Chemistry lecture 1-8

matter

anything that has mass and takes up space

atoms

building blocks of matter, smallest particle of an element

element

substance made up of atoms of one kind, cannot be decomposed into simpler substances

molecule

formed when two or more atoms join together chemically

compound

molecule formed when two or more atoms of different elements join together chemically in a fixed proportion

states of matter

solid, liquid, gas

pure substances

have a definite chemical composition and properties, cannot be separated into simpler substances by physical means

mixture

contains 2 or more pure substances, can be separated by physical means

physical change

change of state in a substance, does not change the composition of the substance eg. freezing, condensation

chemical change

chemical reaction where a new substance is formed and energy is either given off or absorbed eg.combustion, rusting

differences between mixtures and compounds

mixture: components can be separated by physical techniques, composition is variable, properties are related to those of its components;
Compound: components cannot be separated by physical techniques, composition is fixed, properties are unlike those of its components

physical properties

can be observed without changing a substance into another substance, e.g. boiling point, density, mass, volume

chemical properties

can only be observed when a substance is changed into another substance, e.g. flammability, corrosiveness, reactivity with acid

chemical reaction

reacting substances are converted to new substances

intensive properties

independent of the amount of the substance that is present, e.g. density, boiling point, color

extensive properties

depend upon the amount of the substance present, e.g. mass, volume, energy

separation technique : Filtration

Removing a solid from a liquid

Distallation

boiling one or more of the components of a mixture

Chromatography

Separates substances on the basis of different solubility of a solvent

temperature: Kelvin

Temperature in Celsius + 273.15(freezing point)
373.15K(boiling point)
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atomic theory

a theory that states that all matter is composed of tiny particles called atoms, by John Dalton in the19th century

Electrons

negative charge, J J Thomson 1897, 2000 times smaller than orotons

Protons

Ernest Rutherford 1919, 1 amu, +1

Neutrons

James Chadwick 1932, 1 amu, no change

atomic number

the number of protons in the nucleus of an atom Z, in a neutral atom protons= electrons

AMU

atomic mass unit

Isotopes

Atoms of the same element that have different numbers of neutrons, therefore different masses

average mass

calculated from the isotopes of an element weighted by their relative abundances
(ISOTOPE AM1 x %ABUNDANCE)+(ISOTOPE AM2 x %ABUNDANCE) / 100

periodic table

Arrangement of elements in which the elements are separated into groups based on a set of repeating properties.
Rows - Periods
Columns- groups

molecular formula

A chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of the atoms.

Empirical formula

a formula with the lowest whole-number ratio of elements in a compound

Cation

A positively charged ion that loses elections

Anion Gap

A negatively charged ion that gains electrons

lonic compound

Formed between metals and non-metals. They bond so all charges are cancelled out

Combination Reaction

a chemical change in which two or more substances react to form a single new substance

Decomposition Reaction

a reaction in which a single compound breaks down to form two or more simpler substances

combustion Reaction

The process by which a chemical reacts with oxygen to form one or more products as well as heat and usually light eg hydrocarbons

double-displacement reaction

exchange of Ionic partners between two compounds

Avogadro's number

6.02 x 10^23

moles

mass/molar mass

Molarity

moles of solute/liters of solution

limiting reactant

Is the reactant present in the smallest stoichiometric amount it's the reactant youll run out of first

solvent

Dissolving medium

Solute

substance which is dissolved

Solution

Solute + solvent

Titration

A solution of known concentration is used to determine the concentration of another solution.