Flashcards in Topic 1 Deck (15):
What is an atom made out of?
What are the charges of the particles and mass?
Proton- Charge(+1)- Mass(1)
Neutron- Charge(0)- Mass(1)
Electron- Charge(-1)- Mass(0)
What is an element?
A substance made up of atoms that all have the same number of protons in their nucleus.
What is an isotope?
Isotopes are different forms of the same element, which have the same number of protons but a different number of neutrons.
What’s the equation for relative atomic mass?
Relative atomic mass(Ar) = Sum of (isotope abundance x isotope mass number) / sum of abundance of all the isotopes
What is a compound?
Compounds are substances formed from two or more elements, the atoms of each are in fixed proportions throughout the compound and they’re held together by chemical bonds.
What is a mixture?
Where there is no chemical bond between the different parts of a mixture.
What can filtration be used for?
Insoluble solids are separated from a liquid reaction mixture.
What is the process of evaporation?
1) Pour the solution into an evaporating dish.
2) Slowly heat the solution. The solvent will evaporate and the solution will get more concentrated. Eventually, crystals will form.
3) Keep heating the evaporating dish until all you have left are dry crystals.
What is the process of crystallisation?
1) Pour the solution into an evaporating dish and gently heat the solution. Some of the solvent will evaporate and the solution will get more concentrated.
2) Once some of the solvent has evaporated, or when you see crystals start or form, remove the dish from the heat and leave the solution to cool.
3) The start should start to form crystals as it becomes insoluble in the cold, highly concentrated solution.
4) has Filter the crystals out of the solution, and leave in a warm place to dry.
What is the process to separate rock salt?
1) Grind the mixture to make sure the salt crystals are small, so will dissolve easily.
2) Put the mixture in water and stir.
The salt will dissolve, but the sand won’t.
3) Filter the mixture. The grains of sand won’t fit through the tiny holes in the filter paper, so they collect on the paper instead. The salt passes through the filter paper as it’s part of the solution
4) Evaporate the water from the salt so that it forms dry crystals.
What is simple distillation?
Simple distillation is used for separating out a liquid from a solution.
1) The solution is heated. The part of the solution that has the lowest boiling point evaporates first.
2) The vapour is then cooled, condenses and is collected.
3) The rest of the solution is left in the flask.
It can be used to get pure water from saltwater.
The problem with simple distillation is that you can only use it to separate things with very different boiling points.
What is fractional distillation?
If you've got a mixture of liquids you can separate it using fractional distillation.
1) You put your mixture in a flask and stick a fractionating column on top. Then you heat it.
2) The different liquids will have different boiling points - so they will evaporate at different temperatures.
3) The liquid with the lowest boiling point evaporates first. When the temperature on the termometer matches the boiling point of this liquid, it will reach the top of the column.
4) Liquids with higher boiling points might also start to evaporate. But the column is cooler towards the top. So they will only get part of the way up before condensing and running back down towards the flask.
5) When the first liquid has been collected, you raise the temperature until the next one reaches the top.
What was the history of the atom?
John Dalton described atoms as solid spheres, and said that different spheres made up the different elements.
JJ Thomson concluded that they weren't solid spheres as his measurements of charge and mass showed that there must be a smaller negatively charged particles called electrons. He then created the 'plum pudding model' which was a ball of positive charge with electrons stuck in it.
Rutherford and his student Marsden conducted the alpha particle scattering experiments. In which positively charged alpha particles were fired at a thin sheet of gold. It was expected for them to pass right through but some were slightly deflected so the 'plum pudding model' could not be right. Rutherford created the nuclear model of the atom where there's a tiny concentrated, positively charged nucleus at the centre and a 'cloud' of negative electrons surround the nucleus.
Bohr realised that electrons in a 'cloud' around the nucleus of an atom, as Rutherford described would be attracted to the nucleus, causing the atom to collapse. Bohr proposed that electrons orbit the nucleus in fixed shells and aren't anywhere in between. Each shell is a fixed distance from the nucleus.
Chadwick carried out an experiment which provided evidence for neutral particles in the nucleus called neutrons.