Unit 4 - Energy and Society

Question 1

Energy and work

Answer 1

energy = the ability to do work
work = the transfer of energy

Question 2

Types of kinetic energy

Answer 2

heat/thermal = energy of vibrating particles 
sound = energy transferred by particle motion
kinetic = energy of motion

Question 3

Types of potential energy

Answer 3

gravitational = energy stored in an object due to its height in an area where the force of gravity can act on it to make it fall
elastic = energy stored by the bending/stretching or compressing of matter
chemical = energy stored in the chemical bonds of matter and can be released by way of a chemical reaction
electric = energy stored when static electric charges are held a certain distance apart
magnetic = energy stored in the space between two magnets
radiant = energy that is carried by electromagnetic waves
nuclear = energy stored in an atom’s nucleus that is waiting to be released in a nuclear reaction

Question 4

Work

Answer 4

work can be done on an object by applying a force that moves it a certain distance
symbol = W
unit = Joules (J)
it is a scalar quantity
the applied force is used to calculate the work done (when = 0) not the net force

Question 5

Cases when no work is done

Answer 5

the applied force is perpendicular to the displacement
when the displacement is 0
when there is no force

Question 6

Kinetic energy

Answer 6

the energy possessed by an object because of its motion
unit = Joules (J)
the kinetic energy an object has acquired is equal to the work done to accelerate it

Question 7

Gravitational energy

Answer 7

the energy possessed by an object because of its height above the ground
if an object is lowered, the change in gravitational energy is negative
the zero height must be specified
the change in height is always measured vertically, and the route taken is irrelevant

Question 8

Law of conservation of energy

Answer 8

energy can only be transferred from one place to another or transformed from one form to another, it can’t be created or destroyed
in a real system, kinetic and gravitational energy are converted into other forms, most commonly heat and sound
the ultimate “end” of all energy is to become heat, which is then radiated into outer space

Question 9

Energy efficiency

Answer 9

a measure of the completeness of energy transfer
it measures how much of the energy going into a device is actually transformed to the desired type of energy
energy out = amount of desired energy produced
energy in = amount of energy that goes into the system

Question 10

Power

Answer 10

the rate at which work is done and at which energy is transformed
symbol = P
unit = Watts (W) which is equivalent to Joules per second
kWh = unit for energy

Question 11

Kinetic molecular theory

Answer 11

all matter is made of atoms, which group into molecules
these atoms and molecules exert forces on one another that keep them a certain distance apart
the distances between molecules is responsible for the 3 states of matter

Question 12

Thermal energy

Answer 12

heat/thermal energy = energy of motion, or the kinetic energy of matter at the atomic and molecular level
temperature = way to measure the average kinetic energy of all of the particles in a quantity of matter
thermometer = device for measuring temperature, operates according to thermal expansion

Question 13

Units of measurement of temperature

Answer 13

Celsius = water freezes at 0 degrees, water boils at 100 degrees
Kelvin = water freezes at 273 K, water boils at 373 K, 0 Kelvin is absolute zero, the lowest possible temperature when all molecular motion stops

Question 14

Heat pumps

Answer 14

use the heat available outside of the house and transfer it inside, reducing the amount of energy needed to heat the house
circulate a substance called a refrigerant through an evaporation and condensation cycle
in the evaporation cycle, it is evaporated at low pressure and absorbs heat from its surroundings
in the condensation cycle, it is compressed at high pressure and releases the heat gained earlier

Question 15

Methods of heat transfer

Answer 15

conduction = process of transferring heat by particle collisions
metals are good heat conductors because their atoms have mobile electrons which transfer the heat energy
convection = process of transferring heat by a circulating flow of fluid
radiation = process of transferring energy (including heat) by electromagnetic waves, travels at the speed of light, can travel through a vacuum
when radiant energy is absorbed by matter, the particles in the matter increase their vibration, raising the temperature
black particles absorb the most radiation

Question 16

Specific heat capacity

Answer 16

heat transfer to any substance depends on =
change in temperature = more heat flows if the temperature difference is greater
mass = the more mass there is, the more particles there are to absorb/release energy
type of substance = depends on the intermolecular forces
specific heat capacity = the amount of heat energy to raise the temperature of 1.00kg substance by 1 degree Celsius, it is specific to each substance = J/kgC

Question 17

High vs low specific heat capacity

Answer 17

high specific heat capacity = requires more energy to increase its temperature and will cool down at a slower rate (Pyrex therefore can keep food warm)
low specific heat capacity = requires less energy to increase or decrease temperature (Mercury can therefore go through thermal expansion faster and can be used in thermometers)

Question 18

Heat exchange

Answer 18

in every energy transfer, the total amount of energy must remain constant
in a closed system, the total amount of heat lost by one object is equal to the total amount of heat gained by its surroundings
heat transfer stops when the two substances are the same temperature

Question 19

Thermal expansion

Answer 19

substances expand when heated because their particles vibrate faster
thermal expansion can provide a means of measuring temperature
change in length varies directly as the change in temperature and the original length
coefficient of linear expansion = constant which depends on substance, C-1

Question 20

Changes of state

Answer 20

the transfer of heat to or from a substance doesn’t always change its temperature
it may cause a change of state instead
temperature remains constant during changes of state, as the heat energy is all used to break or weaken intermolecular/interatomic bonds
latent heat of fusion = the amount of energy required to melt 1 kg of a substance
latent heat of vaporization = the energy required to evaporate 1 kg of a substance
unit = J/kg

Question 21

Standard notation for nuclear energy

Answer 21

atomic number = number of protons in a nucleus = Z
atomic mass = number of protons and neutrons in a nucleus = A
element symbol = X

Question 22

Nuclear energy

Answer 22

isotopes = atoms of the same element with different numbers of neutrons
they undergo the same chemical reactions as other isotopes of the same element
their physical properties may differ especially density, melting point, and boiling point
some may be radioactive

Question 23

Radioactivity

Answer 23

radioactivity = the release of energy as a result of the disintegration of the nucleus
ionizing radiation = particles or waves of energy that carry enough energy to remove an electron from an atom
may damage DNA and includes UV light, X-rays, and the three types of radioactivity
photon = unit of electromagnetic radiation
natural transmutation = the formation of a new element through the three types of radioactivity

Question 24

Three types of radioactivity

Answer 24

alpha decay = an alpha particle (helium nucleus with 2 protons and 2 neutrons) is emitted, discovered by Marie Curie, penetrates a few cells
beta decay = the emission of an extremely high energy electron, the electron is created when a neutron is converted into a proton and an electron, penetrates a few sheets of aluminum
gamma ray emission and electron capture = a gamma ray is extremely high energy electromagnetic radiation, the nucleus captures an electron and it combines with a proton to form a neutron, penetrates few cm of lead or 2 km of air

Question 25

Half-lives

Answer 25

half-life = the amount of time required for half the number of unstable nuclei in an isotope to decay
produces an inverse variation that does not produce the same constant for each set of variables
rock or brick cannot be dated using carbon-14 as it has never been alive and therefore has not acquired any carbon from its environment

Question 26

Medical uses of isotopes

Answer 26

cobalt 60 = “cobalt bomb”, bombards cancer in a patient using gamma rays, destroying malignant cells
iodine 131 = used in thyroid imaging, injected into blood stream and concentrates in the thyroid area where it decays and kills malignant cells
chromium 51 = injected into the body, radiation produced by decay kills malignant cells, can also determine the blood flow through the heart
gold 198 = tracer that is used to determine the progress of the element through a complex path in the body

Question 27

Background radiation

Answer 27

everyone on Earth is continuously being exposed to ionizing radiation from natural sources
examples = food, rocks, cosmic rays, tobacco

Question 28

Nuclear fission

Answer 28

when nuclear reactions occur, there is heat released and the heat comes from a conversion of mass to energy
Einstein proposed that matter and energy are equivalent

Question 29

Law of conservation of mass and energy

Answer 29

mass can be transformed into energy and vice versa so that the total amount of mass and energy remains constant
mass defect = the decrease in mass that accompanies the release of energy from nuclei
binding energy = the energy used to hold a nucleus together

Question 30

Nuclear fuel

Answer 30

radioactive material is used to power a nuclear reactor
when fission occurs, the binding energy of the nuclei is released as heat
a radioisotope may undergo fission when struck by a neutron travelling at the right speed
result = more neutrons (3), heat energy, and fission products
this occurs naturally and spontaneously and is an example of a fissionable isotope

Question 31

Chain reactions

Answer 31

neutrons released during fission may initiate further fission events
critical mass = mass of fissionable material required to produce a chain reaction
chain reaction = repeated series of reactions in which the products of one fission generate subsequent fissions

Question 32

Neutron moderation

Answer 32

neutrons that have too much energy won’t be captured by another uranium nucleus
a moderator is used to slow them down
moderators include = heavy water (CANDU reactors only), graphite, high pressure regular water (most reactors including submarines, aircraft carriers)

Question 33

CANDU reactors

Answer 33

Canada deuterium uranium
use natural uranium rather than enriched, the proportion of uranium-235 to other isotopes is not increased
controlled by cadmium rods that absorb neutrons, they are inserted vertically and can be promptly dropped in
liquid moderator can be dumped into shielded tanks below the reactor
can be refueled without being shut down

Question 34

Generation of energy

Answer 34

in the reactor core, the uranium fissions, producing other elements, heat energy and neutrons, setting off chain reactions
this causes the release of a large amount of heat energy
the heat is then used to boil water, which turns into high pressure steam
the steam flows through a turbine, turning an electric generator which makes electricity

Question 35

Applications of nuclear energy

Answer 35

electricity production
medical isotopes (treatment or diagnosis)
sterilization of medical supplies
industrial uses (tracers to detect leaks in pipes, test integrity of materials)
ionization smoke detectors
dating archeological and geological samples
food preservation
scientific research
powering submarines, large ships, satellites