Lesson 1: Measurement of Capacity

📘 Introduction

Have you ever filled a water bottle, measured ingredients for cooking, or checked the size of a fuel tank? In all these activities, you are dealing with capacity — the amount of liquid a container can hold.

Capacity is all around us. Knowing how to measure and calculate it accurately helps us make smart choices in daily life, from buying the right amount of milk to filling a swimming pool!

🧠 Key Concepts and Explanations

1. What is Capacity?

Capacity measures the volume of liquid that a container can hold. It is different from weight (mass) — capacity is about space, not heaviness.

Example: A big plastic drum can hold 100 litres of water. That number (100 litres) tells us the capacity — how much space is inside for the water.

2. Metric Units of Capacity

In the metric system, the main units of measuring capacity are:

3. Conversion Between Units

Knowing how to convert between litres and millilitres is very important.

• To convert litres (L) to millilitres (mL), multiply by 1,000.
• To convert millilitres (mL) to litres (L), divide by 1,000.

Formulas:

4. Everyday Examples of Capacity

• A sachet of water = 500 mL
• A medium-sized soft drink bottle = 1.5 L
• A kettle = 2 L
• A jerry can of oil = 25 L
• A big tank = 5000 L

5. Important Visuals

🔍 Step-by-Step Sample Problems

Example 1: Convert 6.75 L to millilitres.

Solution:

Multiply by 1,000:

Example 2: A container has 3,200 mL of water. Express this in litres.

Solution:

Divide by 1,000:

Example 3: A barrel can hold 180 litres of oil. How many millilitres is that?

Solution:

📝 Practice Exercises

A. Basic Conversions

1. Convert 2.8 L to millilitres.
2. Convert 950 mL to litres.
3. Convert 0.45 L to millilitres.

B. Word Problems

1. A milk container holds 1.5 L. How much milk is that in millilitres?
2. John poured 3,750 mL of water into a tank. How many litres of water did he pour?
3. A medicine bottle is labeled 250 mL. How many bottles are needed to make up 2 litres of medicine?

C. Thinking Challenge

A family buys a 15,000 L water tank. They use 800 L of water every week. After how many weeks will the tank be empty?

✅ Answers and Explanations

• 2.8 L = 2.8 × 1000 = 2800 mL
• 950 mL ÷ 1000 = 0.95 L
• 0.45 L × 1000 = 450 mL
• 1.5 L = 1.5 × 1000 = 1500 mL
• 3,750 ÷ 1000 = 3.75 L
• Each bottle = 250 mL, so:2 litres = 2000 mL

  2000 ÷ 250 = 8 bottles

• Tank empties in:15,000 ÷ 800 = 18.75 weeks

  Approximately 19 weeks.

🔁 Recap

In this lesson, we explored what capacity is and how it is measured using litres (L) and millilitres (mL). We practised converting between units, solving real-world problems, and thinking critically about measurements in daily life. Always remember that 1 L = 1000 mL, and 1 mL = 1 cm³.

🪞 Reflection Prompt

How would you explain to a younger sibling the difference between mass (weight) and capacity (volume)? Why is it important to measure liquids accurately?