P3- Particles in Action

P3

HideShow resource information
• Created by: charlotte
• Created on: 26-05-11 16:25

Gases and Temperature

Celcius is used to measure temperature. There is no upper limit to this and the coldest temperature is -273 C

At -273 C the substances are soild and the movement of the particles is an absolute minimum.

At -273 C the particles cannot move any more slowly- although they cannot stop moving altogether.

Absolute Zero- the theorectical temperature at which all particles stop moving- it is impossible to reach.

Kelvin scale- there are no negative temperature values K

An increase/decrease of 1K is the same as an increase/decrease of 1 C

1 of 13

Pressure and Temperature Effects

Particles are ALWAYS moving - they move very quickly in random directions and collide with each other.

As they bounce off the walls the momentum changes- causing a force on the walls - they create an outward pressure (p) (whih is greater than the atmospheric pressure) outside the container.

Gas pressure is normally given in terms of Pascals Pa of (kPa) other units include;

atmospheres- (atm)

bars (or mbar)

WHEN PROBLEM SOLVING CHANGE THE UNITS TO KELVIN RATHER THAN CLECIUS

2 of 13

Atoms and nuclei

The nucleus contains protons and neutrons- collectively called nucleons

Protons are positively charged subatomic particles containing a charge of +1

Neutrons carry no electrical charge

Because neutrons are neutral they are hard to detect

3 of 13

Beta Decay

Beta decay can occur in two different ways - dependan on whether the isotope lies above or below the stability line

A beta particle is released from a nucleus during decay

NEGATIVE BETA DECAY B- occurs in radioisotopes that have too many neutrons> a neutron is converted into a proton and an electron. During B- decay the radioisotope mantains its mass number but its atomic number increases by 1.

POSITIVE BETA DACAY B+- occur in radioisotopes that have too many protons. A proton is converted into a neutron plus a positie beta particle called a positron. During B- decay the radioisotope maintains its mass number but its atomic number decreases by 1.

4 of 13

Alpha Decay/ Fundamental particles

Alpha particle emission - the decay process for a very heavy nuclei with more than 82 protons

An aplha particle contains 2 protons and 2 neautrons

FUNDAMENTAL PARTICLES are the basic building blocks of more complexparticles, and of all matter.

Two types of fundamental particles are LEPTONS and QUARKS

5 of 13

Leptons/Quarks

Two most important leptons are the electron and the positron

The electron and the positron have the same mass

The two most important quarks are the up quark  and the down quark. Quarks carry out fractional electrical charge.

The up quark carries an electrical charge of +2/3

The down quark carrie an electrical charge of -1/3

Protons and neutrons are NOT fundamental particles because they are made up of quarks.

The proton is made from the three quarks u,u,d - giving a total charge of +1

The neutron is amde from the three quarks d,d,u giving it a total charge of 1

6 of 13

Anti matter

Matter made up of aniti-particles entirely is called anti-matter

anti matter isn't found on the earth

Annihilate- when particles of matter come into contact with particles of aniti matter. > these reactions can hav practical implications such as those in the PET scanner for medical imaging.

Producing Anti-Particles- requires;

high energy, high temperatures, high densities

Particle Accelerators- help to find out more about fundamental particles such as quarks, and the properties of anti-matter.

7 of 13

Electron beams/Kinetic energy

When a metal is heated, the energy of the elctrons is 'free' > some gain sufficent energy to escape from the surface- this is called THERMIONIC EMISSION

The rate at which electrons are emitted increases with the metals temperature.

KE = 1/2 MV(2)

In modern electron gun devices the electron beam passes through a doughnut shaped anode ( + charged) (and the cathode is - charged). It then passes through sets of parrallel plates - used to control the beam before it has a fluorescent screen. The parallel plates are positioned at right angles to each other. They move the beam up and down and across the screen to produce an image.

Electron beams include;

oscilloscopes, televisions, computer monitors, x ray-machines

8 of 13

Refraction/Reflection

REFRACTION- when a ray of light passes from one medium into another (changes direction)

REFRACTIVE- When light slows down it is refracted more towards the normal

ENDOSCOPES- are used to see inside the body- they are made of many fibres , of thin flxile glan rods. the bundles are protected by a soft coating-preventing damage to internal organs.

They are used to examine-

the stomach, colon, reproductive system

9 of 13

Pulse Oximetry

Is the non-invasive method that is used to determine the amound of oxygen carried by haemoglobin in a persons blood.

Expenditure of energy

The human body needs energy to function and do work. it is the efficency of transfer of the chemical energy required for the work done.

Basic Metabolic Rate-

The energy requied to keep the body functioning when resting (BMR). It decreases with age and with the loss of mean bosy mass.

10 of 13

Action Potentials

Action potentials- an electrical discharge that travels through a cell membrane.

Action potentials move at a speed that depends on the type and temperature of the cell.

The <3 acts as a double pump

The ECG-

During each heartbeat the spread of action potentials across the heart is conducted through body fluids to the skin.

electrocardiogram- the electrical activity of the heart recorded over a period of time.

Uses- damaged heart muscles, heart blockages, high/low pulse rates, contractions of the ventricles

11 of 13

RADIOACTIVE ISOTOPES- used in the diagnosis and therapy of many medical conditions- including cancer.

They;

emit only gamma radiation, possess a short half life, produce gamma rays, must be readily avaliable and cost-effective.

They are produced in nuclear reactors, particle accelerators, or chemical generators.

Nuclear reactors- produce radioisotopes with long half lives. (treatmen of tumours)

Particle accelerators- provide a method of producing short-lived radioisotopes

12 of 13

Chemical Generators

... are used in nuclear medicine to produce a number of specific radioisotopes which have half lives of approx 6 hours.

PET scanning detects small changes in cells and identifies rapidly growing cells (such as cancer)

Radioisotopes are used ...

for medical diagnosis, and in medical therapy.

Radiotherapy is used to kill cancer cells and shrink tumours.- it destroys the cells by damaging the genetic material- so they cant grow and further divide.

PALLIATIVE CARE- slows down the progress of the disease- improves quality of life.

13 of 13