Matter
LAW OF DEFINITE COMPOSITION
Compounds will have a definite composion
Eg. H2O will be H2O anywhere (always have 2 Hydrogen & 1 Oxygen)
LAW OF MULTIPLE PROPORTIONS
When 2 or more compounds with different proportions of the same elements can be made
Eg. CO2 x2 ->C2O4
Heating Curve of a Pure Substance Notes
Figure 1
A | · Solid: below melting point · Particles are very closely packed together in an orderly manner · Strong forces · Can only vibrate at a fixed position |
A-B | · When heated: heat -> kinetic energy -> increase -> molecules vibrate faster about their fixed position -> temperature increases |
B | · Still solid –melting has begun -> liquid · Temperature remains the same · melting point |
B-C | · exists: solid &liquid state · temperature remains constant because the heat that id supplied to it is used to overcome the forces of attraction that holds the particles together · constant temperature = melting point · heat energy overcomes the intermolecular forces id named as the latent heat of fusion |
C | · all has completely melted · solid -> liquid |
C-D | · liquid state · more heat energy = temperature increase · particles move faster because kinetic energy increases |
D | · liquid starts to boil · molecules have got enough energy to overcome the faces of attraction between the particles in the liquid · some particles will start to move freely · liquid -> gas |
D-E | · liquid & gaseous states · the temperature unchanged · heat energy absorbed to overcome intermolecular forces between the particles of the liquid rather than increase the temperature · boiling point |
E | · all of the liquid has turned into gas |
E-F | · gas particles continue to absorb more energy & more faster |
Here’s a chart that explains the heating and cooling of water:
Figure 2
KINETIC ENERGY is the energy that molecules possess as a resulr of their motion
there are 3 types of Kinetic energy which a molecule can possess
1. rational energy: causes a molecule to rotate around one of its axes; bond lengths ans bond angles don't change
2. vibrational energy: changes the bond lengths and/ or angles between atoms in a molecule
3. tanslational energy: causes the molecule to travel in a straight line from place to place, but has no effect on bond lengths and angles
eg. MICROWAVE OVENS supply energy which causes the water molecules in food and liquids to vibrate. As molecules absorb energy ans bump into each other, the food "heats up".
http://www.youtube.com/watch?v=s-KvoVzukHo
KINETIC ENERGY is the energy that molecules possess as a resulr of their motion
there are 3 types of Kinetic energy which a molecule can possess
1. rational energy: causes a molecule to rotate around one of its axes; bond lengths ans bond angles don't change
2. vibrational energy: changes the bond lengths and/ or angles between atoms in a molecule
3. tanslational energy: causes the molecule to travel in a straight line from place to place, but has no effect on bond lengths and angles
eg. MICROWAVE OVENS supply energy which causes the water molecules in food and liquids to vibrate. As molecules absorb energy ans bump into each other, the food "heats up".
http://www.youtube.com/watch?v=s-KvoVzukHo
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