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;
179 Cards in this Set
- Front
- Back
Ionic compounds |
Giant structures of ions |
|
Ions |
Electrically charged atoms |
|
How ionic compounds are held together |
Strong forces of attraction (electrostatic forces) between oppositely charged ions, that act in all directions |
|
Features of ionic compounds |
Have high melting and boiling points |
|
Ionic bond |
Occurs between a metal and a non metal. Involves transfer of electrons from one atom to the other |
|
What do ionic bonds form |
Electrically charged ions, each of which has a complete outer energy level |
|
Charge of atoms that lose electrons |
Positive |
|
Charge of atoms that gain electrons |
Negative |
|
Name of group one |
Alkali metals |
|
Features of alkali metals |
Have one electron in outermost shell |
|
Name of group 7 |
The halogens |
|
Features of the halogens |
Have seven electrons in their outermost shells |
|
Definition of a mixture |
Two or more elements or compounds that are not chemically combined |
|
Definition of compound |
Substances in which the atoms of two or more elements are chemically combined |
|
Ways atoms form chemical bonds |
Share electrons (covalent bonds) |
|
Arrangement of electrons when atoms form chemical bonds |
Each atom gets a complete outer shell |
|
Substances that consist of simple molecules |
Gases, liquids and solids that have relatively low melting or boiling points, with no overall charge so they can't conduct electricity. |
|
Why do simple molecular compounds have low melting and boiling points? |
They have weak intermolecular forces |
|
Intermolecular forces |
weak Forces between molecules |
|
Covalent bond |
A strong bond between non-metal atoms that is formed when pairs of electrons are shared |
|
Simple covalently bonded structures |
H2, CL2, O2, HCL, H2O and CH4 |
|
Giant covalent structures |
Macromolecules (e.g diamond and silicone) made up of covalent bonds |
|
Properties of covalently bonded atoms |
Low melting and boiling points |
|
Why do covalently bonded atoms have low melting and boiling points |
Because they often form molecules in which there are: |
|
Properties of a giant covalent structure |
All the atoms are linked by strong covalent bonds, which means a very high melting point. |
|
Structure of diamond |
Form of carbon |
|
Structure of graphite |
Giant covalent structure, |
|
Why is Diamond so hard? |
Because it has a large number of covalent bonds |
|
Why is graphite soft and slippery? |
Because it has layers that can slide past each other |
|
Other features of graphite |
Layers held together by weak intermolecular forces, one electron from each carbon atom is delocalised, which allow graphite to conduct heat and electricity. |
|
Why is graphite good at conducting heat and electricity? |
Because one electron from each carbon atom is delocalised |
|
Lattice |
Giant, rigid, covalent structure |
|
Why can metals be bent and shaped? |
Because the layers of atoms are able to slide over each other |
|
Atom |
The smallest particle of a chemical element that can exist. Consists of a nucleus made of protons and neutrons and surrounding rings filled with electrons |
|
Structure of metals |
Giant structure in which electrons in the highest energy level can be delocalised, producing a regular arrangement (lattice) of positive ions that are held together by electrons using electrostatic attraction |
|
Why can metals conduct heat and electricity? |
They have delocalised electrons that can move around freely |
|
Alloy |
Mixture that contains a metal and at least one other element |
|
Why are alloys usually stronger and harder than pure metals? |
Because the added element disturbs the regular arrangement of the metal atoms so the layers don't slide over each other so easily |
|
Monomer |
A small hydrocarbon molecule containing a double bond |
|
Polymer |
A giant, long chained hydrocarbon |
|
Properties affecting polymers |
What monomer is used |
|
One use of low density poly ethene |
Carrier bags |
|
One use of high density poly ethene |
Used to make plastic bottles |
|
Thermo softening |
Polymers that consist of individual polymer chains that are tangled together (like spaghetti) |
|
Thermo-setting |
Polymers that consist of polymer chains that are joined together by cross links between them. |
|
Properties of thermo-softening polymers |
Weak intermolecular forces between all of the polymer chains |
|
Properties of thermo-setting polymers |
Contain cross links, so they don't melt when heated |
|
Nano science |
Study of very small structures, roughly 1-100 nanometers in size |
|
Nanoparticles |
Tiny particles that can combine to form structures called nanostructures |
|
Nanometers |
One billionth of a meter |
|
Atomic (proton) number |
Number of protons in the atom |
|
Equation for number of neutrons |
Number of neutrons = mass number - atomic number |
|
Number of electrons in an atom |
Equal to the number of protons, therefore atom has no overall charge |
|
Relative mass of proton |
1 |
|
Relative mass of neutron |
1 |
|
Relative mass of electron |
Very small (negligible) |
|
Isotopes |
Atoms of the same element that have different numbers of neutrons. They have the same atomic number but different mass number. |
|
Chlorine number of Isotopes |
2 |
|
Relative atomic mass |
Number of protons and neutrons in nucleus, usually the larger number on periodic table |
|
Relative formula mass of a compound |
Relative atomic masses of all it's elements added together |
|
Why are nano particles manipulated? |
So materials can be developed that have new and specific properties |
|
Mass of a compound |
Relative formula mass in grams |
|
Percentage mass= |
Relative mass of element in the compound (divided by) relative formula mass of compound (x100) |
|
Empirical formula of a compound |
The simplest whole number ratio of each kind of atom in the compound |
|
Mole |
A measure of the number of particles contained in a substance |
|
Particle |
Atoms or molecules |
|
Number of particles in one mole of any substance |
6x10 to the power of 23 |
|
Number of moles of substance= |
Mass of substance (divided by) mass of one mole |
|
If substance is a compound, mass of one mole of substance is always equal to... |
Relative formula mass of the substance in grams |
|
Instrumental methods |
Where highly accurate instruments are used to analyse and identify substances |
|
Retention time |
Time taken to pass through gas chromatograph |
|
Properties of nanoparticles |
Different to the properties of the same material in bulk |
|
Gas chromatography linked to mass spectroscopy |
Allows different substances, carried by a gas, to travel through a column packed with solid material at different speeds so they separate out. Each substance produces a separate peak on an output known as a gas chromatograph |
|
Chemical analysis |
Can be Used to identify additives in food |
|
Chromatography |
Can be used to identify artificial colours, by comparing them to known substances |
|
Atoms in a chemical reaction are never... |
Lost or gained |
|
Yield |
Amount of product obtained |
|
Reasons that calculated amount of product may not be obtained |
Reaction is reversible; may not go to completion |
|
Percentage yield = |
Yield from reaction (divided by) maximum theoretical yield (x 100) |
|
Reversible reactions |
When products can react to produce original reactants |
|
What happens to solid ammonium when heated and what is produced? |
Decomposes, produces ammonia and hydrogen chloride gas |
|
Nano particles are sensitive to... |
Light, heat and magnetism |
|
Research into nano particles may lead to the development of new... |
Computers |
|
Nanometers |
One billionth of a meter |
|
Chemical reactions only occur when... |
Particles collide with each other with sufficient energy |
|
Activation energy |
The minimum amount of energy required to cause a reaction |
|
Four factors that affect the rate of a reaction |
Temperature |
|
In a cold reaction mixture the particles... |
Move quite slowly. They collide less often with less energy so fewer collisions are successful. |
|
In a hot reaction mixture the particles... |
Move more quickly. They collide more often, with greater energy, so more collisions are successful |
|
In a low concentration reaction, the particles are... |
Spread out. They collide less often, so there are fewer successful collisions. |
|
In a high concentration reaction, the particles are... |
Crowded close together. They collide more often, so there are more successful collisions. |
|
How to increase frequency of collisions in a concentration reaction. |
Increase the pressure of reacting gasses |
|
Concentration of solutions given in... |
Moles per cubic decimetre (mol/dm3) |
|
Large pieces of solid reactant have a... |
Small surface area in relation to their volume. Fewer particles exposed and available for collisions, which means fewer collisions and a slower reaction. |
|
Small pieces of a solid reactant have a... |
Large surface area in relation to their volume, som more particles are exposed and available for collisions. This means more collisions and a faster reaction. |
|
Catalyst |
Substance that changes the rate of a chemical reaction without being used up or altered in the process. |
|
Different reactions need different catalysts. For example... |
The cracking of hydrocarbons uses broken pottery |
|
A catalyst... |
Reduces the amount of energy needed for a successful collision |
|
What does increasing the rate of a chemical reaction reduce in industry? |
Costs |
|
Rate of reaction= |
Amount of reactant used OR product formed (divided by) time |
|
Two ways to find the rate of a chemical reaction |
Measuring the amount of reactants used |
|
3 things to remember when plotting reaction rates on a graph. |
1. The steeper the line, the faster the reaction |
|
When chemical reactions occur... |
Energy is transferred to, or from the surroundings. |
|
Exothermic reactions |
They give out heat to surroundings |
|
Examples of exothermic reactions |
Neutralising alkalis with acids |
|
Endothermic reactions |
They take in heat from surroundings |
|
Examples of endothermic reactions |
Thermal decomposition |
|
If a reaction is endothermic in one direction... |
It is exothermic in the opposite direction |
|
Aqueous solution |
Produced when a substance is dissolved in water |
|
All state symbols |
(S) solid |
|
Metals react with dilute acid to form... |
A metal salt and hydrogen |
|
Salt |
A word used to describe any metal compound made from a reaction between a metal and an acid |
|
Metal reactions with acid |
Silver- no reaction |
|
Bases |
Oxides and hydroxides of metals |
|
Alkalis |
Soluble bases |
|
Oxides and hydroxides of transition metals are... |
Insoluble |
|
Preparation of salts of oxide and hydroxide metals |
1. The metal oxide or hydroxide is added to an acid until no more will react |
|
Word equation for base salt preparation |
Acid + base = neutral salt solution + water |
|
Neutralisation reaction of solutions of hydroxides with a particular acid |
Acid + alkaline hydroxide solution = neutral salt solution + water |
|
Precipitate |
Solid substance |
|
Insoluble salts made by... |
Mixing appropriate solutions of ions so that a precipitate is formed |
|
Precipitation can be used to... |
Remove unwanted ions from a solution. E.g softening hard water. |
|
How to soften hard water |
Precipitation, so the calcium ions a precipitated out as insoluble calcium carbonate. |
|
Two chemical opposites |
Acids and alkalis |
|
Acids contain... |
Hydrogen ions, H+ (aq) |
|
Alkalis contain... |
Hydroxide ions, OH- (aq) |
|
What happens if acids and alkalis are added together in the correct amounts |
They neutralise each other |
|
Word equation for neutralisation reaction |
H+ + OH- = H2O |
|
Ph1 is... |
Acidic |
|
Ph14 is... |
Alkali |
|
Ph7 is... |
Neutral |
|
Ammonia |
Alkali gas that dissolves in water to make an alkaline solution |
|
Indicators |
Dyes that change colour depending on whether they are in acidic or alkaline solutions |
|
What does ammonia neutralise and produce |
Nitric acid to produce ammonium nitrate |
|
Nitram |
Nitrate of ammonia |
|
Nitrogen-based fertilisers |
Important chemicals that increase the yield of crops |
|
Problems nitrates cause if they reach streams, rivers or ground water. |
Upset the natural balance of water |
|
Ammonium salts produced by.... |
Ammonium hydroxide neutralised with acids |
|
Litmus |
Indicator that changes colour from red to blue or vice versa |
|
Universal indicator |
Mixture of dyes that show a range of colours to indicate how acidic or alkali a substance is |
|
pH scale |
A measure of the acidity or alkalinity of an aqueous solution |
|
What happens when substances dissolve in water? |
They dissociate into their individual ions |
|
Electrolysis |
Breaking down of a compound containing ions into its elements using an electrical current |
|
Electrolyte |
Substance in electrolysis being broken down |
|
Ionic substances |
Chemical compounds that allow a current to pass through when they are molten or dissolved in water |
|
During electrolysis |
Negatively charged ions move to the positive electrode and positively charged ions move to the negative electrode |
|
Electrode |
A piece of metal or carbon that allows electric current to enter and leave during electrolysis |
|
If there is a mixture of ions in a solution, the products formed... |
Depend on the reactivity of the elements involved |
|
Redox reaction |
A chemical reaction where both reduction and oxidation occur |
|
Reduction |
Positively charged ions gain electrons at the negative electrode |
|
Oxidation |
Negatively charged ions lose electrons at the positive electrode |
|
Electroplating |
When electrolysis is used to electroplate objects with metals like copper or silver |
|
Aluminium is obtained by... |
Electrolysis of aluminium oxide mixed with cryolite. |
|
Function of cryolite in extraction of aluminium |
Lowers the melting point of aluminium oxide for cheaper energy costs |
|
Sodium chloride |
Common salt |
|
Reagents produced from electrolysis of brine |
1.Chlorine gas (at positive electrode) |
|
Use of chlorine in industry |
Kill bacteria in drinking water and swimming pools, and to manufacture hydrochloride acid, disinfectants, bleach and PVC |
|
How chlorine is detected in a laboratory |
Bleaches damp litmus paper |
|
What's a fullerenes? |
Giant large like covalent structures of carbon |
|
What are carbon nanotubes? |
Allotropes of carbon with a cylindrical nanostructure |
|
What's an allotropes |
Different physical forms of the same chemical |
|
Factors of simple covelent molecules |
Low melting point and boiling point In soluble ( except from carbon dioxide) No free electrons |
|
What are the covalent bonds like in a simple covalent molecules? And what is are the forces like between the molecules? |
Strong covalent bonds Weak forces off attraction |
|
Factors of ionic molecules |
High booiling and meltin point Are soluble |
|
Can ionic molecules conduct? |
Only when in solution |
|
why do macromolecules not conduct electricity
|
they have no free electrons
|
|
why do macromolecules have a high MP and BP
|
because of strong covalent bonds
|
|
what are fullerenes
|
ball shaped macromolecules of carbon
|
|
what can nanoscience be used for?
|
new industrial catalyst sensors to detect one type of molecule n nothing else stronger lighter building materials new cosmetics |
|
name some properties of theromosoftening polymers
|
individual tangled chains of polymers held together by weak intermolecular forces can slide over each other easy to melt can melt and harden to its new shape easy to remould |
|
name the properties of thermosetting polymers
|
made of crosslinks and held together by strong intermolecular forces solid structure doesn't soften when heated they are strong rigid and hard |
|
what can be separated using paper chromatography?
|
artificial colours |
|
describe the steps of paper chromatography
|
extract colour dye from food sample place in a small cup with a few drops of solvent put spots of coloured solution on a pencil baseline on filter paper put in a beker with some solvent solvent seeps up paper - different dyes from spots in different places |
|
name some advantages of using machines to analysis unknown substances |
very sensitive - can detect the smallest trace very fast very accurate |
|
what does gas chromatograph separate
|
a mixture of compounds and help identify the substances present
|
|
name the steps of gas chroatography
|
gas is used to carry substances through a column packed with a solid material the substances travel through a tube at different speeds-so are seperated the retention time of when they reach a detector can help determine a substance a recorder draws a gas chromatography- the number of peaks so the different compounds in a substance |
|
on gas chromatography what does the peaks on the grapgh show
|
the retention time
|
|
|
|
|
|
|