Unit 3 · Weather, Water & Climate · Week 3
What makes wind?
At the beach on a warm day, a cool breeze blows in from the water around midday. Before a big storm, the wind picks up suddenly. What is actually making the air move — and how does the sun have anything to do with it?
Start here
How we work this lesson (our expectations)
- Connect new ideas to what we've already built
- Explanations need a cause AND an effect
- Ask "what evidence shows that?" before accepting any claim
- All support panels are always available to anyone
30-second check-in self-management + social awareness
Notice the air around you right now. Is it perfectly still, or is there a slight draft from a vent or door? Something is making that air move — energy is driving it. Rate your focus (1–5). Then think: the last two weeks you followed water from evaporation to clouds. Today we add the third ingredient in weather: air movement. Small steps today, and every section has a Listen button.
Do-Now Retrieve Weeks 1–2 + Unit 1
No looking back — pull from memory first. Retrieval now helps the new ideas connect.
- Week 2 spiral From the exit ticket: what connects humidity (lots of water vapor) and strong wind? What prediction did you make?
- Unit 1 spiral In Unit 1, Week 1, we learned that warm particles move faster and spread further apart. What happens to the density of a substance when its particles speed up and spread out — does it get more dense or less dense?
- Week 1 + 2 spiral The sun heats Earth's surface unevenly — a dark asphalt parking lot gets hotter than a lake next to it. The air above the parking lot is warmer than the air above the lake. Using particles, predict: would the warm parking-lot air or the cool lake air be less dense (fewer particles per cubic meter)? Which would rise?
The phenomenon
On a summer afternoon at a coastal beach, you notice a reliable pattern: around noon, a cool breeze begins blowing in from the ocean, even though there is no storm nearby. By evening, the breeze sometimes reverses direction. The same pattern happens on a smaller scale near any large lake. And before a major winter storm, people often describe a sharp, gusty wind picking up for hours before the snow arrives. None of these winds were "turned on" by a machine or fan. Our question: what is causing the air to move, and how does uneven heating by the sun explain both the sea breeze and the storm winds?
At the beach on a sunny day, a cool wind blows in from the ocean around noon. By evening it might reverse. No machine made this wind. What is making the air move? How does the sun heating land and water differently explain it?
Notice & Wonder. Write one thing you notice in the diagram. Then write your wonder: what still confuses you about what drives wind?
Build it Three steps to understand wind
Build the full cause-and-effect chain: sun → uneven heating → density differences → pressure differences → wind.
Step 1 — Uneven heating creates density differences
The sun does not heat all surfaces equally. Dark surfaces (asphalt, soil) absorb more solar radiation and warm faster. Light surfaces (ocean water, snow) absorb less and warm more slowly. When a surface warms, it heats the air directly above it. Warm air molecules move faster, spread further apart, and occupy more space — so warm air is less dense than cool air (fewer molecules per cubic meter). Cool air is denser — more molecules per cubic meter.
The sun heats dark land faster than cool ocean water. Warm air molecules speed up and spread out — so warm air is less dense (fewer molecules per cubic meter). Cool air has more molecules packed together — it is more dense. Density depends on how hot the air is.
Step 2 — Density differences create pressure differences
Dense air is heavy — it presses down harder on the surface below it, creating a region of high pressure. Less-dense (warm) air is lighter and presses less — it creates a region of low pressure. Air moves from areas of high pressure toward areas of low pressure, just as water flows downhill. This pressure-driven flow of air is what we call wind. The bigger the difference in pressure between two regions, the stronger the wind.
Dense cool air presses down more — that's high pressure. Light warm air presses less — that's low pressure. Air flows from high pressure toward low pressure. That flow is wind. Greater pressure difference = stronger wind.
Step 3 — The full convection loop (and the throughline: sun's energy becomes air motion)
The movement of air driven by temperature (and therefore density) differences is called convection. It forms a loop: (1) the sun heats the land surface; (2) the warm surface heats the air above it; (3) warm, less-dense air rises (like a hot-air balloon); (4) surrounding cooler, denser air flows horizontally to fill the gap — this is the surface wind you feel; (5) the risen warm air cools aloft, becomes denser, and sinks elsewhere; (6) the cycle repeats. This is the throughline: the sun's energy → thermal energy in air → kinetic energy of moving air (wind). The energy started as sunlight and ended as wind. Matter (the air) just moved around; it wasn't created or destroyed.
Convection is a loop: (1) sun heats land → (2) warm air rises → (3) cool air flows in to replace it (= surface wind) → (4) warm air cools and sinks elsewhere → (5) repeat. The sun's energy becomes air motion. The air itself cycles around; it doesn't disappear.
Worked example — tracing the sea breeze step-by-step
Cause 1: The noon sun heats the dark sand and asphalt much faster than the ocean water.
Effect 1: Air above the land is warmer than air above the ocean. Warm air = faster particles = less dense.
Cause 2: Less-dense air over land creates low pressure; denser cool air over the ocean is high pressure.
Effect 2: Air flows from the high-pressure ocean toward the low-pressure land. You feel this as the sea breeze — cool air flowing in from the water.
Cause 3: Warm rising land air cools aloft, becomes denser, and flows back out toward the ocean at higher altitude (return flow).
Effect 3: A complete convection loop — a cycle driven entirely by the sun's uneven heating. Energy pathway: sunlight → warm surface → warm air particles (kinetic energy) → rising motion → pressure difference → wind (kinetic energy of air mass).
Show me a cause-and-effect chain diagram Tier 2 · organizer
Fill in the chain with arrows connecting each box:
SUN heats land more than ocean → Land surface is ________ → Air above land is ________ → Warm air molecules ________ (speed up/slow down?) and spread out → Air above land is less ________ → Less-dense air = LOW ________ → Dense cool ocean air = HIGH ________ → Air flows from ________ to ________ → You feel ________
Check: does your chain start with SUN and end with WIND? If yes, you've got the full convection loop.
Your turn Explain a local wind
Apply the convection model to explain a specific real-world wind situation. Choose how you respond.
The task: Choose one scenario and explain all of the following — (1) what surface is unevenly heated and by what, (2) how that creates a density and pressure difference, (3) which direction the wind flows and why, (4) how this connects to the energy-and-matter throughline (sun's energy → air motion).
Scenario A: Why does it get very windy in a parking lot on a summer afternoon?
Scenario B: Why does wind pick up for hours before a large winter storm arrives?
Scenario C (your own): Describe a place you've noticed wind and explain what might be causing it.
I want sentence starters Tier 2 · frames
The surface being unevenly heated is ________, and the energy source is ________.
Because ________ is warmer, the air above it has particles that ________, making it less ________ (dense). This creates a region of ________ pressure.
The cooler, denser air nearby has ________ pressure. Air moves from ________ pressure to ________ pressure, so the wind blows from ________ toward ________.
Tracing the energy: the sun's energy became ________ energy in the surface, which became ________ energy in the air particles, which created ________ (movement of air).
Word bank: convection · pressure · density · dense · less dense · high pressure · low pressure · warm · cool · rises · sinks · sun · kinetic energy · thermal energy · wind · air flow
Let's make it concrete first Tier 3 · re-teach
Analogy — the bathtub drain: Imagine two bathtubs connected at the bottom. One tub is filled higher (more water = more pressure at the bottom). Water flows from the full tub to the emptier one until they level out. Air works the same way: high-pressure air (dense, heavy, lots of molecules) flows toward low-pressure air (light, fewer molecules) until pressures even out. The "hill" that makes the flow happen is created by uneven heating from the sun — the sun made one "tub" lighter (warm air rose, pressure dropped) and left the other "tub" fuller (cool air stayed dense, pressure stayed high).
Fill in: The parking lot asphalt gets ________ (hotter or cooler?) than the surrounding fields. The air above the parking lot is ________ (more or less dense?). This creates ________ pressure above the parking lot. Cool air from the fields has ________ pressure, so it flows ________ toward the parking lot. That moving air is ________.
Say each blank out loud before writing.
Push my thinking Extension
The same convection principle that makes a sea breeze also drives the global wind belts (trade winds, westerlies, polar easterlies). Research (or reason through): (1) The equator receives more direct sunlight than the poles. Using what you know about uneven heating and convection, predict the large-scale wind pattern you would expect — where would air rise? Where would it sink? Which direction would surface winds blow? (2) Why do global wind belts curve (rather than go straight north or south)? Look up the Coriolis effect and explain it in your own words using the idea of Earth rotating under the moving air. (3) Design one testable question about what changes if the surface type under the sun changes (sand vs. water vs. forest).
Check yourself Did it click?
- explain that uneven solar heating creates temperature and density differences in air;
- connect density differences to pressure differences (warm = less dense = lower pressure);
- describe wind as air flowing from high pressure to low pressure, driven by the sun's energy.
A classmate says: "Wind is made by the trees and fans — they push the air around." What is missing from this explanation, and what would you add?
Re-teach: pressure differences cause wind; the sun causes the pressure differences Tier 3
Wind is not made by trees, fans, or Earth's rotation — those things affect local airflow or wind direction, but they are not the root cause of large-scale natural wind. Here is the actual chain of cause and effect:
- The sun heats different surfaces by different amounts (land heats faster than water).
- Warm air above the land has faster-moving molecules → molecules spread out → air is less dense → air weighs less → creates LOW pressure at that location.
- Cooler air nearby has slower, more-packed molecules → more dense → weighs more → HIGH pressure.
- Air flows from HIGH pressure toward LOW pressure — that flow is wind.
The sun is the ultimate energy source. A fan just moves existing air around; it doesn't create the pressure difference that drives sustained directional winds. Re-read option B — it traces this chain correctly.
Reflect, then show what you know
Reflection metacognition + SEL
Before today, when you felt wind, what did you think was causing it? What's one thing about convection that surprised you? Where else in your daily life might you notice pressure-driven airflow? (Think about opening a door to a heated room, or walking from a cool hallway into a warm gym.)
Exit ticket — answer on paper or in your notebook.
- New Describe convection in your own words. Include: what causes air to rise, what fills the gap, and why this creates wind.
- New If the ocean were warmer than the land (this actually happens at night, once the land cools), which direction would the sea breeze blow — from land toward sea, or from sea toward land? Explain your reasoning with density and pressure.
- Spiral — Week 2 Week 2 showed that condensation inside a storm cloud releases energy that warms the air. Using today's convection model, explain how that released energy could make a storm's winds stronger.
- Spiral — Unit 1 Unit 1 taught us that thermal energy is particle motion — faster particles = more heat. How does this explain why warm air is less dense than cool air?
- Transfer → Week 4 Weather maps show "L" (low pressure) and "H" (high pressure) zones. Air masses with different temperatures and moisture levels crash into each other at boundaries. Based on what you know about pressure and convection, predict: what would happen where a warm air mass meets a cold air mass head-on?
Educator panel — facilitation, accommodations, answer key
At a glance
Standards: NGSS MS-ESS2-5 — collect data to provide evidence for how the motions and complex interactions of air masses result in changes in weather conditions. MS-ESS2-6 — develop and use a model to describe how unequal heating and rotation of Earth cause patterns of atmospheric and oceanic circulation that determine regional climates. 3D: SEP Developing & Using Models · DCI ESS2.C + ESS2.D · CCC Energy & Matter + Cause & Effect. Throughline: the sun's energy → thermal energy in air → kinetic energy of wind. This adds the third ingredient (air motion) to the unit arc: W1 (water vapor), W2 (condensation energy), W3 (pressure-driven convection). Transfer item previews W4's fronts.
Facilitation arc (Rosenshine)
- Do-Now: the W2 transfer-item prediction about humidity and wind becomes the opening data — validate or revise with the class (3 min).
- Phenomenon + notice/wonder: display SVG; ask "what do the arrows show?" before any explanation (3 min).
- Build Steps 1–3: read or listen together; stop at Step 2 for a Think-Pair-Share: "In your own words, what causes wind?" (12 min).
- Worked example: walk through aloud; emphasize the energy-pathway sentence at the end (4 min).
- Differentiated practice — circulate; prompt with "what is the root cause?" for any student stopping at "warm air rises" without getting to the pressure-driven flow (14 min).
- Self-check + re-teach branch (5 min).
- Brain break, reflection, exit ticket (9 min).
IEP / 504 accommodation cards
Common accommodations mapped to this lesson
| Accommodation | How it's already built in / what to do |
|---|---|
| Text read aloud | Listen buttons on phenomenon and build section; simplified toggle shortens all text. |
| Reduced reading load | "Reading: Simplified" throughout. |
| Chunking / extended time | Three build steps + a worked example; progress saves automatically. |
| Sentence frames / word bank | Tier-2 panel: causal-chain frames + 15-word bank. |
| Concrete analogy / reduced load | Tier-3 "bathtub drain" analogy with cloze fill-in. |
| Alternative response mode | Write, draw annotated convection loop, or record oral explanation. |
| Behavior / focus (504, ADHD) | Named expectations, 30-sec check-in, kinesthetic brain break (hands near warm surface). |
| Multilingual / EL | Simplified text, SVG with labeled arrows showing direction and pressure, word bank, home-language reflection allowed. |
Exit ticket answer key
- Convection: the sun heats a surface → warms the air above it → warm air molecules speed up and spread out → less dense → rises (like a hot-air balloon). The rising warm air leaves a low-pressure gap. Cooler, denser air from nearby rushes in to fill the gap — that horizontal flow is wind. The risen warm air cools aloft, sinks, and the cycle repeats.
- If the ocean is warmer than the land at night: air above the ocean is warmer → less dense → lower pressure. Air above the cooler land is denser → higher pressure. Air flows from the high-pressure land toward the low-pressure ocean — a land breeze blowing from shore to sea. Opposite direction from the daytime sea breeze.
- Condensation energy warms the air inside the storm cloud → that warm air is now even less dense than the surrounding air → it rises faster and higher → more warm moist air is pulled up from the surface below → more evaporation → more condensation → more energy release → positive feedback loop. The storm intensifies. This is the engine of large convective storms like thunderstorms.
- Faster-moving particles in warm air take up more space (they push each other further apart during collisions). The same mass of air molecules spread over a larger volume = fewer molecules per cubic meter = less dense. Cool air has slower molecules packed closer → more dense. Density is particles per volume, and temperature controls the average spacing.
- (Transfer preview) When a warm air mass meets a cold air mass head-on, the warm (less dense) air will ride up over the cold (more dense) air because it is buoyant. The boundary between them is called a front. At that boundary, rapid rising of warm moist air causes rapid condensation → clouds → precipitation. The collision and the resulting rapid upward motion can create intense weather. (Sets up W4's fronts perfectly.)
Why it's designed this way
The Do-Now retrieves W2's transfer prediction about wind + humidity so students begin Week 3 with their own hypothesis already in hand (prediction-update learning cycle). The sea-breeze SVG was chosen because it is a single, self-contained convection cell that students can fully trace — not a global map that overwhelms. The "bathtub drain" Tier-3 analogy maps pressure-driven flow onto a purely mechanical, everyday experience before introducing the atmospheric context. The misconception in the self-check ("trees and fans make wind") is documented in multiple middle-school science diagnostic studies — it reflects a confusion between proximate agents and ultimate cause (Schoon, 1995). The energy-pathway sentence at the end of each worked example reinforces the year-long CCC "Energy & Matter" throughline: tracing where energy comes from and where it goes.