Earth and space (grade 6) · lesson

The water cycle

💡 Powered by the sun, water evaporates, condenses into clouds, falls as precipitation, and flows back again.

The sun heats water in oceans, lakes, and even wet towels. The water evaporates and becomes water vapor, a gas in the air.

As the vapor rises, it cools and condenses into tiny droplets that form clouds. Vapor also condenses on cold things, like the outside of an icy glass.

Droplets join and fall as precipitation: rain, snow, sleet, or hail. The water flows through rivers back to the ocean, and the cycle goes on.

🧠 Let's work it out

Water is never used up. It just changes form.
If water seems to disappear, ask where it went as a gas.
If water seems to appear, ask what gas cooled and condensed.

What do you think comes next?

evaporate: change from a liquid into a gas
condense: change from a gas into a liquid
precipitation: water falling from clouds as rain, snow, sleet, or hail

🔗 Khan Academy: Weather and climate · Khan Academy ↗

Air masses and weather

💡 When air masses meet, warm air is pushed up and cools, and clouds and rain often form.

An air mass is a huge body of air with about the same temperature and moisture all through it.

Cold air is denser than warm air. When a cold air mass moves in, it slides under the warm air and pushes it up.

Rising air cools, and its water vapor condenses into clouds and rain. That is why falling air pressure, building clouds, and moist air often mean rain is coming.

🧠 Let's work it out

Predict weather from clues.
Falling pressure plus more moisture plus building clouds all point the same way: rain or storms.
Rising pressure and dry air point to clear skies.

What do you think comes next?

air mass: a large body of air with similar temperature and moisture
dense: packed with more matter in the same space

🔗 NOAA JetStream: Air masses · NOAA ↗

The sun heats Earth unevenly

💡 Uneven heating by the sun, at different angles and on land versus water, drives winds and ocean currents.

Near the equator, sunlight hits the ground straight on. Near the poles, it hits at a slant. Slanted light spreads over more ground, so it heats each spot less.

Land heats up and cools down faster than water.

Warm air rises and cooler air moves in to take its place. That moving air is wind. On a sunny day, the land warms first. Warm air rises over the land, and cool air blows in from the sea.

🧠 Let's work it out

Use a flashlight as a model.
Pointed straight down, the spot is small and bright.
Tilted, the same light covers a bigger, dimmer spot.
The poles are like the tilted beam.

What do you think comes next?

equator: the imaginary line around the middle of Earth

Weather and climate

💡 Weather is what the air is doing now, while climate is the usual pattern over many years, shaped by oceans and mountains.

Weather is what happens over hours or days: rain now, wind tomorrow. Climate is the usual pattern over many years, like hot, dry summers.

Oceans warm and cool slowly. So a city on the coast has milder winters than a city far inland at the same distance from the equator.

Mountains matter too. Moist air rises up a mountain, cools, and drops its rain on that side. By the time the air crosses, it is dry.

🧠 Let's work it out

Check the time span.
'It started raining ten minutes ago' is weather.
'We get about 40 cm of snow each winter, on average' is climate.
Words like usually and on average point to climate.

What do you think comes next?

weather: the condition of the air at a certain time and place
climate: the usual weather pattern of a place over many years