OZ 2: Screening the Sun

What kind of radiation causes skin cancer?

high frequency UV radiation

Why can UV lead to skin cancer?

part of its frequency spectrum aligns with the frequency required to break bonds in DNA

so it can damage genes

What can exposure to sunlight do to the skin?

damage proteins

makes people look wrinkly and leathery

What can exposure to sunlight do to the blood vessels?

irritate blood vessels in skin

looks red and sunburnt

Why would you not burn if you sat in front of a window?

the glass lets through visible light but blocks high energy UV radiation

Is it possible to burn in water?

yes, water lets through some UV

What happens to benzene rings or alternating double and single bond molecules when UV radiation is absorbed?

π orbitals are promoted to higher energy levels

How is ozone useful in the stratosphere?

absorbs high energy UV-B and UV-c radiation

What are the 3 dangers of UV-B and UV-C radiation?

1. damages DNA leading to skin cancer

2. damages eyes leading to cataracts

3. damage crops

What are the disadvantages of ozone as photochemical smog in the troposphere?

1. haziness and reduced visibility

2. irritation

3. respiratory problems

Why is there no life in the stratosphere?

high energy UV breaks down molecules

Why is the ionosphere called the ionosphere?

high energy radiation knocks electrons out of atoms forming ions

Equation for the speed of a wave?

c=ƒλ

How can you calculate energy of a wave?

E=hƒ

What happens when EM radiation interacts with matter?

energy is transferred to the chemicals which are changed

What are 4 aspects of molecule behaviour?

1. Translation

2. Rotation

3. Vibration of bonds

4. Electron energy

Electrons ocuppy

definite energy levels

Electronic energy is

quantised

All types of energy are

quantised

The spacing between vibrational energy levels corresponds to the _________ part of the spectrum

infrared

How can you make molecules vibrate?

IR radiation makes bonds vibrate more energetically

molecules have more kinetic energy

Making molecules rotate requires _______ energy than making their bonds vibrate

less

changes in rotational energy correspond to the ________ part of the spectrum

microwave

The spacing between translational energy levels is _________ than for vibrational and rotational

less

Electronic energy changes are _________ energy than vibrational changes

higher

Exciting electron to higher energy levels requires energy corresponding to the _________ and ________ parts of the spectrum

visible

UV

EM radiation reaching the Earth surface

visible
UV

EM radiation given by Earth’s surface

IR

What are the three things that can happen when a chlorine molecule absorbs radiation?

1. Electrons may be excited

2. photodissociation

3. ionisation

How does chlorine get its color?

when electrons are excited to higher energy levels, visible light of such a frequency is absorbed that the remaining light appears green

photodissociation

when absorbed energy causes electrons to no longer bond the atoms together, forming radicals

radicals

Molecules or atoms with at least one unpaired electron, usually very reactive

When are radicals formed by photodissociation?

when so much high energy radiation is absorbed that the bonding electrons can no longer bond the atoms together

What occurs when a molecule absorbs very high energy photons?

An electron may acquire enough energy to leave the molecule, causing ionization