fit with perspiration?
Activity Model atmosphere
Plastic containers, water, masking tape, lamp, sack of sand.
- Put water in one of the containers with the sand bag on one end.
- Invert another container onto the first.
- Seal the two with masking tape.
- Set the device under the lamp and let sit for a few hours.
- What do you observe?
- What would happen if ice were set onto the top of the top container?
- What would happen if the lamp were on the opposite end?
Activity Holding water
Cotton balls, string, eye dropper, water.
- Hang a cotton ball on a piece of string.
- Drop water on the cotton ball.
- What happens?
- What would happen if you added twice as much water to a second cotton ball?
- What would happen if you had a cotton ball that could hold twice as much water?
Sponges of different sizes, string, eye dropper, water.
- Hang a sponge piece on a string.
- Drop water onto the sponge.
- How much will it hold?
- Repeat with different sizes of sponges.
- What do you discover?
Dew Point Temperature degrees F
Water Vapor grams/cubic meter of air
Temperature degrees F
Activity Find a pattern between the recorded dew point, relative humidity, and temperature.
Activity What will air hold?
Vacuum cleaner, ping pong ball.
- Put the hose of the vacuum cleaner so it is blowing air.
- Float the ping pong ball in the stream of air.
- Can you float larger balls?
Activity Cloud in a bottle
2 liter plastic pop bottle, warm water.
- Fill the bottle three-fourths full of very warm water, quickly cap the bottle, gently squeeze and release the bottle.
- You should see a cloud.
- Squeeze again and see what happens.
- If you have a bottle keeper or pump you might want to see how pressure affects clouds.
- If the bottle gets foggy shake the bottle to clear the fog.
- If you cant see a cloud you may want to use a flash light.
- Try all these again with the bottle one-fourth filled with water.
Clouds and Other sky events - Facts and Concepts
- Shapes of clouds are determined by how they are formed (cooling air moving vertically form large billowy clouds (cumulus) and horizontal moving cooling air form layers of clouds (stratus). Clouds can be classified into groups with common properties:
- Cirrus means curl and are thin wisps, streams, or waves 4.5 or more km high of ice crystals.
- Cumulus means heap and pile up like balls of cotton as they show where air is rising. They usually appear in the day, 1.5 km or lower, and disappear at night and are associated with good weather.
- Stratus means layer and are low layers of clouds at .6 km. They usually cover the whole sky and are associated with storms. Only drizzle or small grains of snow precipitate from true stratus. Sometimes two of these names are combined to describe clouds.
- Cirrostratus high thin curly layers of clouds that are transparent to sunlight. Many times they make a halo around the sun or moon indicating the coming of rain or snow.
- Stratocumulus layers of cumulus clouds that cover the sky at 1.5 km, contain more water than altocumulus and generally do not precipitate, especially during the winter.
- Cirrocumulus very small cumulus puffs of fluffy clouds at the cirrus level that are usually ice crystals. Sometimes prefixes are also added like alto meaning high, nimbus or nimbo meaning rain, and fracto meaning broken.
- Altostratus high stratus clouds (2.4 - 3.7 km) that are true rain and snow clouds Sun may shine dimly through these or be hidden.
- Nimbostratus are rain clouds.
- Cumulonimbus are thunder heads, can bring hail, high winds, and tornadoes. Height from .9 - 3.0 km with tops as high as 18 km or more. From a distance tops may look like an anvil.
- Fractocumulus broken cumulus clouds.
- Altocumulus are rounded cumulus at 2.4 - 3.7 km. Generally a fair weather cloud with puffs larger than cirrocumulus.
Other sky events
- Sun dogs are bright colored spots in cirrus clouds at opposite angles to the sun.
- A halo is a ring around the sun or moon
- Crepuscular rays are rays of the sun that shine between clouds.
Activity Classify cloud pictures into categories.
Paper and pencil or white chalk and blue paper, optional camera, collection of cloud pictures.
Keep a log of the clouds in the sky
Activity Cloud height
Materials: temperature, dew point.
Procedure to estimate the height of cumulus clouds
- If the temperature is 60 degrees F and dew point is 60 degrees F, then there is fog and the cloud is at ground level.
- If the temperature is 70 degrees F and the dew point 60 degrees F, then the height is 2,000 feet.
- If the temperature is 80 degrees F and the dew point is 60 degrees F, then the height is 4000 feet.
- Subtract the dew point from the current air temperature.
- For every degree F add 200 feet or 60 m for the height of the cloud base.
- Check a airport weather report for the ceiling to see how accurate you are.
Activity What color are clouds and the sky?
Paint chips or paint
- Use paint chips of blue and gray colors or make your own by putting white paint on a pallet and adding one drop of blue, mix thoroughly and paint a 1 inch square around the edge of the paper. Add one more drop of blue, mix, and paint. Repeat the process until you have the darkest blue you think the sky will ever be. Then repeat the process with gray.
- Use color chipsor your color chart to record the colors of the sky from day to day or hourly.
- Storms, thunder, wind, hail, tornado, hurricane, tropical storms, tropical cyclones, typhoons, cyclones, water spout, lightning, floods
- Warm fronts move up through colder retreating air. The slope of the warm front is gradual and may travel 1600 km (1000 miles) to rise 8 km (5 miles).
- As air rises it becomes cooler and water vapor condenses into large masses of clouds.
- Cold fronts move through warm air and push the warm air up.
- The cold front moves quicker because the cold front is heavier and pushes the lighter front out of the way.
- As the warn air rises very quickly it condenses.
- The quicker it rises the more violent the storm.
- Stationary fronts have the air between the two masses mix over a long period of time and the slope is very gentle like that of a warm front.
- Cold air masses have higher pressures than warm air masses because the cold air is heavier.
- Low pressures have the lowest pressure in their centers and air blows toward the center in a counterclockwise direction (due to the rotation of the Earth).
- High pressure have the highest pressure in their centers and air blows away from the center in a clockwise direction (due to the rotation of the Earth).
- Lows usually bring bad weather because the warmer lighter in the center of the low pressure is pushed away by the heavier colder around it.
- The warmer air rises, cools, and forms precipitation.
- Lows usually travel about 1100 km (700 miles) per day in the winter and 800 km (500 miles) per day in the summer.
- Highs usually bring good weather as the colder heavier air is falling toward the Earth.
- As the cold air falls it becomes warmer and can hold more water vapor and hence no precipitation.
- Tornadoes have wind speeds of 70-300 mph. (120-480 kph).
- The forces from the wind, the sudden change of direction, and flying debris cause great damage.
- Hail is created by accretion and updrafts.
- Thunder and lightning are electric discharges. Lightning is hotter than the sun.
- Why is lightning dangerous?
- Thunder is caused when the air around the lightning is superheated. in less than a second, to 8,000-33,000 degrees Celsius. When air is heated this quickly it explodes.
- In a six hour period in the Midwest there were 15,422 lightning strikes recorded.
- In Florida from 1983-1990 the most common fatalities or injuries from lightning were, in order,
- 1. near or in the water;
- 2. near or under a tree;
- 3. near a vehicle, home, or building;
- 4. On a golf course, ball field, or similar situation.
Clear container (about 5 liters), hot water, and 100 ml of cold milk.
- Put the hot water into the clear container.
- Slowly pour the milk down a narrow side of container.
- You should see a convection current know as a downburst.
Clear container (about 5 liters), hot water, cold water or ice, pepper, plastic bag.
- Put the ice or cold water into the plastic bag and seal it.
- Fill the container with hot water, stir in some pepper until you have a fair distribution of pepper.
- Place the bag into it and observe the convection current.
- Try different temperature differences and see if faster or slower currents are created.
Box or folded oaktag, strip of paper, pencils.
- Cut the box or oaktag so the strip of paper can slip through a hole and create the effect of a moving picture.
- Draw a scene on the oaktag or box.
- Create the weather for three or four days that could travel over and through the scene.
- Label the warm air, cold air, draw clouds, high pressure, low pressure, and other weather events and be ready to explain how the events could actually interact to create a real life series of events.
- Or use weather data and illustrate the events related to the weather data.
- Remember weather is three dimensional.
Describe how each of the following might be explained or try to prove or disprove one or more:
- Red at night, sailors delight. Red in the morning, sailor take warning.
- When clouds appear like rocks and towers the Earths refreshed by frequent showers.
- When the wind is in the east, it is neither good for man or beast.
- With dew before midnight, the next day will surely be bright.
- The more cloud types present, the greater the chance of rain or snow.
- When high and \/or middle-level clouds move from north to south and southwest, precipitation is more likely.
- Precipitation is more likely to occur when clouds at different levels move from different directions.
- A ring around the sun or moon, means rain or snow coming soon.
Safety Use winter gloves to handle the salt and ice container as the container may get cold enough to cause frost bite.
Crushed ice, several large test tubes, 500 ml beaker, salt, water, thermometer, stirring rod.
- Fill a beaker three-fourths full with equal amounts of ice and cold water.
- Use winter gloves to protect hands from frost bite.
- Pour salt into the beaker and stir until salt doesn't dissolve and some remains on the bottom.
- Make sure the test tubes are totally clean and fill with cold water so the level of water is the same as the beaker when they are placed into the salt water in the beaker.
- Put the thermometer into the beaker.
- Put the test tubes into the beaker.
- Allow them to sit for ten minutes and stir inside the beaker occasionally with a stirring rod.
- At the end of ten minutes record the temperature.
- Remove the test tubes and immediately drop a small piece of ice into each.
- Remove the ice and repeat dropping it in.
- Compare results from the other pieces of ice.
- Discuss your results.
Activity Tornado in a bottle
2 liter pop bottle, water, drop of soap.
- Put water into the pop bottle
- Cap the bottle.
- Turn it upside down, swirl it and observe (funnel).
- Might want to add less than a drop of soap and try again.
- Add different objects to the bottle and notice the direction of the current around the funnel and how it changes.
Activity Lightning in bed
Objects with static cling, socks and carpet.
- Create a static spark and snap.
- At night when you go to bed turn all the lights out.
- Get under the covers.
- Separate two blanks or a sheet and blanket and watch your own personal lightning show.
- Watch for lightning.
- When you see some start to count.
- When you hear the thunder stop.
- Take the number you counted to and divide by 5 (light travel about 5 times faster than sound 186,000 mph or 299,000 kph to 1000 feet/sec or 300 m/sec) that will give you the distance the lightning was from where you are.
Saffir-Simpson Hurricane Intensity Scale
Category Pressure Winds Storm Surge Damage 1 28.94 or more 74-95 mph 4-5 feet minimal 2 28.5-28.91 96-110 mpg 6-8 feet moderate 3 27.91-28.47 111-130 mph 9-12 feet extensive 4 27.17-27.88 131-155 mph 13-18 feet extreme 5 27.17 or less Over 155 mph Over 18 feet catastrophic
Cookie sheet, water, hair dryer.
- Fill the cookie sheet with water.
- Hold a hair dryer about 2 feet from the sheet.
- Blow air on low.
- What happens?
Cookie sheet, water, bowl, plastic tube.
- Fill the cookie sheet with water.
- Place the bowl upside down into the water.
- Insert a plastic tube through the water into the bowl and suck air from the bowl.
- What happens to the water level in the bowl?
Sand and lake or ocean.
- Make a sand castle near the shore.
- What happens when the waves wash at the castle?
Cookie sheet, clay, water.
- Create a shore line that looks like Tampa bay or Mobile Bay.
- Add water and tilt the container to simulate a storm surge.
- What happens?
Research newspaper microfilm or other sources from historic hurricanes such as
- Camellia August 14-22, 1969;
- Gilbert September 8-19, 1988;
- Hugo September 16-24 1989;
- Andrew August 22-26, 1993 Miami Herald;
- Hurricane Sandy, 2012;
- Hurricane Katrina, 2005
Wind-chill = air temperature - 1.5 * wind speed wind chill chart
Air is composed of 99% nitrogen and oxygen, the rest is carbon dioxide, water vapor, and argon.
2 test tubes, 500 ml beaker, iron filings or steel wool, stand with supporting clamps, glass marking pencil or pen.
- To find the percent of oxygen in air.
- Put some steel wool or sprinkle some iron filings into a damp test tubes.
- Fill the beaker with water until it is two thirds full
- Invert the two test tubes and attach them so that their mouths are below the surface of the water.
- Let the apparatus sit for 24 hours.
- Mark the water level in both test tubes.
- Let the apparatus sit for 24 more hours.
- Repeat until the water level remains the same for two consecutive days.
- Mark the test tube and calculate the volume of water that has displaced the air.
- This was the percentage of oxygen in the air.
Use the data to interpret your map.