Unit review Flashcards
(32 cards)
Atomic number
the number of protons
atomic mass
number of protons plus neutrons
electrolysis
the passing of a direct current through an electrolyte producing chemical reactions.
law of definite composition
Chemical compounds are made up of constant and specified ratios of elements.
law of conservation of mass
in chemical reactions no matter is gained or lost.
matter is grouped into 2 categories
pure substances and mixture
Pure substances
contains only one kind of matter. This can either be one single element or one single compound
pure substances are classified into?
elements and compounds
elements
An element is a substance that cannot be broken down into any other substance.
compounds
means there are multiple types of atoms (e.g. H2O, S02, CO2, CH4).
mixtures are classified into?
homogeneous and heterogeneous
Homogeneous
means uniform composition. (e.g. vodka, rain, water). Its basically things that you can break down, but you can’t use simple mechanics to separate the things.
Heterogeneous
irregular composition. (e.g. ice in soda, cereal in milk, soil.) Its possible to separate components.
what is the smallest part of a compound?
a molecule
Molecules
A molecule is a group of two or more atoms held together by chemical bonds. its the same element . For example: H2 or N2 or O3
physical change
A physical change is when the form of the matter changes, but the substance does not.
chemical change
A chemical change is when the matter changes and at least one new substance is formed.
evidence of a chemical change
gas bubbles, color change, change in volume e.t.c
evidence of a physical change.
change of size, volume, color (like food coloring), density
Particle model of matter/ Dalton’s theory.
Everything is composed of atoms- indivisible and cannot be destroyed.
All atoms of an element are identical. (The hydrogen in the sun is the same as the hydrogen in a pigs body).
The atoms of different elements vary in size.
Compounds are formed by a combination of two or more different kinds of atoms.
A chemical reaction is a rearrangement of atoms.
Different model of atoms
The plum pudding, planetary model, Bohr model, and electron cloud model.
Plum pudding model
The plum pudding model states that electrons are surrounded by a volume of positive charges.
Planetary model
The atom consisted of a small dense and positively charged nucleus around which electrons orbited in circular rings.
Bohr model
The electrons orbited round the nucleus and the electrons were confined to set orbits around the nucleus.
