Water

• What is a dipole in chemistry?

  A polar molecule with a positive and a negative charge, separated by a very small distance.
• What is a hydrogen bond?

  The weak attractive force between a hydrogen atom with a partial positive charge and an atom with a partial negative charge.
• What role does water play in living organisms?

  • Medium for metabolic reactions
  • Constituent of cells (65-95% of mass)
  • Transport medium for dissolved substances
• What percentage of a human's mass is water?

  About 70%
• Why is water considered a polar molecule?

  Because it has a positively charged end (hydrogen) and a negatively charged end (oxygen).
• What is the significance of hydrogen bonds in water?

  They make water molecules difficult to separate and give water a wide range of physical properties vital to life.
• What are the properties of water that make it essential for life?

  • Excellent solvent for ions and polar molecules
  • Acts as a transport medium in organisms
  • High specific heat capacity
  • High latent heat of vaporisation
  • Cohesion and high surface tension
  • Transparency for photosynthesis
• How does water act as a solvent?

  Water attracts charged particles and polar molecules, allowing them to dissolve and participate in chemical reactions.
• What is hydrolysis in the context of water's role in biochemical reactions?

  It is a reaction where water splits a molecule into smaller parts.
• What is condensation in the context of water's role in biochemical reactions?

  It is a reaction where water is produced as a byproduct.
• Why does water have a high specific heat capacity?

  Because hydrogen bonds restrict the movement of water molecules, requiring a large amount of heat energy to raise its temperature.
• What is the significance of water's high latent heat of vaporisation?

  It allows for cooling through evaporation, which is important for temperature regulation in organisms.
• How does cohesion in water benefit plants?

  Cohesion allows columns of water to be drawn up xylem vessels in plants.
• What is the maximum density of water?

  Water has a maximum density at 4°C.
• Why does ice float on water?

  Because ice is less dense than liquid water due to hydrogen bonds holding the molecules further apart.
• How does water's transparency benefit aquatic plants?

  It allows light to pass through, enabling effective photosynthesis.
• Match the properties of water with their importance to living organisms.

  1. Photosynthesis - C. It is transparent.
  2. Transport - A. Universal solvent.
  3. Insulation - D. In the solid state it is less dense.
  4. Cooling - B. High latent heat of vaporisation.
• What is the highest surface tension of any liquid except mercury?

  Water at ordinary temperatures.
• What is the role of water in cooling mechanisms in organisms?

  Water absorbs heat when it evaporates, cooling the body or surface from which it evaporates.