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Weather

Grade: 

2nd Grade

Subject: 

Science

Lesson: 

1

Objective: 

Define water vapor.

Describe evaporation.

Describe condensation.

Materials: 

Three clear plastic cups with a mark " from the bottom

Pitcher of water

Jar with a lid, ice cubes, a tissue

Instruction/Exercise: 

Procedure

Tell the children that you are going to read a poem which will tell the name of their first science unit for the year. Read the following:

Whether the weather be fine,

Or whether the weather be not,

Whether the weather be cold,

Or whether the weather be hot,

We'll weather the weather

Whatever the weather

Whether we like it or not.

Ask: What is the name of the unit? Ask: Have you seen a puddle disappear or dry up after it rains? Where does the water go? Does all the water soak into the ground? (The water escapes into the air in small droplets that we call water vapor. These drops are too tiny to see as they go into the air.) Today's activity will help you see what happens to the water from the puddle.

Ask three children to come to the front of the room to help you. Give each of the children a clear plastic cup that has a mark " from the bottom of the cup. Now ask each child to pour water into his cup so that it just reaches the line. Ask one child to place his cup in a very warm, sunny location. The second child is to place his cup in a cool, shady location. The third child is to place his cup in a location with a draft. After several hours note what has happened to the water in the cups. The children should see that the water level has gone down more in the cups placed in the warm, sunny location and in the location with the draft than in the shady location. Tell the children that the water has slowly disappeared into the air. It could not possibly soak into the soil in this situation. The way water escapes into the air is called evaporation. The air is full of invisible water vapor because water evaporates from rivers and seas all the time. Ask: What is water vapor? (Tiny drops of water that escape into the air are water vapor.) Ask: What is the process of evaporation and how does it happen? (Evaporation is the process of water escaping

into the air. It happens at all times, but it happens much more quickly when the air is warm and it is windy. Evaporation occurs when water vapor is heated.) Ask: What happens to the water that is in clothing that has been washed and hung on the line to dry? (It evaporates.)

Ask : What happens when you take a can of soda out of the refrigerator and hold the can for a little time? (The outside of the can gets wet.) Tell the children that this is condensation at work. It is the way we get water back into our world. You will show them another example of condensation similar to the one of the soda can. Fill a jar with ice cubes and put a lid on it. The jar is being made very cold. Ask: Does anything happen to the outside of the jar? (Water forms on the jar.) Have a child come up and wipe the jar with a tissue and note that the tissue is wet. Water droplets form on the jar because the air near the jar is cooled by the ice-cold jar. When water vapor in the air cools, the drops get big enough to see. This is called condensation. Condensation can be seen in another way. When water boils, steam is given off. The tiny drops of steam form a mist. The boiling water gives off a hot vapor. This vapor cools as it meets colder air and turns into drops you see as steam. Ask: What is the process of condensation and how does it happen? (Condensation is the process of water returning to the air. It happens all the time. Condensation occurs when water vapor meets cooler air.)

Tell the children that clouds are made up of condensation drops that form when water vapor rises from the ground and meets the cold air above. When tiny drops in the clouds come together and get heavier, they fall as rain.