C1 Flashcards
How many elements are there?
Around 100
Define element
In an element, all the atoms are the same.
Define compound
Contains 2 or more different elements chemically combined in fixed proportions.
How to separate a compound?
Use a chemical reaction.
Define mixture
Different elements or compounds not chemically combined together.
How to separate a mixture
Use a physical separation technique.
Define molecule
Has any elements chemically combined (even if they are the same element). Some molecules can be compunds too.
4 separation techniques
Filtration, chromatography, crystallisation, distillation
Function of filtration
Used to separate an insoluble (will not dissolve) solid from a liquid. (s) and (l)
How to do filtration?
Put filter paper in a filter tunnel and pour the mixture through it. The liquid passes through the tiny pores in the filter paper and the solid is trapped in the filter paper.
Function crystallisation
Used to separate a soluble solid from a liquid. (aq) and (l)
How to do crystallisation?
If you leave the solution for a few days or gently heat the water, then the liquid will evaporate. You have to make sure heating will not affect the chemical that is being crystallised. This will leave behind crystals of the solid. (aq) to (s).
Function of simple distillation
Used to separate a liquid from a solid if we want to keep the liquid,
Function of fractional distillation
Used to separate 2 different liquids, which must have different boiling points. (l) and (l)
How to do simple distillation?
- Evaporate the liquid by heating. 2. Condense the vapour by cooling.
How to do fractional distillation?
- Evaporate mixture by heating. The one with the lower boiling point will evaporate more easily. 2. The liquid with the lowest boiling point will evaporate first and it will reach the top of the column and condense through the condenser. 3. When the first liquid has been collected, you raise the temperature until the next one reaches the top.
How to do fractional distillation?
- Evaporate mixture by heating. The one with the lower boiling point will evaporate more easily. 2. The liquid with the lowest boiling point will evaporate first and it will reach the top of the column and condense through the condenser. 3. When the first liquid has been collected, you raise the temperature until the next one reaches the top.
Function of paper chromatography
Used to seaparate substances based on their different solubilities.
How to do paper chomatography?
- Draw a pencil line near the bottom of chromatography paper. 2. Put dots of each colour on the pencil line. 3. Place the bottom of the paper into a solvent (a liquid that dissolve substances). 4. The solvent makes its way up the paper and dissolves the ink in the dots.
Define stationary phase in paper chromatography
Does not move - paper
Define mobile phase in paper chromatography
Does move - solvent
What happened in 1897?
J. J. Thomson concluded that atoms were not tiny spheres and contained tiny negative particles and called them electrons and had an internal structure. The plum pudding model showed the atom as a ball of positive charge with electrons stuck in it.
What happened in 1909?
Ernest Rutherford conducted the alpha particle scattering experiment. They fired positively charged alpha particles at an extremely thin sheet of gold. Most of the particles passed straight through without changing direction - atoms were mainly empty space. Some were deflected - the centre had a positive charge. Some bounced straight back - the centre had a great deal of mass - known now as the nucleus. Came up with the nuclear model.
What did Neils Bohr discover?
Electrons orbit the nucleus at specific distances. Orbits are now called energy levels or shells. Positive charge is due to positive particles called protons. Updated nuclear model.
What did James Chadwick discover?
The nucleus also contains neutral particles called neutrons. Updated nuclear model.
Radius of an atom
0.1 nanometres (1 x 10^-10m)
Radius of a nucleus
1 x 10^-14m
Relative charge of proton, neutron and electrons
+1, 0, -1
Relative mass of proton, neutron and electrons
1, 1, very small
Where is the atomic number and what does it show?
At the bottom, shows the number of protons (and electrons).
Where is the mass number?
At the top, total number of protons and neutrons.
Define isotope
Atoms of an element with different number of neutrons and same number of protons.
Define ions
Atoms which have an overall charge. They have gained or loss electrons. Positive ions - lost electrons. Negative ions - gained electrons.
Define relative atomic mass
The average of the mass numbers of the different isotopes. Weighted for the abundance of each isotope (how common it is).
How many electrons can each energy level hold?
2, 8, 8, 18
Why do elements in a group have similiar chemical properties?
Have the same numebr of electrons in their outer energy shell.
Who developed the first modern periodic table?
Dmitri Mendeleev
How did Dmitri Mendeleev order the elements?
Started by arranging all the elements in order of increasing atomic weight. He switched the order of elements if he needed to so they fitted the patterns of other elements in the same group and left gaps where he thought an element was missing.
How is the modern periodic table ordered now?
In order of atomic number (number of protons) and has noble gases.
Why are noble gases unreactive?
They have a full outer energy level, which means it is energetically stable and do not need to lose or gain electrons.
What happens to the noble gases as the relative atomic mass increases (down the group)?
The boiling point increases.
How do group 1 elements react with oxygen?
Reacts rapidly as you go down the group.
How do group 1 elements react with chlorine?
Reacts rapidly as you go down the group.
How do group 1 elements react with water?
Reacts rapidly as you go down the group. Metal + water reacts to make metal hydroxide + hydrogen.
Why do group 1 elements get more reactive down the group?
The outer electron becomes less attracted to the nucleus so is easier to lose. There is a greater distance.
How do group 7 elements form molecules?
2 atoms are joined by a covalent bond.
What is room temperature?
Around 20C
What happens to the MP and BP in the group 7 elements?
Increases as you go down the group.
What happens to the relative molecular mass in the group 7 elements?
Increases as you go down the group.
What bonds form when the group 7 elements react with non-metals?
Covalent
What bonds form when the group 7 elements react with metals and what do they end in?
Ionic, -ide (chloride)
What happens to reactivity down group 7 and why?
Reactivity decreases because it becomes harder to gain an electron - greater distance from nucleus and shielding by internal electrons.
