Lesson Notes By Weeks and Term v5 - Grade 5

Lesson Video

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Performance objectives

• Define 'mixture' and 'solution' with examples.
• Tell the difference between different types of mixtures.
• Identify the solute and solvent in a solution.
• Describe how to separate mixtures using filtering and sieving.
• Predict what happens when materials are mixed.

Lesson summary

This week, we delve deeper into the world of matter and materials by focusing on solutions and mixtures. Understanding solutions and mixtures is crucial because we encounter them every day, from the air we breathe to the food we eat. In South Africa, understanding these concepts helps us understand how to make safe drinking water, how our food is prepared, and even how some traditional medicines are made. Think about making Mageu (a traditional maize-based drink) or Rooibos tea – these involve mixing different things together! By understanding how matter behaves when mixed, we can make better choices and solve problems in our daily lives.

Lesson notes

What is Matter? Remember, matter is anything that takes up space and has mass. This includes everything around us - your desk, your pencil, the air, and even you! What is a Mixture? A mixture is a combination of two or more substances that are physically combined, but not chemically bonded. This means that each substance in the mixture keeps its own properties.

Imagine mixing sand and pebbles: the sand is still sand, and the pebbles are still pebbles. You can see them separately.

Heterogeneous Mixtures: These are mixtures where you can see the different parts.

Examples include: A salad with lettuce, tomatoes, and cucumbers. Concrete, which is made of cement, sand, and stones. Soil, which contains rocks, sand, and organic matter.

Homogeneous Mixtures: These are mixtures where you cannot easily see the different parts. They appear uniform throughout. Solutions are a special type of homogeneous mixture. What is a Solution? A solution is a special type of homogeneous mixture where one substance (the solute) dissolves completely into another substance (the solvent). This means the solute spreads evenly throughout the solvent and becomes invisible to the naked eye.

Solute: The substance that dissolves (e.g., sugar in water). Usually present in a smaller amount.

Solvent: The substance that does the dissolving (e.g., water dissolving sugar). Usually present in a larger amount.

Examples of Solutions: Sugar water: Sugar (solute) dissolves in water (solvent).

Salt water: Salt (solute) dissolves in water (solvent).

Air: A mixture of gases like nitrogen, oxygen, and carbon dioxide, where nitrogen acts as the solvent as it is the most abundant.

Rooibos tea: Substances from the Rooibos leaves (solute) dissolve in hot water (solvent).

Important Differences: In a mixture, you can often see the different parts or separate them easily. In a solution, the solute is dissolved completely and evenly distributed, making it hard to see or separate.

Separating Mixtures: We can use different methods to separate mixtures based on their properties.

Two common methods are: Filtering: This is used to separate solids from liquids. A filter (like a coffee filter or a cloth) has tiny holes that allow the liquid to pass through, but traps the solid particles.

Example:* Separating sand from water.

Sieving: This is used to separate solids of different sizes. A sieve has holes of a specific size that allow smaller particles to pass through, while larger particles are retained.

Example:* Separating small stones from sand using a sieve.

Worked example

Example 1: Kool-Aid

Scenario: You mix Kool-Aid powder (a flavored drink mix) with water. Is this a mixture or a solution?

Explanation: When you stir the Kool-Aid powder into the water, the powder dissolves and spreads evenly. You can no longer see the individual Kool-Aid particles. This is a solution.

What is the solute? The Kool-Aid powder.

What is the solvent? The water.

Example 2: Maize meal porridge (Pap)

Scenario: Making pap, you stir maize meal into boiling water.

Explanation: Although the mixture thickens, you can still see the individual grains of maize meal suspended in the water. It's not completely dissolved.

Therefore, this is a mixture, specifically a heterogeneous mixture. The meal isn't dissolved evenly.

Example 3: Separating a Mixture

Scenario: You have a mixture of small rocks and sand.

Explanation: To separate these, you would use a sieve. The sand particles are smaller than the rocks, so the sand will pass through the sieve while the rocks remain behind.

Guided Practice (With Solutions)

Question 1:

Is a bowl of chicken noodle soup a mixture or a solution? Explain your answer.

Solution: