models of light, endo and exothermic reactions

Question 1

waves and particles

Answer 1

1. A wave is a disturbance that travels through space, carrying energy
2. Particles are countable pieces of a substance with particular properties.

Question 2

Wave-particle duality

Answer 2

Sometimes light acts like a wave and sometimes a particle.

1. In each situation either a wave or particle model works better to describe light.
2. EM radiation is both a particle and a wave at the same time.

Question 3

Wave action-reflection

Answer 3

reflect off a surface at the same angle it came in

Question 4

EM radiation evidence-reflection

Answer 4

reflects off a surface at the same angle that it comes in.

Question 5

Particles action- reflection

Answer 5

Bounce off a surface at the same angle that they come in.

Question 6

Wave action- refraction

Answer 6

bends towards the perpendicular line when moving into a “slower” substance.

Question 7

Particle action-refraction

Answer 7

bends away from the perpendicular line when moving into a “slower” substance.

Question 8

EM radiation evidence- refraction

Answer 8

bends towards the perpendicular line when moving into a “slower” substance.

Question 9

Wave action- diffraction

Answer 9

bend around corners, going behind barriers

Question 10

Particle action- diffraction

Answer 10

don’t bend around barriers, go in straight lines

Question 11

EM radiation evidence- diffraction

Answer 11

bends around corners, going behind barriers

Question 12

Wave action- interference

Answer 12

interferes, adding or canceling through constructive and destructive interference.

Question 13

Particle action- interference

Answer 13

they don’t interfere

Question 14

EM radiation evidence- interference

Answer 14

Interferes, adding, or canceling through constructive and destructive interference.

Question 15

Wave action- photoelectric effect, time delay

Answer 15

there should be a time delay between when the light first hits and the electrons get knocked off.

Question 16

Particle action- photoelectric effect, time delay

Answer 16

have no time delay in ejecting electrons since they hit suddenly.

Question 17

EM radiation evidence- photoelectric effect, time delay

Answer 17

there is no time delay.

Question 18

Wave action- photoelectric effect, brightness

Answer 18

brighter light has more energy so it will give the electrons more energy and make them fly off faster.

Question 19

Particle action- photoelectric effect, brightness

Answer 19

brighter light means more photons, which knocks off more electrons but doesn’t affect the energy.

Question 20

EM radiation evidence- photoelectric effect, brightness

Answer 20

brighter light knocks off more electrons but doesn’t give them more energy to fly off faster.

Question 21

Wave action- photoelectric effect, color

Answer 21

the color of the light has no effect on the electrons that are emitted from the metal.

Question 22

Particle action- photoelectric effect, color

Answer 22

higher frequency light means photons have more energy so the electrons are ejected with more energy.

Question 23

EM radiation evidence- photoelectric effect, color

Answer 23

color does matter, higher frequency light makes the electrons go faster.

Question 24

The photoelectric effect

Answer 24

If visible light is shined on metals in specific conditions, the metal will absorb the light and emit electrons.

Question 25

Exothermic reaction

Answer 25

a chemical reaction is exothermic if it gives off heat

Question 26

Endothermic reaction

Answer 26

a chemical reaction is endothermic if it absorbs heat.

Question 27

Chemical energy and thermal energy in chemical reactions

Answer 27

1. In exothermic reactions the chemical energy decreases in the reaction and the thermal energy increases.
2. In endothermic reactions the chemical energy increases in the reaction and the thermal energy decreases.

Question 28

Chemical energy

Answer 28

Chemical energy is a type of potential energy stored in chemical bonds.

Question 29

Making new chemical bonds

Answer 29

When new chemical bonds form atoms move with the attractive force. Therefore, when new chemical bonds form their potential energy drops.

Question 30

Chemical bonds

Answer 30

Chemical bonds are attractive forces between atoms

Question 31

Breaking old chemical bonds

Answer 31

When chemical bonds break, atoms move against the attractive force. Therefore, when old chemical bonds break their potential energy increases.

Question 32

Rate of a chemical reaction

Answer 32

The rate of a chemical reaction is how quickly the reaction occurs

Question 33

High and low reaction rates

Answer 33

Chemical reactions with a high reaction rate occur quickly

Chemical reactions with a low reaction rate occur slowly

Question 34

Factors that can affect reaction rate

Answer 34

1. Temperature
2. Phase
3. Concentration
4. Catalysts

Question 35

Temperature and reaction rate

Answer 35

1. Increasing the temperature of a reaction speeds up the reaction rate
2. Decreasing the temperature of a reaction slows the reaction rate

Question 36

Phase and reaction rate

Answer 36

1. In order for two substances to react, their particles must be in contact
   Gases have the fastest reaction rate
   Liquids have a slower reaction rate
   Solids have the slowest reaction rate

Question 37

Breaking solids and reaction rate

Answer 37

If solid reactants are broken up into smaller pieces more particles can come into contact and the reaction rate will be quicker.

Question 38

Concentration

Answer 38

1. The concentration of a substance is the amount of that substance in a certain space.

Question 39

Concentration and reaction rates

Answer 39

1. Increasing the concentration of a reactant speeds up the reaction rate
2. Decreasing the concentration of a reactant slows the reaction rate

Question 40

Catalysts and reaction rate

Answer 40

A catalyst is a substance that speeds up a chemical reaction without being used up. Using a catalyst increases the reaction rate.