**5. (a) Farming Systems:** (i) **Organic farming** – This method avoids synthetic fertilizers and pesticides, using natural compost and biological pest control. (ii) **Mixed farming** – Farmers grow crops and raise livestock on the same land, creating a sustainable balance between plant cultivation and animal rearing. (iii) **Mixed cropping** – Different crops are planted together to optimize space, reduce pests, and improve soil health. ### **5. (b) Mixtures of Substances:** (i) **Oil and water** – Heterogeneous mixture (the substances do not mix uniformly). (ii) **Salt and water** – Homogeneous mixture (salt dissolves completely, forming a solution). (iii) **Ethanol and water** – Homogeneous mixture (ethanol mixes uniformly with water). ### **5. (c) Renewable Energy & Heat vs. Temperature:** (i) **Why is solar energy renewable?** - The sun continuously produces energy without being depleted. - It is naturally replenished and available indefinitely. (ii) **Differences between heat and temperature:** - **Heat** is the total energy of molecular motion; **temperature** measures its intensity. - **Heat** depends on mass; **temperature** does not. - **Heat** is measured in joules; **temperature** is measured in degrees (Celsius/Kelvin). ### **5. (d) Effects on the Nitrogen Cycle:** (i) **Leaching** – Removes essential nitrogen compounds from soil, reducing fertility. (ii) **Removal of leguminous plants** – Reduces nitrogen fixation, limiting nitrogen availability in the soil.