Olympiad Test: Water - 1 - Class 6 MCQ

Water is essential for all life forms because it is involved in key biological processes such as digestion, nutrient transport, temperature regulation, and chemical reactions in cells. Without water, plants, animals, and humans cannot survive.

About 71% of the Earth’s surface is covered with water, but most of it (97%) is saltwater in oceans. Only around 3% of water is freshwater, and not all of it is easily accessible—much is locked in glaciers or underground.

Freshwater collected from rivers, lakes, or underground sources may contain impurities or harmful microorganisms. Purification processes such as filtration, sedimentation, and disinfection make it safe for human consumption.

Surface water refers to water that is found on the Earth’s surface in rivers, lakes, streams, and ponds. Groundwater is below the surface, while rainwater is a source that replenishes both surface and groundwater.

Groundwater is water stored in underground soil, sand, and rock spaces. It feeds wells, springs, and some rivers, playing a crucial role in water supply, especially in areas with low surface water.

The water cycle begins with evaporation (water turning into vapor), followed by condensation (vapor forming clouds), precipitation (rain, snow, etc.), and collection (water gathering in rivers, lakes, or infiltrating into the ground). Transpiration also contributes by releasing water from plants.

Evaporation is the process where heat energy from the sun converts liquid water into water vapor, which rises into the atmosphere as part of the water cycle.

Plants absorb water from soil, and a portion of it is released as vapor through leaves and stems. This process, transpiration, contributes to atmospheric moisture and the water cycle.

The water cycle maintains the availability of freshwater by recycling water, distributing it across regions, and naturally purifying it through evaporation and precipitation. It is essential for ecosystems, agriculture, and human survival.

Floods occur when excessive rain or melting snow causes water bodies like rivers, lakes, or ponds to overflow. Flooding can damage crops, homes, and infrastructure.