Year 10 GCSE Chemistry - Introducing Chemical Reactions

Avogadro constant

Number of entities in one mole, equal to the number of atoms in 12.0 g of ¹²C atoms, 6.02 * 10 ^ 23 (3 s.f.)

Balanced equation

Model for a reaction showing formulae using symbols, where the numbers of each atom are the same on both sides of the equation. how atoms are rearranged and the relative amounts of each substance involved

Closed system

Apparatus in which substances cannot enter or leave the reaction mixture during it

Compound ion

Ion formed when a group of atoms loses or gains electrons

Half equation

Type of chemical equation that models the change that happens to one reactant in a reaction

Ionic equation

Type of chemical equation that models how oppositely charged ions form an ionic compound

Law of conservation of mass

Principle stating that the total mass remains constant during a chemical reaction, as atoms are not created or destroyed during a chemical reaction, just joined in a different way

Limiting reactant

Present in an amount less than needed to react completely with the other reactant in a chemical reaction, stopping it

Molar mass

Mass in grams of one mole of a substance

Mole

Unit for amount of a substance containing the same number of particles as there are atoms in 12.0 g of ¹²C, 6.02 * 10 ^ 23

Molecular formula

Description of a compound or an element using symbols for atoms and numbers to show the actual number of each element in a molecule

Non-enclosed system

Apparatus in which substances can enter or leave the reaction mixture during it

Precipitate

Insoluble product in the solid state, formed during a reaction involving solutions

Precipitation

Type of reaction in which a precipitate forms

Spectator ion

Charged particle present in a reaction mixture but does not take part in it

State symbol

Letters used to represent the physical state of a substance

aq, example of four state symbols

Means substance is dissolved in water

Stoichiometry

Describes the relative amount of each substance involved in a chemical reaction, the mole ratio; how many moles are reacting with each other

Word equation

Model of a reaction that describes reactants and products using their chemical names

Dmitri Mendeleev

Russian chemist who spent a significant part of his working life, in the second half of the nineteenth century, trying to arrange the chemical elements into some order

What Mendeleev's arrangement was not the first attempt by chemists to do

Organise the elements into a table

What Mendeleev's periodic table was, and what it lead to

The most successful, our modern Periodic Table

Mendeleev had been considering his own and other scientists' -

Evidence about the elements for several years before his first table

Four things Mendeleev's periodic table achieved

Put elements in order of atomic mass, arranged them in columns with similar chemical properties, left gaps for elements yet to be discovered, predicting their properties and switched tellurium and iodine round to make their properties match other elements in the group

Why the modern periodic table has elements arranged in order of atomic number, not atomic mass

Mendeleev did not know about protons, explaining the leaving of gaps and swapping Te and I

What missing elements discovered fit, and how we know

Gaps he left, having his predicted properties

Why noble gases were not discovered in Mendeleev's time

Very unreactive

What Mendeleev changed about his periodic table by 1871

It currently showed groups as rows, so he rotated he rotated the table so groups were in columns

When three of Mendeleev's predicted elements were discovered

Between 1875 and 1886

Who an when discovered that an atom's atomic number was actually the number of protons in its nucleus

Henry Moseley in 1913

Henry Moseley

English physicist

Two things Moseley's work explained or showed there were in the 1913 Periodic Table

Seven gaps to fill and explained why Mendeleev had been right to swap tellurium and iodine

Johann Döbereiner, 1828 - timeline of the Periodic Table

Developed 'triads', groups of three elements with similar properties

Elements forming triad 'number one'

Lithium, sodium and potassium

Elements forming triad 'number two'

Calcium, strontium and barium

Elements forming triad 'number three'

Chlorine, bromine and iodine

John Newlands, 1865 - timeline of the Periodic Table

The known elements, more than sixty, were arranged in order of atomic weights and observed similarities between the first and ninth elements, the second and tenth elements and so on, proposing the 'Law of Octaves'

Three elements with gaps left for, unknown at the time but their properties predicted, Dimitri Mendeleev, 1869 - timeline of the Periodic Table

Gallium, scandium and germanium

William Ramsay, 1894 - timeline of the Periodic Table

Discovered Noble Gases

When Henry Moseley, 1913, was killed - timeline of the Periodic Table

During the first World War

What the result of Moseley being killed in the first World War was

No leading British scientist is now allowed into a situation where there life may be lost during war time

When - ide is used when naming compounds

If it contains just two elements

When - ate is used when naming compounds

If it contains three or more elements, one of which is oxygen

Number of letters in a chemical symbol

One or two

Why the formulae for metal elements are always written as a single symbol

There are too many atoms in a giant metallic lattice to write the numbers involved

What non-metal elements in group zero exist as

Individual atoms, attracted to each other by weak intermolecular forces

What non-metal elements in group seven exist as

Diatomic molecules, attracted to each other by weak intermolecular forces

Diatomic molecule

Contains two atoms covalently bonded together

Three diatomic molecules not in group seven

Hydrogen, nitrogen and oxygen

What other non-metal elements, such as carbon and silicon exist as

Giant covalent lattices

What other non-metal elements, such as sulphur, exist as

Large molecules

What these other non-metal elements [those forming giant covalent lattices and large molecules] are notated using

The chemical symbol for these elements

Exception to using chemical symbol for these other [those forming giant covalent lattices and large molecules] non-metal elements

Phosphorus, P₄

What the molecular formula for a simple covalent compound shows

Symbols for each of the elements it contains and number of atoms of each elements in one of its molecules

Ensure I know formulae of common ions, find on page titled "Formulae of Common Ions to Learn"

Completed

Hallogens

Group-seven elements

Transition elements can be -

Shaded

Charges of transition-metal ions

Can vary but are given by roman numerals in brackets e.g. Fe(II) = Fe²⁺ ions

What an ionic compound contains

Positive and negative ions

Why knowing a substance is an ionic compound allows you to find its chemical formula

It has no overall charge - this fact can be used

Example of chemical reaction where mass will decrease, if carried out in a non-enclosed system, and why

Calcium carbonate chips in dilute hydrochloric acid, where bubbles of carbon dioxide would then escape

What there are between the substances in a chemical reaction, ignoring coefficients. Example is shown in image attached

Fixed ratios between them

State that sodium metal reacts with water in

Liquid

What sodium metal reacting with water produces

Sodium hydroxide dissolved in water and hydrogen in the gas state

Example of balanced chemical equation using state symbols, that expresses the word equation sodium + water → sodium hydroxide + hydrogen

2Na(s) + 2H₂₂O(l) → 2NaOH(aq) + H₂(g)

Mass of one mole of a substance =

Molar mass, measured in g mol ^ - 1, or its relative atomic mass or relative formula mass

moles =

mass / Mᵣ

Two things moles can be used to calculate

Mass of product made or reactant needed in a chemical reaction

What you do not include when calculating reacting mass equations, when finding Mᵣ values

Coefficients

Reactant in excess

One that is not used up, present in an amount greater than that needed to react with the other reactant

Type of reactant used to calculate reacting masses

Limiting

What Mᵣ is the sum of multiple, when calculating

Relative atomic masses

Mᵣ

Relative atomic mass of one unit of a compound