Nuclear physics

Question 1

Name the two substances in common use in nuclear reactors, and why can we use them?

Answer 1

Uranium-235 and Plutonium-239

They are fissile or fissionable

Question 2

Define nuclear fission

Answer 2

The splitting of an atomic NUCLEUS

Question 3

First step of nuclear fission

Answer 3

Uranium-235 or Plutonium-239 nucleus absorbs a neutron

Question 4

Second step of nuclear fission

Answer 4

The nucleus splits into two smaller nuclei and two or three neutrons and energy is released

Question 5

Third step of nuclear fission

Answer 5

The neutrons are fired off with enough energy that they might cause the fission of other nuclei if they collide

Question 6

How does nuclear fission work in a power station?

Answer 6

Fission releases energy, which heats water and turns it into steam to spin a turbine, which is connected to a generator that generates electricity

Question 7

Advantages of fusion over fission

Advantages of both over conventional electricity generation

Answer 7

Plentiful supply of fuel (formed from sea water and lithium) as opposed to limited amounts of uranium and plutonium
No radioactive byproducts
Fail-safe and shuts down automatically if there is a fault
Both give out no greenhouse gases

Question 8

How do stars release energy?

Answer 8

Nuclear fusion

Question 9

When do stars form? When do planets form?

Answer 9

When enough dust and gas from space is pulled together by gravitational attraction
When smaller masses form and are attracted by a larger mass i.e. a star

Question 10

At the beginning of the universe, what did it contain?

Why does it now contain a large variety of elements?

Answer 10

Only hydrogen
Fusion in stars - 2H fused to form He, 2He fused to form Be, etc. Supernovas (explosions of very big stars) then distribute them across the universe

Question 11

What is the main sequence period of a star?

Answer 11

A period in its life cycle wherein the forces are balanced (gravity balances against the outwards forces from explosive fusion), making it stable

Question 12

What determines which life cycle a star goes through?

Answer 12

The size

Question 13

Describe the life cycle of a star about the same size as the Sun

Answer 13

Protostar -> Main sequence star -> Red Giant -> White Dwarf -> Black Dwarf

Question 14

Describe the life cycle of a star much bigger than the Sun

Answer 14

Protostar -> Main sequence star -> Red Super Giant -> Supernova -> Neutron Star OR Black hole