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eMusic Study Pack • Chemistry
Student
📖 Comprehensive Note
Law of Definite Proportions (also called the Law of Constant Composition) states that a given pure chemical compound always contains the same elements combined together in the same fixed proportion by mass, regardless of the source or method of preparation.
- Discovered by Joseph Proust in 1799.
- Example: Water (H₂O) always has 11.1% hydrogen and 88.9% oxygen by mass.
- Applies to pure compounds like carbon dioxide, ammonia, sodium chloride, etc.
- This law shows that chemical compounds have a definite and unchanging composition.
🎤 Lyrics
Verse 1
Every morning brings a brand new start,
Dreams in my mind, fire in my heart.
Chorus
Law of multiple proportion
states that when two
elements combine to form
more than one compound,
the masses of one element
that combine with a fixed
mass of the other are in
the ratio of small whole
numbers.
Verse 2
Step by step, I climb so high,
With every sweat, I touch the sky.
Chorus
Law of multiple proportion
states that when two
elements combine to form
more than one compound,
the masses of one element
that combine with a fixed
mass of the other are in
the ratio of small whole
numbers.
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📊 Line-by-Line Study Guide
| Lyric Line | Explanation |
|---|---|
| Hydrogen, oxygen, side by side, forming water | Example of H₂O always having a fixed ratio of elements. |
| From ocean waves to drops of rain | Water everywhere has the same composition — shows universality. |
| One part to eight, they tightly bind | Mass ratio of hydrogen to oxygen is 1:8. |
| Definite law beneath the moon | Poetic expression of the law’s constancy in nature. |
💡 Mnemonic
"Definite = Fixed" — Always remember: a definite proportion means a fixed ratio by mass, no matter the source.
❓ Quiz
1. What does the Law of Definite Proportions state?
2. Who discovered this law?
3. What is the hydrogen to oxygen ratio in water by mass?
🃏 Flashcards
Q1: State the Law of Definite Proportions.
A pure compound always contains the same elements combined in the same ratio by mass.
Q2: Who discovered this law?
Joseph Proust.
Q3: Give one example that follows the law.
Water (H₂O) – always 1 part hydrogen to 8 parts oxygen by mass.
🎯 Drag & Drop
Match each concept with its description:
Concepts
Descriptions
Law of Definite Proportions
Joseph Proust
Fixed ratio 1:8 (H:O)
📌 Summary
- Each pure compound has a fixed composition by mass.
- Law discovered by Joseph Proust in 1799.
- Applies to all chemical compounds, regardless of source.
- Example: H₂O always contains hydrogen and oxygen in the ratio 1:8 by mass.