Water and Seawater ! Flashcards
describe the number of water molecules in a single droplet of water.
A single droplet of water contains more water molecules than are are grains of sand on a large beach
Explain why a water body, like a lake or the ocean, freezes from the top down.
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
List the three fundamental subatomic particles, and state which two are in the nucleus.
Proton
Neutron
Electron
Only protons and Neutrons reside in the nucleus
Give the relative charges for a proton, a neutron, and an electron.
Protons and neutrons have about the same mass (extremely small)
1/2000 the mass of either a proton or neutron
Explain why most atoms are electrically neutral.
Balance
equal amounts of proton and electrons
Define ion
An atom that becomes electrically charged by gaining or losing electrons
gain => negative charge
loss => positive charge
Define molecule.
A group of two or more atoms held together by mutually shared electrons.
Describe a water molecule’s shape
A central oxygen atom covalently bonded to two hydrogen atoms, separated by an angle of 105 degrees
Which end of the dipolar water molecule is negative and which is positive?
side of the oxygen atom is slightly positive
side of the hydrogen atom is slightly negative
Define hydrogen bond.
an intermolecular bond that forms within water because of the dipolar nature of water molecules
Contrast the strengths of hydrogen bonds between water molecules and the covalent bonds within a water molecule.
Hydrogen bonds are weaker than the covalent bonds
Explain why water has a high surface tension.
Waters ability to form hydrogen bonds causes it to have the highest surface tension of any liquid except mercury
Define ionic bonding
A chemical reaction formed as a result of the electrical attraction
Explain how water molecules break ionic bonds, e.g. NaCl.
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
Explain why water is called the universal solvent.
Water molecules interact with other water molecules and other polar molecules thus enabling it to dissolve nearly everything.
List the three states of water on Earth’s surface.
solid, liquid, gas
What is required to break bonds to change the state of matter?
Energy in the form of heat
Define heat
Energy transfer from one body to another due to a difference in temperature
Define calorie
A unit of heat defined as the amount of heat required to raise the temperature of 1 gram of water 1 degree C
Define temperature
A direct measure of the average kinetic energy of the molecules of a substance
contrast the relative amounts of bonding in ice, water, and water vapor.
Ice - hydrogen bonds between all water molecules
water- some
gas-none
temperatures at which pure water freezes and boils.
0C,100C
. Explain why water’s condensation and boiling points are high compared to similar substances
Additional heat energy is required to overcome its hydrogen bonds and van der Waals forces
Define heat capacity.
The amount of energy required to raise the temperature of 1 gram of a substance 1 degree C
Give the specific heat capacity of water in calories
1.0 cal/g/C
Give water’s latent heat of melting in calories.
80 cal/g
Define latent heat of melting.
the heat energy that must be added to one gram of a substance at its melting point to convert it to a liquid
Define latent heat of vaporization.
The heat of energy that must be added to one gram of a substance at its boiling point to convert it to a vapor.
Give water’s latent heat of vaporization in calories.
540 cal/g
Explain why water’s latent heat of vaporization more than 7x greater than its latent heat of melting
From liquid to gas all the hydrogen bonds need to be broken while from solid to liquid only some needs to be
Define evaporation
The process of changing from the liquid to the vapor state at a temperature below the boiling point of a substance.
Explain how evaporation cools matter.
The molecules left being have lost heat energy to those that evaporated.
Give water’s latent heat of evaporation at 20oC.
585 cal
Describe water’s global thermostatic effects.
properties that act to moderate changes in temperature which in turn affects the climate.
