OZ1 + OZ2: Light and Energy

Question 1

How do you convert from ppm to %?

Answer 1

Divide by 10,000

Question 2

How do you convert from % to pmm?

Answer 2

Multiply by 10,000

Question 3

In which two ways is light described as?

Answer 3

• A wave

- A particle

Question 4

What is the equation for working out the speed of light?

Answer 4

Speed of light (c) = wavelength (λ) x frequency (v)

Question 5

What is the speed of light?

Answer 5

3.00 x 10^8 ms^-1

Question 6

What is the unit for wavelength?

Answer 6

m (metres)

Question 7

What is the unit for frequency when working out the speed of light?

Answer 7

s^-1

Question 8

What is the equation for working out energy using plank’s constant?

Answer 8

Energy (E) = Plank’s constant (h) x frequency (v)

Question 9

What is the unit for energy?

Answer 9

J (Joules)

Question 10

What is Plank’s Constant?

Answer 10

6.63 x 10^-34 JHz^-1

Question 11

What is the unit for frequency when working out energy?

Answer 11

Hz (hertz)

Question 12

What is the equation for working out energy with both speed of light and Plank’s Constant?

Answer 12

E = h x c/ λ

Question 13

What does energy’s interaction with chemicals depend on? (2)

Answer 13

• The type of chemical

- The amount of energy involved

Question 14

What 4 types of behaviour do molecules have in order of which requires the most energy to which requires the least?

Answer 14

• Electronic energy
• Vibrational energy
• Rotational energy
• Translational energy

Question 15

Why do changes in rotational energy require a lower frequency of light on the EM spectrum to be absorbed than changes in vibrational energy?

Answer 15

Making molecules rotate requires less energy than making bonds within a molecule stretch

Question 16

What energy and type of light on the EM spectrum does changing the electronic energy level correspond to?

Answer 16

• 1x10^-19 to 1x10^-16 J

- UV and visible

Question 17

What energy and type of light on the EM spectrum does changing the vibrational energy level correspond to?

Answer 17

• 1x10^-20 to 1x10^-19 J

- Infrared

Question 18

What energy and type of light on the EM spectrum does changing the rotational energy level correspond to?

Answer 18

• 1x10^-22 to 1x10^-20 J

- Microwave

Question 19

Why are the amounts of energy required for different energy changes given in ranges?

Answer 19

The size of the energy change depends on the strength of the substance’s bond

Question 20

What three types of electronic changes occur when molecules absorb UV light (in order of increasing energy absorbed)?

Answer 20

• Electrons are excited to a higher energy level
• Photodissociation
• Ionisation

Question 21

How are electrons excited to a higher energy level?

Answer 21

They absorb the UV energy and jump up

Question 22

What is photodissociation?

Answer 22

• So much energy is absorbed that bonding electrons cannot keep atoms together.
• Radicals are formed.

Question 23

What is ionisation?

Answer 23

When an electron leaves a molecule turning it into an ion