Physics P4: Fission and fusion

What is nuclear fission?

A type of nuclear reaction that is used to release energy from large and unstable atoms by splitting them into smaller atoms.

What type of fission rarely happens?

Spontaneous fission.

Why?

Because the nucleus usually has to absorb a neutron before it will split.

Fill in the blanks:

When the atom splits it forms ________ ________ ________ ________ that are roughly the ________ ________.

two, new, lighter, elements, same, size.

What is a chain reaction?

When an atom splits and two or three neutrons are released, if any are moving slow enough to be absorbed by another nucleus, another reaction will occur. This can repeat, causing a chain reaction.

The energy not transferred to the kinetic energy store of the products in fission reactions is carried away by what?

Gamma rays.

The energy carried away by the gamma rays and in the kinetic energy stores of the remaining free neutrons and the other decay products can be used for what?

Heating water to make steam to turn turbines for generators.

What controls the amount of energy produced by fission in a nuclear reactor by changing the speed of the reaction?

Control rods.

How?

By absorbing neutrons to slow down the chain reaction.

How do nuclear weapons create an explosion?

Lots of uncontrolled chain reactions which lead to lots of energy in the form of an explosion.

What is nuclear fusion?

When two light nuclei collide at high speed and join (fuse) to create a larger, heavier nucleus.

Fill in the blanks:

The heavier nucleus produced by fusion ________ ________ have as much ________ as the two lighter nuclei

does, not, mass.

Based on this, what is some of the mass of the lighter nuclei converted to?

Energy released as radiation.

Does fusion release more or less energy than fission?

More.