C3 - Structure and Bonding Flashcards
States of matter: Solids
Solids have a fixed shape and volume, are packed and vibrate.
States of matter: Liquids
Liquids also have a fixed volume but they can flow and change their shape, they are packed and slide over one another.
closely spaced but still in constant motion and therefore are constantly colliding
States of matter: Gases
Gasses have no fixed shape or volume, can be compressed easily and have lots of space and so can move randomly in all directions.
widely spaced and in constant motion. Collisions are frequent and elastic
Physical Changes: How to get from one state to another
solid to liquid: melting liquid to gas: evaporating/boiling gas to liquid: condensing liquid to solid: freezing solid to gas: sublimation gas to solid: deposition
Melting and boiling – energy transferred from surroundings
Freezing and condensation – energy transferred to surroundings.
Limitations of the particle model
– atoms, molecules and ions are not all the same shape and size,
atoms are mainly empty space and not solid.
How do atoms become ions and types of bonding
atoms either lose or gain electrons to have full outer shells so they are stable.
Ionic bonding = transferring electrons
Covalent Bonding = sharing electrons
Ionic Bonds
- strong electrostatic attraction between oppositely charged ions, thse forces act in all directions in the lattice forming a giant structure/ lattice
- compound formed when metals react with non-metals
Ionic compound properties
Ionic compounds have high melting and boiling points, as the strong electrostatic attractions are hard to overcome.
When in molten or in solution, ionic compounds can conduct electricity as the lattice breaks apart and ions can carry charge.
Covalent Bonds
- compounds formed when non-metals react with non-metals
- many covalent compounds consist of small molecules e.g. water
- strong covalent bonds but weak intermolecular forces
- simple molecules have no overall charge so they don’t carry electricity
Giant covalent structure
huge network of atoms connected by strong covalent bonds
- high mpt and bpt
- insoluble in water
- hard
- do not conduct electricity except graphite
Comment on the Melting point curve
A pure solid will melt at a fixed temperature and the line will stay horizontal when it is melting.
The temperature does not rise when the solid is melting because the heat is absorbed to break the bonds between the solid particles.
The temperature will start to rise again when all the solid has melted.
Empirical formula
The empirical formula is the simplest ratio of ions in a compound.
Intermolecular force
force of attraction between molecules. These forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.
Polymers
they are made up of a long chain of molecules so there are more intermolecular forces, and higher melting/ boiling points than in smaller molecules.
Model of Graphite and properties
Graphite has giant hexagonal layers with weak intermolecular forces. The layers can slide over each other.
Since each carbon atom only forms 3 covalent bonds in each layer this leaves 1 electron which moves freely in between the layers of carbon.
Due to this spare delocalised electron graphite can conduct electricity and heat.