Natural Resources — Air, Water, Pressure

Overview

Natural resources form the foundation of Environmental Science in MAHA TET Paper II, connecting physical science concepts with real-world applications. This topic specifically addresses the composition and properties of air, the concept of atmospheric pressure, and water as a vital resource — all essential for upper-primary science teaching.

For MAHA TET, expect questions that test your understanding of air composition percentages, demonstrations of atmospheric pressure (like the inverted glass experiment), and the water cycle. Questions often link scientific concepts to everyday phenomena that teachers must explain to students. Mastery requires knowing exact figures (nitrogen 78%, oxygen 21%), understanding pressure concepts qualitatively, and connecting water resource management to environmental awareness.

This topic bridges physics (pressure) and environmental science (resources and conservation), making it a favourite for integrated questions in the exam.

Key Concepts

• **Air is a mixture, not a compound**: Air contains nitrogen (78%), oxygen (21%), and other gases including carbon dioxide, argon, water vapour and trace gases (together about 1%). These gases retain their individual properties and can be separated by physical means.

• **Atmospheric pressure is the weight of air above us**: The column of air extending from the earth's surface to the upper atmosphere exerts pressure in all directions. At sea level, this equals approximately 101.3 kPa or 760 mm of mercury.

• **Pressure decreases with altitude**: As we go higher, there is less air above us, so atmospheric pressure falls. This is why ears pop during flight and why cooking takes longer at hill stations.

• **Water exists in three states and cycles continuously**: The water cycle (hydrological cycle) involves evaporation, condensation, precipitation and collection. Solar energy drives this cycle, making it a natural purification process.

• **Only 3% of Earth's water is fresh**: Of this, about 68% is locked in glaciers and ice caps, 30% is groundwater, and less than 1% is easily accessible surface water in rivers and lakes.

• **Air exerts pressure equally in all directions**: This is why a filled balloon expands uniformly and why atmospheric pressure does not crush us — internal body pressure balances it.

• **Water pressure increases with depth**: Unlike atmospheric pressure, water pressure increases as we go deeper because more water weight presses down from above.

Formulas / Key Facts

| Concept | Key Fact | |---------|----------| | Nitrogen in air | 78.09% (approximately 78%) | | Oxygen in air | 20.95% (approximately 21%) | | Carbon dioxide in air | 0.04% (but vital for photosynthesis and climate) | | Standard atmospheric pressure | 101.325 kPa = 1 atm = 760 mm Hg = 1013.25 millibar | | Pressure formula | Pressure = Force ÷ Area (P = F/A) | | Unit of pressure | Pascal (Pa); 1 Pa = 1 N/m² | | Fresh water on Earth | About 3% of total water | | Accessible fresh water | Less than 1% of total fresh water | | Water cycle stages | Evaporation → Condensation → Precipitation → Collection | | Boiling point variation | Water boils below 100°C at high altitudes due to lower pressure |