Water

Question 1

What is water composed of?

(Elements + bond)

Answer 1

2 Hydrogen atoms share electrons with 1 oxygen atom (covalent bond)

Question 2

HINT: Unevenly distributed elecrtical charge

How is water a polar molecule & a dipole?

(2 points)

Answer 2

1. Oxygen is more electronegative than hygrogen
2. The shared negative electron are pulled towaes the oxygen atom

Question 3

What charge is on the hygrogen atoms in water?

(δ)

Answer 3

A slighty positive charge - delta positive (δ+)

Question 4

What charge is on the oxygen atoms in water?

(δ)

Answer 4

A slightly negative charge - delta negative (δ-)

Question 5

What is hydrogen bonding in water ?

Answer 5

The delta (δ) hydrogen atoms are attracted to the lone pair of other oxygen atoms of the water molecules

(Dotted lines are used to show the hydrogen bonding in diagrams)

Question 6

What are useful properties of water?

(4 points)

Answer 6

1. Strong Adhesion
2. Good Solvent
3. Higher latent heat of vaporisation

(3 = high specific heat capacity + high boilling point)

Question 7

What does cohesive mean?

Answer 7

Cohesion is the attraction between molecules of the same type

Question 8

Why is water being cohesive useful?

(3 points)

Answer 8

1. Helps water flow well
2. Useful for transporting substances
3. Makes it possible to pull water uphill

(3= eg. in xylem)

Question 9

Define solvent

Answer 9

A liquid that other substance can dissolve in

Question 10

What types of substances dissolve in water?

(2 points)

Answer 10

1. Ionic
2. Polar

Question 11

What substances cannot dissolve in water?

Answer 11

Non Polar

Question 12

Why is water being a solvent useful?

Answer 12

Substances for important reactions can dissolve in it, to be transported

Question 13

Why do ionic substances dissolve in water?

(6 points)

Answer 13

1. Water is polar
2. The H

Question 13

**HINT: **How molecules surround and are attracted to ions

Why do ionic substances dissolve in water?

(6 points)

Answer 13

1. Water is polar
2. The H δ+ end of the water molecule is attacted to the negative ion
3. The O δ- end of the water molecule is attracted to the positive ion
4. All the small chatges in water add up together to equal the charge of the ion
5. The ion breaks free
6. Ions are hydrated, completely surrounded by water molecules and have dissolves

Question 14

What does water having a high letent heat of vaporisation mean?

(2 points)

Answer 14

1. Lots of energy is needed to break hydrogen bonds
2. Uses lots of energy to evaporate so it has a cooling effect