Grade 2 Science Week 16 | Student Textbook

Grade 2 | SCIENCE

WEEK 16 • STUDENT TEXTBOOK • DAYS 76–80

Read each lesson with a parent or teacher and study the worked example. Then answer the questions for that day in the Week 16 Practice Workbook.

Week 16 Student Textbook | Week 16 Practice Workbook | Week 16 Teacher Guide | Week 15 Student Textbook | Grade 2 index

Day 76: Heating Changes Matter: Melting

Heating can change matter. When some solids get warm enough, they melt and become liquids. Ice melts into water, and butter softens and melts in a warm pan.

Different materials need different amounts of heat to change. Some materials do not change at all when they are only a little warm. An adult must always do any heating with a stove, oven or microwave.

Worked example: A snowman melts on a sunny day. What made it change?

The sun warmed the snow.
Heat made the solid snow melt.

Worked answer: Heat from the sun.

Day 77: Cooling Changes Matter: Freezing

Cooling can change matter too. When water or juice gets cold enough, it freezes and becomes a solid. A freezer is cold enough to freeze water.

Scientists record what a material is like before a change, after it, and after they try to change it back. These observations are evidence.

Worked example: A puddle has turned to ice on a cold morning. What made it change?

The air was very cold.
Cold made the liquid water freeze.

Worked answer: Cold air froze the water.

Day 78: Changes That Can Be Undone and Changes That Cannot

Some changes can be undone. After the change, the material can be warmed or cooled back to what it was like before. Other changes cannot be undone. The material stays different, even after it cools or warms again.

Scientists do not guess which kind of change it is. They compare observations: what the material was like before, right after the change, and after they tried to change it back. Then they decide from the evidence.

Worked example: A wax candle stub is warmed by an adult until it is soft. When it cools, it is hard wax again. Can this change be undone?

Before: hard wax. After warming: soft wax.
After cooling: hard wax again, like before.

Worked answer: Yes, because the wax went back to how it was before.

Day 79: Evidence Test: Chocolate and Dough

Today you will gather evidence. You will watch two materials being heated and then cooled, and you will record what you see before, during and after.

Use only your observations to decide which change can be undone. If the material goes back to a state like the one it started in, the change can be undone. If it stays different after cooling, it cannot.

Worked example: Why must an adult do all the heating in this test?

A stove, oven, hot water and melted food can burn skin.
An adult can handle hot things safely.

Worked answer: Because heating can cause burns, and an adult can do it safely.

Day 80: Independent Check: Heating and Cooling

Today you will answer on your own.

Use what you learned this week: heating and cooling change matter, and evidence tells whether a change can be undone.

Worked example: Ice is left in a warm room. What happens to it?

Heat from the room warms the ice.
Warm ice melts.

Worked answer: It melts into liquid water.