Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
144 Cards in this Set
- Front
- Back
|
What is a compound? |
A substance made of multiple atoms chemically bonded together |
|
|
Elements react to form compounds in two ways - what are they? |
By sharing, or by losing/gaining electrons. |
|
|
Ions are formed when ___________ are transferred |
Electrons |
|
|
Ionic compounds are held together by strong forces between the oppositely charged ions. This is called... |
Ionic bonding |
|
|
The structure of an ionic compound is known as a... |
Lattice (giant structure) |
|
|
The structure of NaCl is a ________ lattice |
Cubic |
|
|
All __________ compounds are neutrally charged |
Ionic |
|
|
The formula of an ionic compound shows the ________ of ions present in the compound |
Ratio |
|
|
A covalent bond is formed when two atoms ____________ a pair of electrons |
Share |
|
|
Atoms of non-metals always need to _________ electrons to achieve stable electronic structures |
Gain |
|
|
Substances that are made of covalently bonded atoms are called... |
Molecules |
|
|
How many covalent bonds do each group form and why? |
Group 1 forms a single bond as it only needs one more electron for a stable outer shell. Group 2 forms a double bond as it needs two electrons for a stable outer shell, etc. |
|
|
One covalent bond only acts between two atoms, so many covalent substances are... |
Small/simple |
|
|
Some atoms such as _________ can form several bonds, so form giant structures |
Carbon |
|
|
Giant covalent structures are known as... |
Macromolecules |
|
|
Explain how a metallic bond works. |
When metal atoms are packed together, the electrons with the highest energy level "delocalise" (come free) and begin to move freely through the substance. This causes a lattice of positive ions in a "sea" of moving electrons. The negative, delocalised electrons strongly attract the positive ions, holding the giant structure together. |
|
|
The atoms in metals are __________ packed together and are arranged in ___________ layers |
Closely, regular |
|
|
Strong ______________ forces hold giant ionic structures together |
Electrostatic |
|
|
Because of strong electrostatic forces, ionic bonds are hard to... |
Break |
|
|
Because it is hard to break ionic bonds, ionic lattices have high __________ and ___________ points |
Melting and boiling |
|
|
Why are ionic compounds able to carry a charge when they are melted? |
When They are solid, the ions vibrate around fixed positions so they cannot move. As a liquid, the ions move so are free to carry an electrical charge. |
|
|
Some ionic compounds can also carry a charge when they are dissolved in... |
Water |
|
|
____________ bonds in a molecule only act between atoms within the molecule, so simple molecules have _________ _________________ forces. |
Covalent, weak, intermolecular |
|
|
Because simple molecular substances have weak intermolecular forces, they have low... |
Melting and boiling points |
|
|
Why can't simple molecular substances carry an electrical charge? |
Because molecules have no overall charge |
|
|
The __________ the molecules in a simple molecular structure, the ____________ the intermolecular forces |
Larger, stronger |
|
|
Substances with large molecules have stronger intermolecular forces, so are more likely to be _________ at room temperature |
Liquids |
|
|
Some elements can form several covalent bonds, so they can join together in... |
Giant covalent structures |
|
|
What are giant covalent structures referred to as? |
Macromolecules |
|
|
Describe a giant covalent structure. |
Every atoms is joined to several other atoms by strong covalent bonds |
|
|
What are some characteristics of macromolecules? |
They have extremely high melting and boiling points |
|
|
Describe the structure of diamond. |
Diamond is a form of carbon with a regular 3-D structure. Each carbon atom is covalently bonded to three other carbon atoms, making diamond hard and transparent. |
|
|
Describe the structure of graphite. |
Graphite is a form of carbon which is arranged in giant hexagonal 2-D layers. Each carbon atom is covalently bonded to three others. Each layer is not bonded, so they slide over each other. As a result graphite is slippery and grey. |
|
|
Why is graphite able to conduct electricity? |
As only three carbons are bonded to each carbon in graphite, one electron from each carbon atom is left delocalised, so it is free to carry an electric charge. |
|
|
What are fullerenes? |
Giant molecules formed from hexagonal rings of carbon atoms, some being nano-sized. |
|
|
What are some applications that fullerenes are being developed for? |
Drug delivery into the body, lubricants, catalysts, and reinforcing materials |
|
|
Why can metals bend? |
Metal atoms are arranged in layers. when a bending force is applied, these layers slide over each other without breaking. |
|
|
Why are alloys harder than pure metals? |
Because different metals have different-sized atoms, when they are mixed the regular layers of each metal is distorted. This means the layer cannot slide over each other as easily. |
|
|
What is a shape memory alloy and what can it be used for? |
Shape memory alloys are metal alloys which can return to their original shape after being bent, by heating. They are used in dental braces. |
|
|
Why are metals good conductors? |
They have delocalised electrons, which are free to move throughout the metal and can transfer energy quickly. |
|
|
What two things influence the properties of polymers? |
The monomers used to make them, and the reaction conditions under which they were made. |
|
|
What properties of polymers can be changed? |
Density, softening temperature, melting temperture |
|
|
Describe the structure of a thermosoftening polymer, and its properties. |
Thermosoftening polymers are made of polymer chains which are tangled together. |
|
|
What is nanoscience? |
The study of small particles that are between 1 and 100 nanometres in size. |
|
|
A nanometre is one ____________ of a metre |
Billionth |
|
|
Nanoparticles have different _______________ to the bulk materials they are made from |
Properties |
|
|
What are some uses of nanoparticles? |
Highly selective sensors, super efficient catalysts, construction material enhancements, coatings, cosmetics |
|
|
What is a danger of using nanoparticles? |
As they are used more and more, the risk of them entering our bodies will increase, which could have dangerous effects on us |
|
|
What is the relative mass of protons and neutrons? |
1 |
|
|
The total number of protons and neutrons in an atoms is called the... |
Mass number |
|
|
The atomic number represents... |
The number of protons and electrons in an atom |
|
|
Atoms of the same element always have the same atomic number, but the ______ ____________ can vary |
Mass number |
|
|
Why can the mass number vary in atoms from the same element? |
Atoms of the same element can have different number of neutrons |
|
|
What are isotopes? |
Atoms of the same element with different numbers of neutrons |
|
|
How is the amount of neutrons calculated? |
Mass number - atomic number |
|
|
What is the relative atomic mass? |
An average value for the isotopes of an element |
|
|
What is the relative formula mass? |
The relative atomic masses of all the atoms in a formula added up |
|
|
What is a mole? |
The relative formula mass in grams |
|
|
What is the unit used for moles? |
g/mol |
|
|
What is the symbol for relative atomic mass? |
Ar |
|
|
What is the symbol for relative formula mass? |
Mr |
|
|
How can the percentage of an element in an compound be calculated? |
(Relative atomic mass/relative formula mass) x 100 |
|
|
What is the empirical formula? |
The simplest ratio of atoms in a compound |
|
|
How can the empirical formula be calculated? |
1) Divide the mass of 100g of the element of the compound by the relative atomic mass (Ar) - this gives the ratio 2) Divide each number by the smallest part of the ratio - this gives the simplest ratio |
|
|
_______________ symbol equations can be used to calculate the masses of reactants and products in a reaction |
Balanced |
|
|
What is the yield of a reaction? |
How much product is made |
|
|
What is the percentage yield? |
The percentage of product made out of the maximum amount that could have been made |
|
|
How is percentage yield calculated? |
(Amount of product made/Maximum amount possible) x 100 |
|
|
Why is it important to get maximum yield? |
To conserve resources |
|
|
What is a reversible reaction? |
When the products of a reaction can react together to form the original reactants. |
|
|
What is an example of a reversible reaction? |
The heating of ammonium chloride |
|
|
Substances added to food are called... |
Food additives |
|
|
Additives in food can be checked by.... |
Chemical analysis |
|
|
Why are two methods of chemical analysis? |
Paper chromatography and mass spectrometry |
|
|
How does paper chromatography work? |
A droplet (e.g. food colouring) is added to paper, and a solvent (e.g. water) is allowed to travel through it. different colours move different distances depending on their solubility, separating and revealing them. |
|
|
Compounds in a mixture can be separated using... |
Gas chromatography |
|
|
How does a GC-MS analysis work? |
The mixture is carried through a column by a gas. the column is full of solid particles. Each compound travels through the column at different speeds, so when they come out they are separate and can be identified by a mass spectrometer. They can also be recognised by analysing their retention times. |
|
|
What is retention time? |
The time it takes for a compound to travel through the column of a gas chromatography machine |
|
|
What two things have to be measured to find the rate of a reaction? |
The amount of a reactant used over a certain time, or the amount of product made over a certain time |
|
|
The rate of reaction can be found from the _____________ a of line on a graph |
Gradient |
|
|
What is collision theory? |
A theory that states that reactions can only happen if particles collide with enough energy to form new substances. |
|
|
Particles need a minimum amount of energy when they collide to for new substances - what is this energy called? |
Activation energy |
|
|
The rate of reaction can be increased by two things - increasing the chance of ______________ , and increasing the _____________ of the particles. |
Collisions, energy |
|
|
What are five ways of increasing the rate of reaction? |
Increasing the: - Surface area - Temperature - Concentration - Pressure Or by adding a catalyst. |
|
|
Why does increasing surface area increase the rate of reaction? |
Breaking down a solid exposes new surfaces, creating more surface area. More surface means collisions can happen more frequently. Thus, the reaction rate increases. |
|
|
How does a catalyst increase the rate of reaction? |
It lowers the activation energy |
|
|
Why does increasing temperature increase the rate of reaction? |
Increasing the temperature gives the particles more speed and energy. More speed means they collide more often, and more energy means more particles are above the activation energy - Both of these increase the rate of reaction. |
|
|
Why does increasing the concentration and pressure increase the rate of reaction? |
Increasing the concentration/pressure means that there are more particles in the same volume. this means they are closer together. Because they are closer together, they collide more often - this increases the reaction rate. Increasing the pressure |
|
|
A catalyst is not _______ ___ during a chemical reaction |
Used up |
|
|
To make a catalyst as effective as possible, its _____________ _________ can be increased |
Surface area |
|
|
Why are catalysts used in industry? |
They reduce costs/the impact on the environment |
|
|
Many traditional catalysts are ______________ metals |
Transition |
|
|
What are two modern catalysts being developed? |
Nano particles and enzymes |
|
|
A reaction that transfers energy from the reactants to its surroundings is called... |
Exothermic |
|
|
A reaction which takes energy from its surroundings into the reactants is called... |
Endothermic |
|
|
If a reversible reaction is exothermic in one direction, then it is... |
Endothermic in the other direction |
|
|
The a reversible reaction, the amount of energy released in one direction is _________ to the amount of energy taken in in the other direction |
Equal |
|
|
What are two applications of exothermic and endothermic reactions? |
Exothermic reactions can be used in hand warmers Endothermic reactions can be used in instant cold packs for injuries |
|
|
Pure water has a pH value of... |
7 |
|
|
A liquid with a pH value of 7 is known as... |
Neutral |
|
|
What is an acid? |
A substance that produces hydrogen ions, H+(aq) when added to water |
|
|
When a substance is dissolved in water, it makes an... |
Aqueous solution |
|
|
Hydrogen ions make a solution... |
Acidic |
|
|
What is an acidic solution? |
A solution with a pH value of less than 7 |
|
|
_______ react with acids and neutralise them |
Bases |
|
|
What is an alkali? |
A base that produces hydroxide ions, OH-(aq), when added to water. |
|
|
When dissolved in water, alkalis create a solution with a pH value ____________ than 7. |
Greater |
|
|
What is the range of the pH scale? |
0-14 |
|
|
_____________ _____________ can be used to test the pH of a solution |
Universal Indicators |
|
|
How does a universal indicator tell us the pH of a solution? |
It has different colours at different pH values |
|
|
Acids will react with metals that are above _____________ in the reactivity series. |
Hydrogen |
|
|
When an acid reacts with a base, a ______________ reaction occurs |
Neutralisation |
|
|
What two things are produced in a neutralisation reaction? |
A salt and water |
|
|
What two things are produced when an acid reacts with a metal? |
A salt and hydrogen gas |
|
|
How can a salt be crystallized? |
By evaporating off the water in the solution |
|
|
Metal _________ and _____________ are bases |
Oxides and hydroxides |
|
|
What can be used to tell when a neutralisation reaction is complete? |
An indicator |
|
|
_____________ salts can be produced by reacting two solutions to form a ______________ . |
Insoluble, Precipitate |
|
|
What are three types of salts? |
Chlorides, nitrates, and sulphates |
|
|
Some pollutants such as __________ ______ can be removed from industrial waste water by ______________ . |
Metal ions, precipitation |
|
|
___________________ splits up substances using electricity |
Electrolysis |
|
|
What must be done to an ionic compound before it can be electrolysed? |
It must be made molten or dissolved in a solution |
|
|
Why must an ionic compound be dissolved or molten for electrolysis? |
So the ions are free to move |
|
|
The substance being broken down in electrolysis is called the... |
Electrolyte |
|
|
The electrodes used in electrolysis are made of substances which will not react with the electrolyte - this is called being... |
Inert |
|
|
Positive ions move to the negative electrode and form either __________ or _____________ . |
Metals or hydrogen |
|
|
Negative ions move to the negative electrode to form a __________________ element. |
Non-metallic |
|
|
When positive ions get to the negative electrode they _______ an electron to become neutral atoms. |
Gain |
|
|
Gaining electrons is called... |
Reduction |
|
|
Losing electrons is called... |
Oxidation |
|
|
When an aqueous solution is electrolysed, __________ gas is produced at the negative electrode, unless the solution contains the ions of a metal that is more reactive than ___________ . |
Hydrogen |
|
|
Aluminium can only be extracted from its ore by electrolysis because it is more reactive than... |
Carbon |
|
|
_______________ __________ is electrolysed to produce aluminium |
Aluminium oxide |
|
|
Aluminium is mixed with molten cryolite for electrolysis - why? |
melting pure aluminium would require to much energy and would be too expensive. The aluminium oxide - cryolite mixture has a lower melting point, making the process much more cost efficient. |
|
|
What two products are formed during the electrolysis of aluminium oxide, and at which electrodes? |
Aluminium is formed at the negative electrode, Oxygen is formed at the positive electrode |
|
|
Why are the carbon electrodes regularly replaced in the electrolysis of aluminium oxide? |
They react with the oxygen and gradually burn away |
|
|
What is brine? |
A solution of sodium chloride in water |
|
|
What four ions does brine contain? |
Sodium ions, chloride ions, hydrogen ions, and hydroxide ions |
|
|
What is produced at the negative electrode when brine is electrolysed? |
Hydrogen gas |
|
|
What is produced at the positive electrode when brine is electrolysed?
|
Chlorine gas |
|
|
What solution is left over from the electrolysis of brine? |
Sodium hydroxide solution |
|
|
What is electroplating? |
Using electrolysis to coat an object in a thin layer of metal |
|
|
What are some purposes of electroplating? |
- To make an object look more attractive - To protect a metal from corroding - To increase the hardness of a surface - To reduce costs by using a thin layer of metal instead os a pure metal. |
|
|
How does electroplating work? |
The object to be plated is made the negative electrode. the plating metal is made the positive electrode. the solution contains ions of the plating metal. At the positive electrode, the plating metal atoms lose an electron to become ions and go into the solution. these ions go to the negative electrode where they gain an electron to become atoms, and are deposited. |
