Molecular bonding + Properties of Water Flashcards
Define electronegativity
The ability of atoms of elements to pull shared electrons
–> can depend on th number of protons in the nucleus
What causes a bond to be polar?
The difference in electronegativity, and sometimes the shape of atom
How is a water molecule polar?
- 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
Define hydrogen bond
Slightly positive H atom will attract slightly negative atoms of other molecules
What is stronger: a hydrogen bond or a covalent bond?
Covalent bonds because hydrogen bonds are between molecules whereas covalent bonds are between atoms
What are the properties of water?
- 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
What is the impact of water being a liquid at room temperatures?
- provides habitats for living things
- forms major components in tissues
- provides a reaction medium for chemical reactions + transport medium
Explain how ice is less dense than water
- 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
What is the impact of the density of water?
- currents can circulate food
- insulation
- animals can move and survive
How is water a solvent?
- 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
What is the impact of water being a solvent?
Allows for:
- reactions to occur
- hydrolysis
- transport
How does water have cohesion?
Hydrogen bonds between molecules pull them together, so it retains its shape
How does water have surface tension?
Hydrogen bonds among the surface water molecules resist stretching or breaking the surface
What is the impact of water’s cohesion and surface tension?
- enables transpiration in plants - water pulled up
- provides a habitat
Define high specific heat capacity
Energy needed to raise the temperature of 1 kg of a material by 1degree c
What is the impact of water’s high specific heat capacity?
Provides a stable environment for:
- enzyme controlled reactions
- aquatic animals to live in
Define high latent heat of vaporisation
Energy requires to change the state of 1kg of a material
What is the impact of water’s high latent heat of vaporisation?
Can help cool living things and keep their temperature stable
Why does water have a high latent heat of vaporisation?
- molecules are held together by hydrogen bonds
- relatively large amount of energy required to break them
Define condensation reaction
Occurs when 2 molecules are joined together with the removal of water
Define hydrolysis
2 molecules being split apart thanks to the addition of water
What is a condensation reaction?
- reaction of 2 -OH groups
- involves the breaking and frmation of covalent bonds
What elements are present in carbohydrates?
C, H, and O
What elements are present in proteins?
C, H, O, N, and S
What elements are present in nucleic acids?
C,H,O,N and P
What is the monomer for carbohydrates?
Monosaccharides
What is the monomer for proteins?
Amino acids
What is the monomer for nucleic acids?
Nucleotides
What is the polymer for carbohydrates?
Polysaccharides
What is the polymer for proteins?
Polypeptides + proteins
What is the polymer for nucleotides?
DNA + RNA
