Chemistry exam revision Flashcards
What are the properties of solids?
Very low energy, vibrate, very close to each other.
What are the properties of liquids?
Still close to each other, have enough energy to slide over each other.
What are the properties of gasses?
Have lots of energy, lots of space between particles, and collide frequently.
Explain ionic bonds
Happens between a non-metal and a metal.
Metal loses electrons by transferring it to non-metals. Non-metal gains electrons.
What are elements?
Substances that are made of one type of atom.
What are molecules?
Two or more atoms joined together.
What are compounds?
Two or more elements chemically joined together.
What is a mixture?
Two or more substances that are not chemically combined.
What is the structure of an Ionic Compound?
Giant Ionic Lattice
What are the properties of ionic compounds?
High melting and boiling points. Does not conduct electricity when solid but conducts when in (aq) form.
Why does ionic compounds have high melting and boiling points?
Has strong electrostatic forces between ions and therefore needs lots of energy to break the bonds between oppositely charged ions.
Why does ionic compounds conduct electricity in solution form but not in solid form?
When in solid form ions are not able to move freely therefore not able to carry any electrical charge.
What are the two types of covalent compounds?
Simple molecular and giant covalent
What is covalent bonding?
The sharing of electrons between two non-metals.
What is the properties of simple molecules?
Low melting and boiling points, does not conduct electricity in any state.
Why does simple molecules have a low melting and boiling point?
Have strong covalent bonds but weak intermolecular forces which do not need lots of energy to break.
Why do simple molecules do not conduct electricity?
They have no overall charge and no free moving electrons.
What are examples of giant covalent?
Diamond, graphite, and silicon dioxide
What are polymers?
Polymers are made up of many small molecules to form a long chain.
What’s the formula to calculate the relative atomic mass of an atom?
(abundance of isotope 1 x mass of isotope 1) + (abundance of isotope 2 x mass of isotope 2)/ 100
What is one use of diamonds?
Embedded in the drills used by oil companies. So that they can drill through layers of rock.
What are the properties of the giant covalent structure?
Very high melting and boiling points, insoluble in water, apart from graphite they do not conduct electricity.
How many bonds are connected by one atom of carbon in graphite?
Each carbon atom in graphite is covalently bonded to 3 other carbon atoms.
How many bonds are connected by one atom of carbon in diamond?
Each carbon atom in diamond is covalently bonded to 4 other carbon atoms.
What shape does the carbon atoms form when in graphite?
Hexagons which are arranged in a giant layer.
Why is graphite a soft material that feels slippery to touch?
There are no covalent bonds between the layers, only weak intermolecular forces allowing the layers to slide over eachother easily.
Why does graphite conduct electricity?
Each carbon atom in graphite is covalently bonded to 3 other carbon atoms. Carbon atoms have 4 electrons in its outer shell for bonding. This leaves one other electron to roam around freely. These are called delocalised electrons.
What are fullerenes?
Carbon which from into shapes like cylinders, cages and tubes.
What are fullerenes use for?
To transport drugs inside the body, and to reinforce composite materials.
What are the characteristics of graphene?
A single layer of graphene is one atom thick and has excellent electrical conductivity.
What is the arrangement of a metal?
Metal atoms are arranged in regular layers.
Why do metals conduct electricity?
Have a sea of delocalized electrons which can carry electric current.
What is metallic bonds?
They contain a sea of free moving electrons which are attracted to the positive metal ions.
Why are pure metals malleable and ductile?
The atoms in a pure metal are held together in a giant metallic structure. The regular arrangement allows the atoms to slide over each other quite easily.
What are alloys?
A mixture of two or more element, at least one of which is a metal.
Why are alloys harder than pure metals?
They have a controlled amount of another atom inside the metal which has a different size compared to the other atoms. This makes it hard for the layers to slide over each other.
What allows nanoparticles have different properties compared to bulk materials?
They have a high surface to area to volume ratio, with high percentage of atoms exposed at the surface.
What are the use of nanoparticles?
1 Sun creams - nanoparticles are affective at blocking the Sun’s rays.
2. Cosmetics - used in face creams, deodorants and shaving products.
3. Medicine - use of nanocages to deliver drugs to sites where they are needed in the body.
4. Catalysts - used in fuel cell materials.
5. Bactericides - nanoparticles can be used to inhibit the growth of bacteria. Used in fridges, sprays used to clean hospitals.
6. Composite materials - incredibly strong yet light nanotubes are being used to reinforce materials.
What are the risks of nanoparticles?
Can damage lungs or enter our blood stream if breathed in and if a spark is made by accident near a large quantity of catalyst there could be a violent explosion.
