Water and Seawater !

Question 1

describe the number of water molecules in a single droplet of water.

Answer 1

A single droplet of water contains more water molecules than are are grains of sand on a large beach

Question 2

Explain why a water body, like a lake or the ocean, freezes from the top down.

Answer 2

Water expands as it freezes
ice floats
The ice formed on top acts as an insulative cover to protect the marine organisms that live in the liquid water below

Question 3

List the three fundamental subatomic particles, and state which two are in the nucleus.

Answer 3

Proton
Neutron
Electron
Only protons and Neutrons reside in the nucleus

Question 4

Give the relative charges for a proton, a neutron, and an electron.

Answer 4

Protons and neutrons have about the same mass (extremely small)
1/2000 the mass of either a proton or neutron

Question 5

Explain why most atoms are electrically neutral.

Answer 5

Balance

equal amounts of proton and electrons

Question 6

Define ion

Answer 6

An atom that becomes electrically charged by gaining or losing electrons
gain => negative charge
loss => positive charge

Question 7

Define molecule.

Answer 7

A group of two or more atoms held together by mutually shared electrons.

Question 8

Describe a water molecule’s shape

Answer 8

A central oxygen atom covalently bonded to two hydrogen atoms, separated by an angle of 105 degrees

Question 9

Which end of the dipolar water molecule is negative and which is positive?

Answer 9

side of the oxygen atom is slightly positive

side of the hydrogen atom is slightly negative

Question 10

Define hydrogen bond.

Answer 10

an intermolecular bond that forms within water because of the dipolar nature of water molecules

Question 11

Contrast the strengths of hydrogen bonds between water molecules and the covalent bonds within a water molecule.

Answer 11

Hydrogen bonds are weaker than the covalent bonds

Question 12

Explain why water has a high surface tension.

Answer 12

Waters ability to form hydrogen bonds causes it to have the highest surface tension of any liquid except mercury

Question 13

Define ionic bonding

Answer 13

A chemical reaction formed as a result of the electrical attraction

Question 14

Explain how water molecules break ionic bonds, e.g. NaCl.

Answer 14

The positive atom is attracted to the negatively ends of the water molecule
The negative atom is attracted to the positive end of the water molecule

Question 15

Explain why water is called the universal solvent.

Answer 15

Water molecules interact with other water molecules and other polar molecules thus enabling it to dissolve nearly everything.

Question 16

List the three states of water on Earth’s surface.

Answer 16

solid, liquid, gas

Question 17

What is required to break bonds to change the state of matter?

Answer 17

Energy in the form of heat

Question 18

Define heat

Answer 18

Energy transfer from one body to another due to a difference in temperature

Question 19

Define calorie

Answer 19

A unit of heat defined as the amount of heat required to raise the temperature of 1 gram of water 1 degree C

Question 20

Define temperature

Answer 20

A direct measure of the average kinetic energy of the molecules of a substance

Question 21

contrast the relative amounts of bonding in ice, water, and water vapor.

Answer 21

Ice - hydrogen bonds between all water molecules
water- some
gas-none

Question 22

temperatures at which pure water freezes and boils.

Answer 22

0C,100C

Question 23

. Explain why water’s condensation and boiling points are high compared to similar substances

Answer 23

Additional heat energy is required to overcome its hydrogen bonds and van der Waals forces

Question 24

Define heat capacity.

Answer 24

The amount of energy required to raise the temperature of 1 gram of a substance 1 degree C

Question 25

Give the specific heat capacity of water in calories

Answer 25

1.0 cal/g/C

Question 26

Give water’s latent heat of melting in calories.

Answer 26

80 cal/g

Question 27

Define latent heat of melting.

Answer 27

the heat energy that must be added to one gram of a substance at its melting point to convert it to a liquid

Question 28

Define latent heat of vaporization.

Answer 28

The heat of energy that must be added to one gram of a substance at its boiling point to convert it to a vapor.

Question 29

Give water’s latent heat of vaporization in calories.

Answer 29

540 cal/g

Question 30

Explain why water’s latent heat of vaporization more than 7x greater than its latent heat of melting

Answer 30

From liquid to gas all the hydrogen bonds need to be broken while from solid to liquid only some needs to be

Question 31

Define evaporation

Answer 31

The process of changing from the liquid to the vapor state at a temperature below the boiling point of a substance.

Question 32

Explain how evaporation cools matter.

Answer 32

The molecules left being have lost heat energy to those that evaporated.

Question 33

Give water’s latent heat of evaporation at 20oC.

Answer 33

585 cal

Question 34

Describe water’s global thermostatic effects.

Answer 34

properties that act to moderate changes in temperature which in turn affects the climate.