Topic 4

Atom has a charge of...?

Zero (neutral)

Most of an atoms volume is...?

Empty space

Most of an atoms mass is in the...?

Nucleus

Number of negative electrons is equal to the number of...?

Positive protons

Atomic number?

Number of protons in the nucleus of an atom.

Mass number?

Number of particles in the nucleus (proton +neutron).

Isotope?

Same number of protons and different number of neutrons.

Ions?

Atom that has lost or gained electrons.

Positive ion...?

Lost (negative) electrons.

Negative ion...?

Gained (negative) electrons.

All matter is made from..?

Atoms

Atoms have no overall charge so they are...?

Neutral

Half life definition?

Half life is the time taken for half the radioactive nuclei in a sample to decay.

What is the unit for radioactivity?

Becquerel (Bq)

Is irradiation radioactive?

No

Are contaminated atoms radioactive?

Yes

Irradiation definition?

Process of exposing an object to nuclear radiation. Bad for health, however also has benefits.

Give examples of how radiation can harm?

Canter acts in the eyes

Cancer

Sterility

Radiation skin burns

Damaged immune system

Vomiting

Bleeding

What type of nuclear radiation is best for turning atoms into ions?

Alpha particles.

What type of nuclear radiation is stopped by a thick sheet of lead?

Alpha, Beta, Gamma

What type of nuclear radiation is stopped by paper, skin or 5cm to 6cm of air?

Alpha

What type of nuclear radiation is stopped by a thin sheet of aluminium?

Alpha, Beta

Why is alpha radiation the most ionising?

It only goes to around 5cm to 6cm.

Safety with handling radioactive items?

Limit exposure time

Use shielding

Monitor exposure

What is a radiation dose measured in?

Milliseverts (msv) and sieverts (sv)

Where does natural radiation come from?

Gas from ground

Buildings + ground

Cosmic rays

Food + drink

ARTIFICIAL SOURCES (CHECK THIS)

Where does artificial radiation come from?

Medical

Nuclear power + weapons test

Other sources

ARTIFICIAL SOURCES (CHECK THIS)

Tracer definition?

Substances that can follow the behaviour of various physical, chemical or biological processes.

Tracer characteristics?

Gamma sources

Can pass through body

Least ionising

Half life of a few hours

Are all isotopes radioactive?

No

Radioactive tracers used for medical diagnosis have a...?

Short life

Which type of radiation is most dangerous to swallow?

Alpha

Nuclear alpha radiation is used in...?

Smoke alarms

An isotope with an unstable nucleus is called a...?

Radioactive isotope

Can gamma radiation be deflected?

No

What are gamma rays given out from?

The nucleus of radioactive atoms

What radiation is the most penetrating?

Gamma

What is irradiation?

When an object is exposed to nuclear radiation.

Mutation definition?

If humans are exposed to radiation, this an cause a change in the DNA base sequence.

What is cosmic radiation?

Radiation that reaches earth from space.

What does it mean if Alpha, Beta and Gamma are all somewhat ionising?

They can kill cells or make them become cancerous.

Gamma rays are used for?

Sterilising medical equipment.

What can ionising radiation do?

Treat cancer

Which radiation is most hazardous outside of the body?

Gamma

Where is nuclear fission used?

In nuclear reactors to produce energy and form electricity.

What is nuclear fission the process of?

Splitting large unstable nuclei.

Can nuclear fission happen randomly?

Yes (rarely)

How can we make nuclear fission happen?

By making the nucleus absorb a neutron.

How does nuclear fission work?

A nucleus is so large, it is always unstable. I can break apart into two smaller (daughter) nuclei, releasing a lot of energy.

ooo > energy > 2 daughter nuclei?

Nuclear fission

How does a chain reaction work in fission?

A chain reaction keeps going once you have started and produces more and more energy.

What is at risk with an uncontrolled chain reaction in fission?

A bomb could form.

What is controlled chain reactions in fission?

Nuclear power stations

What happens if you got enough uranium (50kg)?

It is enough to start an unstoppable chain reaction.

What is energy from nuclear fission mostly released as?

Kinetic energy

What does it mean if uranium is very dense (non renewable)?

A lot of energy from a little amount of fuel.

What can nuclear fission be used to produce?

Power in power stations.

Shielding?

Made of thick concrete layer to stop gamma radiation escaping.

Control rods?

Made of Boron and absorb the neutrons and stop them moving between fuel rods (slows down chain reaction by reducing the amount of fission reactions occurring).

Moderator?

Slows down neutrons more likely to react with 235U.

How does making electricity in nuclear power stations work and what does nuclear fission actually do?

1. Nuclear rods get hot by fission

2. Water is turned to steam by heat

3. Steam turns the turbines

4. The turbine turns the generator

What are the two small nuclei called?

Daughter nuclei

What two types of heavy isotopes are commonly used in nuclear reactors for nuclear fission?

Uranium and plutonium

What else is released from nuclear fission?

Nuclear waste, energy and gamma rays.

How can fission of one nucleus lead to a chain reaction and potentially an explosion?

If the nucleus absorbs a neutron then there is energy union that goes in form of gamma radiation making the two daughter nuclei.

What famous equation describes the amount of energy released from the nucleus in a nuclear reaction?

mc(squared)

Describe how rate of reaction in a nuclear power station can be increased or decreased?

Control rods added in decrease the rate of reaction. Control rods taken out increase rate of reaction.

Fusion naturally happens in...?

Stars

The sun releases energy through...?

Nuclear fusion

What is nuclear fusion?

The joining of two light nuclei to form a heavier nucleus.

Give an example of nuclear fusion?

2 light hydrogen nuclei fuse together to form an isotope of a helium nucleus.

How is the energy from nuclear fusion given out?

Radiation

Does fusion release a large or small amount of energy?

A huge amount

When fusion occurs, some of the mass of the particles is converted to...?

Energy

E = mc(squared) > some mass > ?

Energy

C = speed of light = ?

300,000,000 m/s

Energy produced through fusion in stars is...?

Radiated

Fusion on Earth key points?

1) Fusion - releases lots of energy

2) Hydrogen - cheap to obtain + plentiful

3) Hydrogen + Helium = pretty safe

4) Almost no radiation waste made

5) No risk of nuclear accident

Like charges...?

How do we fix this?

Repel, has to be very hot to be fixed

What do scientists use to make fusion happen on Earth?

Fusion reactor

Why do like charges repel?

They have the same charge = forced to repel.

Why is making fusion happen on Earth not going well?

Extremely expensive, very difficult and currently uses more energy to work than it produces.

What problems do fuel rods cause the environment?

High level of nuclear waste + remain dangerous for a long time.

What are two benefits of nuclear fission in comparison o fossil fuel power stations?

Fission doesn't produce CO2 + No burning or noise.

What are the particle(s) within a hydrogen nucleus?

1 proton

What are the particle(s) within a helium nucleus?

2 protons, 2 neutrons

The particle with a positive charge is...?

A proton

The particle with the smallest mass is...?

An electron

The particle with no charge is...?

A neutron

Negatively charged particles are called?

Electrons

How do you work out PNE?

P+E = Same = Atomic number

N = Top - Bottom

What atoms are in nucleus?

Protons + Neutrons

Where is most of the mass of an atom contained?

In the nucleus

The nucleus is 1/? of the size of an atom?

1/10,000

Nucleus ~ ?

1 x 10 (to the -14) m

Atom ~ ?

1 x 10 (to the -10) m

Who invented the plum pudding modal?

JJ Thomson

Electrons were discovered by...?

JJ Thomson

Neutrons were discovered by...?

James Chadwick

Who proved neutrons are in the nucleus?

James Chadwick