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Chemistry (solubility (solution=A mixture formed in which the solute is…
Chemistry
Basic facts
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The masses of subatomic particles are tiny so we use their masses relative to each other which is the same when it comes to charges
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Relative masses: proton=1 neutron=1 electron=1/2000 or 0.0005 relative charge: proton=1 neutron=0 electron=-1
An atom consists of a central nucleus, composed of protons and neutrons
key words
Atoms of an element that have the same no. protons but different no. neutrons in their nuclei are called isotopes
relative atomic mass=the mean relative mass of the atoms of the different isotopes in an element. no. times heavier than a twelfth of a carbon 12 atom
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Atomic number=number of protons in an atom no. protons determines the element no. protons=no. electrons = no charge
Periodic table
The group means every element in that group will have the same number of electrons in its outer shell
An isotope= an element with a varying mass number meaning that it can have different numbers of neutrons
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electronic configuration
After ionic bonding the ion is left with a full outer shell. when metal atoms ionise they lose an electron whereas non metals gain an electron when ionising
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The electron configuration of an element can be determined from its atomic number in an element no. protons=no. electrons
Different shells hold different maximum numbers of electrons. Electrons occupy shells starting with the innermost and than move on to the next once full
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solubility
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solubility= The mass of solute that can be dissolved at a constant temperature measurement=g of solute per 100g of solvent
Heating up the solvent gives the molecules more kinetic energy the extra kinetic energy means that the solvent and solute molecules collide with greater frequency and force both of these factors increase the solubility
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states of matter
solid-liquid=melting liquid-gas=boiling gas-liquid= condensation liquid-solid=freezing solid-gas=sublimation
Diffusion is when liquids/gases move from areas of high concentration to areas of low concentration=uniform concentration
solid particles vibrate liquid particles move around each other and gas particles move quickly in all directions
If two pads are soaked in ammonia solution and hydrochloric acid and were then placed at opposite ends of a test tube a white ring of ammonia chloride would form because of diffusion
Particles in a solid are close together in a regular pattern particles in a liquid are close together in a random arrangement and particles in a gas are far apart with a random arrangement
separating mixtures
A pure substance has a fixed melting and boiling point but a mixture may melt and boil over at a range of different temperatures
chromatograms can be used to distinguish between pure and impure substances e.g one spot=pure more than one=impure
element= a substance that cannot be broken down into another substance=made up from its own type of atom
A paper chromatogram can also be used to identify substances by comparing them to other known substances If the spots travel the same distance up the page and have the same colour they are the same substance
compounds are substances made from atoms of different elements joined by chemical bonds. A mixture is made by mixing elements and compounds=no new bonds are formed
Irregular charges
some steps for writing balanced equations are 1) check the formula for the equation is correct 2) deal with one element at a time
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hydrogen (H+), hydroxide (OH–), ammonium (NH4 +), carbonate (CO3 2–), nitrate (NO3 -), sulfate (SO4 2–).
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Ag+, Cu2+, Fe2+, Fe3+, Pb2+, Zn2
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If the particles are heated they move faster and have more energy meaning there are more collisions taking place and more are successful
The rates of two or more reactions can be compared using graphs of volume of product produced against time
If you increase the concentration the reaction rte goes up because there are more of the particles to collide as the concentration goes up thus increasing the rate of reaction
This is because more reactant particles are exposed at the surface and thus the frequency of successful collisions between reactant particles increases
A catalyst increases the rate of reaction but does not get used up the mass and chemical formula is unchanged
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atom=the smallest particle of a chemical element that can exist.
molecule=A molecule is made of a fixed number of atoms bonded together.
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Rf values can be used to identify unknown chemicals if they can be compared to a range of different reference substances. It is calculated by distance travelled by substance/distance travelled by solvent ranges from 0-1