LESSON PLAN: AVOGADRO’S LAW
Grade Level: Grade 10 (Junior High School)
Subject: Science (Chemistry)
Time Allotment: 45 Minutes
Reference Materials: Phoenix Publishing, Diwa, Rex Chemistry Textbooks
Lesson Objectives:
By the end of the lesson, learners should be able to:
1. Cognitive: Explain Avogadro’s Law and its relationship between the volume and number of moles of a
gas at constant temperature and pressure.
2. Psychomotor: Solve numerical problems involving Avogadro’s Law using the mathematical equation.
3. Affective: Appreciate the importance of Avogadro’s Law in real-life applications, such as balloon
inflation and gas reactions.
I. ENGAGE (Motivation: Four Pics, One Word Activity – 5 minutes)
Activity: Display three sets of four pictures, each set representing a key term related to Avogadro’s Law.
Instructions: Show images that depict concepts related to moles, volume, and gas. Let students guess the oneword answer for each set.
Ask guiding questions:
1. "What do these images have in common?"
2. "How does this word relate to gases?"
3. "What do you think will be our topic today?"
II. EXPLORE (Hands-on Activity – 5 minutes)
Activity: Inflating a Balloon
Materials: Balloons
Procedure:
a.
b.
c.
d.
Give each student a deflated balloon.
Ask them to blow a small amount of air into the balloon and observe its size.
Instruct them to blow more air into the balloon and observe how it expands.
Ask: "What happens to the balloon as more air is added?"
Guide Questions:
1. How does the size of the balloon change as more air is added?
2. What does this tell us about the relationship between gas volume and the amount of gas?
III. EXPLAIN (Concept Discussion – 10 minutes)
Definition:

Avogadro’s Law states: At constant temperature and pressure, the volume (V) of a gas is directly
proportional to the number of moles (n) of the gas.

Mathematically, it is expressed as:
Concept Explanation:

If the number of gas molecules (moles) increases, the volume also increases, provided temperature and
pressure remain constant.

If the number of gas molecules decreases, the volume decreases proportionally.
Real-life Applications:

Inflating a balloon: The more air you blow, the larger it gets.

Lungs expanding when we inhale and contracting when we exhale.

Aerosol cans: More gas means more pressure inside, leading to a higher volume when released.
IV. ELABORATE (Problem-Solving – 15 minutes)
Example 1 (Guided Example)
A gas sample has a volume of 5.0 L when containing 2.0 moles of oxygen gas. If the number of moles is
increased to 6.0 moles, what will be the new volume, assuming temperature and pressure remain constant?
Answer: The new volume is 15.0 L.
Example 2 (Independent Practice)
A gas in a balloon occupies 8.0 L when containing 4.0 moles of helium. If the number of moles is reduced to
2.0 moles, what will be the new volume?
Answer: The new volume is 4.0 L.
V. EVALUATE (Assessment – 5 minutes)
Exit Ticket: Students will answer the following:
1. State Avogadro’s Law in your own words.
2. How does increasing the number of moles affect the volume of gas?
3. Solve the following problem:

A gas with a volume of 12.0 L contains 3.0 moles of gas. If the amount of gas is increased to 6.0
moles, what is the new volume?