C456 Twenty first century

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  • Created by: Tami
  • Created on: 11-06-17 17:46
What is an element?
An element contains the same type of atoms.
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How did Dimitri Mendeleev arrange his periodic table?
He arranged his into groups (vertical columns) and periods (horizontal rows) according to their relative atomic masses and patterns in their properties. He left gaps for undiscovered elements and predicted their properties.
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How did Dobereiner arrange his periodic table?
He arranged his in triads and the first and last element had a mean average atomic mass of the middle element. This was rejected because most elements did not fit this pattern.
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How did Newlands arrange his periodic table?
He arranged his in octaves and every eighth element had similar properties.His idea was rejected because most elements did not fit their pattern.
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What does a group show in a periodic table?period?
A group shows the number of electrons on an elements outer shell. A period shows the amount of shells an element has.
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How did Dmitri Mendeleev predict undiscovered elements?
He saw that the physical and chemical properties of elements were related to their atomic mass. so he arranged them so that groups of elements with similar properties fell into vertical columns. This left gaps for elements he predicted.
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Name the chemical symbols for Lithium, Sodium and potassium?
Li- Lithium Na-sodium K-potassium
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What is the relative atomic mass?
It is the number of protons + number of neutrons.
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Properties of group 1 alkali metals?
They are soft metals that can be cut with a knife.The freshly cut surface is shiny but tarnishes in moist air due to oxygen.
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How can you identify metals in a periodic table? non-metals?
Atoms of elements with up to 3 electrons on their outer shell are metals. (group 1,2 and 3). Non metals have 5 or more electrons in their outer shell (group 5 or above)
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What is the trend in group 1 alkali metals? Why?
They increase reactivity as they descend and this is because the outer electron is easier to lose if the atom is bigger (shielding causes weak attraction forces between nucleus and electron on outer shell).
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What happens when you react group 1 metals with water? What is the trend as you descend down the group?
metal + water ---> alkaline metal (metal hydroxide)+ hydrogen . When water reacts with lithium and sodium, the metal fizzes and moves around water. When potassium is reacted with water it explodes and rubidium explodes more violently.
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How do you test for hydrogen?
Light a match and if it releases a pop sound then hydrogen has been made
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Name some hazards with using Group 1 alkali metals? What precautions need to be taken when using them?
They are flammable and their hydroxides are corrosive and harmful. They should be kept away from water and naked flames.
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What does the hazard symbol with a skull mean? What does the one with the fire mean? What does the one with the X mean?
-Toxic -flammable -harmful
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What does the hazard symbol with a fire containing a hole mean? What does the hazard symbol with the chemical being poured on a hand mean? What does the hazard symbol with lines coming out of a broken sphere mean?
-oxidizing -corrosive -explosive
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What do alkali metals react with chlorine to form?
metal + chlorine ---> salt (sodium chloride) . It forms a colourless salt.
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Name the symbol equations for chlorine, iodine and bromine?
Cl-chlorine Br-bromine I-iodine
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What state (and colour) are these group 7 halogens at room temperature? fluorine,chlorine, bromine and iodine
Fluorine is pale yellow, chlorine is a pale green gas, bromine is a red-brown liquid and iodine is a dark grey solid.
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What is the trend in melting points and boiling points as you go down group 1 alkali metals?
Lithium has the highest melting and boiling point in the group. The melting and boiling points decrease as you go down the group.
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What is the trend in densities as you go down group 1 alkali metals?
Lithium has the lowest density in the group. The densities then generally increase as you go down the group.
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What colour are group 7 halogens as gases?
chlorine is pale green. bromine is red-brown and iodine is purple.
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Halogens are diatomic, what does that mean?
They have 2 atoms joined in each molecule.
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What is the trend in melting and boiling points as you go down group 7?
The melting points and boiling points increase.
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How is the new periodic table arranged?
It is arranged in order of atomic number (proton number).
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What are the hazards with using group 7 halogens? what precaution have to be taken for safety?
They are corrosive and toxic, therefore they are using in a fume cupboard.
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What is the trend in reactivity as you go down group 7?
They become less reactive as you go down the group. This is because as you go down the group, there are more shells and this means the electrostatic forces between the nucleus and electrons are weak. It is harder to pull electrons.
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What are displacement reactions?
This is when a more reactive halogen takes they place of a less reactive one. E.G Chlorine is more reactive than bromine and will take the place of bromine in potassium bromide --> potassium chloride + bromine
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Describe the structure of an atom?
There is a nucleus which contains protons and neutrons. There are then electrons arranged around the nucleus in shells .
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What are the masses and charges of protons? electrons ? neutrons?
Neutrons have a mass of 1 and no charge. Protons have a mass of 1 and a + charge. Electrons have a negligible mass (almost 0) and a negative charge.
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What is the number of protons equal to?
The number of protons is equal to the number of electrons.
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All of the atoms in the same element have the same number of what?
protons
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What do some elements emit when heated?
Some elements emit distinct flame colours when heated. The coloured light can then be split into a line spectrum
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How did the development of spectroscopy help scientists discover new elements?
Helium was was discovered when scientists looked at the line spectrum of the sun.
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Draw a diagram showing the electrons in oxygen?
-First you draw a circle or put a dot in the centre of your page -Then you draw a ring around you dot and mark 2 electrons with an X. - Repeat this again except mark 6 electrons with an X
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How are chemical properties of elements affected by electron configuration?
Chemical properties are affected by electron configuration and this is shown in group 1 and 7 elements. The more electrons in the atom, the more shells and the weaker the electrostatic attraction between nucleus and outer shell.
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What is chemical properties?
The characteristic of a substance that describes its ability to change into different substances. E.G reactivity,
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What are ionic compounds?
Compounds of metals and non-metals elements. They are solids composed of ions arranged in a regular crystal lattice.
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Describe the properties of ionic compounds?
They are soluble in water. They have high melting and boiling points. They conduct electricity when molten or dissolved but not in a solid because the ions can not move to carry a charge.
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What is an ion?
A charged particle that has either lost or gained electrons. E.G group 1 elements lose electrons to become positive oins and group 7 elements gain electrons.
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Na- + Cl+ --->
NaCl
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What does dry air consist of?
78% Nitrogen, 21% oxygen, 1% argon and 0.04% carbon dioxide. Dry air consists of both elements (oxygen, nitrogen and argon) and compounds (carbon dioxide).
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What are the symbols for water, carbon dioxide and oxygen ?
Water(H-O-H), Carbon dioxide (O-C-O), Oxygen (O-O)
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What are most non-metal elements and compounds between non-metals?
They are molecular E.G H2,O2,N2 and Cl2 . This also works for compounds between non-metal like carbon dioxide - CO2, ammonia - NH3, Methane- CH4
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What are atoms in molecules held together by?
They are held together in covalent bonds (They share electrons). They are held together as the positive nuclei of both atoms are electro-statically attracted to the shared electrons. This holds the atoms together.
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What are the properties of molecular compounds?
There are weak inter-molecular forces between them for example 2O2 can be easily broken into O2 + O2. This means they have low melting/boiling points. However they have strong covalent bonds between atoms, so it requires a lot of energy to break O2.
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Why do molecular compounds not conduct electricity?
Because their molecules are not charged (They do not contain ions)
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What is the earth's hydrosphere?
All the water on Earth including oceans, seas, rivers and lakes
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What else does the hydrosphere contain?
It contains dissolves salts.
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Describe an ionic bond?
It is the strong force of attraction between positively charged and negatively charged ions.
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How can ions in an ionic compound be detected?
They often have distinct properties. E.g Compounds containing copper ions are often blue.
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When two solutions of ionic compounds are mixed together what is formed?
Some of them may make a precipitate of an insoluble compound. This can then be identified due to its distinct colour
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How can (positive) metal ions be identified using sodium hydroxide?
When sodium hydroxide (an alkali) is added to a solution it can form insoluble metal hydroxides with characteristic colours. The metal can be identified by its colour.
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How can some (negative) non-metal ions be identified in a solution?
When reagents like (Silver nitrate or Barium chloride) are added to ionic compounds. They form insoluble solid precipitates and this indicates which negative ions are in the salt.
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What is the lithosphere?
It is the rigid outer layer of the earth composed of crust and upper mantle.
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What else does the lithosphere contain?
It contains rocks and minerals
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What are minerals?
Minerals are solids with atoms arranged in a regular lattice.
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What are ores?
They are rocks that contain metal minerals.
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What are diamond and graphite?
They are minerals made of carbon atoms.
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Describe the properties of diamond?
-High melting and boiling point due to its strong covalent bonds. -Does not dissolve in water -There are no free electrons so it does not conduct electricity.
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Describe specifically the carbon atoms in a diamond?
Each carbon atom is covalently bonded to 4 other atoms in a tetrahedral 3-D lattice.
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Describe the properties of graphite?
-Sheets are strong but it has weak forces between sheets and due to this, they can slide over each other and graphite is soft. -It conducts electricity due to free electrons between sheets.
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Describe specifically the carbon atoms in graphite?
Each carbon atom is covalently bonded to 3 others in sheets.
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Name some abundant elements of the earth's lithosphere?
Silicon, oxygen and aluminium
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How is silicon and oxygen present in the earth's crust?
It is present in the Earth's crust as silicon dioxide
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Describe the properties of Silicon dioxide?
It is similar to diamond in the sense that it is hard, has high melting and boiling points and it can not conduct electricity. These properties are due to its strong covalent bonds between silicon and oxygen. It requires a lot of energy to separate.
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The amount of minerals in an ore varies. Describe why this could be a problem?
Sometimes they may only be small amounts of minerals in ores. This means that huge amounts of rocks need to be mined for small amounts of minerals. E.G small amounts of copper are found after mining huge amounts of rock.
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Name the metals that can be extracted from their ores through heating with carbon? Give a word equation for it/
Iron, zinc and copper. E.G Zinc oxide + carbon --> zinc + carbon dioxide
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What is reduction? What is oxidisation? what is a redox reaction?
Reduction is when oxygen is lost. Oxidisation is when oxygen is gained. A redox reaction is when both redction and oxidisation take place, something loses oxygen while another thing gains oxygen.
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What can aluminium be obtained by heating with carbon?
It is so reactive that it can not be obtained by heating with carbon
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What is relative atomic mass? What is relative formula mass?
Relative atomic mass is the mass of an atom compared to carbon. Relative formula mass is the sum of all the relative atomic mass of atoms in the compound.
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What is gram formula mass?
It is the relative formula mass or relative atomic mass in grams
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What is the formula to work out the percentage of metal in a mineral?
Total mass of metal atoms ÷ gram formula mass x 100
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What is electrolysis?
Passing an electric current through an ionic compound when it is either molten or dissolved.
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What happens in electrolysis?
-Positive ions go to negative cathode and gain electrons to form neutral atoms -Negative ions go to positive anode and lose electrons to form neutral atoms.
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Describe the properties of puremetals?
They are malleable, strong and can conduct electricity.
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Why does metal have these properties?
Its atoms are held together by metallic bonds in regular giant lattice pattern. Metallic bonds are strong and need lots of energy to break. Metal atoms lose their outer-shell electron to form positive ions, they have sea of electrons.
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Some more explanation behind the properties of metals?
- High melting and boiling points because seas of electrons are strongly attracted to positive ions. Atoms all the same size and can roll over each other (They are malleable even though they have strong bonds)
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Name some poisonous metals ?
lead, mercury and cadmium
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Name problem with extracting metals using mining?
-Some metals are found in compounds with sulfur and when extracted this makes sulfur dioxide which is a pollutant that causes acid rain. -It requires large amounts of energy -large amounts of rock processed for little amounts of metals
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What do we need copper for?
Electrical wiring and circuits, pipes and building material.
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What is chemical synthesis?
Using simple substances to make new and useful chemical compounds.E.G dyes, paints, food additives, medicines and fertilisers
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What is PH? How can you find the PH?
PH is a scale that tells you how strong or an alkali or acid something is. Acid is Red and alkali is blue. PH can be found using universal indicator or Litmus paper
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Metal + acid = ?
Metal+acid= metal acid +hydrogen
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Metal oxide + acid = ?
Metal oxide + acid = metal acid + water
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Metal hydroxide + acid=?
Metal hydroxide + acid= metal acid + water
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Metal carbonate + acid=?
Metal + acid = water + carbon + metal acid
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What is titration?
It is a neutralisation reaction used to measure the volume of acid or alkali needed exactly to react together.
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In titration how is the equipment set up?
A specific volume of an acid or alkali of known concentration is placed into a burette. Universal indicator is added to the conical flask. The other acid or alkali is placed (specific volume)in a conical flask .
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After setting up the equipment for titration what do you do?
First a rough measurement is taken, The acid in the burette is dropped in the conical flask and then the conical flask is swirled . This happens repeatedly until the alkali changes colour in the conical flask.
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Why is titration repeated?
To check that the results are close together.
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How do you measure how much of the substance in the burette is needed to neutralise the substance in concical flask?
You read how much of the substance in the burette has been used by looking at the measurement from the bottom of the meniscus.
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What is an exothermic reaction?
It is a reaction that gives out heat and the products have less energy than the reactants.
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What is an endothermic reaction?
It is a reaction that takes in heat and the reactants have less energy than the products.
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Describe neutralisation and give a word equation for it?
It is when an acid reacts with an alkali to form salt and water. Acid+ alkali= salt +water
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Why is filtration important?
Some substances need to be very pure to be used. For example medicines need to be pure
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Describe the process of crystallisation?
-Dissolve product in water -filter any impurity that does not dissolve -Evaporate and product is left in crystals -dried is oven -
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What is the formula for percentage yield?
actual yield ÷ theoretical yield x 100
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How can the rate of reaction be measured?
It is either the amount of products made or the amount of reactants used up. E.G measure mass of substances or gas syringe
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How to change rate of reactions?
-higher temperature = faster reaction -higher concentration = faster reaction -smaller particles = bigger surface area = faster reaction
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Other cards in this set

Card 2

Front

How did Dimitri Mendeleev arrange his periodic table?

Back

He arranged his into groups (vertical columns) and periods (horizontal rows) according to their relative atomic masses and patterns in their properties. He left gaps for undiscovered elements and predicted their properties.

Card 3

Front

How did Dobereiner arrange his periodic table?

Back

Preview of the front of card 3

Card 4

Front

How did Newlands arrange his periodic table?

Back

Preview of the front of card 4

Card 5

Front

What does a group show in a periodic table?period?

Back

Preview of the front of card 5
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