Water

Question 1

How are hydrogen bonds in water formed?

Answer 1

In water, a slightly negatively charged oxygen atom is bonded to 2 slightly positively charged hydrogen atoms. This results in water becoming a polar molecule. Slightly positive hydrogen atoms on one water molecule are attracted to slightly negative oxygen atoms on other water molecules. This force of attraction is called the hydrogen bond.

Question 2

Why does water have a relatively high boiling point?

Answer 2

The hydrogen bonds between water molecules are relatively strong require lots of heat energy to break. At room temperature, not enough heat energy is available to break the hydrogen bonds between the water molecules and turn water into a gas, so water has quite a high boiling point.

Question 3

What is the importance of water having a high boiling point?

Answer 3

1. Water is a liquid for most temperatures on the earth’s surface.
2. Provides a habitat for aquatic plants and animals.
3. Acts as a transport medium in multicellular organisms.

Question 4

What is the importance of ice being less dense than water?

Answer 4

1. Ice floats on water in freezing temperatures.
2. This provides a habitat for animals such as the polar bear to hunt and travel.
3. Ice forms an insulating layer on the surface of lakes and ponds, which prevents water below from freezing, protecting the aquatic organisms living in the water.

Question 5

Why does water have a relatively high specific heat capacity?

Answer 5

When water is heated, a lot of the heat energy goes towards breaking the hydrogen bonds between the water molecules rather than raising the temperature of the water.

Question 6

What is the significance of water having a relatively high specific heat capacity?

Answer 6

1. Water does not undergo dramatic temperature changes even when the surroundings do. This provides organisms in lakes, ponds and oceans with a relatively stable living environment.
2. This also provides organisms with a relatively stable internal environment.

Question 7

Why is water a good solvent?

Answer 7

Ionic and polar compounds are attracted to the polar water molecules. This attraction can be strong enough to break the interactions between themselves, allowing solids to dissolve. Water molecules then surround the polar molecules, preventing them from interacting with each other, therefore dissolving the substance.

Question 8

What is the significance of water being a good solvent?

Answer 8

Water the the main medium for metabolic reactions to take place. This means that dissolved chemicals are able to react with each other in the cytoplasmic water of cells in metabolic processes like respiration and photosynthesis.

Question 9

What is the significance of cohesion between water molecules?

Answer 9

1. Cohesion is the cause of surface tension which some small organisms use to move around.
2. Cohesion is the main process behind cohesion-tension theory which generates the transpiration pull that move water from the roots to the leaves in plants.

Question 10

What is the significance of water as a metabolic chemical?

Answer 10

1. Water is an important reagent in photosynthesis.

2. Water used in hydrolysis reactions that break up bigger biological molecules into smaller, more useful ones.

Question 11

What is the significance of water having a high latent heat of vaporisation?

Answer 11

Water requires a lot of heat energy to evaporate. It may steal this heat energy from the skin of organisms, cooling the organism down.