3.1 Chemical Elements And Water

Question 0

State 5 other elements needed by living organisms

Answer 0

Calcium (Ca)
Iron (Fe)
Sodium (Na)
Phosphorous (P)
Sulphur (S)

(CaFe NaPS)

Question 1

State the four most frequently occurring chemical elements in living things.

Answer 1

Carbon
Hydrogen
Oxygen
Nitrogen

(CHON)

Question 3

State one role of calcium

Answer 3

Mineral component of animal bones and teeth

Question 4

State one role of iron

Answer 4

Found in haemoglobin in animals, allowing for oxygen transport.

Question 5

State one role of sodium

Answer 5

Needed for nerve impulses to be sent.

Question 6

State one role of phosphorous

Answer 6

Constituent of ATP and nucleic acids.

Question 6

State one role of sulphur

Answer 6

Found in some amino acids.

Question 7

Outline the structure of a water molecule

Answer 7

Water molecules consist of two hydrogen atoms covalently bonded to one oxygen atom.

Question 8

Outline the polarity of a water molecule

Answer 8

The hydrogen atoms have a slightly positive charge, while the oxygen atom has a slightly negative charge. This gives water polarity (it has positive and negative poles).

Question 9

State the type of bond between the hydrogen atom of one water molecule, and the oxygen atom of another

Answer 9

Hydrogen bond.

Question 10

Outline the thermal properties of water

Answer 10

Water has a high specific heat capacity (can absorb much heat energy before changing temperature).
Water has a high heat of vaporisation.
Water is able to evaporate at temperatures below boiling.

Question 11

Outline the cohesive properties of water

Answer 11

Stick together due to the hydrogen bonds between them.
Attract other nearby water molecule.
Tend to stick to other charged or polar molecules (adhesion).

Question 12

State a property of water which makes it important for photosynthesis

Answer 12

Transparency.

Question 13

Outline the solvent properties of water

Answer 13

Small size of water molecules allows them to surround small molecules and break them apart.
Water can dissolve other polar molecules.
Water can disassociate ionic compounds into their positive and negative ions.

Question 14

Explain how water is used as a coolant in living organisms.

Answer 14

Both plants and animals use the evaporation of water from the surfaces of their bodies to facilitate cooling. Blood (mainly composed of water) is able to carry heat from warmer parts of the body to cooler parts.

Question 15

Explain how water is used as a medium for metabolic reaction in living organisms

Answer 15

Nearly everywhere on earth, water is in a liquid state, and liquid water is he medium for metabolic reactions. Water can dissolve many organic and inorganic substances to facilitate chemical reactions. Water can absorb thermal energy released at a by-product of chemical reactions.

Question 16

Explain how water is used as a transport medium in living organisms

Answer 16

Water is an effective transport medium for dissolved substances. In animals, water in the blood is used to transport oxygen, glucose, and urea. In plants, minerals from the soil ad sugars from leaves are transported in water through the xylem of plants.

Question 17

Explain how the surface tension of water is useful to living organisms

Answer 17

The force of attraction between water molecules makes water sufficiently dense, allowing small animals to move across it (The Jesus Christ lizard).