C3 Flashcards
Liquid and solid changing state
When a solid heats up, it’s particles vibrate faster until they break free from neighbouring particles
Energy transfers whilst changing state
When heating a solid, the temperature stops rising at the melting point. At the melting point, the energy transferred from the surroundings goes into breaking the bonds
What is a compound
A substance containing two or more elements, chemically bonded together
What ion forms when loosing electrons
Positive
What ion forms when gaining electrons
Negative
How do we represent ionic structure
(2,8,4
How do we represent ionic bonding
Dot and cross diagrams
How does ionic bonding work
Atoms react to from negative and positive ions. These ions are held together by very strong forces of attraction between the oppositely charged ions acting in all directions
What is a giant ionic lattice
Arrangement of ions in ionic bonding in a steady, repeated pattern
What ions do each group produce
Group 1 - 1+
Group 2 - 2+
Group 3 - 3+
Group 4 - don’t
Group 5 - 3-
Group 6 - 2-
Group 7 - 1-
Group 8/0 - don’t
Properties of a giant, ionic lattice
Very tightly packed, forces act in all directions, hard to break up due to the electrostatic forces, high melting and boiling points
What happens when ionic compounds melt
The ions are free to move so can carry an electrical charge
What happens when an ionic compound mixes with water
Most will dissolve to form an ionic compound solution which can carry an electrical charge
What type of atoms are involved in ionic bonding
Non metal and a metal
What charge do metal ions have
Positive
What charge do non metals have
Negative
Explain simple covalent bonding
When two non metals react together, they both want to gain electrons but neither can give them away. They complete their full outer shell by sharing electrons. These strong bonds are known as covalent bonds
How to draw covalent bonding
Dots and crosses putting the shared electrons in the overlap between the atoms
Cons of ball and stick diagrams
Does not show the true shape of the molecule, bonds aren’t in the right places
Intermolecular bonds in covalent bonding
Each covalent bond is very strong but the individual molecules are quite spread out. This is because the force of attraction between molecules is weak or the intermolecular bonding is weak
How do intermolecular forces in covalent structures change with the size of molecule
As the size of molecule increases, so does the intermolecular bond so large structures like polymers actually have quite strong intermolecular forces
Giant covalent structures
Formed from large networks of atoms held together by covalent bonds
Diamond
- carbon atoms
- 4 covalent bonds on each
- does not conduct electricity
- hard
- high melting and boiling points
Graphite
- made of carbon
- 3 covalent bonds on each
- layers of delocalised electrons
- made of layers of hexagonal rings of carbon atoms
- layers slide over each other
- conducts electricity
What are fullerenes
Carbon structures where the atoms join together to form large, hollow cages in all different shapes
What are cylindrical fullerenes
Fullerenes where their length is much longer than their diameter
Properties of cylindrical fullerenes
High tensile strength and high electrical and thermal conductivity
Uses of fullerenes
Deliver drugs in bodies, lubricants, catalysts due to their very high surface are to volume ratio
Metallic bonding
- between metals
- lattice of positively charged ions
- arranged in regular layers
- outer electrons form a sea of freely moving electrons holding positive ions in place
- actually delocalised electrons surrounding positive ions
Properties of metallic bonding
Pure metals can be bent/ hammered into shape as the layers of ions slide easily over each other
Alloys
A mixture of two or more element, at least on is a metal (usually both are metal)
Properties of metals
- conduct electricity due to delocalised electrons
- malleable due to layers
- ductile (can be made into wires)
- good thermal conductors due to delocalised electrons
Nano particles and nano science
- 1nm = 1x10^-9 m
- nano science deals with structures between 1-100 nm
- high SA:V ratio makes them highly reactive
Nano tube
- like a layer of graphene rolled into a tube
- very long compared to width
- withstand high tensions
- conduct electricity due to delocalised elecrtrons
What is graphene and it’s properties
- single sheet of carbon atoms from graphite
- very good electrical conductor
- low density
- most reactive form of carbon
- strong for its mass
Uses for nano particles
- used in windows to trigger break down of dirt
- used in sunscreen, coat nano particles in silica
- used in face creams as they are absorbed further into the skin
- deliver drugs through blood stream
Risks of nano particles
- highly reactive
- could get into the atmosphere
- breathing them in could damage the lungs
Limitations of particle model
Assumes particles are solid spheres with no forces operating between them
