Chemisty - End or year 10

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  • Created by: Alex_04
  • Created on: 04-06-19 21:30
Why do scientists use chemical formulae?
-To show the different elements in a compound -To show how many atoms of each element one molecule of the compound contain
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What two ways can compounds be seperated?
By chemical reactions or electroloysis
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What is a mixture?
Something that consists of two or more elements or compounds, which are not chemically combined. The components retain their own properties e.g magnetic
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How can mixtures be separated?
Filtration, Crystallisation, Simple distillation, Fractional distillation & Chromatography
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What did Thomson discover about the atom? (1)
They had electrons and he thought that they were negatively charged because atoms were neutral. He came up with the plum-pudding model
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What did Geiger and Marsden discover from the gold foil experiment? (2)
Most of the positively charged alpha particles went straight through the gold however few were deflected. They realised that the positive charge was concentrated in a small area of an atom, the nucleus
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What was the gold foil experiment? (2)
A thin sheet of gold was bombarded with alpha particles - some went straight through, others were slightly deflected, very few went straight back to the source
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What did Bohr realise? (3)
Electrons must orbit the nucleus at specific distances, otherwise they would spiral inwards
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What did James Chadwick discover? (4)
He discovered that there was neutrons within the nucleus
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What are the relative masses of protons, neutrons and electrons?
Protons - 1 Neutrons - 1 Electrons - Almost 0
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What are the relative charges of protons, neutrons and electrons?
Protons - +1 Neutrons - 0 Electrons - -1
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What is the atomic number?
The number of protons in an atom
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What is the mass number?
The sum of protons and neutrons in an atom
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What is an isotope?
An element that has the same number of protons but a different number of neutrons e.g same atomic number but different mass number
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How does an atom become an ion?
-A metal atom loses an electron to become a postitive ion -A non-metal atom gains an electron to become a negative ion
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How was the first form of the periodic table arranged?
In order of atomic weight, however there were gaps in the table as only 63 elements had been discovered
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How did Mendeleev arrange the periodic table? (2)
-He knew that not all elements had been discovered so left gaps -Re-ordered some elements -Elements with similar properties were arranged in vertical columns (groups) -Arranged in order of increasing atomic number
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What are the properties of noble gases (Group 0)?
-All have a full outer shell of electrons so are very unreactive -Non-metals -Boiling points increase down the group
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What are the properties of alkali metals (Group 1)?
-One electron in their outershells -Low melting and boiling points that decrease down the group -Low density -Become more reactive down the group
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Why are alkali metals so reactive?
The outer electron is further away from the influence of the nucleus so can be lost more easily
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What are the properties of transition metals?
-Can be used as catalysts -Good conductors or heat and electricity -Can be easily bent
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How are ions formed?
When atoms gain or lose electrons, which gives them an overall charge
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What are the properties of ionic compounds?
-High melting and boiling points -Do not conduct electricity when solid but do when molten
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What is a metallic bond?
The attraction between positive ions and the delocalised negatively charged electrons
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What is a covalent bond?
A shared pair of electrons between atoms
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What is the equation for percentage yield?
Actual yield produced / Maximum theoretical yield x100
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What happens in a displacement reaction?
A more reactive metal displaces a less reactive metal from a solution of it's salt
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What is the anode (and the cathode)?
The positive (negative) electrode used in electrolysis - Negatively (Positively) charged ions move here
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What does a catalyst do?
-Reduces the amount of energy needed for a successful collision -makes more collisions successful -Speeds up the reaction -Provides a surface for the molecules to attatch to, which increases the chances of collisions
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What is the general formula for alkanes?
CnH2n+2 (Carbon & Hydrogen)
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What is the general formula for alkenes?
CnH2n (Carbon & Hydrogen)
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What is the difference between alkanes and alkenes?
Alkanes have only contain single bonds and are described as saturated whereas alkenes have at least one double bond so are unsaturated
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Card 2

Front

What two ways can compounds be seperated?

Back

By chemical reactions or electroloysis

Card 3

Front

What is a mixture?

Back

Preview of the front of card 3

Card 4

Front

How can mixtures be separated?

Back

Preview of the front of card 4

Card 5

Front

What did Thomson discover about the atom? (1)

Back

Preview of the front of card 5
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