Inorganic Ions and Water

Question 1

Organic Ions

Answer 1

Molecules that have a high proportion of carbon atoms and hydrogen atoms

Question 2

Inorganic Ions

Answer 2

A molecule or ion that has no more than one carbon atom or hydrogen atom

Question 3

Micronutrients

Answer 3

a chemical element or substance required in trace amounts for the normal growth and development of living organisms (e.g. copper, zinc)

Question 4

Macronutrients

Answer 4

a chemical element required in large amounts (e.g. potassium, magnesium, calcium)

Question 5

Magnesium - Mg 2+

Answer 5

An important constituent of chlorophyll and is therefore essential for photosynthesis. Mammals need magnesium for their bones

Question 6

Iron - Fe 2+

Answer 6

A constituent of haemoglobin, which transports oxygen in red blood cells. A lack of iron in the human diet can lead to anaemia

Question 7

Calcium - Ca 2+

Answer 7

Like phosphate , its an important structural component of bones and teeth in mammals and is a component of plant cell walls, providing strength

Question 8

Phosphate - PO4 3-

Answer 8

Used for making nucleotides, including ATP, and are a constituent of phospholipids, found in biological membranes

Question 9

Water polarity

Answer 9

Water is a polar/dipole molecule - one end is slightly positive and one end is slightly negative but no overall charge

• Hydrogen is Positive
• Oxygen is Negative

Question 10

Hydrogen Bonding

Answer 10

Hydrogen bonds are weak but many hydrogen bonds give strength

Question 11

Covalent Compounds - Polarity

Answer 11

Slight charges are formed during the sharing of electrons

• Equal sharing - nonpolar
• No slight charges formed
• Unequal sharing - polar
• Slight differences in EN - charges
• Forms two poles or dipole

Question 12

Universal Solvent

Answer 12

Water is a polar molecule that can dissolve polar and ionic substances eg salt
Biological Importance
As chemicals can dissolve in water, it acts as transport medium in eg
-Blood - nutrients
-Phloem - sugar
-Xylem - water - nutrient ions

Question 13

Cohesion

Answer 13

Water molecules show a strong attraction or “stickiness” to one another.
Biological Importance
-Cohesion tension theory - tall columns of water can be drawn up xylem vessels in plants
-Transpiration - evaporation of water from a plant through stomata

Question 14

Surface Tension

Answer 14

The cohesive forces between molecules down into a liquid are shared with all neighbouring molecules.
Those on the surface have no molecules above, and exhibit stranger attractive forces upon their nearest neighbours on the surface. They therefore ‘pull’ together more strongly at the surface and this called surface tension causing it to behave like an elastic sheet
Biological Importance
-Organisms can walk on the surface of water so they can escape from predators
-Beading of rain water to run back down to the roots

Question 15

Colour - Transmissions of Light

Answer 15

Water is colourless and is therefore transparent to light
Biological Importance
-light can pass through enabling aquatic plants to photosynthesise
sunlight can reach the cells and pass through them so that photosynthesis may occur

Question 16

Latent Heat

Answer 16

While changing state, a substance will take in heat energy (solid>liquid>gas), or give out heat energy (gas>liquid>solid) without a change in temperature. This is termed latent heat. Water has large latent heat of vaporisation, and therefore absorbs a large amount of heat energy while changing from water to vapour.
Biological Importance
Sweating cools the body as water evaporating absorbs a large amount of heat energy from it.

Question 17

State at Room Temperature

Answer 17

Water is a liquid at room temperature. However, all other similar molecules are gases Hydrogen bonding act between the water molecules, and they attract them enough so that it behaves as a liquid

Question 18

Specific Heat Capacity

Answer 18

The heat needed to raise the temperature of 1kg of water by 1’c is termed the Specific Heat Capacity. Water has a large specific heat capacity, and therefore can absorb large amounts of heat energy before its temperature raises a significant amount
Biological Importance
-This prevents large fluctuations in the temperature of water and maintains constant temperatures
-It keeps the temperature of aquatic habitats stable so that organisms do not have to endure extremes of temperature

Question 19

Density of Water

Answer 19

Unlike other substances, water expands as it freezes. Water molecules in ice form a rigid structure so that there is more space between them. This means that ice is less dense than water, and will therefore floats on top of it
Biological Importance
-Ice forms an insulating layer and allowing organisms to survive
-It prevents further heat loss and all water freezing over
-Allows fish to survive in lakes during winter and animals such as frogs to hibernate at the bottom of ponds

Question 20

Metabolite

Answer 20

Water has a role of a metabolite as it is:

• product of aerobic respiration and condensation reactions
• a reactant in photosynthesis and hydrolysis