Topic 1: atomic structure and the periodic table Flashcards
what is an atom
the smallest part of an element that can exist
what is an element
a substance made up one type of element only
how are the elements listed
periodic table
how many elements approx
100
elements can be classified into two groups based on properties, what are they
metals and non-metals
elements may combine through chemical reactions to form new products, what are the new products called
compounds
what is a compound
two or more elements combined chemically in fixed proportions which can be represented by formulae
do compounds have the same properties as their constituent elements
no - have different properties
what is a mixture
consists of two or more elements not chemically combined together
do mixtures have the same chemical properties as its constituent materials
yes, they have the same chemical properties
what are the methods mixtures can be separated
filtration
crystallisation
simple distillation
fractional distillation
chromatography
do methods separating mixtures involve chemical reactions
no they do not
what is simple distillation used for
simple distillation is used to separate liquids from a solution
explain simple distillation
the liquid boils off and condenses in the condenser
the thermometer will read the boiling point of the pure liquid
what is crystallisation?
the process of formation of solid crystals from solution, melt or by deposition directly from a gas phase.
explain crystallisation?
removing some of the solvent by evaporation to form a saturated solution. then cool down the solution. as its done, you do this the solid starts to crystallise, and less soluble at lower temperatures. the crystals can be collected and separated from the solvent via filtration
what is evaporation
technique for separation of a solid dissolved in a solvent from a solvent
what is fractional distillation
a technique for separation of a mixture of liquids.
only works when liquids have varied boiling points
explain fractional distillation
the fractioning column contains glass beads, that septette the compounds. the column is hot at the bottom and cooler at the top. the liquids rise and condense when they reach their boiling point. the lower boiling point compounds will rise higher and condense.
what is filtration
filtration is used to separate an insoluble solid is suspended in liquid
explain filtration
the insoluble solid gets caught in the filter paper, because the particles are to big to fit through the paper. the filtration in the substance that comes through.
apparatus for filtration
filter paper
funnel
apparatus for fractional distillation
similar to the one for simple distillation
additional fractioning column placed on top of a heat source
what is chromatography
used to separate a mixture of substances dissolved in a solvent
explain chromatography
in paper chromatography, a piece of paper with a spot containing a mixture in a beaker with some solvent. the bottom of the paper has to be in contact with the solvent. the solvent level will start to rise, thus separating the spot into few different ones
what is a separating funnel
a separator funnel is an apparatus for separating immisbiscle liquids. two immiscible liquids of different densities will form 2 distinct layers In the separator funnels. we can run off the bottom layer to a separate vessels
describe the plumb-pudding model
the atom is a ball of positive charge with negative electrons embedded in it
describe the nuclear model
electrons orbit the nucleus at specific distances
how did the nuclear model come about
from the alpha scattering experiment
later experiments led to the discovery of smaller, positive particles in the nucleus, what are they?
protons
what did the work of James Chadwick provide
the existence of neutrons in the nucleus
describe the structure of an atom
the atom has a small central nucleus around these are electrons
what is the nucleus made of
protons and neutrons
relative charge of protons
1
relative charge of neutrons
0