Chemical_Reactions_Overview_Grade11.pptx

overview of chemical reactions

1. Overview of Chemical Reactions Grade 11 | General Science Presented by: Kip Aiza F. Gabawa

2. Learning Objectives • Define chemical reactions. • Identify signs that a chemical reaction has occurred. • Describe the parts of a chemical equation. • Classify types of chemical reactions. • Appreciate their importance in everyday life.

3. What is a Chemical Reaction? • A process in which one or more substances (reactants) are transformed into new substances (products). • Atoms are rearranged to form new bonds. • No atoms are created or destroyed – only rearranged.

4. Reactants and Products • Reactants: starting substances that change. • Products: new substances formed. Example: Hydrogen + Oxygen → Water

5. The Chemical Equation • Represents what happens in a reaction. Example: 2H₂ + O₂ → 2H₂O • Arrow (→) means 'yields' or 'produces'. • Coefficients show the number of molecules involved.

6. Law of Conservation of Mass • Mass is neither created nor destroyed. • Total mass of reactants = total mass of products. • Equations must be balanced.

7. Signs of a Chemical Reaction • Change in color. • Formation of a precipitate (solid). • Gas production (bubbling or odor). • Temperature or light change. • Irreversibility of the process.

8. Energy in Chemical Reactions • Reactions may absorb or release energy. • Endothermic – absorbs energy (e.g., photosynthesis). • Exothermic – releases energy (e.g., combustion).

9. Types of Chemical Reactions 1. Combination (Synthesis) Reaction 2. Decomposition Reaction 3. Single Replacement Reaction 4. Double Replacement Reaction 5. Combustion Reaction

10. Combination (Synthesis) Reaction • Two or more substances combine to form one product. Example: 2H₂ + O₂ → 2H₂O

11. Decomposition Reaction • A compound breaks down into simpler substances. Example: 2H₂O → 2H₂ + O₂

12. Single Replacement Reaction • One element replaces another in a compound. Example: Zn + 2HCl → ZnCl₂ + H₂

13. Double Replacement Reaction • Exchange of ions between two compounds. Example: NaCl + AgNO₃ → NaNO₃ + AgCl

14. Combustion Reaction • A substance reacts rapidly with oxygen, releasing heat and light. Example: CH₄ + 2O₂ → CO₂ + 2H₂O

15. Importance of Chemical Reactions • Basis of biological processes (respiration, photosynthesis). • Essential in industry – fuels, medicines, plastics. • Helps understand environmental and energy changes.

16. Summary • Chemical reactions rearrange atoms to form new substances. • They follow the law of conservation of mass. • Main types include synthesis, decomposition, replacement, and combustion. • They are vital in sustaining life and modern technology.