Unit 3 · Weather, Water & Climate · Week 1

Where does water in the air come from, and where does it go?

A puddle on the sidewalk disappears on a sunny morning with no drain, no towel, no one touching it. Where did the water go? And why does your breath make a little cloud on a cold day?

SEP: Developing & Using Models · Constructing Explanations DCI: ESS2.C The Roles of Water in Earth's Surface Processes CCC: Energy & Matter — matter is conserved; energy drives the cycle

NGSS MS-ESS2-4 ~50 minutes Learner code: —

Make this lesson work for you:

Start here

How we work this lesson (our expectations)

Wonder out loud — questions are the work
Build ideas from evidence, not just intuition
Reasoning matters more than speed
All support panels are for everyone — open any you want

30-second check-in self-management

Take a slow breath. Think about the air around you right now — you can't see it, but water is hiding in it. On a scale of 1 (foggy) to 5 (alert), where is your focus? Whatever number you picked, the steps in this lesson are small on purpose. Use the Listen button on any paragraph if reading is hard today.

Do-Now Quick recall

No looking back — pull from memory. Retrieval practice makes ideas stick better than re-reading.

From Unit 1: when a liquid evaporates, does the matter (the water molecules) disappear, or go somewhere? What did we call that idea?
Name the three states of matter and describe how the particles are arranged in each one.
Where does the energy come from that heats the sidewalk on a sunny morning? (Best guess is fine.)

The phenomenon

Left: a puddle on a sunny sidewalk shrinks and vanishes — no drain, no wind. Right: on a cold day, your warm breath makes a little puff of cloud the moment it hits the cold air.

On a sunny February morning, a puddle of melted snow on the school sidewalk is about the size of a textbook. By noon — no rain, no one sweeping it, no drain nearby — it is gone. Not a drop remains. Meanwhile, every time you breathe out on that same cold morning, a little puff of white mist appears in front of your mouth for a second, then vanishes. Both phenomena involve water going somewhere invisible and then reappearing. Our question: where did the puddle water go, and why does breath make fog?

Notice & Wonder. Write one thing you notice and one thing you wonder. Hold onto your wonder — that's the question we are answering today.

Build it Three big ideas, one small step at a time

Read (or listen to) each step. We build in order — each step is the foundation for the next.

Step 1 — Water changes state when energy is added or removed

Water is made of molecules. When liquid water absorbs enough energy — especially from sunlight — individual molecules near the surface gain enough speed to escape into the air as water vapor, an invisible gas. This process is evaporation. It is a physical change: the molecules are the same water molecules; only their arrangement (and speed) has changed. In a solid (ice), molecules are locked in place. In a liquid (water), they slide. In a gas (water vapor), they fly apart freely.

Step 2 — The water didn't disappear; it moved (conservation of matter)

When the puddle "disappeared," every single water molecule was still there — floating as invisible vapor in the air above the sidewalk. This is the law of conservation of matter: matter is never created from nothing and never destroyed into nothing. It only changes form or moves from place to place. The puddle water is now part of the atmosphere, carried upward by air currents. If you could weigh all the air above the puddle, it would be heavier by exactly the amount the puddle lost.

Step 3 — The sun's energy drives the whole water cycle

The energy that makes water evaporate comes mainly from the sun. Solar radiation heats Earth's surface — land, oceans, lakes, puddles. As the surface warms, water molecules gain energy and evaporate. The vapor rises (warm air is less dense and floats upward), cools as it climbs higher into the atmosphere, and eventually condenses back into tiny liquid droplets — forming clouds. Those droplets can fall as rain or snow. Then the sun heats the surface again. This continuous movement of water — evaporation → rise → condense → precipitate → evaporate again — is the water cycle. The sun is the engine; water is the matter being cycled.

Worked example — tracing the puddle water (watch how an expert reasons)

Before: A puddle sits on a concrete sidewalk. The concrete is being warmed by the sun. The water molecules at the puddle's surface are jiggling faster as they absorb solar energy.
During: The fastest-moving surface molecules break free from the liquid and launch into the air as invisible water vapor. The puddle gets smaller as more and more molecules escape.
After: The sidewalk looks dry. But we can account for every molecule: the same mass of water now exists as vapor mixed into the air. The matter was conserved; the energy came from the sun.
Why does breath fog? Your warm body turns water from food and air into warm, moist exhaled air. When that warm vapor hits the cold winter air, the vapor molecules lose energy rapidly — fast enough to condense back into tiny liquid droplets you can see: a brief visible cloud. Then those droplets evaporate again into the still-cold (but slightly warmer) air around you, and the fog vanishes.

Show the water cycle as a labeled diagram Tier 2 · visual organizer

Draw four boxes connected in a loop with arrows:

Box 1: LIQUID WATER (ocean, puddle, lake) — molecules close together, sliding.

Box 2: EVAPORATION — sun's energy → molecules escape → become gas (water vapor). Arrow goes UP.

Box 3: WATER VAPOR IN AIR — molecules spread apart, invisible. Rises, cools.

Box 4: CONDENSATION / PRECIPITATION — vapor cools enough → droplets form → clouds → rain or snow. Arrow comes DOWN back to Box 1.

Label the energy source (sun) next to the evaporation arrow, and write "matter conserved" across the whole loop.

Your turn Explain where the puddle went

Use a Claim–Evidence–Reasoning model to answer our question. Choose how you respond — all are equally valid.

✍️ Write it 🎨 Draw a labeled water-cycle diagram 🗣️ Record yourself explaining it

The task: Where did the puddle water go? Make a claim, give evidence from the build section, and explain your reasoning using matter conservation and the sun's energy. Then explain the breath-fog using the same model.

I want sentence starters Tier 2 · frames

Claim: The puddle water went into ________ as ________.

Evidence: I know this because the molecules didn't disappear — they ________ when the sun's energy ________.

Reasoning: This shows conservation of matter because ________. The energy came from ________, which drove the change from ________ to ________.

Breath fog: My warm breath contains ________. When it hits cold air, the vapor ________ because ________. The fog disappears again because ________.

Word bank: evaporation · water vapor · condense · gas · liquid · matter conserved · sun · energy · molecules · atmosphere · invisible · escape · surface

Let's make it concrete first Tier 3 · re-teach

Analogy — the invisible crowd: Imagine a crowd of people (water molecules) packed together in a room (a puddle). The sun is like a heater turned up. The fastest, most energetic people near the door escape outside (into the air). The room gets less crowded. But the people didn't disappear — they're just outside now, spread out and invisible in a big open space (the atmosphere). Later, if the outside gets cold, those same people huddle together again (condense) and you can see them as a crowd again (cloud, fog, rain).

Fill in: Water evaporated from the puddle, which means the molecules from the liquid surface into the air. The energy for this came from . The matter was — it didn't disappear, it just changed from to .

Say your answer out loud, then write it. One sentence per blank is enough.

Push my thinking Extension

The water cycle moves enormous amounts of water and energy. Estimate: if a 1-square-meter puddle that is 1 cm deep evaporates in 4 hours on a sunny day, how many grams of water enter the atmosphere from just that puddle? (Hint: 1 cm³ of water = 1 g.) Now think bigger: the Atlantic Ocean covers about 106 million km². If even 0.001 cm of its surface evaporated per day, how many kilograms is that? What does this tell you about how much energy the sun delivers to Earth's surface? Design one testable question about what variables speed up or slow down evaporation.

Check yourself Did it click?

Success criteria — I can:

describe evaporation as water molecules escaping from a liquid surface into the air as vapor;
explain that the water is still there (conserved) — it changed form, not quantity;
identify the sun as the energy source driving evaporation and the water cycle.

A classmate says: "The puddle water was used up by the sun — it doesn't exist anymore." What would you say to correct this idea?

Re-teach: water is never destroyed when it evaporates Tier 3

Evaporation is a physical change, not a chemical one. The water molecules are not broken apart or turned into something else. They gain enough energy from the sun to break free of the attractions holding them together as a liquid, and they escape into the air as invisible gas. The same H₂O molecules that were in the puddle are now floating in the air above the sidewalk. If you could cool that air suddenly (like cold glass does), those same molecules would condense back into liquid water droplets you could collect and weigh — and you would get back the same mass that left the puddle. Matter was conserved the whole time. Re-read option B and notice how it says "changed from liquid to gas" — that's the key phrase.

Reflect, then show what you know

Reflection metacognition + SEL

Which idea surprised you most — that the puddle water is still out there in the air, or that breath fog is just condensation? What connection can you make between what we learned today and something you've seen outside your classroom or home?

Exit ticket — answer on paper or in your notebook.

New In your own words, what is evaporation? Include the words molecules, energy, and gas.
New Why does the puddle vanish faster on a hot, sunny day than on a cold, cloudy day? Use the idea of energy to explain.
Spiral — Unit 1 Unit 1 taught us that matter is conserved when a popsicle melts. How is the puddle evaporating the same idea? How is it different?
Spiral — Unit 1 What state of matter is water vapor? How do we know the molecules are still there if we can't see them?
Transfer → Week 2 You've seen dew on the grass early in the morning — tiny droplets that weren't there the night before. Where did they come from, and what do you predict had to happen for liquid water to appear on the grass overnight?

Educator panel — facilitation, accommodations, answer key

At a glance

Standard: NGSS MS-ESS2-4 — develop a model to describe the cycling of water through Earth's systems driven by energy from the sun and the force of gravity. 3D: SEP Developing & Using Models · DCI ESS2.C Roles of Water · CCC Energy & Matter. Throughline: launches Unit 3's anchor storm by establishing that water moves through Earth's systems as matter (conserved) driven by energy (sun). Spirals Unit 1's conservation of matter and states of matter. Transfer item previews Week 2's condensation.

Materials (optional): no lab required; the SVG and text carry the phenomena. Optional demo: put a small amount of water on a dark paper and watch it evaporate; breathe onto a cold window.

Facilitation arc (Rosenshine)

Do-Now retrieval while taking attendance — activates Unit 1 conservation model (3 min).
Phenomenon: display the SVG; cold-call students for notice/wonder (3 min).
Build Steps 1–3: read or listen together; stop after each for a "turn and talk — what did we just learn?" (12 min).
Worked example: walk through it aloud; ask "where is the energy coming from at each arrow?" (5 min).
Differentiated CER practice — circulate and note which tier supports students reach for (15 min).
Self-check + re-teach branch for A/C responders (5 min).
Brain break, reflection, exit ticket (7 min).

IEP / 504 accommodation cards

Common accommodations mapped to this lesson

Accommodation	How it's already built in / what to do
Text read aloud	Every passage and the phenomenon have a Listen button (TTS); simplified toggle shortens all text.
Reduced reading load	"Reading: Simplified" replaces all passages with plain-language versions.
Chunking / extended time	Three short build steps; progress saves automatically to localStorage.
Sentence frames / word bank	Tier-2 panel provides CER frames and a 13-word bank.
Concrete analogy / reduced load	Tier-3 "invisible crowd" analogy with cloze fill-in.
Alternative response mode	Write, draw a labeled water-cycle diagram, or record an oral explanation — all accepted.
Behavior / focus (504, ADHD)	Named expectations (PBIS), 30-sec check-in, built-in brain break with evaporative-cooling demo.
Multilingual / EL	Simplified text, SVG with labeled diagram, word bank, home-language reflection allowed.

Exit ticket answer key

Evaporation is the process by which liquid water molecules gain enough energy (from the sun or other heat sources) to escape the liquid surface and enter the air as an invisible gas (water vapor).
On a hot, sunny day the sun delivers more energy to the puddle surface, so more molecules gain enough speed to escape per minute. On a cold, cloudy day less energy reaches the surface, so evaporation is slower.
Same idea: matter (water molecules) is conserved — molecules don't disappear in either case. Different: melting is solid → liquid; evaporation is liquid → gas. Both require energy input, but the amount differs (vaporization requires more energy per gram than melting).
Water vapor is a gas. We know the molecules are still there because if you cool the air (e.g., onto a cold window), the vapor condenses back into visible liquid water droplets — the same matter reappears.
(Transfer preview) Dew forms when water vapor already in the air cools down overnight, loses energy, and condenses into liquid droplets on cold surfaces like grass or car hoods. The vapor was already in the atmosphere from earlier evaporation — it didn't come from nowhere. Cooling causes condensation. (This sets up Week 2 perfectly.)

Why it's designed this way

The Do-Now explicitly retrieves Unit 1's conservation and states-of-matter model (spacing + interleaving, Roediger & Karpicke, 2006; Rohrer, 2012) so that connecting the water cycle to prior knowledge is the first cognitive act of the lesson. The "invisible crowd" Tier-3 analogy makes the abstract particle model concrete (Sweller, 1988; van Merriënboer & Sweller, 2005). The self-check's wrong options mirror the two most documented evaporation misconceptions: (A) that water is chemically changed/destroyed by the sun, and (C) that wind, not evaporation, is responsible for disappearance — both consistent with research on middle-school Earth-science misconceptions (Henriques, 2002). The exit ticket's transfer item (dew) provides data for Week 2's opening: students' own predictions become the class's opening evidence base for condensation.