Unit 9: Energy in Chemical Reactions

Question 1

define energy

Answer 1

the ability to do WORK, produce HEAT, or CHANGE matter

-drives all chemical reactions

•some releases energy and others need to take in energy (photosynthesis ☀️)

Question 2

list two types of energy and the differences

Answer 2

potential energy:

-energy that is available due to position or composition

kinetic energy:

-energy due to the motion of the object, depends on mass and velocity

Question 3

list the microscopic examples of potential energy and kinetic energy

Answer 3

potential: ATP is a biological molecule that has the ability to RELEASE energy when one of the bonds is REARRANGED

kinetic: movement of molecules or atoms made possible by the energy release when the phosphate bond is BROKEN

Question 4

define temperature

Answer 4

measure of average kinetic energy of the particles in a substance

Question 5

define electromagnetic radiation

Answer 5

form of energy traveling as a wave 🌊 + visible light that we can see 😏

-moves at the speed of light 3.0 x 10^8 m/s)

Question 6

wavelength and energy

Answer 6

amount of energy has determines its color

less energy = longer wavelength (red)

more energy = shorter wavelength (ultraviolet)

Question 7

According the the first laws of thermodynamics, the energy of the universe ____

Answer 7

is CONSTANT

energy can be converted to sound, vibration, and heat - but remains UNCHANGED

Question 8

what is the system (in chemistry 🧪)

Answer 8

what you are looking at

Question 9

what is the surrounding

Answer 9

everything else besides the system 💀

Question 10

exothermic vs endothermic

Answer 10

exothermic: energy release from the system into the surroundings

endothermic: energy absorbed into the system from the surroundings

Question 11

list examples of exothermic

Answer 11

combustion, oxidative respiration, freezing water, condensing water vapor

Question 12

list examples of endothermic

Answer 12

ammonium salt, photosynthesis, melting ice, boiling water

Question 13

how do chemical reactions happen (in what 2 parts)

Answer 13

breaking bonds:
-alway REQUIRES energy (endothermic)

forming new bonds:
-always RELEASES energy (exo, and no, not the kpop group)

Question 14

Endothermic reactions: energy absorbed by breaking bonds is ___ than the amount of energy by making new bonds

Answer 14

MORE

Question 15

Exothermic reactions: energy absorbed by breaking bonds is ___ than the amount of energy by making new bonds

Answer 15

LESS

Question 16

define heat flow and what makes heat flow possible (hint: law)

Answer 16

heat flow is the energy due to a difference in temperature, 2nd law of thermodynamics:
the entropy (disorder) of the universe is increasing

*more disorder tend to spread out

Question 17

when does heat flow stop?

Answer 17

no net heat transfer between the two objects

Question 18

name three ways how heat energy can spread and describe them

Answer 18

• conduction
  transfer of heat energy to another substance or object with which it is in contact

-convection
when a warm substance rises above its cooler surroundings

-radiation
when electromagnetic waves carry energy from an energy source

Question 19

endo or exo? when you feel cold

Answer 19

endothermic