chem

Created by

h2rizon

Cards (80)

what are the three states of matter
solid, liquid, gas
what processes take place at melting point
freezing and melting
what processes take place at boiling point
boiling and condensing
what does the energy needed to change state depend on
the strength of force between the particles of the substance
what does higher strength of forces between particles mean
the higher the melting and boiling point of the substance
what are some limitations of the simple model
there are no forces between particles

all particles are represented as spheres

the spheres are solid
what is the simple model
diagrams that represent the three states of matter in which particles are represented by small solid spheres
what are the letters used for each processes in chemical equations
(s) solid, (l) liquid, (g) gas, (aq) aqeous
what is an atom
the smallest part of an element that can exist
how are compounds formed 
from elements by chemical reactions
what do chemical reactions involve
the formation of one or more new substances, and often involve a detectable energy change
what are compounds
two or more elements chemically combined together in fixed proportions and can be represented by formulae
can compounds be separated into elements
yes but only by chemical reactions
the mass of products equals...
the mass of reactants
why is the last statement true
no atoms are lost or made during a chemical reaction
why may some reactions appear to involve a change in mass
a reactant or product is a gas and its mass has not been taken into account
what is a mixture
two or more elements or compounds, not mixed with any other substance
what is a pure substance
a substance where nothing has been added to it, so it is unadulterated and in its natural state
how do pure elements and compounds melt and boil
they melt and boil at specific temperatures , it can be used to distinguish pure substances from their mixtures
what is a formulation
a mixture that has been designed as a useful product
how are formulations made 
by mixing the components in careful measured quantities to ensure that the product has the required properties
name some examples of formulations
fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods
what is a composite
two materials, a matrix surrounding and fibres/fragments of the other material (the reinforcement)
what are some examples of composites
fibreglass, carbon fibre, concrete, wood
what is chromatography used for
to separate mixtures and can give information to help identify substances
what is the process of the mixtures separating in chromatography 
involves a stationary phase and a mobile phase
what does separation in chromatography depend on
the distribution of substances between the phases
what is the Rf value in chromatography
the ratio of the distance moved by a compound (centre of spot from origin) to the distance moved by the solvent
do all compounds have the same Rf value
no different compounds have different Rf values in different solvents, which can be used to help identify the compounds
what will happen if there was a pure compound in chromatography
it would produce a single spot in all solvents
what will happen if there was compounds in a mixture in chromatography
the compounds would seperate into different spots depending on the solvent
what happens if there is new experimental evidence
may lead to a scientific model being changed or replaced
what were atoms thought to be before the discovery of the electron
tiny spheres that could not be divided
what discovery led to the plum pudding model
discovery of electrons
what model did jj thompson propose
the plum pudding model
what was the plum pudding model
an atom is a ball of positive charge with negative electrons embedded in it
why was the plum pudding model wrong
there was actually a positively charged nucleus at the centre, because during the alpha particle scattering experiment it showed the particles were deflected
explain the alpha scattering experiment
rutherford fired positively charged alpha particles at an extremely thin sheet of gold

they expected the particles to pass straight through the sheet or at most be slightly deflected

however some were deflected more than expected and a small amount were deflected backwards
what was niels bohrs contribution to the structure of the atom
electrons are found in distinct 'shells' surrounding the nucleus (not orbiting)
what was the nuclear model
a positively charged nucleus surrounded by a cloud of negative electrons