الأسبوع 30 · مراجعة الفصل الدراسي الثاني: دورة الماء والطقس والتكيف والوراثة والتربة وحماية البيئة · 3 دروس
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Review: the water cycle, wind and weather
Science P6: Term 2, Units 3–4
GoalReview the water cycle, wind and weather tools with new mixed tasks.
New words
water cycle · the movement of water between the sea, air and landconvection · heat carried by moving liquids or gasesmeteorologist · a scientist who studies and predicts the weather
Explanation
The Sun’s energy and gravity drive the water cycle. Water evaporates from oceans, lakes, soil and leaves and becomes invisible water vapour. High in the air the vapour cools and condenses into tiny droplets that form clouds, which are droplets, not steam. Precipitation brings the water back as rain, snow or hail. Some water collects in rivers and the sea and some runs off the land. Uneven heating also makes wind: warm air rises and cooler air flows in, as in a sea breeze. Mountains can make a rain shadow, with rain on one side and dry air on the other. Forecasters use a thermometer, an anemometer, a barometer, a rain gauge, radar and satellites, and they remember that forecasts are less certain for later days. Extreme weather includes floods, droughts and sandstorms.
sun heats water→evaporation: vapour rises→condensation: clouds form→precipitation: rain or snow→collection and runoff
Worked examples
Put these in order: rain falls, vapour rises, water runs to the sea, clouds form. The order is vapour rises, clouds form, rain falls, water runs to the sea.
land warms faster→air above land rises→cool sea air flows in
Why does a sea breeze blow by day? The land warms faster than the sea. Air above the land rises and cooler sea air flows in to replace it.
A town lies behind a mountain and gets little rain. Wet air rose on the other side, cooled and rained there, then came down dry. This is a rain shadow.
Class activity
Water cycle story. With a grown-up, draw five comic panels telling the journey of one drop of water from the sea to a cloud, to the ground and back. Use the words evaporation, condensation, precipitation and runoff. Add one panel about what a meteorologist measures.
Practice
1
Which tool measures air pressure?
The barometer.
2
A puddle disappears on a sunny day. Where did most of the water go?
It evaporated into the air as water vapour.
3
Why are clouds not made of steam?
Clouds are tiny droplets of liquid water; steam is vapour.
