Chemistry - Additional Chapter 1-3 Flashcards
What are atoms that have lost or gained an electron called?
Ions
What do ions have the structure of?
A noble gas
What do ionic bonds between particles result in?
Giant structure of giant lattice
Describe a simple molecular bond
The atoms form very strong covalent bonds but there are weak intermolecular forces of attraction between the particles
- low melting and boiling points as less energy is required to break the bonds therefore they are easily oarted
- gases and liquids at room temperature
- do not conduct electricity as there are no ions therefore no electrical charge
Describe a giant covalent structure
- no charged ions but other then that it is similar to a giant ionic structure
- they are bonded to each other by strong covalent bonds so therefore they have high melting and boiling points so a lot of energy is needed to break them apart
- do not conduct electricity even when molten
Describe a diamond
- giant covalent
- each carbon atom forms 4 covalent bonds
- rigid structure which makes it hard and it has high melting and boiling point
Describe silicon dioxide
- giant covalent structure
- silicon and oxygen
- high melting and boiling point
Describe graphite
- giant covalent
- each carbon atom has 3 covalent bonds
- layers of atoms which slide over one another
- layers are loosely held together by weak intermolecular forces so can be rubbed off onto paper
- can conduct electricity as each carbon atom has one delocalised electron
Describe a metallic structure
- giant structure
- has free electrons which come from the other shell of every metal atom in the the structure this can make it transfer energy
- strong electrostatic attraction between the positive metal ions and negative electrons
- layers so the my can slide and be bent and shaped
Descrie an alloy
- harder than pure metals
- different elements have different sized atoms this means it will have distorted layers and irregular layers so they can no longer slide over one another making them harder
What is a compound?
Two or more elements which are chemically combined
What are shape memory alloys?
They can be bent into different shapes, but when you heat them they can go back to there original shape
What are shape memory alloys used in?
- braces
- glasses frames
- broken bones - they cool the alloy then put it around the bone, then when the alloy is heated it goes back to its original shape and pulls the bone with it
Describe thermosoftening polymers
- weak forces and have individual chains of polymers, these are held together by weak intermolecular forces, therefore they are free to slide over one another
- easy to melt and remould
Describe thermosetting polymers
- strong forces due to the strong intermolecular forces with crosslinks that hold the chain firmly in place
- solid structure and doesn’t soften when heated therefore they are strong hard and rigid
What effects a polymers properties?
The temperature and pressure you make it at
- low density - high temperatures and pressures, these are flexible so they can be used for bags and bottles
- high density - low temperatures and pressures but with a catalyst to speed up the reaction, these are more rigid so are used for water tanks and drainpipes
What is nano science?
The study of very tiny particles and structures
What is a fullerene?
Molecules of carbon shaped like a hollow ball or tube
- used to reinforce graphite in a tennis racket
What can nano science be used for?
- stronger, lighter building materials
- conduct electricity so electrical circuits and computer chips
- nano medicine - fullerenes are absorbed by the body easily so can go to cells where they are needed
- cosmetics - sun cream and deodorant
What is a problem with nanoparticles?
Due to the large surface area, if they are exposed to a spark they can explode
Whats a property of nanoparticles?
Large surface area to volume ratio
What is the relative mass of an proton, neutron and electron?
1, 1 , o or very little
What is an isotope?
Atoms of the same element with a different number of neutrons
Do isotopes always have the same atomic number or mass number?
Atomic number
- they have a different mass number
Are all isotopes radioactive?
Sometimes, but not all this is because they have extra neutrons which make the nucleus unstable and radioactive
What are the properties of an isotope?
Physical properties - different - they have different densities and may not be radioactive
Chemical properties - the same - as they will always have the same number of electrons
What is the relative atomic mass?
The average mass of the atoms of an element compared with carbon -12
What is the relative formula mass?
The relative atomic masses added together
What is a mole equal to?
1 mole is equal to its relative formula mass in grams
How do you work out the number of moles?
Number of moles= mass (g) / relative formula mass
How do calculate the percentage mass of an element in a compound?
Percentage mass of an element in a compound = relative formula mass x number of atoms of that element / relative formula mass of the whole compound
Revise empirical formula
Revise empirical formula a
How do you calculate a mass of an element in a compound?
- Work out balanced equation
- Work out relative formula mass
- Divide to get 1 than multiply to get all of them
How do you work out the percentage yield?
Percentage yield = actual yield/ predicted yield x 100%
Why is the yield always less than 100%?
- The reaction is reversible, this means that the reactants will all never completely be turned into products as the reaction goes both ways. Some of the products are alway reacting together to change back to the original reactants this will mean a lower yield is created
- Filtering, when you filter to remove some of the solid particles you will always lose some liquid or solid
- Not going to plan, an unexpected reaction may use up some of the reactants so there is not as much
Why is the percentage yield important for sustained development?
So we don’t use resources faster than they need to be used so theres enough for future generations e.g using little energy possible to produce the highest yield
How do work out the different colourings in food colourings?
- Extract colour form food sample and put it in a small cup with a few drops of solvent
- Put the spots of the coloured solution on the pencil baseline - pen will dissolve in the water and run this will ruin the experiment
- Roll up the sheet and put it in the beaker with some solvent, keep the baseline above the solvent
- As the solvent sweeps upwards the colourings move up the paper
- 4 dots does not mean 4 colourings two might be in the same place
What are the advantages and disadvantages of machines for substances?
\+ sensitive \+ fast \+ accurate - special training - expensive - results that are given have to be compared
How does gas chromatography work?
- Mixture is vaporised
- Then a carrier gas moves the vaporised gas through a coil
- The vaporised compounds have different attractions, the bigger there attractions the longer the retention time
- The recorder then draws a gas chromatography graph, the number of differ et peaks show the number of different compounds
On a gas chromatography what does the position of a peak show?
The retention time
What does gas chromatography do?
Separates a mixture of compounds
What does the mass spectrometer do?
It identifies the substances leaving the column accurately and the molecular ion peak (its always the last one)
