Chemistry Flashcards
what does a chemical reaction always result in?
an energy change.
what is usually produced by an energy change in a chemical reaction?
heat, light or sound energy.
what do u need to measure the energy changes in most chemical reactions?
the temperature of the reactant and product.
what occurs in an endothermic reaction?
the products contain more energy than the reactants.
what occurs in an exothermic reaction?
the reactants contain more energy than the products.
chemical reactions can be followed by measuring changes in what?
Volume of gas produced, mass, concentration, pH.
how do you calculate the average rate of reaction?
average rate = change in quantity/ time taken.
what are protons, neutrons and electrons known as?
sub-atomic particles.
what is the mass of an electron?
1/2000.
what is the mass number of an element equal to?
the number of protons plus the number of neutrons.
what is the RAM of an element?
the average mass of the isotopes of the element.
elements with the same number of outer electrons have what in common?
there in the same group and have similar chemical properties.
how many electrons does the first energy level hold up to?
2.
how many electrons does the second energy level hold up to?
8.
how many electrons does the third energy level hold up to?
8.
what is an ion?
an atom that has become electrically charged.
how do you work out the number of protons from chemical notation of an ion?
it equals the atomic number.
how do you work out the number of electrons from chemical notation of an ion?
look at the charge of the ion, if it is negatively charged the ion has gained electrons, if it is positively charged the ion has lost electrons.
how do you work out the number of neutrons from chemical notation of an ion?
the mass number minus the atomic number.
what is a covalent bond?
a shared pair of electrons between 2 atoms (usually non-metals).
what holds the two atoms together in a covalent bond?
the force of attraction between the positive nuclei and the bonded (or shared) electrons.
what is a molecule?
a group of atoms joined by covalent bonds.
what is a diatomic molecule?
a molecule that contains only two atoms joined by a covalent bond.
compounds that are solid at 20 degrees celcius can be what?
ionic or covalent.
Give a reason for covalent compounds being liquids or gases at 20 degrees celcius.
they contain many millions of atoms joined by very strong covalent bonds in a network, or, they are made from small, discrete molecules held together by weak forces of attraction between the molecules.
compounds that are liquids or gases at 20 degrees celcius are what?
covalent only.
some covalent substances are insoluble in water but soluble in what other kind of solvents?
non-aqueous solvents.
what is the prefix for 1 atom?
mono…
what is the prefix for 2 atom?
di…
what is the prefix for 3 atom?
tri…
what is the prefix for 4 atom?
tetra…
what is the prefix for 5 atom?
penta…
what is the prefix for 6 atom?
hexa…
what method do you use to write chemical formulae?
symbol, valancy, swap.
what is the valency number of an element?
the number of electrons available to form bonds.
name the seven diatomic elements.
hydrgen, oxygen, nitrogen, fluorine, chlorine, bromine, iodine.
why do atoms form bonds?
to achieve a stable electron arrangement, full outer shell.
what is a bond?
a force of attraction between ions or atoms.
what holds ions and atoms together?
bonds.
how are elements arranged in the periodic table?
by increasing atomic number.
what are isotopes?
atoms of the same element with different mass numbers.
how are electrons arranged outside the nucleus?
in different energy levels, known as the electron arrangement.
what are elements made up of?
very small particles called atoms.
where are protons and neutrons found?
in the nucleus of an atom.
where are electrons found?
moving in the space around the nuleus of an atom.
what charge does a proton have?
positively charged.
what charge does a neutron have?
nuetral - have no charge.
what charge does a electron have?
negatively charged.
why are atoms neutral?
they have equal numbers of protons and neutrons.
what is the law of conservation of mass?
the total mass of the reactants must equal the total mass of products in a chemical reaction.
what happens to the temperature in an endothermic reaction?
it falls.
what happens to the temperature in an exothermic reaction?
it rises.
what are the variables that can affect the rate of a chemical reaction?
particle size, concentration, temperature and adding a catalyst.
what happens to the rate of a reaction when the particle size is decreased?
it increases.
what happens to the rate of a reaction when the concentraion is increased?
it increases.
what happens to the rate of a reaction when the temperature is decreased?
it decreases.
what happens to the rate of a reaction when a catalyst is added?
it increases.
what is a catalyst?
a substance that can be used to speed up a chemical reaction but are not used up during the reaction and can be recovered chemically unchanged.
what is an enzyme?
a biological catalyst.
give 2 examples of an exothermic reaction.
combustion and neutalisation reactions.
all substances (reactants and products) contain what?
chemical potential energy.
how are positively charged ions formed?
when metal ions loose electrons.
how are negatively charged ions formed?
when non-metal atoms gain electrons.
what is an ionic bond?
the strong force of attraction between positive metal ions and negative non-metal ions.
ionic compounds exist as what?
lattices of positive and negative ions.
why are ionic compounds solids at 20 degrees celcius?
because there are very strong forces of attraction between oppositely charged ions.
what happens to an ionic lattice dissolves in water?
it breaks up completely.
do ionic compounds conduct electricity when solid? and why?
no. because the ions are not free to move.
ionic compounds conduct electricity when in what 2 states?
in an aqueous solution or molten.
what is electrolysis?
the movement of electricity through an ionic compound that separates it in to elements.
why can electrolysis only take place in ionic compounds?
because they contain ions.
what happens when electricity passes through an ionic compound in solution.
elements are formed at each electrode.
what is an electrolyte?
an ionic compound dissolved in water or molten that conducts electricity.
what kind of current must be used during electrolysis? and why?
d.c. because it allows the products to form and be identified.
what happens to the positively charged metal ions during electrolysis?
they accept electrons from the negative electrode and become neutral atoms.
what happens to the negatively charged non-metal ions during electrolysis?
they donate electrons to the positive electrode and become neutral molecules.
why are some ionic compounds coloured?
because some metal ions are coloured.
what can experiments using coloured ions be used for?
to show that ions are charged particles.
what three elements react with oxygen to produce (element)dioxide?
sulfur, nitrogen and carbon. all non- metal oxides.
carbon dioxide, sulfur dioxide and nitrogen dioxide dissolve in water to produce what? and what does this do?
acids. increases the hydrogen ion (H+).
state two ways carbon dioxide can be produced.
naturally by respiration and by burning fossil fuels.
state two ways nitrogen dioxide can be produced.
naturally during lightening storms and by the sparking of air on a car engine.
how is sulfur dioxide produced?
by burning fossil fuels, especially coal.
give 3 effects of acid rain.
leaves on trees are damaged and fall off, corrosion of metals is increased, aluminium ions washed into lakes kill fish.
how is acid rain produced?
when sulfur and nitrogen dioxide dissolve with water in the atmosphere.
name 3 common household acids.
vinegar, lemon juice, fizzy drinks
name 3 common household alkalis.
soap, bleach, toothpaste
what do acidic and alkaline solutions contain?
ions.
what is the pH of a solution?
a measure of the concentration of hydrogen ions (H+).
what can water molecules do?
dissociate into hydrogen and hydroxide ions.
what is the test for hydrogen?
it burns with a pop.
what kind of ions do all acidic solutions contain?
(H+(aq)).
what kind of ions do all alkaline solutions contain?
(OH-(aq)).
metal oxides and metal hydroxides dissolve in water to make what and what does that change?
alkaline solutions. increases the concentraion of hydroxide ions.
what happens when you dilute an acid with water?
makes it less acidic, decreases the concentration of H+ ions, increases its pH towards 7 and decreases its electrical conductivity.
what happens when you dilute an alkali with water?
makes it less alkaline, decreases the concentration of OH- ions, decreases its pH towards 7 and decreases its electrical conductivity.
how do you calculate the formula mass of a compound?
by adding together the relative atomic masses of the elements present in the formula.
what is gram formula mass?
the formula mass of a substance expressed in grams
what is gram formula mass also known as?
relative formula mass.
what is the gfm equal to?
one mole of a substance.
what is the equation relating: gram formula mass, mass and number of moles?
m = n x gfm
what is the equation relating: volume, mass and concentration?
n = v x c
what is the concentration of a solution?
a measure of how much of a substance is dissolved in 1 litre of water.
give four examples of neutralisers or bases.
metal oxides, metal hydroxides, metal carbonates and MAZITL metals.
what is a base?
a substance which neutralises an acid.
what does a reaction between an acid and a base always produce?
a salt.
metal oxide + acid =?
a salt + water.
metal hydroxide + acid =?
a salt + water.
metal carbonate + acid =?
a salt + water + carbondioxide.
MAZITL metal + acid =?
a salt + hydrogen.
what are spectator ions?
ions that do not take part in a chemical reaction.
what happens in a precipitation reaction?
2 solutions react to form a precipitate (an insoluble solid).
give 2 examples of everyday neutralisation reactions.
reducing the acidity of soil by adding lime, reducing the effects of acid rain on lakes by adding lime or treating acid indigestion.
what happens when acid rain reacts with metal structures?
it causes them to corrode.
what is a fuel?
a chemical which burns to produce energy.
what happens to the boiling point as the size of the molecules increase?
it increases.
what happens to the flammability as the size of the molecules increase?
it decreases.
what happens to the viscosity as the size of the molecules increase?
it increases.
in car engines what does the energy from the spark of the spark club cause?
the nitrogen and oxygen from the air to combine to make nitrogen oxides.
what are biofuels?
liquid or gaseous fuels made form plant or animal material.
what is a homologous series?
a chemical family with the same general formula and similar chemical properties.
what is cracking?
an industrial process for producing smaller more useful molecules using larger unwanted molecules.
what are isomers?
molecules with the same molecular formula but different structural formula.
give 2 properties of the alkanes.
insoluble in water and very flammable.
give 2 properties of the alkenes.
insoluble in water and very flammable.
give 2 properties of the cycloalkanes.
insoluble in water and very flammable.
give 2 properties of the alcohols.
some are soluble in water and all are very flammable.
give 3 properties of the carboxylic acids.
soluble in water, very flammable and pH<7.
give an example of a rechargeable battery.
a car battery.
how is a simple cell made?
by connecting 2 different metals together and placing them in an electrolyte.
give an example of an electrolyte.
sodium chloride, NaCl(aq).
why does the metal higher in the ecs loose electrons in a displacement reaction?
to form ions and the metal ions in the solution gain these ions to become atoms.
