Unit 1- Water

Question 1

What is an organic compound?

Answer 1

A compound containing a carbon-carbon bond

Question 2

What is an inorganic compound?

Answer 2

A compound not containing a carbon-carbon bond

Question 3

What are the 4 main types of organic molecules found in living organisms

Answer 3

Carbohydrates
Lipids
Proteins
Nucleic acids

Question 4

Properties of covalent bonds:

Answer 4

• very strong
• cannot be spontaneously broken or formed in living organisms temps
• only really broken by enzymes

Question 5

Properties of ionic bonds:

Answer 5

• fairly strong (weaker than covalent)

- formed between positive and negative ions

Question 6

Properties of hydrogen bonds:

Answer 6

• weakest bond
• formed between delta positive and delta negative atoms
• spontaneously broken and made in living cells

Question 7

Examples of an ionic bond and hydrogen bond?

Answer 7

Ionic- found in protein molecules (-COO- and NH3+)

Hydrogen- between water molecules (H - - - O)

Question 8

Description of water molecules:

Answer 8

• charged dipole

- slightly negative oxygen and slightly positive hydrogen

Question 9

Properties of water: (6)

Answer 9

• good solvent
• high specific heat capacity
• high latent heat
• cohesive and adhesive
• incompressible

Question 10

What makes water a good solvent and a use of this?

Answer 10

• water dipoles stick to atoms in almost all crystalline solids, causing them to dissolve
• polar molecules are hydrophilic so dissolve like sugars, amino acids
• non polar molecules are hydrophobic so are insoluble
  Eg, cell sap

Question 11

Benefit of water having a high specific heat capacity: and what this means

Answer 11

• means water takes a lot of energy to heat, and temperature doesn’t fluctuate much
• sea water temps are constant yearly

Question 12

Water has a latent heat, what does this mean and what’s a use of his in plants and animals

Answer 12

• water requires a lot of energy to change state into a gas, due to the abundance of hydrogen bonds
• so as it evaporates water extracts heat from around
  Eg, to cool animals (sweating) or plants (transpiration)

Question 13

Water is considered cohesive and adhesive give the meaning and a use of these properties

Answer 13

• cohesive means the water molecules stick together
  Eg long column of water in transpiration which don’t break and surface tension which allows pond skaters to walk on water
• adhesive means water molecules stick to surfaces
  Eg, capillary action where water is drawn up a narrow xylem and meniscus

Question 14

What temp is water most dense and what’s the benefits of this (3)?

Answer 14

4 degrees C

• ice floats on water surface forming an insulating layer, so aquatic organisms can survive ice ages
• expansion of water as it freezes causes freeze thaw erosion or rocks which forms soil for plant life
• cold water sinks and warm water rises creating currents

Question 15

Water is incompressible why? And what is a use of this?

Answer 15

• hydrogen bonds hold water molecules so close they can’t be compressed any further
• when a force is applied water will move, gives rise to blood flow, how the eye keeps a spherical shape, the turgor in plant cells