Lesson Plan

• Describe the difference between mass and weight and the relationship W = mg.
• Explain how a beam balance compares masses by achieving equilibrium.
• Apply the balance procedure to determine the mass of an unknown object.
• Calculate the weight of the unknown object using the measured mass.

• Beam balance with tare function
• Set of standard masses (10 g, 20 g, 50 g, 100 g, etc.)
• Unknown objects (e.g., metal block)
• Worksheet with practice questions
• Calculator
• Projector for diagram demonstration

Begin with a short video showing a balance in a kitchen scale, asking students what they think is being measured. Review the definitions of mass and weight and state that today they will learn how a balance lets us compare them. Success criteria: students will be able to explain the balance principle and determine an unknown mass.

1. Do‑now – 5 min: Quick quiz on mass vs. weight concepts.
2. Mini‑lecture – 10 min: Explain the balance principle, equilibrium, and the W = mg relationship.
3. Demonstration – 10 min: Teacher shows how to zero the balance, place an unknown, add standard masses, and read equilibrium.
4. Guided practice – 15 min: Students work in pairs using balances and standard masses to find the mass of an unknown object, recording results.
5. Check for understanding – 5 min: Students answer Practice Question 1 on the worksheet; teacher circulates and provides feedback.
6. Recap & misconceptions – 5 min: Discuss common errors (e.g., thinking the balance measures weight directly) and reinforce key ideas.

Summarise how achieving equilibrium allows us to equate masses and therefore compare weights. Have students write one‑sentence exit ticket answering: “Why does a balance give the same reading on Earth and the Moon?” Assign homework to complete the remaining practice questions and calculate the weight of a second unknown object.