Chemical Reactions & Equations

Chemical Reactions & Equations

• Chemical reactions involve the transformation of one or more substances into different substances.
• Examples include rusting of iron, setting of milk, digestion, and respiration.
• Chemical changes indicate that a chemical reaction has occurred.
• A chemical equation represents a chemical reaction using symbols and formulae of the substances involved.
• Characteristics of chemical reactions include the formation of new substances with different properties, changes in colour, evolution of gases, changes in energy (heat absorption or release), formation of precipitates, and irreversibility (in many cases).
• Examples: Reactant + Reactant → Product + Product

Balanced Chemical Equations

• A balanced chemical equation ensures an equal number of atoms of each element on both sides (reactants and products).
• This reflects the law of conservation of mass.
• Mass of reactants = Mass of products.

Activity Examples

• Activities demonstrate chemical reactions, like magnesium reacting with oxygen.
• Observations are recorded, and the balanced chemical equation is used to show the reaction.
• For example, magnesium ribbon burning with a white flame is a chemical reaction creating magnesium oxide.
• Sandpaper helps remove oxide layer from the magnesium to ensure pure magnesium is reacted with oxygen.

Types of Chemical Reactions

• Combination reactions involve two or more reactants combining to form a single product.
• Decomposition reactions involve a single reactant breaking down into two or more products.
• Example: 2H₂ + O₂ → 2H₂O (Combination)

Balancing Chemical Reactions

• Balancing equations ensures a balanced number of atoms for each element in both the reactants and product sides.
• The process involves adjusting coefficients in front of the formulas to achieve this balance.

Examples of Reactions with State Symbols

• The concept of balancing reactions while specifying the physical states of substances (e.g., solid, liquid, gas, aqueous solution) is often introduced.

Double Displacement Reactions

• In double displacement reactions, two ionic compounds in solution swap ions.
• Two new compounds are formed, one of which is often an insoluble precipitate.
• Examples:
  • NaOH(aq) + HCl(aq) →NaCl(aq) + H₂O(l)

Redox Reactions

• Redox reactions involve both oxidation and reduction.
• Oxidation involves gaining oxygen or losing hydrogen.
• Reduction involves losing oxygen or gaining hydrogen.
• Reactions where one substance loses electrons is oxidation while the other gains electrons is reduction.

Effects of Oxidation Reactions (Everyday Life)

• Corrosion is the gradual destruction of metals by chemical reactions.
• Rancidity is the spoilage of fats and oils.
• Oxidation contributes to various everyday phenomena.

Top 7 Questions

• Addressing a variety of concepts, including explaining reactions in terms of energy transfer, identifying reactant classifications, explaining chemical reactions and energy transfers.

Explore the fascinating world of chemical reactions and how they transform substances. This quiz covers key concepts such as balanced equations, the characteristics of chemical changes, and examples of significant reactions. Test your knowledge and understanding of this fundamental chemical principle.