Lesson Notes By Weeks and Term v5 - Grade 4

Lesson Video

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Performance objectives

• Identify materials that change when heated or cooled.
• Describe changes like melting, freezing, and boiling.
• Explain how heating and cooling change the state of matter.
• Compare how different materials react to heat and cold.
• Predict how a material might change.

Lesson summary

This week, we'll explore how some materials change when we heat or cool them. Think about melting ice cream on a hot day, or how your mom cooks pap – the maize meal changes when it's heated with water! Understanding these changes is important because it helps us understand how the world around us works, from cooking food to building houses. In South Africa, where temperatures can vary drastically, knowing how materials behave under different conditions is very important for everyday life, such as keeping our food fresh or knowing which building materials are best for our climate. This knowledge helps us design and build things that are safe and useful.

Lesson notes

Matter: Matter is anything that takes up space and has mass. Everything around us is made of matter!

Materials: Materials are the different types of matter used to make things. Examples include wood, plastic, metal, and water.

Properties: Properties describe what a material is like.

Examples include: Hardness: How easily a material can be scratched. A diamond is very hard!

Flexibility: How easily a material can bend without breaking. A rubber band is very flexible.

Texture: How a material feels to the touch (smooth, rough, bumpy).

State: Whether a material is a solid, liquid, or gas.

Changes of State: Heating or cooling a material can cause it to change its state: Melting: When a solid changes to a liquid. This happens when you heat ice to make water.

Freezing: When a liquid changes to a solid. This happens when you cool water to make ice.

Boiling/Evaporation: When a liquid changes to a gas. This happens when you heat water to make steam. The evaporation of water from a puddle on a warm day is also an example, even without boiling.

Condensation: When a gas changes to a liquid. This happens when steam touches a cold window and turns into water droplets.

Heating: Adding energy (usually in the form of heat) to a material.

Cooling: Removing energy (heat) from a material.

Worked example

Example 1: Melting Chocolate

Imagine you leave a chocolate bar in the sun on a hot South African summer day. What happens?

Material: Chocolate

Process: Heating (from the sun)

Change: The solid chocolate melts and turns into liquid chocolate.

Explanation: The heat from the sun gives the chocolate molecules more energy, causing them to move faster and break free from their solid structure, transforming into a liquid.

Example 2: Freezing Water to Make Ice

You put a jug of water into the freezer. What happens?

Material: Water

Process: Cooling (by the freezer)

Change: The liquid water freezes and turns into solid ice.

Explanation: Removing heat from the water slows down the water molecules. They lose energy, move closer together, and form a solid structure: ice.