Science - Chemistry
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What are the Noble Gases ?
Helium(He), Neon (Ne), Argon (Ar), Krypton(Kr) Xenon (Xe) and Radon (Rn).
What are the properties of the Noble Gases?
- Group 0(sometimes called 8)
- Full outer shell
What are the Alkali Metals?
Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Caesium (Cs) and Francium (Fr).
What are the properties of the Alkali Metals?
- Group 1
- React vigorously with water
- Become more reactive as you go down the group
What are the Halogens?
Fluorine (F), Chlorine (Cl), Bromine(Br), Iodine (I) and Astatine (At).
What are the properties of the Halogens?
- reactive non-metals
- darker as you go down the group
- reactivity decreases as you go down the group
- boiling points increases as you go down the group
What is the Mass of a Proton?
What is the Mass of a Neutron?
What is the Mass of an Electron?
Negligible/ Nearly 0
What is the charge of a Proton?
What is the charge of a Neutron?
What is the charge of an Electron?
Where in an atom would you find Protons?
Where in an atom would you find Neutrons?
Where in an atom would you find Electrons?
Energy shells around the Nucleus
What does AMU stand for ?
Atomic mass unit
What does the Atomic Number show?
The number of protons
What are equal to protons in an atom?
What is the mass Number ? (atomic mass)
- mass of nucleus
- (protons + neutrons)
How do you work out the number of neutrons?
No. neutrons = mass number - atomic number
Why are atom neutrally charged?
They have an equal amount of protons and electrons
What are isotopes?
- Atoms of the same element that have different number of neutrons in their nucleus
- e.g.146C 126C
True or False the chemical properties of isotopes are different ?
False because they have the same number of electrons
What is the relative atomic mass? (Ar)
- The average mass of all isotopes taking into account their relative abundance
- abundance - how much
How do you work out the Ar ?
How do you work out the mass of a compound?
- Add up the relative atomic mass of each atom
How many electrons in shell ...
What is Ionic Bonding?
- Bonding between a Metal and a Non- metal
- The metal loses an electron and the non-metal gains it.
- Held together through electrostatic attraction.
What are the properties of an Ionic compound?
- Conduct electricity When molten or dissolved in Water
- Form an ionic lattice
- High melting and boiling points
- Hard to separate
- can decompose back to their elements
What is covalent bonding?
- Bonding between two Non-metals
- They share electrons to achieve a noble gas state
- Held together by intermolecular forces
What are the properties of a simple covalent structure?
- Do not conduct electricity in any state
- Low melting and boiling point (even when the force is strong)
- Insoluble in water (may dissolve in other liquids)
- Liquid or gas at room temperature
What are the properties of a giant covalent structure?
- Regular arrangement e.g. a diamond
- High melting point
- Very hard
- Don't generally conduct electricity
- Insoluble in all liquids
What are the properties of a Diamond?
- Hardest natural substance known on earth
- Shiny / sparkly
- very high melting point 3500°c +
- held together by strong covalent bonds
- each carbon has four bonds
- made entirely of carbon
- Does not conduct electricity because all the electrons are held together between atoms
What are the properties of Graphite?
- Made entirely of carbon
- used in pencils
- has a layered structure
- held together by strong covalent bonds but with weak intermolecular forces allowing them to slide
- high melting point
- each carbon atom uses three of its bonds
- has delocalised electrons as only 3 are used in bonding
- can conduct electricity
what are the properties of silicon dioxide?
- High melting point
- strong covalent bonds
- used in sandpaper
- each silicon atom makes four bonds to oxygen atoms
What's a thermosetting polymer?
It can only be moulded once as it sets when it comes into contact with heat
What's a thermo softening polymer?
Can be moulded many times as when it comes into contact with heat it melts
Do Polymers have a melting range or point?
Melting range as they are not pure subatances
Why can thermosetting only be moulded once?
They have cross links that hold them in position
What difference makes LDPE and HDPE?
They are made under different conditions and have a different catalyst
What does malleable mean?
Can change shape (soft / flexible)
What does ductile mean?
Can stretch without snapping
what does sonorous mean?
When it is struck it will make a sound
Why do metals conduct electricity well?
They have free moving electrons (delocalised)
What are properties of metal?
- have high melting pints
What is metallic bonding?
- Bonding between two metals
- Atoms become positively charged as the free electrons move away
- The sea of electrons mean the atoms are attracted
How do you work out the percentage of an element in a compound?
- Atomic mass of the element
- divided by
- atomic mass of compound
- then times 100
- % of Carbon in CO212/44 x 100 = 27.27 %
What is the empirical formula?
The smallest, whole, number of atoms in a formula
9g of Aluminium reacts with 35.5g of Chlorine
What is the empirical formula?
- element Al Cl
- 9g 35.5g
27/9 = 0.33333...
- empirical formula AlCl3
Instructions for Empirical formula
- Draw a table with the number of elements +1 columns
- Draw 6 rows Labelled Element, Mass, Ar, Mass/Ar Mole ratio (/ smallest) and Empirical formula
- In the rows fill in the information
- Make sure the numbers that are created after /smallest are whole numbers
- if not times to make the smallest whole number (e.g. 1.5 and 2 times them both by 2 to get 3 and 4)
- write your numbers in the correct places after the right element and you have your empirical formula
how to work out the mass that can be made from so much of an element?
What mass of TiO2 can be made from 3.4g of Ti?
- Ti + 02 → TiO2
- 1 mole of .... is
- Ti = 48g O2 =32g TiO2 = 80g
- For Ti M=W/R = 3.4/48= 0.070833333... mol
- For TiO2 We make 0.070833333 mol
- W=MxR = 0.07083333... x 80
- = 5.666...g
How much limestone would you need to make 5.6g of quick lime?
- CaCO3 → CaO + CO2
- =100g 56g 44g
- 5.6 = 56/10
- 100/10= 10
- 10g of CaCO3
How much MgO will be made from 2g of Mg?
- 2Mg + O2 → 2MgO
- W=2g M=? R=24
- 2/24 =0.0833333..
- Molar ratio is 1:1 so 0.083333. mol of Mg makes 0.08333... of MgO
- W= 0.08333.. x 40 = 3.3333...g
We expected to get 3.333..g of MgO ut we only got 1.65g
What's the percentage yield?
- 1.65/3.333333... x100 = 49.5%
Percentage yield = actual yield /theoretical yield x100
What is chromatography used for ?
To separate different substances dissolved in a liquid
How is gas Chromatography carried out?
The sample is dissolved in a solvent, then injected into one end of the column.An unreactive gas - usually nitrogen - carries the sample through the column.Different substances in the sample travel through the column at different speeds and so become separated from each other.The separated substances leave the column one after the other. As they leave, they are detected by a detector.
What is the retention time ?
The time taken for a substance to travel through the column
What do the peaks show?
the number of compounds present in the sample
What does the position of each peak show?
the retention time
What does a mass spectrometer do?
A mass spectrometer is able to identify substances very quickly and accurately. It can detect very small amounts
what is a GC-MS?
this combined GC-MS method allows the separated substances leaving the column of the GC machine to be detected.
mass spectrometry -higher
The mass spectrometer can be used to identify substances quickly and accurately, and in very small amounts. It can also provide the relative formula mass of the substances separated by gas chromatography. The peak furthest to the right in a mass spectrum is called the 'molecular ion peak'. Its relative mass is the relative formula mass of the substance being analysed.
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