Section 1 - Pgs 3-9, 16-28 Flashcards
What is an atom?
A particle, without charge, that is made up of protons, neutrons and electrons.
What is a molecule?
Two or more atoms joined together by covalent bonds.
What is the structure of atoms?
- Central nucleus containing protons and neutrons
- Surrounded by shells of electrons
What is the charge of the nucleus?
Positive
What does the nucleus contain?
Protons and neutrons
Relative to the whole atom, how big is the nucleus?
Tiny
What do electrons move around the nucleus in?
Energy levels called shells
What is the mass of each sub-atomic particle?
Proton = 1 Neutron = 1 Electron = 0.0005
What is the charge of each sub-atomic particle?
Proton = +1 Neutron = 0 Electron = -1
In a neutral atom, the number of electrons…
… Equals the number of protons.
What happens if electrons are added to or removed from an atom?
It becomes charged and is now an ion.
What is an ion?
A charged atom.
What is the mass number?
The total number of protons and neutrons.
What is the atomic number?
The number of protons.
What defines which element an atom is of?
The number of protons (atomic number).
Which number (mass or atomic) is larger?
Mass number
How do you work out the number of neutrons in an atom?
Mass number - Atomic number = No. of Neutrons
What are isotopes?
Different atomic forms of the same element, which have the same number of protons but different numbers of neutrons.
What sub-atomic particles define the chemical properties of an atom?
The number of electrons.
Are isotopes chemically identical and why?
Yes, because they have the same number of electrons, which is what defines the chemical properties.
What is relative atomic mass?
The weighted average mass of the isotopes of that element. It is measured on a scale where carbon is exactly 12.
How many electrons can occupy each of the first 3 shells?
1st shell: 2
2nd shell: 8
3rd shell: 8
What is the significance of an atom having an outer shell which is not full?
It makes the atom want to react so that it has a full outer shell.
What do atoms want in terms of outer shells?
They want a full outer shell.
What is relative abundance of an isotope?
- How much of a certain isotope there is compared to the total amount of the element in the world.
- It can be a ratio, fraction or percentage.
How is relative atomic mass symbolised?
Ar
How do you calculate Ar (relative atomic mass)?
1) Multiply the mass of each isotope by its relative abundance.
2) Add those together.
3) Divide by the sum of relative abundances.
Which shell can actually hold more than 8 electrons?
3rd
How many different atoms are there?
About 100 or so.
What is a diatomic molecule?
A molecule with two atoms in it.
What is an element?
A material made up of only one type of atom.
What is it called when atoms go round in pairs?
Diatomic molecules
What is a compound?
A compound made of two or more different elements which are chemically bonded together.
Are the properties of a compound similar to those of the original elements it is made from?
No, they are often very different.
What is a mixture?
A combination of elements, which are not chemically bonded together.
How can the chemical properties of a mixture be described?
A mixture of the separate parts.
Compare how easily compounds and mixtures can be separated out.
Compounds are difficult to separate out, while mixtures are easy to separate out.
Is crude oil a compound or mixture?
A mixture of different length hydrocarbons.
What is filtration used for?
Separating an insoluble solid from a liquid (often in purification)
Describe filtration.
A liquid with a solid innit is passed through filter paper in a funnel.
What is distillation used for?
The separating of mixtures that contain liquids.
What are the types of distillation?
Simple and fractional
What is simple distillation used for?
Separating a liquid from a solution.
Describe simple distillation.
- Solution is heated
- Part of solution with lowest boiling point evaporates
- Vapour is cooled, condensed and collected
- Rest of solution stays in flask
(This only works with things with very different boiling points)
What is the problem with simple distillation?
It can only be used to separated out things with very different boiling points.
What process is used to separate water from seawater?
Simple distillation
What is fractional distillation used for?
Separating out a mixture of liquids with similar boiling points.
Describe fractional distillation.
- Put mixture in a flask and put a fractionating column on top
- Heat the mixture
- Different liquids evaporate different temperatures -> This allows them to be collected separately
- Once all of one liquid is collected, raise the temperature until the next liquid can be collected
What is the difference between when you might use simple distillation and fractional distillation?
Simple distillation is used to separate things with completely different boiling points (e.g. salt and water), while fractional distillation is used to separate liquids with similar boiling points (e.g. crude oil).
How many elements are there?
About 100
What is the periodic table sorted by?
Increasing atomic number
What are vertical columns in the periodic table called?
Groups
What does an element’s group tell us?
The number of electrons it has in its outer shell.
What are group 1 elements called?
Alkali metals
What are group 7 elements called?
Halogens
What are group 0 elements called?
Noble gases
What determines an element’s properties?
The number of electrons (in the outer shell).
What is crystallisation used for?
Separating a soluble solid from a solution.
Describe crystallisation.
- Pour the solution in an evaporating dish
- Slowly heat the solution until crystals start to form
- Let the solution evaporate -> Creates big crystals
- Dry the crystals using a drying oven or desiccator
What is rock salt made of?
Mixture of salt and sand
How can rock salt be separated?
- Grind the rock salt with a pestle and mortar.
- Dissolve in a beaker.
- Filter through filter paper.
- Evaporate the solution in an evaporating dish.
What is chromatography?
The separating of mixtures (usually dyes)
Describe the process of chromatography.
- Draw a line near the bottom of some filter paper.
- Add spots of different dyes along the line at regular intervals
- Put the sheet in a beaker of solvent
- The solvent depends on what’s being tested
- Make sure the dyes aren’t touching the solvent
- Place a lid on the beaker -> Stops evaporation
- Solvent seeps up the paper, carrying the dyes with it
- Each dye will form a spot