Definitions [3]
Define rusting?
Rusting: Slow conversion of iron into its hydrated oxide in the presence of moisture and air is called rusting.
Define the following:
Respiration
Respiration: Respiration is a chemical process that takes place in all living beings (slow in plants). In this process, oxygen present in inhaled air reacts with the digested food material in the body. This results in the release of energy, carbon dioxide, and water.
Sugar + Oxygen → CO2 + Water + Energy.
Definition: Anomalous behaviour of water
The behaviour of water between its temperature from 0 °C to 4 °C is called anomalous behaviour of water.
Key Points
Key Points: Properties of Water
- Water makes up 90–95% of plant cells and tissues and is called the "elixir of life" as it is essential for all biological processes.
- It has a neutral pH in pure form and is the best solvent, making it ideal for transporting dissolved minerals and food throughout the plant.
- Due to high specific heat, heat of vaporisation, and heat of fusion (caused by H-bonds), water acts as a thermal buffer protecting cells from temperature changes.
- Strong adhesive and cohesive forces, along with high surface tension, allow water to rise easily in capillaries.
- It is the best medium for all biochemical reactions in cells and also a raw material for photosynthesis.
Key Points: Anomalous behaviour of water
- Anomalous behaviour of water refers to its contraction when heated from 0°C to 4°C, unlike most liquids that expand on heating.
- At 4°C, water attains its minimum volume and hence its maximum density.
- This behaviour is studied using Hope’s apparatus, in which temperature changes at the upper (T₂) and lower (T₁) parts of the water are recorded over time.
- As cooling begins, denser water at 4°C sinks, causing T₁ to fall rapidly, while T₂ falls more slowly.
- Once water cools below 4°C, its density decreases, causing it to rise, which in turn makes T₂ drop faster, while T₁ remains stable at 4°C briefly before decreasing.
