Water

Question 1

What is a covalent bond?

Answer 1

Bond formed when atoms share electrons

Question 2

What is a polar covalent bond and why does it form

Answer 2

Bond formed by the unequal sharing of electrons
The nucleus of the oxygen atom is more attractive to electrons as compared to the nuclei of hydrogen atoms

Question 3

Why does O have partial negative charge and H partial positive charge

Answer 3

1) Because of polarity, unequal sharing of electrons
2) Water molecules are bent rather than linear, 2 H atoms are on the same side forming a pole

Question 4

Define hydrogen bond

Answer 4

The intermolecular force formed when a hydrogen atom in one polar molecule is attracted to a slightly negative atom of another polar covalent molecule (in this case, oxygen)

Question 5

If hydrogen bonds are weak how is the attraction so strong

Answer 5

Because water molecules are small, so there are many of them per unit volume

Question 6

What are the properties of water? what explains them?

Answer 6

Cohesion
Adhesion
High Specific heat capacity
High latent heat of vapourisation
High boiling point
Solvent

Hydrogen bonding and dipolarity explain them

Question 7

What is cohesion?

Answer 7

Refers to the binding together of two molecules of the same type, eg water molecules

Question 8

Application of cohesion

Answer 8

Water is sucked through the xylem at low pressure, and this is only possible if the water molecules are not separated by forces. Cohesion keeps them together

Cohesion leads to surface tension- because of which lighter insects skate on the surface

Question 9

What is adhesion

Answer 9

Hydrogen bonds formed between water and other polar molecules

Question 10

Application of Adhesion

Answer 10

Water adheres to the cellulose in the cell wall of plant cells. If water evaporates from the cell wall, adhesion causes water to be drawn out from nearby xylem vessels keeping the walls moist to absorb CO2

Water wets cloth

Question 11

What is specific heat capacity

Answer 11

The amount of energy required to increase the temperature of 1g of a substance by 1C

Question 12

Why does water have high specific heat capacity

Answer 12

Increases in temperature require hydrogen bonds to break, and they restrict the motion. Large amount of energy is required to increase or decrease the temperature even by a small amount.

Question 13

Applications of High specific heat capacity

Answer 13

Stable habitat for aquatic animals, lakes don’t freeze over
Formentation

Question 14

What is High latent heat of vapourisation

Answer 14

The amount of energy required to change 1g of water in it’s liquid state to it’s gaseous state at constant temperature.

Question 15

Why does water have a high latent heat of vapourisation

Answer 15

Considerable amounts of heat are required to to break the hydrogen bond

Question 16

Applications of High latent heat of vapourisation

Answer 16

Sweating

Question 17

What is boiling point

Answer 17

The highest temperature of a substance that it can reach in a liquid state.

Question 18

Why does water have a high boiling point

Answer 18

A large amount of energy is required to break the hydrogen bonds

Question 19

Why is water a good solvent

Answer 19

The polar nature of water means it forms shells around charged and polar molecules preventing clumping. Both poles dissolve positively charged particles and negatively charged particles respectively

Question 20

What is cytoplasm

Answer 20

A complex mixture of of dissolved substances in which the chemical reactions of metabolism occurs

Question 21

What are hydrophobic and hydrophilic substances

Answer 21

Hydrophilic- water loving, describes substances that are chemically attracted to water, all substances that dissolve, polar molecules of glucose, sodium, chloride, cellulose

Hydrophobic- insoluble, non polar, lipids, fats, oils

Question 22

What happens if a non polar molecule is surrounded by water molecule

Answer 22

hydrogen bonds form between the water molecules around the non polar ones
the non polar molecules are slightly attracted to each other, like oil drops