Molecular bonding + Properties of Water

Question 1

Define electronegativity

Answer 1

The ability of atoms of elements to pull shared electrons
–> can depend on th number of protons in the nucleus

Question 2

What causes a bond to be polar?

Answer 2

The difference in electronegativity, and sometimes the shape of atom

Question 3

How is a water molecule polar?

Answer 3

• the O atom has more protons + stronger attraction for the shared electrons, making it more electronegative, and therefore slightly negative
• this makes the H atoms slightly positive
• when this happens, we say the molecule is polar

Question 4

Define hydrogen bond

Answer 4

Slightly positive H atom will attract slightly negative atoms of other molecules

Question 5

What is stronger: a hydrogen bond or a covalent bond?

Answer 5

Covalent bonds because hydrogen bonds are between molecules whereas covalent bonds are between atoms

Question 6

What are the properties of water?

Answer 6

• liquid at room temperatures and low viscosity
• ice is less dense than water
• solvent
• cohesion and surface tension
• high latent heat of vaporisation
• high specific heat capacity

Question 7

What is the impact of water being a liquid at room temperatures?

Answer 7

• provides habitats for living things
• forms major components in tissues
• provides a reaction medium for chemical reactions + transport medium

Question 8

Explain how ice is less dense than water

Answer 8

• water becomes more dense as the temperature drops until around 4 degrees
• then from 4 degrees to 0 degrees, it expands because of its polar nature

Question 9

What is the impact of the density of water?

Answer 9

• currents can circulate food
• insulation
• animals can move and survive

Question 10

How is water a solvent?

Answer 10

• the positive and negative parts of water molecules are attracted to the positive and negative parts of the solute
• the water molecules form a cluster around the solute’s ions - separates them and keeps them apart
• causing them to dissolve and form a solution

Question 11

What is the impact of water being a solvent?

Answer 11

Allows for:
- reactions to occur
- hydrolysis
- transport

Question 12

How does water have cohesion?

Answer 12

Hydrogen bonds between molecules pull them together, so it retains its shape

Question 13

How does water have surface tension?

Answer 13

Hydrogen bonds among the surface water molecules resist stretching or breaking the surface

Question 14

What is the impact of water’s cohesion and surface tension?

Answer 14

• enables transpiration in plants - water pulled up
• provides a habitat

Question 15

Define high specific heat capacity

Answer 15

Energy needed to raise the temperature of 1 kg of a material by 1degree c

Question 16

What is the impact of water’s high specific heat capacity?

Answer 16

Provides a stable environment for:
- enzyme controlled reactions
- aquatic animals to live in

Question 17

Define high latent heat of vaporisation

Answer 17

Energy requires to change the state of 1kg of a material

Question 18

What is the impact of water’s high latent heat of vaporisation?

Answer 18

Can help cool living things and keep their temperature stable

Question 19

Why does water have a high latent heat of vaporisation?

Answer 19

• molecules are held together by hydrogen bonds
• relatively large amount of energy required to break them

Question 20

Define condensation reaction

Answer 20

Occurs when 2 molecules are joined together with the removal of water

Question 21

Define hydrolysis

Answer 21

2 molecules being split apart thanks to the addition of water

Question 22

What is a condensation reaction?

Answer 22

• reaction of 2 -OH groups
• involves the breaking and frmation of covalent bonds

Question 23

What elements are present in carbohydrates?

Answer 23

C, H, and O

Question 24

What elements are present in proteins?

Answer 24

C, H, O, N, and S

Question 25

What elements are present in nucleic acids?

Answer 25

C,H,O,N and P

Question 26

What is the monomer for carbohydrates?

Answer 26

Monosaccharides

Question 27

What is the monomer for proteins?

Answer 27

Amino acids

Question 28

What is the monomer for nucleic acids?

Answer 28

Nucleotides

Question 29

What is the polymer for carbohydrates?

Answer 29

Polysaccharides

Question 30

What is the polymer for proteins?

Answer 30

Polypeptides + proteins

Question 31

What is the polymer for nucleotides?

Answer 31

DNA + RNA