Science - Chemistry - Atomic Structure - C1 Flashcards
what is an atom ?
the smallest part of an element that can exist
what is an element ?
a substance made of one type of atom only
what are chemical symbols ?
symbols that represent elements
what element is O ?
oxygen
what is the chemical symbol for sodium ?
Na
how are groups on the periodic table arranged ?
numbered, from 1 to 7 then 0
what side of the stepped line are non - metals ?
right side
what is a chemical formula used for ?
representing and element or compound in balanced chemical equations
what is a compound ?
a substance formed by the chemical union of 2 or more elements
what is a balanced chemical equation ?
a chemical equation written using the symbols and formulae of reactants and products, so that the number of units of each element present is the same on both sides of the arrow
what is a molecule ?
a collection of 2 or more atoms held together by chemical bonds
how many hydrogen atoms and oxygen atoms are in h20 ?
hydrogen - 2 oxygen - 1
what are chemical reactions ?
a change in which atoms are rearranged and joined together differently to make new substances
what is an ion ?
an electrically charged particle, formed when an atom or molecule gains or loses electrons
what is an ionic compound ?
when a negative ion joins with a positive ion
what is a negative ion ?
an ion that has gained an electron
what is a positive ion ?
an ion that has lost an electron
what is a word equation ?
an equation in which only the names of the products and reactants are used to model a reaction
what is a reactant ?
a substance that reacts together with another substance to form products in a chemical reaction
what is a product ?
a substance formed in a chemical reaction
show products and reactants in a word equation
reactants -> products
potassium hydroxide reacts with sulfuric acid. potassium sulfate and water are formed in the reaction, show this in a word equation
potassium hydroxide + sulfuric acid -> potassium sulfate + water
what are state symbols ?
a symbol used in a chemical reaction to see if the substance is a solid, liquid, gas or aqueous solution
what are the state symbols for solids, liquids, gases and aqueous ?
s - solid l - liquid g - gases aq - aqueous
what is the law of conservation of mass ?
the total mass of reactants before a reaction is equal to the total number of products after a reaction, because no atoms can be created or destroyed so the mass must be unchanged
balance - N2 + H2 -> NH3
N2 + 3H2 -> 3NH3
what is a ‘pure’ substance ?
a substance that consists of only one element or compound
what is a mixture ?
a mixture consists of 2 or more different substances, not chemically combined
can different substances in a mixture be separated ?
yes, mixtures can be separated by a physical process, that do not involve chemical reactions and no new substances are made
what is filtration ?
method used to separate insoluble solid from a liquid using a physical barrier such as filter paper
how does filtration work ?
filter paper has tiny holes in it, which are large enough to let small molecules and dissolved ions through but not the larger particles of undissolved solid
explain filtration (experiment)
- 1 beaker contains mixture of solid and liquid, the other contains a funnel with filter paper
- solid and liquid mixture is poured into filter funnel
- liquid drips through the filter paper but solid particles are caught in the filter paper
what is crystallisation ?
process of producing crystals from a solution by evaporating the solvent
explain crystallisation (experiment)
- solution is placed in an evaporating basin and heated with a bunsen burner
- volume of solution has decreased as some water has evaporated, solid particles begin to form in the basin
- all water has evaporated, leaving solid crystal behind
give an example of a solution that uses crystallisation
copper sulfate - copper sulfate crystals form from copper sulfate solution
what is simple distillation ?
separation method used to separate a solvent from a solution
what is a solvent ?
the liquid in which the solute dissolves to form a solution
what is a solution ?
mixture formed by a solute and a solvent
what is a boiling point ?
temperature at which a substance changes quickly from liquid to gas
define dissolved
when a substance breaks up and mixes completely with a solvent to produce a solution
what is a vapour ?
gas formed below the boiling point of a substance
what is condensation ?
a change in state in which a gas becomes liquid by cooling
how does simple distillation work ?
the dissolved solute has a higher boiling point than a solvent
when solution is heated, solvent vapour leaves the solution and becomes cooled and condensed.
the remaining solution becomes more concentrated as the amount of solvent in it decreases
explain simple distillation (experiment- seawater/salty water)
- salty water is heated
- water vapour cools in the condenser and drips into a beaker
- the water is condensed and is now in a beaker the salt stays behind
what is fractional distillation ?
a mixture of several substances is distilled, and the evaporated components are collected as they condense at different temperatures
give an examples of when fractional distillation is used ?
useful for separating ethanol and water
how does fractional distillation work ?
different liquids have different boiling points
explain fractional distillation (experiment- water and ethanol)
-water and ethanol solution is heated
-ethanol evaporates first, cools, then condenses
- the water left evaporates, cools, then condenses