P4 - Forces

Question 1

How has the model of the atom changed over time

Answer 1

• 1804 John Dalton agreed the atom was made up of tiny spheres (atoms) which couldnt be broken up. He also believed each element was made up of a different atom.
• 1897 - J.J Thompson discovered particles called electrons could be removed from the atom Thompson suggested atoms were spheres of positive charge with tiny negative electrons stuck in them *like fruit in plum pudding) therefore the plum pudding model
• 1909 - Ruthfords lab tried firing a beam of alpha particles at thin gold foil. This was the scattering experiment

Question 2

History of the atom

Answer 2

From the plum pudding model it was expected the particle to go straight through, or be slightly deflected. However some came back. Something the plum pudding model couldnt conclude or explain. The scientists realised most of the mass must be concentrated at the centre of a tiny nucleus. The nucleus must have a positive charge as it repelled the positive alpha particle. They also realised that most of the atom would therefore just be an open spave. This was the first nuclear model.

Question 3

Conclusion of timetable of the atom

Answer 3

1804 - John Dalton - tiny spheres (atoms) couldnt be broken up. Each element = different atom.
1897 = J.J Thompson - plum pudding model
1909 - Rutherford and alpha particles - gold foil experiment.
1913 -Bohr in rutherford’s lab made current model

Question 4

What is EM radiation

Answer 4

Electromagnetic radiation

Question 5

What happens to an electron if the atom it is in releases EM radiation

Answer 5

The electrons move their location within the atom

Question 6

Who provided evidence to suggest the existance of the neutron

Answer 6

James Chadwick

Question 7

Do atoms have an overall charge

Answer 7

Yes - positive

Question 8

What happens to an atom if it loses one or more of its electrons

Answer 8

The ion becomes a positively charged ion

Question 9

What is the atomic number

Answer 9

The bottom number to the left of the element symbol

Question 10

What is the mass number

Answer 10

The top number to the left of the element symbol

Question 11

What number defines what elenent an atom is

Answer 11

The atomic number (bottom)

Question 12

What is an isotope

Answer 12

Different variations of the same element. Same atomic number, but different mass number

Question 13

Are isotopes usually stable

Answer 13

There are many isotopes to each element, usually only one or two are stable.

Question 14

What is radioactive decay

Answer 14

Radioactive decay is when unstable isotopes decay into other elements and give out radiation as they try to become more stable.

Question 15

What may be emitted during radioactive decay

Answer 15

Radioactive substances

Question 16

What are the types of ionising radiation. Give their ionising power and range in air

Answer 16

Types : alpha, beta, gamma

Alpha (a) = strongly ionising but only travel a few cm.
Beta (b) = moderately ionising a few metres range in air
Gamma (y) = weakly ionising but can travel long distances through air

Question 17

Why can alpha radiation not be used to check the thickness of metal sheets

Answer 17

Because they can be absorbed by a single sheet of paper. They dont penetrate very far into substance

Question 18

What type of nuclear ldecay doesnt change the mass or chargeof nucleus

Answer 18

Gamma (y)

Question 19

What is the activity of a source and its units

Answer 19

The rate at which a source decays Bequerels Bq (where 1 Bq is 1 decay per second)

Question 20

Define half - life

Answer 20

Half - life is the time taken for the number of radioactive nuclei in an isotape to halve

Question 21

True or false?

A short half - life means a small proportion of atoms are decaying per second

Answer 21

False

Question 22

What are the dangers of a radioactive source with a long half-life

Answer 22

Nearby areas can be radioactive for many years. Sometimes millions of years

Question 23

How would you find the half life of a source if you had a graph with its activity over time

Answer 23

Find the time on the bottom axis corresponding to a halving of the activity on the vertical axis (i.e 800 to 400)

Question 24

Define radiation dose

Answer 24

Radiation dose is the risk of harm to body tissue due to exposure to radiation. Measured in sievers (Sv)

Question 25

Name aspects of your lifestyle that can affect your radiation dose

Answer 25

Where you live and if you have a job that involves radiation. It can also be medically put into your system to treat illnesses

Question 26

Define irradiation

Answer 26

When you are exposed to background radiation.

Question 27

Define contamination

Answer 27

Radioactive particles are inside a substance

Question 28

Compare the hazards of being irradiated / contaminated by an alpha source, gamma and beta

Answer 28

Irradiation from beta and gamma is very dangerous. But is almost impossible from alpha

Question 29

Examples of how to protect against contamination and irradiation

Answer 29

Contamination is HIGHLY dangerous from alpha, mediocre from beta and weak from gamma

Question 30

Describe risks involved with using radiation

Answer 30

Radiation can enter living cells and kill them. Lower doses lead to mutant cells which divide uncontrollably- cancer. Higher doses can cause radiation sickness (vomiting) tiredness and hair loss

Question 31

Explain the ways in which radiation is used in medicine.

Answer 31

Medical tracers and cancer treatment. Radiation kills the cancer cells

Question 32

Difine fission

Answer 32

Fission releases energy from large and unstable atoms. Splitting them into smaller atoms

Question 33

Define fusion

Answer 33

Fusion joins 2 nuclei to create a larger atom

Question 34

True or false? Fissia is usually spontaneous

Answer 34

False

Question 35

Describe what a chain reaction is and what happens when it is uncontrolled

Answer 35

When an atom splits if any neutrons are moving slow enough to be absorbed by another nucleus, more fission occurs. When it is uncontrolled, lots of energy is given out which causes explosions.

Question 36

Explain the difference between fission and fusion

Answer 36

Fission splits the nucleus. Fusion re-joins the nucleus