4) States of matter Flashcards

1
Q

Gas pressure

A
  • gases in a container exert a pressure as the gas molecules are constantly colliding with the walls of the container
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2
Q

Changing gas volume
(decreasing it at constant temperature)

A
  • causes molecules to be squashed together which results in more frequent collisions with the container wall
  • pressure of the gas increases
  • volume is therefore inversely proportional to the pressure
  • graph of volume of gas plotted against 1/pressure gives a straight line
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3
Q

Changing gas temperature
(increasing it at constant volume)

A
  • causes molecules to gain more kinetic energy
  • the particles will therefore move faster and collide with the container walls more frequently
  • pressure of gas increases
  • temperature is therefore directly proportional to pressure
  • graph of temperature of gas plotted against pressure gives a straight line
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4
Q

Kinetic theory of gases states that molecules in a gas are constantly moving and makes the following assumptions:

A
  • the gas molecules are moving very fast and randomly
  • the molecules have negligible volume
  • no intermolecular forces
  • no kinetic energy is lost when the gas molecules collide with each other (elastic collisions)
  • temp of gas is related to average kinetic energy of the molecules
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5
Q

Ideal and real gases

A

Ideal- gases that follow the kinetic theory

Real gases- do not fit the kinetic theory of gases but may come very close to it

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6
Q

The volume than an ideal gas occupies depends on ?

A

Temperature
Pressure

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7
Q

When a gas is heated (at constant pressure) …

A
  • the particles gain more kinetic energy and undergo more frequent collisions with the container wall
  • to keep the pressure constant, the molecules must get further apart and therefore the volume increases
  • volume is directly proportional to temperature (at constant pressure)
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8
Q

Volume and temperature

A
  • volume is inversely proportional to pressure
  • temperature is directly proportional to pressure
  • volume is directly proportional to temperature
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9
Q

Limitations of the ideal gas law
At very high pressure and low temperature real gases do not obey the kinetic theory as under these conditions:

A
  • molecules are close together
  • there are id-id or pd-pd forces between the molecules and these forces pull the molecules away from the container wall
  • volume of the molecules is not negligible
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10
Q

Real gases therefore do not obey the following kinetic theory assumptions at high temperatures and pressures, however ideal gases do because:

A
  • there are no intermolecular forces of attraction between molecules
  • volume of the gas molecules can be ignored
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11
Q

Ideal gas equation

A

pV=nRT
or
Mr= mRT/pV

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12
Q

Lattice structures of a crystalline solid

A
  • most ionic, metallic and covalent compounds are crystalline lattices
  • there molecules, atoms, ions are arranged in a regular repeating arrangement
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13
Q

4 types of structures

A

1) Giant ionic- sodium chloride and magnesium oxide
2) Simple molecular (covalent) - iodine, buckminsterfullerene C60 and ice
3) Giant molecular (covalent)- silicon IV oxide, graphite and diamond
4) Giant metallic- copper

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14
Q

Giant ionic

A
  • high m.p and b.p
  • only conduct electricity when molten or in a solution so that ions can move freely and conduct
  • soluble in water and form ion-dipole bonds
  • strong due to electrostatic forces (ionic crystals can be split apart)
  • solid at room temp
  • electrostatic attraction between ions
  • ions
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15
Q

Giant metallic

A
  • moderately high m.p and b.p
  • conduct electricity when solid or liquid as there are mobile electrons
  • insoluble, but some can react
  • hard due to strong attractive forces between metal ions and delocalised electrons
  • malleable
  • solid at room temp
  • positive ions in a sea of delocalised electrons
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16
Q

Simple molecular (covalent)

A
  • low m.p and b.p
  • do not conduct electricity as there are no charged particles
  • usually insoluble unless they are polar
  • soft
  • solid, liquid or gas at room temp
  • weak intermolecular forces
  • small molecules
17
Q

Giant molecular (covalent)

A
  • very high m.p and b.p due to large number of covalent bonds and intermolecular forces between the molecules
  • do not conduct electricity (except for graphite which 3C atoms and 1 delocalised electron between the layers) Diamond and silicon (IV) oxide don’t as all their 4 outer electrons are involved in a covalent bond therefore no free electrons
  • insoluble
  • very difficult to break due to 3D network of strong covalent bonds (diamond, SiO2) or soft as the forces between the carbon layers are weak (graphite)
  • solid at room temp
  • electrons in covalent bond s between the atoms
  • atoms
18
Q

Allotropes

A

graphite, diamond and C60 are different structural forms of the same element (in this case carbon)

19
Q

Solid

A
  • regular particle arrangement and are tightly packed together
  • cant be compressed
20
Q

Liquid

A
  • tightly packed together but have a random arrangement
  • cant be compressed, but fits in the container that they are in
21
Q

Gas

A
  • have a random arrangement and move around more freely
  • they fill the space of the container they are in and can be compressed