Weather and Water

Weather and Water

Middle School

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Learning Objectives

• Describe how solar energy and gravity drive the water cycle on Earth.

• Explain how moving air masses from high to low pressure change weather conditions.

• Describe how Earth's rotation and unequal heating create ocean and atmospheric circulation patterns.

• Analyze how radiation, conduction, and convection transfer energy throughout Earth's systems.

• Differentiate between types of severe weather and explain their atmospheric causes.

Key Vocabulary

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Atmosphere

The atmosphere is the essential layer of gases that surrounds a planet like our Earth.

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Hydrologic Cycle

The hydrologic cycle is the continuous movement of water on, above, and below Earth's surface.

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Evaporation

Evaporation is the process where liquid water heats up and changes into a gas or vapor.

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Transpiration

Transpiration is the process of water vapor being released from the leaves of living plants.

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Condensation

Condensation is the change of water from its gaseous form, called water vapor, into liquid water.

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Crystallization

Crystallization is the process where water vapor or liquid water freezes and forms solid ice crystals.

Key Vocabulary

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Precipitation

Precipitation is any form of water, like rain, snow, or hail, that falls to Earth.

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Air Mass

An air mass is a large body of air with uniform temperature and humidity.

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Salinity

Salinity is the scientific measure of the total amount of dissolved salt content in water.

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Air Pressure

Air pressure is the force that is exerted on a surface by the weight of the air.

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Convection

Convection is the process of energy transfer through the movement of fluids like liquid or gas.

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Coriolis Effect

The Coriolis Effect is the apparent curving of winds and ocean currents due to Earth's rotation.

The Water Cycle

• The sun's energy heats water, causing it to evaporate into the air.

• The water vapor cools and condenses, forming clouds in the sky.

• Water falls back to Earth as rain or snow, called precipitation.

Multiple Choice

What is the primary role of the sun's energy in the water cycle?

• To cause water to evaporate into the air

• To make clouds move across the sky

• To turn water vapor directly into snow

• To help rain soak into the ground

Multiple Choice

What process directly leads to the formation of clouds?

• Water vapor cools and condenses

• The sun's energy heats the air

• Rain and snow mix together in the sky

• Wind pushes evaporated water downwards

Multiple Choice

What would be the most likely outcome if the process of condensation stopped happening in the water cycle?

• Precipitation would not occur

• The sun would stop heating the water

• Water would no longer evaporate

• Oceans would immediately dry up

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Earth's Atmosphere: Composition and Layers

Atmosphere Composition

• Earth's atmosphere is a mixture of gases, mostly permanent ones like nitrogen and oxygen.

• Nitrogen makes up 78% of the atmosphere, while oxygen accounts for about 21%.

• It also contains variable gases like water vapor and carbon dioxide (CO₂).

Layers of the Atmosphere

• The atmosphere is divided into layers based on how temperature changes with height.

• We live in the troposphere, the lowest and densest layer where weather occurs.

• The stratosphere above contains the ozone layer, which absorbs the Sun's harmful UV radiation.

Multiple Choice

Which statement best describes the composition of Earth's atmosphere?

• It is mostly made of nitrogen and oxygen.

• It is entirely made of water vapor and carbon dioxide.

• It is mainly composed of ozone and water vapor.

• It consists only of permanent gases like helium.

Multiple Choice

What is the primary basis for dividing the atmosphere into different layers like the troposphere and stratosphere?

• The layers are organized based on how temperature changes with altitude.

• The layers are separated based on the different types of gases they contain.

• The layers are defined by the amount of water vapor present in each one.

• The layers are structured according to their distance from the Sun.

Multiple Choice

If you were to travel upward from Earth's surface through the first two atmospheric layers, what sequence of characteristics would you encounter?

• You would travel from the layer containing weather to the layer that absorbs harmful UV radiation.

• You would pass from the densest layer directly into the layer made mostly of oxygen.

• You would leave the layer that absorbs UV radiation and enter the layer where weather occurs.

• You would find that both weather and the ozone layer are present in the lowest layer.

Energy Transfer in the Atmosphere

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Radiation

• Energy travels as waves, like visible light from the sun.

• The heated Earth's surface radiates heat as infrared energy.

• Greenhouse gases like CO₂ trap this outgoing heat.

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Conduction

• This is the transfer of energy through direct physical contact.

• Air particles that touch the warm surface gain energy.

• This process is most effective at the Earth's surface.

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Convection

• This is the transfer of energy through fluid movement.

• Heated air near the ground becomes less dense and rises.

• Cooler, denser air sinks, creating a circular convection cell.

Multiple Choice

Which of the following describes the transfer of energy through the movement of a fluid like air?

• Radiation

• Conduction

• Convection

• Insulation

Multiple Choice

What is the relationship between the sun's radiation and the heating of the atmosphere?

• The sun's waves directly heat air particles through physical contact.

• The sun's waves are trapped by greenhouse gases, which prevents the Earth from warming.

• The sun's waves heat the Earth's surface, which then radiates heat that is trapped by greenhouse gases.

• The sun's waves cause cool, dense air to rise and warm air to sink.

Multiple Choice

Which statement best explains the complete process that causes air near the ground to warm and then rise on a sunny day?

• Convection currents in the air transfer heat directly to the ground through conduction.

• Radiation from the sun heats the ground, which heats the air by conduction, causing the warmer air to rise by convection.

• Conduction transfers heat from the sun to the air, which then uses radiation to heat the ground.

• Cooler, denser air is heated by the sun's radiation, causing it to sink and warm the ground by convection.

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Air Pressure and Density

• Atmospheric pressure is the force from air's weight; it decreases with higher elevation.

• Air density is the amount of mass in a certain amount of space.

• Heated air expands, becomes less dense than the cooler air, and begins to rise.

• Air flows from high-pressure areas to low-pressure areas, which creates wind.

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Multiple Choice

What is atmospheric pressure?

• The force created by the weight of the air

• The amount of mass in a certain amount of space

• The movement of air from one place to another

• The speed at which air molecules are moving

Multiple Choice

What happens to air when it is heated?

• It becomes less dense and rises.

• It becomes denser and sinks.

• It increases in pressure and stays in place.

• It loses its mass and disappears.

Multiple Choice

At night, land cools off faster than the ocean. Based on the principles of air pressure and flow, what is most likely to happen?

• Wind will blow from the cooler land toward the warmer ocean.

• Wind will blow from the warmer ocean toward the cooler land.

• The air will remain still with no wind.

• The air over the land will become denser than the air over the ocean.

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Air Masses and Weather

• Air masses are huge air bodies with uniform temperature, humidity, and pressure.

• They can be warm, cold, humid, or dry depending on where the air mass forms.

• Air masses move from high pressure to low, bringing temperature and humidity changes over time.

• A front forms where different air masses meet; cold fronts lift warm air, causing thunderstorms.

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Multiple Choice

What is the best definition of an air mass?

• A large body of air with uniform temperature and humidity.

• A boundary between two different weather systems.

• A type of cloud that produces thunderstorms.

• A pattern of wind moving from west to east.

Multiple Choice

What is the primary effect of an air mass moving from a high-pressure area to a low-pressure area?

• It causes the Earth to spin faster.

• It brings changes in temperature and humidity to the new area.

• It always forms a hurricane.

• It stops all other weather from occurring.

Multiple Choice

Based on the principles of air mass interactions, what is the most probable outcome when a cold air mass collides with and lifts a warm air mass?

• The two air masses will mix peacefully.

• The weather will become clear and sunny.

• Thunderstorms are likely to form.

• The area will experience a long, gentle rain.

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Global and Local Winds

Global Winds

• ​Wind is air moving from high pressure to low pressure, caused by Earth's unequal heating.

• ​​The Coriolis effect, from Earth's rotation, deflects air into predictable prevailing winds.

• ​Landforms like mountains also affect winds by deflecting them or forcing them to rise.

Local Winds

• ​During the day, cool air from the water moves inland, creating a sea breeze.

• ​​At night, land cools faster than water, and cool air moves toward the sea.

• ​This reversal of wind between day and night is what creates local breezes.

Multiple Choice

What is the fundamental cause of wind?

• The movement of air from a high-pressure area to a low-pressure area.

• The rotation of the Earth on its axis.

• The presence of mountains and other landforms.

• The daily change in temperature between the land and the sea.

Multiple Choice

What is the primary reason that local wind patterns, like sea breezes, reverse between day and night?

• The Earth's rotation deflects the air.

• Land and water heat and cool at different rates.

• Mountains block the path of the wind.

• Global winds are stronger than local winds.

Multiple Choice

A large mass of air is moving from a high-pressure zone towards a low-pressure zone over a continent. What two factors would cause its path to be deflected or altered?

• The daily reversal of sea and land breezes.

• The Coriolis effect and nearby mountain ranges.

• The heat of the sun and the pull of the moon.

• The speed of the wind and the time of day.

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Types of Severe Weather

• Thunderstorms bring lightning and rain; severe ones can create tornadoes with rotating winds.

• ​Hurricanes are large, rotating storms that form over warm oceans, causing coastal flooding.

• Blizzards are severe winter storms with strong winds, blowing snow, and low temperatures.

• Floods are an overflow of water, while droughts are long periods of low precipitation.

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Multiple Choice

Which type of severe weather is defined as a winter storm with strong winds, blowing snow, and low temperatures?

• Blizzard

• Hurricane

• Thunderstorm

• Flood

Multiple Choice

What is the relationship between a severe thunderstorm and a tornado?

• Severe thunderstorms can create tornadoes.

• Tornadoes form over warm oceans to become thunderstorms.

• Thunderstorms are a result of tornadoes.

• Tornadoes bring lightning, and thunderstorms bring rotating winds.

Multiple Choice

A large storm forms over a warm ocean, causing an overflow of water in a coastal area. Which two types of severe weather are described in this event?

• A hurricane and a flood

• A tornado and a drought

• A blizzard and a thunderstorm

• A hurricane and a blizzard

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The Ocean's Role in Weather

• The ocean absorbs the sun's energy, releasing it slowly to influence weather.

• ​Ocean currents are driven by wind, tides, and differences in water density.

• Cold, salty water is denser and sinks, driving deep ocean circulation.

• Surface currents form large, rotating systems called gyres due to Earth's rotation.

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Multiple Choice

What is the primary way that the ocean influences weather?

• By absorbing and slowly releasing the sun's energy

• By reflecting all of the sun's energy back into space

• By creating wind through its constant wave action

• By directly causing rain to fall over continents

Multiple Choice

What is the relationship between wind, water density, and the Earth's rotation?

• They are all forces that drive the movement of ocean currents.

• Ocean currents cause changes in wind and water density.

• They are separate systems that do not interact with each other.

• Only the Earth's rotation is strong enough to create currents.

Multiple Choice

What would most likely happen in the deep ocean if a large mass of cold, salty water meets a large mass of warmer, less-salty water?

• The cold, salty water would sink and flow underneath the warmer water.

• The warmer water would sink and flow underneath the cold water.

• The two masses of water would immediately and evenly mix.

• The cold, salty water would float on top of the warmer water.

Factors That Determine Regional Climate

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Latitude

• ​Areas near the equator receive more direct sunlight and have higher temperatures.

• ​​Areas near the poles receive less direct sunlight and have lower temperatures.

• ​This difference in sunlight creates distinct temperature zones on our planet.

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Altitude

• ​As a general rule, higher elevations have much lower average temperatures.

• ​​For example, the tops of mountains are colder than the valleys below.

• ​This happens because the atmosphere is thinner at these higher altitudes.

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Geography

• ​Continental climates away from oceans have large seasonal temperature changes.

• ​​Marine climates that are near oceans have smaller temperature changes.

• ​This is because water heats and cools much more slowly than land.

Multiple Choice

Which of the following is a key factor that helps determine a region's climate?

• The number of rivers in the area

• The type of soil in the area

• The altitude of the area

• The population of the area

Multiple Choice

Why do coastal areas experience smaller temperature changes between seasons compared to inland areas?

• Because oceans create strong winds that cool the land.

• Because water heats up and cools down much more slowly than land.

• Because land absorbs more direct sunlight than water does.

• Because coastal areas are always at a lower altitude.

Multiple Choice

A city is located near the equator but at a very high altitude. What would its climate most likely be like?

• Hot, because it receives direct sunlight from being near the equator.

• Cold, because the atmosphere is thinner at high altitudes.

• Moderate, because the effects of sunlight and altitude cancel each other out.

• Hot and with large seasonal temperature changes.

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Climate Change and Prediction

• Global warming is a long-term change in Earth’s climate caused by greenhouse gases.

• Humans release gases like carbon dioxide (CO₂) by burning fossil fuels.

• This warming melts glaciers, raises sea levels, and increases extreme weather events.

• Because global warming affects weather patterns, scientists use probability—not certainty—to predict future climate and weather changes.

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Multiple Choice

What is global warming?

• A long-term climate change caused by greenhouse gases.

• The daily change in temperature and precipitation.

• The prediction of weather using probability.

• The melting of glaciers in the arctic.

Multiple Choice

What is the relationship between burning fossil fuels and melting glaciers?

• They release greenhouse gases that lead to warming, which melts glaciers.

• They create clouds that block the sun, causing cooling.

• They use up the oxygen that glaciers need to stay frozen.

• They directly heat the oceans, causing water to expand.

Multiple Choice

A scientist states there is a high probability of more extreme weather in the future due to climate change. Why would the scientist use the word 'probability' instead of 'certainty'?

• Because weather is complex and cannot be predicted with absolute certainty.

• Because scientists are not sure if climate change is real.

• Because the burning of fossil fuels might stop unexpectedly.

• Because sea levels might stop rising next year.

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Common Misconceptions

Misconception	Correction
Weather and climate are the same thing.	Weather is short-term; climate is the long-term average over 30+ years.
The seasons are caused by the Earth getting closer to the Sun.	The 23.5-degree tilt of Earth's axis causes the seasons.
Clouds are made of water vapor.	Clouds are made of tiny liquid water droplets or ice crystals.

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Summary

• The water cycle is driven by solar energy through evaporation, condensation, and precipitation.

• Interacting air masses cause weather changes, which are why weather is predicted probabilistically.

• The unequal heating of Earth and its rotation create global wind and ocean currents.

• Human-caused greenhouse gases are the primary drivers of long-term climate change.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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