Grade 10 SCIENCE | Quarter 4 Module 5A | Balancing Chemical Reactions

Introduction to Chemical Reactions
📌 A chemical reaction is a process where original substances change into new substances with different physical and chemical properties.
🔥 Examples of chemical reactions include fireworks and the rusting of a metal nail.
💧 Physical changes, like the melting of ice to water ($\text{H}_2\text{O}$ remains $\text{H}_2\text{O}$), do not alter the substance's chemical identity.

Evidences and Components of Chemical Reactions
🌟 Evidences of a chemical reaction include a change of color, formation of gas, temperature change, change in smell, and the formation of a precipitate (a cloudy substance).
🧪 A chemical reaction consists of reactants (substances entering the reaction) and products (substances produced).
🔄 Chemical reactions involve the rearrangement of atoms in compounds, not the change of elements themselves.

The Law of Conservation of Mass
⚖️ The Law of Conservation of Mass dictates that matter is neither created nor destroyed in any chemical reaction; thus, the total mass of reactants must equal the total mass of products.
🌿 Photosynthesis is used as an example: $\text{CO}_2 + \text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + \text{O}_2$.
🧪 Carbonic acid breakdown in soda is another example: $\text{H}_2\text{CO}_3 \rightarrow \text{CO}_2 + \text{H}_2\text{O}$.

Anatomy of Chemical Formulas and Balancing Equations
🔢 In a chemical formula like $3\text{CO}_2$, the number 3 is the coefficient (a whole number multiplier), and the 2 in $\text{CO}_2$ is the subscript (indicating the number of atoms of an element within a compound).
⚛️ When counting atoms in formulas with parentheses, like $\text{Mg}(\text{NO}_3)_2$, the subscript outside the parenthesis multiplies everything inside (e.g., Nitrogen atoms = $1 \times 2 = 2$).
⚖️ Balancing chemical equations requires adding coefficients (whole numbers $\ge 1$) to reactants or products until the count of each element is identical on both sides of the reaction arrow ($\rightarrow$).

Balancing Examples
💥 The reaction $\text{Al} + \text{O}_2 \rightarrow \text{Al}_2\text{O}_3$ is balanced by adding coefficients to yield $4\text{Al} + 3\text{O}_2 \rightarrow 2\text{Al}_2\text{O}_3$.
🔥 Methane combustion, $\text{CH}_4 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}$, is balanced to $\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}$.

Key Points & Insights
➡️ Identify reactants and products correctly by understanding which substances combine and which are formed in the described reaction text.
➡️ Master the difference between coefficients and subscripts as they are crucial for correctly counting atoms before and after balancing.
➡️ Chemical equation balancing is primarily a trial-and-error process involving adding integer coefficients to ensure conservation of mass is upheld ($\text{Reactants} = \text{Products}$).

📸 Video summarized with SummaryTube.com on Mar 10, 2026, 12:55 UTC