Welcome to Week 5 of Year 7 Chemistry! This week, we’ll explore the exciting world of chemical reactions. You’ll learn how to recognize when a reaction is happening, understand energy changes in reactions, and even conduct an experiment to observe these changes at home.
Hour 1: What Are Chemical Reactions?
Learning Objectives
By the end of this hour, you will:
Identify the signs of a chemical reaction.
Understand the difference between physical and chemical changes.
Signs of Chemical Reactions Explained with Examples
Chemical reactions are processes where substances change to form new materials. These reactions can be identified by several signs:
Colour Change: When a substance changes colour during a reaction, it’s a strong indicator of a chemical change. For example, when iron rusts, it turns reddish-brown.
Gas Production: Bubbles or fizzing indicate that a gas is being released, like when vinegar reacts with baking soda to produce carbon dioxide.
Temperature Change: If the reaction gives off heat (exothermic) or absorbs heat (endothermic), it signals a chemical reaction. Burning wood releases heat and light.
Formation of a Precipitate: When two liquids react and form a solid that settles out, it’s called a precipitate. For instance, mixing solutions of silver nitrate and sodium chloride forms a white solid.
Odour Change: Some chemical reactions produce a noticeable new smell, like the sour odour of spoiled milk.
Read and Watch
Read pages 4-10 and 18-19: "Chemical Reactions" The first section will be a bit of revision of content you have covered in previous weeks. The second section will look at reactions and energy.
Watch: Chemical Reactions (Next Generation Science) to learn how to spot chemical reactions in everyday life.
Read: pages 44-46 in "What's Chemistry all About?".
Task: Spot the Reaction
Make a list of three examples of chemical reactions you’ve observed or know about (e.g., rusting metal, baking a cake, or fireworks).
For each example, explain what changes occur and how you know a reaction is happening.
Hour 2: Energy in Chemical Reactions
Learning Objectives
By the end of this hour, you will:
Differentiate between exothermic and endothermic reactions.
Understand how energy is absorbed or released during reactions.
Read and Watch
Watch: Exothermic and Endothermic Reactions (MooMoo Maths and Science) for an engaging explanation of energy in reactions.
Read: The presentation
Practical Activity: Hot or Cold Reaction?
What You Need:
Baking soda
Vinegar
A small resealable plastic bag
Hand warmer or instant cold pack (optional)
Steps:
Place a few tablespoons of baking soda in the plastic bag.
Add a small amount of vinegar and quickly seal the bag.
Observe the reaction—feel the temperature of the bag and note whether it gets warmer (exothermic) or cooler (endothermic).
(Optional) Compare this with a commercial hand warmer or cold pack.
Reflection Questions:
What did you notice about the temperature change during the reaction?
Why do you think some reactions release heat while others absorb it?
Hour 3: Rosalind Franklin and DNA Structure
Learning Objectives
By the end of this hour, you will:
Learn about Rosalind Franklin’s contributions to science, particularly her role in discovering DNA’s structure.
Reflect on how scientific collaboration leads to major breakthroughs.
Read and Watch
Read: A short biography of Rosalind Franklin in "Women in Science: 50 Fearless Pioneers Who Changed the World" .
Watch: Rosalind Franklin (Ted-Ed) to explore her groundbreaking work with X-ray crystallography.
Task: Understanding DNA’s Structure
Write a short paragraph explaining how Rosalind Franklin’s X-ray images helped reveal DNA’s double helix structure.
Reflect: Why is understanding DNA’s structure important for modern science and medicine?
Quick Activity: Model a DNA Strand
What You Need:
Coloured beads or paper strips (to represent bases: A, T, G, C)
String or pipe cleaners (to represent the backbone)
Steps:
Pair the bases (A-T, G-C) using beads or strips.
Attach them to the backbone to create a double helix model.
Take a photo of your model and label the parts.
Summary and Reflection
Reflect on the Week:
What surprised you most about chemical reactions?
How does Rosalind Franklin’s work inspire you as a budding scientist?
Can you think of other examples where collaboration has led to scientific breakthroughs?
Looking Ahead: Next week, we’ll delve deeper into acids and alkalis. Get ready to make your own pH indicator and test common household substances!
Excellent work finishing week 5!
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