C1.1 - C1.8 Atoms,bonding,moles✔️ Flashcards
What is an element?
Substance made of only one type of atom
What does each group contain?
Elements with similar chemical properties - and electrons in outer shell
What are compounds?
2 or more different types of elements bonded together - chemical bonds hold atoms tightly
Law of conservation of mass?
The total mass of the products formed in a reaction is equal to the total mass of reactants
What is aqueous solution?
Substances dissolved in water - (‘aq’ is the symbol)
What is an atom?
Atom smallest part of an element that can exist
What is filtration?
Technique used to seperate substances that are insoluble in a particular solvent from those that are soluble
What were Dalton ideas/beliefs about atoms?
-In chemical reactions - atoms rearanged themselves and combined with other atoms
-atoms could not be divided or split
What was JJ Thomson discovery?how did he discover it?
-End of 1800s discovered the electron
-experimenting by applying high voltages to gasses at low pressure
-electons negativley charged
What were the elements origionaly ordered in the early perodic table?
By order of atomic mass however early perodic table incomplete because not all elements were discovered
Thomsons plum pudding model?
Negative electrons embedded in a cloud of positive charge - like bits of plum in a plum puding
What was Niels bohrs suggestion/idea ?
Electrons orbit the nucleus - at fixed energy levels(shields)
What did James Chadwick disscover?
1932 - disscovered neutrons
What is an ion
An ion is a charged atom or group of atoms
What is an isotope?
Atoms of the same element with different number of neutrons - same atomic number but different mass number
Properties of isotopes?
-different density
-may be radioactive
-always have same chemical properties - same number of electrons - electronic stucture unchanged
How can mixtures be seperated?
Seperated by physical means such as filtration,crystallisation and simple distlation
What is a mixture?
Mixture is made up of two or more substance that are not chemically combined together
What is paper chromatography?
A technique used to seperate and indetify substances from mixtures in solutions
How does paper chromatography seperate mixtures?
Seperates mixtures of substance dissolved in a slovent as they move up a piece of chromatography paper
How do you obtain crysals through crystalisation?
To obtain a sample of pure salt you would need to filter the solution then heat with a bunsern burner until point of crystalisation and then leave the rest to evaporate in a flat bottom dish like a petri dish to give a large surface area for water to evaporate from
How do you know a soluion is at the point of crystalisation?
Crystals first appear arround the edges of the solution or on a drop of solution extracted with a glass rod
Define crystalisation?
Seperating a soluble solid from a solvent to produce samples of pure salt
Explain the process of distilation?
1)solution is heated and boiled to evaporate the solvent
2)vapour then enters a condenser
3)condenser is an outer glass tube with water flowing through it and acts as a cooling “jacket” arround the inner glass tube
4)vapour condenses and turns back into liquid
5)collected in a flash/beaker
Uses of distilation?
In countries where there is a lack of fresh water sources - They can purify sea water to obtain drinkable water
What is a condenser used in distilation?How does it work?
condenser is an outer glass tube with water flowing through it and acts as a cooling “jacket” arround the inner glass tube - vapour enters and cools and condenses back into a liquid
Define a mixture?
Mixture - made up of two or more substances that are not chemicaly combined - no chemical bonds between atoms of different substances
How can elements in a compound be seperated?
Chemical reaction must be used to seperate the elements
4 physical methods to seperate mixtures?
-filteration
-crystalisation
-distillation
-chromatography
Explain how paper chromatography seperates mixtures?
Substances dissolved in a solvent move up a piece of chromatogtaphy paper and the different substances are seperated because of their different solubilities in the solvent used
When did JJ Thomsom descover the electron?
End of 1800s
How did JJ Thomson discover the electron?
Applyed high voltages to gases at low pressure and did experiments on the beams of particles - they were attracted to positive chage shwoing they must be negativley charged
Why was it hard for James chadwick to discover the neutron?
Neutrons have no charge therefore they are very difficult to detect only when he did an experiment that could only be explained by the existence of neutrons
What was Geiger and marsdens experiment,and what did it lead to?
Experimenting with radioactive particles by firing dense positivley charged particles (alpha particles) at a thin piece of gold foil expecting all to go through instead not all did suggestig the plum pudding model was wrong
What is atomic number?
Number of protons - equal number of electrons and protons
What is mass number?
Number of protons + neutrons
What is the insoluble solid that remian behind during filtaration?
Residue
Define distilation?
Used to seperate and recover a solvent from a solute
Why is fractional distillation an effective way of seperating miscible liquids?
Allows you to seperate and collect the liquid with the lowest boiling point as the miscible liquids will have different boiling points
