Answer:

Exothermic Reactions:

Exothermic reactions are chemical reactions that release energy in the form of heat, light, or sound. In these reactions, the energy of the products is lower than the energy of the reactants, leading to the release of energy.

Example: A mixture of sodium (Na) and chlorine (Cl₂) reacts to form table salt (NaCl). This is a combination reaction that releases energy in the form of heat and light.

2 Na (solid) + Cl2 (gas) → NaCl (solid)

Substances Involved:

• Sodium (Na) – Solid
• Chlorine (Cl₂) – Gas
• Sodium chloride (NaCl) – Solid

Endothermic Reactions:

Endothermic reactions are chemical reactions that absorb energy or require energy in order to proceed. In these reactions, the energy of the products is higher than the energy of the reactants, leading to the absorption of energy.

Example: Photosynthesis is an example of an endothermic reaction. In this process, plants use the energy from sunlight to convert carbon dioxide (CO₂) and water (H₂O) into glucose (C₆H₁₂O₆).

6 CO2 (gas) + 6 H2O (liquid) → C6H12O6 (aqueous) + 6 O2 (gas)

Substances Involved:

• Carbon dioxide (CO₂) – Gas
• Water (H₂O) – Liquid
• Glucose (C₆H₁₂O₆) – Aqueous
• Oxygen (O₂) – Gas

Catalyst: Sunlight (provides energy for the reaction)