Grade 4 - Melting and freezing

Chapter 4:

States of Matter: Melting and Freezing

Mr. Najib

Sekolah Lentera Kasih Makassar

Introduction

Review time

Hello everyone! Today, we're going to review our topic about permanent and temporary changes that materials can undergo when they gain or lose heat.

1. Each MCQs question has 1 mark.

2. Each Short Answer Question has 2 marks.

3. MCQs (30 s)

4. Short Answer (3 minutes)

MCQ & Short Answer Questions

• Your participation will be based on your active participation in our activities.

• Your score on this lesson will be taken as your classwork score.

In the middle of the presentation there will be:

Heat and Temperature

What is heat?

Heat is a type of energy that can be transferred between materials. When a material gains heat, its temperature increases. When it loses heat, its temperature decreases.

Multiple Choice

What is heat?

• A type of coldness

• A type of energy

• A type of light

Multiple Choice

What happens when you take away heat from an object?

• It gets hotter

• It gets cooler

• It stays the same

Open Ended

Explain the difference between heat and temperature.

Open Ended

Give an example of how you can use heat to make something warmer and how you can use heat to make something cooler.

Some changes that happen to materials are permanent. That means that once they happen, they can't be undone. For example, when a piece of paper is burned, it turns into ash, which cannot be turned back into paper.

Permanent Changes

Multiple Choice

What is a permanent change in materials?

• A change that can be undone

• A change that occurs naturally

• A change that cannot be undone

Multiple Choice

Which of the following is an example of a permanent change in materials?

• Melting an ice cube

• Dissolving sugar in water

• Burning a piece of wood

Multiple Choice

Why are permanent changes irreversible?

• The molecular structure of the material is not altered

• The material is exposed to extreme heat

• The molecular structure of the material is altered in a way that cannot be reversed

Other changes are temporary. That means that the material can change back to its original state. For example, when ice melts into water, it's a temporary change because you can freeze the water back into ice.

Temporary Changes

Multiple Choice

What is a temporary change in materials?

• A change that can be undone

• A change that cannot be undone

• A change that occurs naturally

Multiple Choice

Which of the following is an example of a temporary change in materials?

• Burning a piece of wood

• Bending a paper clip

• Rusting iron or metal

Open Ended

How does a temporary change in materials differ from a permanent change?

Melting point

Every material has a melting point. The melting point is the temperature at which a material changes from a solid to a liquid. When a material gains heat and its temperature increases above its melting point, it will melt. For example, the melting point of ice is 0 degrees Celsius. When you add heat to ice, its temperature will rise. When the temperature reaches 0 degrees Celsius, the ice will start to melt and become liquid water.

Let's look at an example. When you put an ice cube on a table, it will eventually start to melt. The ice cube is gaining heat from the table, and its temperature is increasing. Once its temperature reaches its melting point, it will melt into water.

Multiple Choice

What is the melting point of ice?

• 0 degrees Celsius

• 10 degrees Celsius

• 20 degrees Celsius

Multiple Choice

What happens to a material when it reaches its melting point?

• It turns from a liquid to a solid

• It turns from a solid to a liquid

• It turns from a gas to a liquid

Open Ended

What is the melting point, and how does it help us understand how materials can change from a solid to a liquid?

Open Ended

Give an example of a material that you can heat to make it melt and explain what happens to it when it reaches its melting point.

Freezing Point

What is freezing point?

Every material also has a freezing point. The freezing point is the temperature at which a material changes from a liquid to a solid. When a material loses heat and its temperature decreases below its freezing point, it will freeze.

Let's look at an example of freezing. When you put water in a freezer, it will eventually turn into ice. The water is losing heat to the freezer, and its temperature is decreasing. Once its temperature reaches its freezing point, it will freeze into ice.

Multiple Choice

What is the freezing point of a material?

• The temperature at which it changes from a solid to a liquid

• The temperature at which it changes from a liquid to a gas

• The temperature at which it changes from a liquid to a solid

Multiple Choice

What happens to a material when it loses heat and its temperature decreases below its freezing point?

• It turns into a gas

• It turns into a liquid

• It freezes into a solid

Open Ended

Describe the process of water freezing in a freezer. What happens to the temperature of the water during this process, and how does this relate to the concept of the freezing point?

Open Ended

How is the process of water freezing similar to the process of ice melting, and how are they different?

Open Ended

Give an example of a situation where you might see water freezing in your daily life.

Recap

So just to recap, materials can undergo permanent and temporary changes when they gain or lose heat. Every material has a melting point and a freezing point, which are the temperatures at which they change from a solid to a liquid or from a liquid to a solid.

Mr. Najib

I hope you enjoyed learning about permanent and temporary changes and how they relate to heat and temperature. Keep exploring the world around you and discovering new things about materials!