Chapter 2 - Water

Question 1

What makes up a water molecule?

Answer 1

Two hydrogen molecules covalently bonded to 1 oxygen molecule, forming a triangular shape

Question 2

What is a covalent bond?

Answer 2

A strong chemical bond formed by sharing one or more electrons between two atoms, forming a molecule

Question 3

What is a polar molecule?

Answer 3

A molecule with regions of negative and positive charge

Question 4

Why does the water molecule have an overall neutral electrical charge?

Answer 4

Because the the overall oxygen charge is slightly negative and the overall hydrogen charges are slightly positive so balance each other out

Question 5

Why do two separate water molecules attract one another?

Answer 5

Because of weak hydrogen bonds, which form between a hydrogen and oxygen atom of adjacent water molecules

Question 6

What can water molecules do, due to there attraction to one another?

Answer 6

Flow together as a liquid, and are attracted to all charged molecules/surfaces

Question 7

Why do hydrogen bonds need to be weak between adjacent water molecules?

Answer 7

So that the bonds can form and break easily, water flows quickly

Question 8

Why is water an ideal habitat?

Answer 8

It remains a liquid between 0-100 degrees which is perfect for living things to survive in

Question 9

Why is water an efficient coolant?

Answer 9

It has a high specific heat capacity (absorbs a great amount of heat relative to its mass)

Question 10

What happens to water at 0 degrees or lower?

Answer 10

The molecules loose KE and hydrogen bonds stop breaking easily, forming a rigid structure that no longer flows

Question 11

What happens to water at 100 degrees?

Answer 11

The hydrogen bonds are weakened by the heat and escape one another, water becomes gas (water vapour)

Question 12

What happens to water at 0 degrees, precisely?

Answer 12

The newly forming solid water/ice is less dense than the water underneath it, so this sheet of ice floats on top of the water, providing an insulating layer which keeps the water underneath at a constant temperature (where living things may still survive)

Question 13

What is a solution?

Answer 13

A solvent (the liquid), with dissolved solutes in it (solids/liquids/gasses)

Question 14

How does water act as a solvent?

Answer 14

It surrounds the solute molecules, keeping them in a solution

Question 15

What can easily dissolve in water?

Answer 15

Polar charged molecules

Question 16

Why can carbon containing molecules (with charged ionised groups, e.g. (COOH-), or amino groups (NH3+) dissolve?

Answer 16

They can form hydrogen bonds with the atoms of there opposite charge e.g. the oxygen will bond to the amino group solutes

Question 17

How do ionic substances dissolve?

Answer 17

They release pos charged ions (cations) and negatively charged ions (anions) and water clusters around each

Question 18

Why is water a necessity in living things?

Answer 18

Allows chemical reactions within a cell, allows molecules to be dissolved in the systole, ideal transport medium as dissolves polar molecules & ions

Question 19

What is cohesion?

Answer 19

Property of water - water molecules are attracted to each other due to hydrogen bonding

Question 20

What is tension?

Answer 20

A force that tends to stretch something

Question 21

What is adhesion?

Answer 21

Property of water - water molecules are attracted to surfaces such as walls of cells/vessels/tubes

Question 22

What creates surface tension?

Answer 22

Hydrogen bonds pulling the molecules inwards at the surface

Question 23

What happens to non-polar molecules when dissolving in water?

Answer 23

They cannot dissolve, they are hydrophobic and are repelled