O 3 - Energy and Matter

Question 1

What is the ‘greenhouse effect’?

Answer 1

• The sun produces mainly UV, visible and IR radiation which is partially reflected back into space when it reaches Earth
• Yet, some is absorbed by the Earth’s surface, causing it to heat up
• The Earth emits this energy back out as IR
• This IR radiation emitted by the earth can be absorbed by gases in the troposphere and become trapped
• IR radiation is then re-emitted in all directions, some back towards the earth. This causes a heating effect

Question 2

Why does the absorption of IR by greenhouse gas molecules increase the atmosphere’s temperature?

Answer 2

• Absorbing IR causes the bond to vibrate more as it has more energy
• This energy is transferred to other surrounding molecules via collisions
• This increases the kinetic energy and therefore temperature of the molecules