AS Chem - Elements of Life

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  • Created by: KHill
  • Created on: 18-11-14 11:41
Define isotope
Atoms of the same element with the same no. of p+ but different no. of neutrons.
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Isotopes with higher mass have...
...Higher mass, density, mp and bp. Also slower rates of diffusion. However they have the SAME chemical reactivity.
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Cl occurs naturally w/ 75% Cl-35 and 25% Cl-37. What is the RAM of Cl?
((35 x 75) + (37 x 25)) / 100 = 35.5
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Define Radioisotope
Isotopes have unstable nuclei which breakdown .'. are RADIOACTIVE
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Name 3 kinds of emissions
Alpha; Beta; Gamma
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Describe ionisation of an atom
Emissions knock e-s out of atom they collide with
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Alpha particles are like...
4/2 He nuclei
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Write the Nuc. Eqn of Alpha Decay of U-283
238/92-U --> 234/90-Th + 4/2-He
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Beta particles are like...
A single e-
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Write the Nuc. Eqn of Beta Decay of C-14
14/6-C --> 14/7-N + e-
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Which particle converts to another during Beta decay?
A neutron is converted to a p+
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What does Gamma decay emit?
Energy from the nucleus changing from a high level to a lower one.
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Radioisotopes used as tracers should...
...Be gamma emitters to minimise ionisation of cells; Have short H-L to minimise harm to patient
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Describe the conditions for Nuc. Fusion
Vry high temps (nuclei must have enough energy to move more quicjly & collide with enough energy to overcome repulsion of +ive nuclei); 2 nuclei must be very close so that strong nuclear forces holding 'p+'s & neutrons fuse nuclei together
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Where do fusion reactions take place?
In gas clouds (to form new elements), where the energy causes the clouds to glow
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At high temps in gas clouds 'e-'s have enough energy to....
....escape nuclei
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Describe plasma
Gases existing in an ionised form, in which +ive nuclei exist in a sea of delocalised 'e-'s
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What are the problems with attempting to harness fusion reactions for electricity production?
Difficult to safely generate & contain plasma at high temps needed (+10 to 7 degrees C) and make process sustainable & economic
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Each nucleus in a sample of an isotope decays...
...at random
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In a compund or in a free state, Uranium would decay...
...in the same way
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As more nuclei in a sample decay, the sample becomes....
....less radioactive
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Define Half-Life
The time for half of the nuclei in a sample to decay
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Sample of radioisotope has count rate of 52 counts/min & 4hrs later is 13 counts/min. Calculate the H-L
After 1 H-L the count rate would be 26 .'. after 2 H-Ls it would be 13 .'. 2H-LS = 4hrs so 1H-L = 2hrs
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H-L can be used to calc...
...time for activity/mass of isotope to fall to a certain value; Mass of isotope/its activity after its decayed for a certain time
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Meteors are composed similarly to earth and are similar age suggesting...
...they formed aroun the same time as the solar system .'. earth formed around 4.6 bill yrs ago
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Ratio of C-12:C-14 in living org.s doesn't change but after death C-14 not replenished so ratio..
...increases '.' amount of C-12 increases
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If ratio of C-12;C-14 can be measured...
...age of material can be estimated
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Remains older than 50,000yrs old cannot be dated '.' ...
...Remaining amount of C-14 is difficult to measure .'. errors become too large for sensible range to be produced
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Define spectroscopy
Study of how light & matter interact
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Light is one form of ? radiation
Electromagnetic
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The speed of light (C) is ? for all kinds of light when travelling in a vacuum
The SAME or 3.00 x 10to8 ms-1
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What is the equation for the constant or speed of light?
Wavelength x Frequency = Constant (Speed of light)
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Behaviour of light is easier to explain when you think in terms of...
...Particles
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The particle theory of light regards light as...
...a stream of tiny 'packets' of energy (Photons)
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The energy of Photons is related to...
....the position of the light in the elec.mag. spec
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The 2 theories of light (wave and photon/particle models) are linked by...
E=hv (Energy of photon = frequency x Planck constant)
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What is the value of the Planck constant?
6.63 x 10to-34 J/Hz
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There are 2 atomic spectra. Name them.
Emission spectrum and Absorption spectrum
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Atoms become 'excited' by ? energy and when they lose energy they return to their ? ?
absorbing.........Ground state
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Energy is usually emitted as ? ? and can be split into the atomic spectrum by ? ? ?
elec.mag. radiation........passing it through a prism/diffraction grating
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An emission spectrum is caused by....
....light emitted by excited atoms
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In the visible region, the spectrum consists of ? lines on a ? background
Coloured....Black
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A continuous spectrum cannot be produced from an emission spectrum because....
....atoms only emit certain (precise) frequencies
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An Absorption spectrum is caused by...
...light absorbed by atoms
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During absorption, when white light passes through a sample ? lines appear on a
Black.....Coloured
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Other cards in this set

Card 2

Front

...Higher mass, density, mp and bp. Also slower rates of diffusion. However they have the SAME chemical reactivity.

Back

Isotopes with higher mass have...

Card 3

Front

((35 x 75) + (37 x 25)) / 100 = 35.5

Back

Preview of the back of card 3

Card 4

Front

Isotopes have unstable nuclei which breakdown .'. are RADIOACTIVE

Back

Preview of the back of card 4

Card 5

Front

Alpha; Beta; Gamma

Back

Preview of the back of card 5
View more cards

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