الأسبوع 11 · المحور الثاني «المادة والطاقة»، الوحدة الثانية «حركة الجسيمات»، المفهوم 2.2 «وصف المادة وطرق قياسها» (ب) والمفهوم 2.3 «مقارنة تغيرات المادة» (أ): الخصائص المفيدة وبداية التغيرات · 3 دروس
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What happens to melting ice?
Discovery Education Science P5: Term 1, Unit 2, pp. 173–177
GoalDescribe what happens as ice melts, tell solids, liquids and gases apart by their properties, and ask open-ended questions.
New words
melt · to change from a solid to a liquid when warmedcontainer · something that holds a liquid or a gas, such as a cup or a balloonopen-ended question · a question that has many possible answers, not just yes or no
Explanation
Hana’s family has a picnic by the Nile. They put juice cartons in a metal bowl full of ice. An hour later the cartons float in water. What happened? Warmth from the air and from the juice moved into the ice, and the ice melted. Ice is a solid: it keeps its own shape and size. Water is a liquid: it flows and takes the shape of its container, but the amount of water stays the same. A gas, such as the air in a balloon, spreads out to fill the whole container. So matter can change from one state to another. A big question comes next: when ice melts, does the amount of matter change? To find out, scientists ask good questions. A yes-or-no question has one short answer. An open-ended question, such as “What changes as the ice melts?”, has many answers and makes us look closely.
State
Shape
Space it takes up
solid
keeps its own shape
a fixed amount
liquid
takes the shape of its container
a fixed amount
gas
spreads to fill the container
fills all the space it can
Worked examples
In the picnic story, warmth from the air moves into the ice. The ice melts and becomes water. It is the same water, now in a different state.
Sorting by properties: a brick, a key and ice keep their shape, so they are solids. Milk and juice flow and take the shape of the cup, so they are liquids. The air inside a balloon fills the whole balloon, so it is a gas.
Kind of question
Example
yes or no
Is ice cold?
open-ended
What happens to ice on a warm plate?
Two questions about the same ice cube. “Did the ice melt?” can only be answered yes or no. “How does the ice change as it gets warmer?” is open-ended, because there are many things to describe.
Class activity
Melting watch (a grown-up helps). Put one ice cube on a saucer in the shade and an identical ice cube on a saucer in a warm, sunny place. Do not look at the Sun. Look every 5 minutes and write how long each takes to melt. Then write three open-ended questions about melting ice.
Practice
1
Juice is poured from a tall, thin glass into a wide bowl. What changes and what stays the same?
The shape of the juice changes, because it takes the shape of its container. The amount of juice stays the same.
2
Which picture shows something filled with a gas? Say the letter.
C: the air inside the football fills it completely.
3
Turn this yes-or-no question into an open-ended one: “Did the ice melt?”
For example: What happens to the ice as it gets warmer?
4
Why does an ice cube keep its shape on a plate, but water does not?
Ice is a solid and keeps its own shape. Water is a liquid and takes the shape of what holds it.
