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Chemistry Topic Test
Transcript of Chemistry Topic Test
Year 10 Chemistry Topic Test Revision notes/help.
Hope they help :)
Did water to gas experiments, and discovered that atoms differ between elements and atoms can combine.
Created Periodic Table based on valency, periodicy, atomic weight, with groups of likeness.
Discovered the Avogadros Constant.
Suggested subatomic particle called electron as fundamental unit of atoms.
Discovered nucleus by shooting alpha particles through gold foil.
Fixed the atomic numbers on the Periodic Table. Showed gaps in the sequence, and predicted elements.
Produced Bohr model of atoms. Theorized that electrons can jump from one orbit to another.
Discovered and proved existence of isotopes of elements.
Proved existence of neutrons with radio.
Atomic Structure Models
Periodic Table Of Elements
You need to have memorised the first 20 elements. All the ones I haven't crossed through.
Valency and Position
Group 1 is 1+,
Group 2 is 2+,
Group 3/13 is 3+,
Group 4/14 is 4+,
Group 5/15 is 3-,
Group 6/16 is 2-,
Group 7/17 is 1-,
Group 8/18 is 0.
The valency of the Electrons effects where they are on the table.
Atomic number is the number of protons in an element.
Mass number is the number that refers to the weight of protons and neutrons over. The decimals are in reference to isotopes and their % in nature.
An isotype is an element with more or less neutrons than normal.
For example Hydrogen has no neutrons, Deutrium has one, and Tritium has two. They all have the same number electrons and protons, but the number of neutrons and weight changes.
There are three different models for the table.
The standard table is the most commonly used and is on your data sheet.
The spiral is when the elements start at Hydrogen and continue in a circle, until you get to the end.
The layered version is when the elements are raised
according to their electronegativity with the more
electronegative elements raised higher than the
less electronegative ones.
Using this info, one can predict the group an element is in given it's valency.
The electronic structure of an element affects it's positioning on the Periodic Table and it's properties because depending on how many valence electrons and electron shells, the reactivity and ability to bond differs.
Compare and Contrast group I and VII
The group I elements are willing to give an electron while group VII are willing to accept an electron. They both have valency of 1, but they are + and -.
Reactivity increases as you go down group I because the
electrons are less attached to the nucleus, and they are
more likely to go away. While as you go down group
VII, the nucleus has a harder time keeping the
electrons in place, and are less likely to pick up
Create your own
One of the things says that 'I can create an element'. I am going to use the example of Uuo, Ununoctium, which is the 118th element. Although this element hasn't been synthesised, it still has it's place.
It is also assumed that you can create your own version of the Period Table given your understanding of the patterns.
Types of Reaction
When a compound breaks down into parts.
Elements are joined together to form a compound.
An element switches with another element in a compound.
When a hydrocarbon and oxygen combine.
An acid and alkali combine and form a salt and water.
Aqueous reaction that forms a solid.
Types of bonding
Between metals only, interlocking grid of nucleus with a 'sea' of electrons.
When the electrons are shared between elements.
When the electrons leave the element creating ions, that then bond.
The electrons in the outer shell of an element.
of Ionic Bonds
Ionic bonds form when an element/compound gives away it's valence electrons to an elememt/compound. Two ionic elements/compounds are formed which due to magnetic attraction bond.
The names of covalent compounds often tell you what it involves. Some things like methane (CH4), Ammonia (NH3), Nitric Acid (HNO3), etc., you should know by heart.
The formula for an ionic compound can be found by taking the valency of the two elements/compounds and swapping them. e.g. Aluminium is 3+, and Oxygen is 2-, giving you Al203.
The numbers should be in subscript.
The elements are organised in groups according to valency. Therefore if you go down a group all the elements should have the same charge of ions, excluding metals which are almost always 2+. The ions produced are just the element with the valency in superscript.
Given the word equation, each compound named has it's own molecular formula. By knowing the name of the compound you should be able to say it's formula.
Word Equation to Chemical Equation
By knowing the formula for the compounds all you have to do is write it beneath the word equation and add in state symbols.
By using the Periodic Table, you can make sure you have the correct formula and, then you can balance your equations. Remember that both sides of the arrow need to have an equal number of atoms. It helps to balance polyatomic ions as one, and do Oxygen last. If it doesn't work double the co-efficients or trying using different ones.
What it is
What that means
Avogadro's number also called Avogadro's constant is a number that refers to the number of atoms of any element in a mole. This number is 6.022x10^23. This number can be found on your data sheet.
A mole is a very important unit of measurement as it is a constant, and currently the only way to measure atoms on a large scale.
Atomic Mass, Molar Mass, and Moles
Atomic Mass is the mass of all the protons and neutrons is one atom.
Molar mass is the mass given on your periodic table, this is the average weight given the atomic weights and percentages of the isotopes of an element.
The name given to the unit of measurement
regarding how many atoms being used. 1 mol =
Applications of Knowledge
Predicting Molar Mass
Using your periodic table, if you know the formula for any given compound you can easily work it out. e.g. Methane (CH4) is 1x12.01+4x1.008=16.042. Most of the time you only need 3 sig. fig.
Calculating Number of Moles
n=m/M where n is number of moles, m is mass and M is Molar Mass.
If I have 12g of carbon-12, how many moles do I have?
The molar mass of carbon-12 is 12, and the mass is 12. Given this you can do 12/12=1, therefore n=1.
For You To Try
1. 73g of Hydrochloric Acid
2. 16.5g of Water
3. 50g of Mercury
4. 42g of Sodium Fluoride
5. 224.32g of Calcium Oxide
1. 2 mol
2. 0.5 mol
3. 0.25 mol
4. 1 mol
5. 4 mol
m=nxM where n is number of moles, m is mass and M is Molar Mass.
If I have 1 mol of carbon-12, how much does it weigh?
Carbon-12's M=12. m=nxM, m=1x12, m=12.
1. 2 mol of Potassium
2. 0.5 mol of Sodium
3. 1 mol of Acetic Acid
4. 3 mol of Beryllium
5. 0.25 mol of Sulfur
If I have 1 mol of Oxygen gas, how many litres do I have?
v=nx22.71, v=1x22.71, v=22.71L
1. 2 mol of Nitrogen gas
2. 0.5 mol of Cabon Dioxide
3. 22.71L of Hydrogen
4. 45.42L of Xenon
5. 11.355L of Chlorine Gas
3. 1 mol
4. 2 mol
5. 0.5 mol
Make Your Own
Make your own problems like these, they can be as easy or as complex as you like. If you want you can comment them below or get your friends to do them. The more you practise these questions the better you'll be.
What is it?
When you react two aqueous solutions and a solid is formed this solid is called a precipitate. It can only be classified as a preicipitate if it comes from two aqueous solutions.
In experiments things happen, you need to be able to describe these things. If the test tube goes cold it's endothermic, i it goes hot it's exothermic. If a solid forms it's a precipitate, if something disappears it dissolves. If nothing happens nothing happens. Remember you can't name anything if it changes, because you don't know for certain what it is.
When will it occur?
Precipitates form when one or more of the
products from a reaction are insoluble. Using
the solubility table, you can say whether or
not something will form.
Net Ionic Equations
What is looks like
A net ionic equation only involves the parts that change state. e.g. Ag + Cl ==> AgCl
It can be described as an equation that removes the spectator ions in an aquoeous reaction.
How to describe it
When you react two aqueous solutions and something else is formed, you can create a net ionic
equation. You start with a balanced equation, and
then remove the spectator ions.
1. Lithium chloride reacts with Potassium Hydroxide
2. Lead nitrate and sodium sulphate
3. Potassium chloride and Sodium Iodide
4. Lead nitrate reacts with Ammonium bromide
5. Ammonium carbonate and Sodium ethanoate
1. Li + OH ==> LiOH
2. Pb + SO ==> PbSO
3. No net ionic equation required
4. Pb + 2I ===> PbI
5. No net ionic equation required
What it is
A limiting reagent is a substance that is entirely used up in a reaction, while the other substances required are in excess. A limiting reagent limits the amount of product made.
How it helps
In a reaction you can find out which substance will limit the reaction and from there how much
you need of the other reactant(s) so that you
don't waste the excess.
An outcomes is easily predicted if you know
what is reacting, and from that you can say what the products are
You can use your observations from a reaction to say what kind ocurred.
If you know what type of reaction is ocurring you can make generalised statements about the outcome. i.e. Neutralisation forms water and a salt.
By using your periodic table and knowledge of reactions you theorise as to what will happen.
You can do this by knowing what kind of substances have more violent or fast
Reflect on this story
It is possible to synthesise elements
In Japan element 113 has been synthesised
113 was created by Zinc and Bismuth combining
Elements decay by shedding alpha particles
Scientists keep trying to 'find' new elements.
Elements past Mendelevium don't exist naturaly for long.
Applying your understanding you should be able to investigate different reactions and observe if a precipitate forms. This means that you should be able to tell what kind of reaction will produce a precipitate, and then testing this.
Hypothesis and Inference
What you see, smell, hear, feel, (or taste, generally you don't taste it. You can not name what is produced.
What you think/predict will happen.
What you can assume because you know what else is going on. This is when you can name substances.
They all help to explain what happened.
Observation is only facts,
Hypothesis is an idea.
Inference is what likely happened based on facts,
I highly recommend doing any questions you can because practise will help. If you want to comment problems of your own for people to solve, please do so. I will try to post some as well.
Also, if I have got anything wrong, please tell me and I will try to fix it asap. If you have any questions feel free to message me.