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106 Cards in this Set
- Front
- Back
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What is a compound? |
Substances in which atoms of two or more elements are chemically combined |
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What is chemical bonding? |
Sharing or transferring electrons in the highest occupied energy levels of atoms in order to achieve the electronic structure of a noble gas. |
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How are ions formed? |
When atoms form chemical bonds by transferring electrons, they form ions. |
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Ions have the electronic structure of a __________ |
noble gas (Group 0) |
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What are the group 1 elements called? |
Alkali Metals |
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What ions do alkali metals form? |
+1 charged ions |
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What are the group 7 elements called? |
Halogens |
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What charge do the halide ions have when reacted with alkali metals? |
-1 charge |
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What is an ionic compound? |
A giant structure of ions |
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What is an ionic compound held together by? |
Strong electrostatic forces of attraction between oppositely charged ions |
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How are strong covalent bonds formed? |
When two or more non-metals share pairs of electrons |
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What are macromolecules? |
Giant covalent structures such as diamond |
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Describe the structure of a metal |
Metals consist of giant structures of atoms arranged in a regular pattern |
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Why are metals so strong? (3 points) |
The electrons in the last energy level are delocalised so are attracted to the structure of positive ions, holding them together by strong electrostatic attractions. |
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What is a molecule? |
A particle containing two or more atoms which are covalently bonded
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What are the properties of substances with simple molecules? |
Low melting and boiling points |
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Why do simple molecules have low melting and boiling points? |
They have strong covalent bonds but have weak intermolecular forces between the molecules which can easily be overcome with heat. |
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Why do simple molecules not conduct electricity? |
They have no overall electric charge |
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What is the structure of an ionic compound? (2) |
They have regular structures (giant ionic lattices) In which there are strong electrostatic forces in all directions between positively charged ions |
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Why do ionic compounds have high melting and boiling points? |
Large amounts of energy is needed to break the electrostatic forces
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When do ionic compounds conduct electricity and why? |
When melted or dissolved in water because the ions are free to move to carry the current |
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What is the structure of diamond? |
Each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard |
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Why is graphite so soft and slippery? |
Each carbon atom is bonded to three others, forming layers. The layers can slide over each other due to the weak intermolecular forces between the layers |
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Why is graphite similar to metal? |
One electron from each carbon atom is delocalised. These electrons allow graphite to conduct heat and electricity |
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What is the structure of a fullerene? |
Hexagonal ring of carbon atoms |
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Give uses of fullerenes (4) |
Drug delivery in the body Lubricants Catalysts Nanotubes for reinforcing materials |
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Why are metals easily bent and shaped? |
The layers of atoms are able to slide over each other |
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What are alloys? |
A mixture of two or more different metals |
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Why are metals harder than alloys? |
The different sized atoms of the metals distort the layers in the structure, making it more difficult for them to slide over each other |
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What are shape memory alloys? Give an example |
Shape memory alloys can return to their original shape after being deformed Example Nitinol |
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How do you change the properties of a polymer? |
Produce them using different catalysts and reaction reactions |
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Give examples of polymers (4) |
High density poly(ethene) Low density poly(ethene) Thermosoftening polymers Thermosetting polymers |
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Give the structure of a thermosoftening polymer |
Consists of individual tangled polymer chains with weak intermolecular forces between the chains, therefore easy to melt |
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Give the structure of a thermosetting polymer |
Consists of polymer chains with cross-links between them so that the don't melt when heated |
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What is nanoscience? |
Structures that are 1-100nm in size, a few hundred atoms |
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What are the properties of a nanoparticle? (2) |
Different properties to the same materials in bulk Have a high surface area to volume ratio |
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Give uses of nanoparticles (6) |
New computers New catalysts New coatings Highly selective sensors Stronger, lighter building materials New cosmetics |
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What is the mass of a proton, neutron and electron respectively? |
1, 1, Very small |
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What is the mass number? |
The total number of protons and neutrons |
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What are isotopes of an element? |
Atoms that have different number of neutrons |
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What is the relative atomic mass of an element in terms of isotopes? |
The relative atomic mass (Ar) compares the mass of atoms of the element with the Carbon-12 isotope. It is an average value for the isotopes of the element. |
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What is the relative formula mass (Mr) of a compound? |
The sum of the relative atomic masses of the atoms in the numbers shown in the formula |
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What is a mole of a substance? |
The relative formula mass in grams of a substance is known as one mole of a substance |
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What are the advantages of using instrumental methods to detect elements? (4) |
Accurate Sensitive Rapid Good for very small samples |
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What is paper chromatography used for? (2) |
Identifying additives in foods Finding artificial colours |
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Explain how a compound is separated in gas chromatography |
Different substances, carried by a gas, travel through a column packed with solid material at different speeds, so that they become seperated |
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What is the retention time and how can we find it? |
The retention time is the time a substance takes to travel through the column. We can find it by looking at the position of peaks on the output |
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What do the number of peaks show? |
Number of compounds present |
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What does the retention time show us? |
It helps us identify the substance |
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Mass spectrometer ion peak can also give the ________________ of each substance |
Relative molecular mass |
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How do you find the percentage of an element in a compound? |
Ar of element/Mr of compound x 100 |
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How do you find the empirical formula? |
Divide the mass by Ar for each element Use the percentage as mass if percentages are given Divide each mole number by the smallest mole of each of the elements Write the formula in terms of ratios |
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Why is it not always possible to obtain a calculated amount of product? (3) |
Reversible reaction, so may not go to completion Some product may be lost during seperation Some reactants may react in a different way |
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What is the yield? |
Amount of product obtained |
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How to calculated percentage yield? |
(amount produced/maximum amount possible) x 100 |
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What is a reversible reaction? |
When in a chemical reaction, the products of the reaction can react to produce the original reactants. |
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Give an example of a reversible reaction (Hint: Ammonia) |
Ammonium Chloride <--> ammonia + hydrogen chloride |
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What are the steps for mass calculation of compound reactions? |
1) Write the equation for the reaction, and use the big numbers to find the proportion of reactant to product 2) RFM of product/RFM of reactant 3) Above answer x proportion of reactant x mass of reactant (Make sure you read the question properly and see what mass of what is making what) |
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Formula for rate of reaction (2) |
amount of reactant used/time amount of product formed/time |
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What is activation energy? |
The minimum amount of energy particles must have to react (collide with each other) |
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What does increasing the temperature do? |
Increases speed of reacting particles so they collide more frequently and energetically, which increases rate of reaction |
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What does increasing pressure do? |
Increases speed of reacting particles so they collide more frequently , which increases rate of reaction |
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What does increasing concentration do? |
Increases speed of reacting particles so they collide more frequently , which increases rate of reaction |
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What does increasing surface area do? |
Increases speed of reacting particles so they collide more frequently , which increases rate of reaction |
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What is the job of a catalyst? Why are they used in industry? |
Increase rate of reaction without getting used in the process Used in industry to reduce costs |
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What is an exothermic reaction? |
Reaction that transfers energy to the surroundings |
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Give examples of an exothermic reaction (3) |
Combustion Many Oxidization reactions Neutralization |
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Give every-day uses of an exothermic reaction (2) |
Self-heating cans Hand warmers |
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What is an endothermic reaction? |
Reaction that takes energy from the surroundings |
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If a reversible reaction is endothermic in one direction, it is _____________ in the opposite direction |
Exothermic |
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Give an example of a reversible reaction (Hint: hydrated copper sulfate (blue)) |
hydrated copper sulfate (blue) <--> anhydrous copper sulfate (white) + water |
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blue to white is endothermic? or the opposite? In terms of (an)hydrous copper sulphate |
Endothermic, white to blue is exothermic |
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What are the four state symbols? |
(s), (l), (g) and (aq) |
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What are the substances that can be reacted with acids to form soluble salts? (3) |
Metals, insoluble bases and alkalis |
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Can all metals be used to make soluble salts?
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No, some are too reactive/not reactive enough |
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How are insoluble bases used to make soluble salts? |
Base is added to the acid until no more will react Excess water is filtered |
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How do you know when the alkali and the acid has formed a soluble salt? |
Using an indicator |
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What can salt solution be formed into? |
Solid salts |
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Give the steps of an acid + insoluble base to form a named soluble salt (3) |
Keep adding copper oxide to sulphuric acid Warm the solution and see if the copper sulphate has stopped reacting Filter any excess copper oxide to get copper sulphate solution |
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How are insoluble salts formed? |
By mixing appropriate solutions of ions so that precipitate is formed. |
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What does precipitation do? |
Removes unwanted ions from solutions
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Give uses of precipitation (2) |
Treating water for drinking Treating effluent |
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Give the equation for formation of named soluble salt (Hint: lead iodide) |
Lead nitrate + Potassium Iodide = lead iodide (solid precipitate) Pb2+ + I- |
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What is a base? |
Metal oxides and hydroxides |
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What is an alkali |
Soluble hydroxide |
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The salt produced in an acid/base/alkali reaction depends on what? (2) |
The acid used The metal in base/alkali |
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What is ammonium salt formed from? |
Ammonia plus water = alkaline solution |
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What is the use of ammonium salts? |
Fertiliser |
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What is the pH scale? |
The measure of the acidity or alkalinity of a solution |
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What ions form acidic ad alkaline solutions? |
Hydrogen (H+) forms acidic Hydroxide (OH-) forms alkaline |
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GIve the symbol equation for neutralisation |
H+(aq) + OH–(aq) --> H2O(l) |
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What happens when an ionic substance is melted? |
The ions are free to move about within the liquid or solution |
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What is electrolysis? |
Process of passing an electric current through molten ionic substances to separate them down into elements. |
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What is the electrolyte |
Substance being broken down by electrolysis |
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Where do the positive ions move to during electrolysis? |
They move to the negative electrode |
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Where do the negative ions move to during electrolysis? |
They move to the positive electrode |
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What is electroplating? |
Using electrolysis to coat a metal with another metal eg. spoon coated with silver |
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What does OIL RIG stand for? |
Oxidation is loss, Reduction is gain (of electrons) |
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What substance becomes an element when the electrolyte is in a solution? |
The least reactive of the substances eg. Na+ and H+ --> Hydrogen is formed (H2) |
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Here is an example of a half equation |
2Cl– Cl2 + 2e– |
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What is added to Aluminium Oxide before melting electrolysis? |
Cryolite |
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Why is Cryolite added to Aluminium Oxide before melting and electrolysis? |
To reduce the melting point so save energy costs |
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How is the oxygen removed from aluminium oxide during electrolysis? |
The positive electrode is made of carbon, which reacts with the oxygen to form CO2 |
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What does the electrolysis of Sodium Chloride solution produce? |
Hydrogen, Chlorine and Sodium Hydroxide |
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What is the use for sodium hydroxide? |
Production of soap |
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What is the use for Chlorine? |
For bleach and plastics |
