Planning for Effective Teaching: Condensation

The mains aims of this activity are:

To introduce the concept of water condensation (steam turns into water as it cools).

DEVELOPMENT OF THE ACTIVITY

1. We are going to use questions to help the children remember what they know about evaporation (heat turns liquid water into steam, in cold weather waterturns into snow/ice).

2. Tell the story of Masha and the Witch. Use the pictures for catch their attention:

Once upon a time, a young girl called Masha went mushroom picking in the forest. The sun shone brightly. lt was very hot, as it so often is in the summer. lt wasn't at all like cold frosty winter when your breath comes out in mists. Masha spent such a long time picking mushrooms that she grew very thirsty. However, there was no water nearby. Masha was so thirsty that she began to long for the icy winter when there is plenty of snow everywhere. lf she wanted a drink in the winter she could...what could she do? Yes, she could melt some snow in her hands or her mouth, and turn it into water to satisfy her thirst. But it was the middle of summer and there was no snow. Masha searched for a stream - in those days you could usually a find a stream of clean water to drink from in the forest. But today, she could not find a stream anywhere. Suddenly, out of nowhere she saw a hut in a little clearing in the forest. The door of the hut was open, but Masha was a poliie child, so she knocked before she went in. lt was a witch's hut.
Masha realised this as soon as she saw the witch! But Masha was very brave and she did not let that frighten her. "Good afternoon," she said to the Witch.
"Good afternoon, Masha", the Witch replied. "Why have you come?"
"l'm so thirsty," said Masha. "Won't you please give me a glass of water?"
The Witch was very crafty. She decided to test Masha. ln the middle of the hut there stood a huge stove with a huge cauldron full of water on it. The Witch lit a hot fire. Soon the water in the cauldron was bubbling, hissing and boiling fiercely. Hot white steam rose up into the air. (Boil the kettle; let the children watch steam rising).
The Witch looked at Masha slyly. "So you want a drink of water do you?" she said.
"Well I know a beautiful little stream of cool clear water, and I will show you where it is. But first you must solve my puzzle. And if you can't you must stay here forever and pick mushrooms for me! The puzzle is - drink a glass of water from my hissing cauldron!" Masha looked at the cauldron with the clouds of steam rising from it. The water was far too hot! Masha knew that if she tried to drink that water her tongue would blister and burn. But she was so thirsty. And she did not want to stay with the Witch forever, picking mushrooms! Masha thought carefully and then she....do you know what she did? (Ask for ideas!!!).
"lf the water is too hot, and I need to drink some, then I must cool it down!" thought Masha. Now Masha always kept a little mirror in her bag. Masha touched the mirror. lt was just as she thought. The mirror's surface was cold. (Let the children touch the cool surface of a mirror.)
"That's it!" thought Masha. "l can't drink the boiling water. And if I try to put some in a glass I will scald my hands. However, steam turns into water when it cools! And I can cool the steam, if I am very careful. All I have to do is hold my mirror up to the steam. When the steam touches my cold mirror, it will turn back into water. Then I can collect the water in the Witch's glass."
And that is what Masha did. Working very carefully - for after all she did not want the boiling water or the hot steam to scald her - Masha held her cold mirror up to the steam. As the steam touched her mirror it turned into drops of water. The drops of water ran down the mirror, and Masha collected them in the Witch's glass (Use steam from the kettle, a cold mirror, and a glass to
demonstrate how Masha condensed water from steam and collected the water drops in a glass).
The Witch was shocked, but she had to keep her promise. "You are a clever girl, Masha," she said. "You have outwitted me! Now I will show you the stream".
The Witch showed Masha a beautiful little stream of cool clear water, and Masha drank her fill. Then the Witch gave Masha some berries and extra mushrooms to put in her bag.
What a good thing it was that Masha had a cold mirror in her bag. And what a good thing it was that she knew how to use it to turn steam into water. And if ever you should meet a sly Witch who asks difficult puzzles, I do hope that you will remember too."

TIPS TO TELL THE STORY

When the witch shows Masha the cauldron of boiling water, show the children steam coming from a kettle of boiling water; remind them that steam is very hot and will scald if they touch it.