Lesson Notes By Weeks and Term v5 - Grade 4

Lesson Video

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Performance objectives

• Identify different methods of processing materials.
• Explain how processing changes a material's properties.
• Give examples of simple products made in South Africa.
• Describe safety precautions for processing.
• Distinguish between raw materials and processed products.

Lesson summary

Introduction: Welcome, Grade 4 learners! This week, we are diving into the fascinating world of processing! Processing is all about how we change materials into useful things we use every day. Think about the bread you eat – it starts as wheat growing in a field. How does it become a soft, delicious loaf? That's processing! Or think about the clothes you wear – cotton plants become t-shirts. We'll be learning about the different ways we process materials, from simple tasks like sorting and washing to more complex changes like mixing and shaping. Understanding processing helps us appreciate where things come from and the work that goes into making them.

Lesson notes

What is Processing? Processing is the act of changing raw materials into different forms to make them more useful. A raw material is a basic substance in its natural, unmodified form, like raw wool from a sheep, wood from a tree, or iron ore from the ground. A processed product is the result of changing that raw material, like a wool sweater, a wooden table, or a steel pot. Processing can involve many different steps, and the type of processing depends on the material and what we want to make.

Some common processing methods include: Sorting: Separating materials based on their properties (size, shape, colour, etc.). Imagine sorting different coloured beads for a necklace.

Cleaning/Washing: Removing dirt and impurities. Think about washing vegetables before cooking them.

Cutting/Chopping: Reducing the size of materials. Chopping wood for a fire is an example.

Mixing: Combining different materials together. Like mixing flour, sugar, and eggs to make cake batter.

Heating/Cooling: Changing the temperature of a material. Baking bread involves heating dough. Freezing water makes ice.

Shaping/Moulding: Changing the form of a material. A potter shapes clay on a wheel.

Drying: Removing moisture from a material. Drying maize kernels after harvesting helps preserve them.

How Processing Changes Properties: When we process a material, we often change its properties, such as its: Texture: How it feels (rough, smooth, soft, hard). Think about the difference between raw cotton (fluffy) and a cotton shirt (smooth).

Shape: Its physical form. A tree trunk (round) becomes a wooden plank (flat).

Size: How big or small it is. We chop large logs into smaller pieces for firewood.

Colour: Sometimes the colour changes during processing, especially when heating or adding other materials.

Taste/Smell: Processing can change the taste and smell of foods. Baking a cake changes the smell and taste of the ingredients.

Examples of Processing in South Africa: Here are a few examples of processing materials into simple products in South Africa: Maize to Maize Meal: Maize (a raw material) is harvested, dried, and then ground into maize meal. Maize meal is used to make pap, a staple food in South Africa. The processing involves drying and grinding.

Grapes to Raisins: Grapes (a raw material) are dried in the sun to become raisins (a processed product). This process preserves the grapes and changes their texture and sweetness.

Clay to Bricks: Clay (a raw material) is dug from the ground, shaped into brick moulds, dried in the sun, and then fired in a kiln (a type of oven). This process hardens the clay and creates bricks for building houses.

Sugar Cane to Sugar: Sugar cane (a raw material) is harvested and crushed to extract the juice. The juice is then boiled and processed to crystallize into sugar (a processed product).

Safety Precautions: It's important to be safe when processing materials!

Here are some examples: When cutting or chopping materials, always use sharp tools carefully and under supervision. When working with heat, be careful not to burn yourself. Use gloves and tongs. When grinding or crushing materials, wear a mask to avoid breathing in dust.

Worked example

Example 1: Imagine you want to make orange juice. The raw material is oranges. What processing steps do you need to take to get orange juice?

Solution: First, you need to wash the oranges to remove any dirt. Then you cut the oranges in half. Finally, you squeeze the juice out of the oranges. The result is orange juice, a processed product.

Example 2: How is wool processed to make a knitted scarf?

Solution: First, the raw wool is obtained by shearing sheep. The wool is then cleaned to remove dirt and debris. Next, it is spun into yarn. The yarn is then knitted to create the scarf.

Example 3: You have a pile of mixed recyclable materials (paper, plastic, glass). What processing step is necessary before any of the materials can be recycled?

Solution: The first step is sorting the materials. The paper, plastic, and glass need to be separated into different piles so they can be processed appropriately.

Guided Practice (With Solutions)

Question 1: Name two raw materials and the processed products that can be made from them.