Matter Flashcards
What is chemistry?
The branch of science concerned with the substances which compose matter, the investigation of their properties and reactions and the use of reactions to form new substances
What is matter?
The physical material of the universe and has mass and occupies space
What is a mixture?
A combination of two or more substances in which each retains its own chemical identity and can be separated from each other
What is the difference between heterogenous and homogenous mixtures
- homogenous mixtures are uniform throughout whereas,
- heterogenous mixtures does not have the same composition, properties and appearance throughout
What is a pure substance?
Matter that has distinct properties and a composition that doesn’t vary from sample to sample eg. salt
Define the states of matter
- solids have a definite shape and a definite volume
- liquids have definite volume but no specific shape
- gases have neither
What are physical changes?
Observed without changing a substance into another substance eg. volume etc.
What are chemical changes?
Observed when a substance is changed to another eg. during combustion etc
What is a chemical reaction?
A process in which atoms of the same or different elements rearrange themselves to form a new substance
Tell me about compounds
they can be broken down into elemental particles
What is distillation?
Separation of a homogenous mixture by boiling point
What does filtration do?
Separates solid substances from liquids and solutions
Define mass
A measure of the amount of material in an object. The SI base unit of mass is the kg
Convert degrees C to K
add 273.15K
Define energy
The ability to do work
What is kinetic energy
Energy of motion and potential energy is stored energy
Compare exact and inexact numbers
- exact: counted/given by definition
- inexact: measured and depend on how they are determined
What is precision
A measure of how closely individual measurements agree with one another
What is accuracy
How closely individual measurements agree with the correct or ‘true’ value
Name the atomic theory
- Each elements is composed atoms
- All atoms of a given elect are identical but atoms of one element are different from the atoms of all other elements
- Atoms of one element cannot be changed into those of another by reactions and can’t be created or destroyed in those chemical reactions
- Compounds are formed when more than one element’s atoms combine. The compounds always have the same relative number and kind of atoms
Name 2 of Dalton’s laws
- Matter cannot be created or destroyed
- If two elements, A and B, form more than one compound, the masses of B that combine with a given mass A are in the ratio of small whole numbers (law of multiple proportions)
How were subatomic molecules discovered
A ray of fluorescent negatively charged particles from cathode tubes are deflected by a magnet - charge was measured by charge/mass ratio using a Millikin’s Oil drop
Define radioactivity
Spontaneous emission of high-energy radiation by an atom
What types of particles are there?
alpha - positive
beta - negative
gamma - rays that have no charge
What is the structure of the atom
- originally the plum pudding theory with a positive sphere and negative electrons dotted around in it
- now when alpha particles were fired at gold, they scattered at different angles -> electrons on the outside and condensed positivity in the centre
What are isotopes?
Atoms of the same element (same proton number) with different masses (neutrons)
What is the atomic weight?
An average mass of an element that is found using all isotopes of an element weighted by their relative abundances relative to that of carbon 12 [ie. (75/100 of 55u) + (25/100 of 50u) = atomic weight of 53.75u]
How is atomic weight measured?
Using a mass spectrometer you can identify the mass and relative abundances of the isotopes
How is the periodic table arranged?
Arranged in periods = rows based on increasing atomic number
columns = groups
List the seven diatomic molecules
Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine and iodine
Define empirical formula
Lowest whole-number ratio of atoms of each element in a compound
What is the molecular formula
Exact number of atoms of each element in a compound
What is a structural formula
Formula that shows the order in which atoms are attached (no 3-D shape)
What is an ion?
An atom that has lost or gained electrons (+ve ions are cations and -ve ions are anions)
Polyatomic ions are a group of atoms that gain or lose electrons
Define radioactivity
Spontaneous emission of high energy radiation by an atom
alpha particles are positive
beta are negative and gamma rays are nothing
What was the initial atom (Circa) model like
plum pudding (ball with positive throughout and negative particles embedded around) firing of alpha particles at a thin gold foil found that some were deflected at large angles
