Curriculum
Science — Second Preparatory
Unit 1: Matter and Energy
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Unit 2: Matter and Chemical Reactions
0/6
Unit 3: Energy Flow in Photosynthesis and Respiration
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Unit 4: Geological Processes
0/4
Text lesson
The Chemical Equation
The Chemical Equation
Symbols, formulas and coefficients
Symbols, formulas and coefficients
| Part | Meaning | Example |
|---|---|---|
| Chemical symbol | Represents one atom of an element | O is one oxygen atom |
| Chemical formula | Represents a substance and the atoms in it | H₂O is a water molecule with two hydrogen atoms and one oxygen atom |
| Subscript (small number) |
|
In CO₂ the subscript 2 refers to oxygen |
| Coefficient (number in front) |
|
In 2H₂O the coefficient is 2 |
- When balancing, only the coefficients are changed.
- Subscripts are never changed, because changing them would give a different substance.
The Chemical Equation · 2 / 7