SCI 207

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sci207.w5.lab_.pdf

Lab 5 Weather and Climate Change

Weather and Climate Change

Concepts to Explore

• Atmosphere

• Weather

• The Water Cycle

• Climate Introduction

The Earth’s atmosphere is composed of 21% oxygen (O2), 78% Nitrogen (N2) and approximately 1% other gases (including water vapor, argon, carbon dioxide, hydrogen, and helium). Oxygen is essential for life and is used by most organisms for cellular respiration while carbon dioxide is used by plants and certain bacteria for photosynthesis.

Figure 1: Clouds are visible accumulation of water droplets that accumulate in the Earth’s lowest layer of the atmosphere, the troposphere.

Our atmosphere is composed of five layers:

1. Troposphere - Nearest to the Earth’s surface; layer in which weather occurs (rising and falling air); comprises one half of total atmosphere; air pressure is decreased to 10% of that at sea level.

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Weather and Climate Change

2. Stratosphere - Contains the ozone layer (important for UV ray absorption).

3. Mesosphere - Layer which meteors burn up in upon entering the Earth’s atmosphere.

4. Ionosphere/Thermosphere - Locations of auroras (e.g., aurora borealis); layer in which the space shut- tle orbits.

5. Exosphere - Upper limit of the Earth’s atmosphere; layer where Earth’s atmosphere merges with outer space.

Weather is the state of the atmosphere at a given time and place and includes temperature, pressure, the type and amount of precipitation, wind, clouds, etc. Weather conditions can change hour to hour, day to day, and season to season. Our weather is caused by uneven heating of the Earth from the sun. The resulting temperature differentials generate wind that forces warm air to flow to regions of cooler air. This flow can oc- cur both horizontally across the surface of the Earth (i.e., from tropical to polar regions) and vertically, causing clouds, rain, and storms to develop as warm, moist air cools and condenses as it rises. In addition to driving our weather, the sun’s energy also is responsible for regulating how water moves on, above, and below the Earth’s surface through the water cycle.

Figure 2: The water cycle - can you name the steps? Refer to Lab 2 for help!

The water cycle describes how the amount of water on Earth remains constant over time. Water exists in three different states (in solid form as ice, as liquid water, and in a gas as water vapor) and cycles continuous-

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Weather and Climate Change

ly through these states. The temperature and pressure determine which state water is in. The water cycle consists of the following processes:

• Evaporation of liquid water to a gas (water vapor)

• Condensation of water vapor to liquid water

• Sublimation of solid water (ice) to water vapor (think dry ice)

• Precipitation occurs when water vapor condenses to clouds/rain

• Transpiration occurs when liquid water moves through plants from roots to leaves, changes to water vapor and is released to the atmosphere through holes (stoma) in the leaves

• Surface Run-off occurs when water moves from high to low ground

• Infiltration occurs when water fills porous spaces in the soil

• Percolation occurs when ground water moves in a saturated zone below Earth’s surface

Figure 3: Clouds.

Clouds form at many different altitudes in the troposphere when water vapor in warm air rises and cools. The water vapor condenses on microscopic dust particles in the atmosphere and transforms into either a liquid or solid and is visible as clouds. Warm air can hold more water vapor than cool air so clouds often form over the

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Weather and Climate Change

tops of mountains and over large bodies of water since the air over these formations is typically cooler than the surrounding air.

Climate is defined as the long-term average pattern of weather in a given region. Our climate is influenced by five components: the atmosphere, the hydrosphere (mass of liquid water), the cryosphere (mass of solid wa- ter; ice), the land surface, and the biosphere (life on Earth). Climate change refers to the observed accelerat- ed increase in the Earth’s temperature over the past 100 years and its predicted continued increase. The Earth’s average temperature has increased approximately 1 - 1.5 degrees F since 1900 (see figure below) and is projected to rise an additional approximately 3 - 10 degrees F over the next 100 years.

Figure 4: Global Temperature Anomalies. Source: www.nasa.gov

Changes in the Earth’s atmosphere have contributed to global warming. Global warming is due to the accu- mulation of “greenhouse gases”: carbon dioxide (CO2) from burning fossil fuels (oil, gas, and coal); methane (CH4) from agriculture, landfills, mining operations and gas pipelines; chlorofluorocarbons (CFCs) from refrig- erants and aerosols; and nitrous oxide from fertilizers and other chemicals. Increased temperature results in increased evaporation, accelerated polar ice melting, increased number of extreme temperature days, heavier rains/floods, and more intense storms. These changes will have important implications across public health, infrastructure, energy, economic, and political arenas.

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Weather and Climate Change

Experiment 1: Modeling the Water Cycle

In this lab, you will construct a model of the Earth’s surface/atmosphere to explore how energy drives weather. Follow the procedure below to complete Demonstration 1 on modeling of the water cycle.

Materials

100 mL Graduated cylinder

Canning jar

Petri dish

Thermometer

*Hot water

*Water

*Ice cubes

*You must provide

Procedure

1. Using a graduated cylinder, carefully pour 20 mL of warm water (60 °C) into canning jar and secure the

lid.

2. Fill the petri dish with ice and place on top of the canning jar’s lid.

3. After 30 minutes, remove the petri dish, carefully remove the lid, and look at the underside. Then, answer

the Post-Lab Questions on the Week 5 Lab Reporting Form.

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Weather and Climate Change

Experiment 2: Assessing Infiltration

Water movement among phases and sources is based on a number of environmental climatic factors. In this experiment you will test how water moves between land and the atmosphere based on differences in weather conditions. Follow the procedure below to complete Experiment 1 on water movement.

Materials

(2) 9 x 12 in. Bags

250 mL Beaker

200 mL Sand

*Water

*A sunny location (window sill, outside porch, etc.)

*A shady location

*You must provide

Procedure:

1. Read through the Experiment 1 procedure and then record your hypothesis on the effects of sunlight on

evaporation on the Week 5 Lab Reporting Form.

2. Add 200 mL of sand to two separate plastic re-sealable bags.

3. Add 200 mL of room temperature water to each bag.

4. Seal each bag, leaving a bit of air in each.

5. Place 1 bag in a sunny location and 1 bag in a shady location (complete this in the day when the sun is out).

6. Observe the bags immediately after sealing and again after 3 hours. Answer the Post-Lab Questions on the Week 5 Lab Reporting Form based on your observations.

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Appendix Good Lab Techniques

Good Lab Techniques

Good Laboratory Techniques

Science labs, whether at universities or in your home, are places of adventure and discovery. One of the first things scientists learn is how exciting experiments can be. However, they must also realize science can be dangerous without some instruction on good laboratory practices.

• Read the protocol thoroughly before starting any new experiment. You should be familiar with the action required every step of the way.

• Keep all work spaces free from clutter and dirty dishes.

• Read the labels on all chemicals, and note the chemical safety rating on each container. Read all Material Safety Data Sheets (provided on www.eScienceLabs.com).

• Thoroughly rinse lab ware (test tubes, beakers, etc.) between experi- ments. To do so, wash with a soap and hot water solution using a bottle brush to scrub. Rinse completely at least four times. Let air dry

• Use a new pipet for each chemical dispensed.

• Wipe up any chemical spills immediately. Check MSDSs for special handling instructions (provided on www.eScienceLabs.com).

• Use test tube caps or stoppers to cover test tubes when shaking or mixing – not your finger!

A B C

Figure 1: A underpad will prevent any spilled liquids from contaminating the sur- face you work on.

Figure 2: Special measuring tools in make experimentation easier and more accu- rate in the lab. A shows a beaker, B graduated cylinders, and C test tubes in a test tube rack.

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Good Lab Techniques

• When preparing a solution, refer to a protocol for any specific instructions on preparation. Weigh out the desired amount of chemicals, and transfer to a beaker or graduated cylinder. Add LESS than the required amount of water. Swirl or stir to dissolve the chemical (you can also pour the solution back and forth between two test tubes), and once dissolved, trans- fer to a graduated cylinder and add the required amount of liquid to achieve the final volume.

• A molar solution is one in which one liter (1L) of solution con- tains the number of grams equal to its molecular weight.

For example:

1M = 110 g CaCl x 110 g CaCl/mol CaCl

(The formula weight of CaCl is 110 g/mol)

Figure 3: Disposable pipettes aid in ac- curate measuring of small volumes of liquids. It is important to use a new pi- pette for each chemical to avoid con- tamination.

• A percent solution can be prepared by percentage of weight of chemical to 100ml of solvent (w/v) , or volume of chemical in 100ml of solvent (v/v).

For example:

20 g NaCl + 80 mL H2O = 20% w/v NaCl solution

• Concentrated solutions, such as 10X, or ten times the normal strength, are diluted such that the final concentration of the solution is 1X.

For example:

To make a 100 mL solution of 1X TBE from a 10X solution:

10 mL 10X TBE + 90 mL water = 100ml 1X TBE

• Always read the MSDS before disposing of a chemical to insure it does not require extra measures. (provided on www.eScienceLabs.com)

• Avoid prolonged exposure of chemicals to direct sunlight and extreme temperatures. Immediately se- cure the lid of a chemical after use.

• Prepare a dilution using the following equation:

c1v1 = c2v2

Where c1 is the concentration of the original solution, v1 is the volume of the original solution, and c2 and v2 are the corresponding concentration and volume of the final solution. Since you know c1,

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Good Lab Techniques

c2, and v2, you solve for v1 to figure out how much of the original solution is needed to make a cer- tain volume of a diluted concentration.

• If you are ever required to smell a chemical, always waft a gas toward you, as shown in the figure below.. This means to wave your hand over the chemical towards you. Never directly smell a chemical. Never smell a gas that is toxic or otherwise dangerous.

• Use only the chemicals needed for the activity.

• Keep lids closed when a chemical is not being used.

• When diluting an acid, always slowly pour the acid into the water. Never pour water into an acid, as this could cause both splashing and/or an explosion.

• Never return excess chemical back to the original bottle. This can contaminate the chemical sup- ply.

• Be careful not to interchange lids between different chemical bottles.

• When pouring a chemical, always hold the lid of the chemical bottle between your fingers. Never lay the lid down on a surface. This can contaminate the chemical supply.

• When using knives or blades, always cut away from yourself.

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© 2012 eScience Labs, LLC - All rights reserved

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  • Lab 5
    • Concepts to Explore
      • Introduction
      • Experiment 1: Modeling the Water Cycle
      • Procedure
      • Experiment 2: Assessing Infiltration
    • Materials
      • Procedure:
  • Appendix
    • A B C
      • © 2012 eScience Labs, LLC - All rights reserved