Unit 2.2 Water

Question 1

Essential idea of water unit

Answer 1

Water is the medium of life

Question 2

Water chemical composition

Answer 2

One oxygen, 2 hydrogen joined by covalent bond

Question 3

Covalent bond in water

Answer 3

• electrons shared but not evenly
• oxygen acts as negative due more protons to attract electrons than hydrogen, giving its a slight negative charge (delta negative)
• hydrogen then acquires a delta positive charge
• making water polar

Question 4

Hydrogen bonding in water

Answer 4

• polarity allows formation of hydrogen bonds
• delta positive hydrogen are attracted to the delta negative oxygens of other molecules
• hydrogen bonds form weak interactions between molecules and allow for properties incl. cohesion and adhesion
• hydrogen bonds from between water molecules, and between water and other polar or ionic molecules
• each water molecule can potentially form four hydrogen bonds

Question 5

Cohesion

Answer 5

• the tendency of water molecules to stick to each other due to hydrogen bonds forming between them
• hydrogen bonds are weak, but in large quantities lead to cohesion
• cohesion creates surface tension

Question 6

Adhesion

Answer 6

• interaction between water molecules and other, different molecules
• explains why water molecules stick to other polar compounds
• rescapons I le for capillary action

Question 7

Capillary action

Answer 7

Movement of water molecules and all things dissolved in it within thin spaces against gravity
- allows water to be transported along plant cells

Question 8

Thermal properties of water

Answer 8

• the hydrogen binds that hold water together crate unique thermal properties
• high specific heat capacity = amount of head that must be absorbed for one mg to heat 1 degree
• makes water an excellent coolant
• temp in aquatic ecosystems doesn’t change easily creating stability

Question 9

Latent heat of vaporisation

Answer 9

Amount of heat 1 ml of liquid must absorb in order to change state into a gas

Question 10

Water as a coolant

Answer 10

High latent heat of vaporization and specific heat capacity make water an excellent coolant. When water is sweat it evaporates and loses heat in a cooling process

Question 11

Water as a solvent

Answer 11

• Water is one of the best known solvent, sometimes called the universal solvent
• dissolves ionic compounds and polar molecules
• all reactions in a cell occur in a liquid medium
• molecules are dissolved in water in the blood and transported around the cell

Question 12

Benefit to living organisms (cohesive properties)

Answer 12

• water can be pulled up from roots to leave of plants

- surface tension means lights density insects and organisms can float on water to catch prey

Question 13

Benefit to living organisms (adhesive properties)

Answer 13

• capillary action powered through adhesive properties helps plants and the heart pump blood through blood vessels

Question 14

Benefit to living organisms (thermal properties)

Answer 14

• evaporation of sweat from body’s surface involves heat loss, creating a cooling effect that helps thermorégulation
• high latent heat of vaporization and high specific heat capacity make marine ecosystems stable

Question 15

Benefit to living organism (solvent properties)

Answer 15

• dissolves minerals in spoil and transports them up the plant
• water in blood plasma carries dissolved solvents and gasses so that blood can transport nutrients
• medium for many biochemical reaction