Water - 3.2 (1)

Question 1

How do atoms form molecules?

Answer 1

they join together by making bonds with each other

Question 2

In ionic bonds, what do atoms do?

Answer 2

they give or receive electrons

Question 3

What do the atoms form?

Answer 3

negative or positive ions that are held together by the attraction of the opposite charges

Question 4

When do covalent bonds occur?

Answer 4

when atoms share electrons

Question 5

What is not always shared equally by the atoms of different elements?

Answer 5

the negative electrons

Question 6

In covalent bonds, what will the electrons spend more time closer to?

Answer 6

one of the atoms than to the other

Question 7

What will the atom with more negative electrons be in comparison with the other atom in the bond?

Answer 7

slightly negative (delta negative) and the other atom will therefore be slightly positive (delta positive)

Question 8

The molecules where this occurs in are..

Answer 8

polar

Question 9

What is meant by polar?

Answer 9

this means that they have regions of negativity and regions of positivity

Question 10

What are oxygen and hydrogen examples of?

Answer 10

elements that don’t share electrons equally in a covalent bond

Question 11

Oxygen always has a much greater share of what?

Answer 11

the electrons in an O-H bond

Question 12

What do many organic molecules contain?

Answer 12

oxygen and hydrogen bonded together which are called hydroxyl (OH) groups (so they are then slightly polar)

Question 13

What is water (H2O) an example of?

Answer 13

a molecule that is polar

Question 14

What does water contain?

Answer 14

two of the hydroxyl groups

Question 15

How do polar molecules, including water, interact with each other?

Answer 15

as the positive and negative regions of the molecule attract each other and form bonds

Question 16

What are these bonds called?

Answer 16

hydrogen bonds

Question 17

What are hydrogen bonds?

Answer 17

weak interactions which break and reform between the constantly moving water molecules

Question 18

Although hydrogen bonds are weak interactions, they occur in…

Answer 18

high numbers

Question 19

What gives water its unique characteristics which are essential for life on this planet?

Answer 19

hydrogen bonding

Question 20

What kind of boiling point does water have?

Answer 20

a high boiling point

Question 21

Is water a small molecule that is much lighter than the gases carbon dioxide or oxygen?

Answer 21

yes

Question 22

Unlike oxygen and carbon dioxide, water is a liquid at…

Answer 22

room temperature, and this is due to the hydrogen bonding between water molecules

Question 23

What does it take a lot of to increase the temperature of water and to cause water to become gaseous (or to evaporate)?

Answer 23

a lot of energy

Question 24

When water freezes, what happens?

Answer 24

it turns to ice

Question 25

How are most substances in their solid state than in their liquid state?

Answer 25

more dense

Question 26

When water turns into ice, what happens?

Answer 26

it becomes less dense

Question 27

Why does water become less dense when it turns into ice?

Answer 27

because of the hydrogen bonds that are formed

Question 28

As water is cooled below 4 degrees celsius, what do the hydrogen bonds do?

Answer 28

they fix the positions of the polar molecules slightly further apart than the average distance in the liquid state

Question 29

What does this produce?

Answer 29

a giant, rigid, but open structure, with every oxygen atom at the centre of a tetrahedral arrangement of hydrogen atoms

Question 30

What does this result in?

Answer 30

a solid that is less dense than liquid water