C1-PARTICLES Flashcards
what is a particle
A tiny bit of matter
what does the particle model describe
how particles are arranged and how they move in solids,liquids and gases
solids as descibed in the particle model
regular arrangement
very close distance between particles
vibrate around fixed positions
liquids as descibed in the particle model
random arrangement
close distance
move around eachother
gases as descibed in the particle model
random arrangement
far apart
move quickly in all directions
why can you not compress a substance that is in its solid or liquid state
There is no space for the particles to move into
why can a solid not flow
particles vibrate around fixed positions and cannot move from place to place.
what is a physical change
when a substance changes shape or state,but no new substances are made.Rversible
examples of physical changes
mixing sand with water
dissolving sugar and water
what is a chemical change
a change that produces a new substance.They may look or taste different,or be in a different state.Irreverisble
example of chemical changes
cooking eggs
steel rusting
acid reacting with alkali to make salt and water
what happens to particles during change
physical-particles stay the same but arrangement and movement change
chemical-particles break up and then join together in different ways.This is how new substances are made
What are atoms
smallest part of an element that retains the properties of that same element
size of atoms
radius of 1x10^-10
mass of about 10^23
formula for ratio of distance to diameter
ratio of distance to diameter=distance between atoms/diameter of atoms.
what are the forces between particles
electrostatic forces of attraction between positive and negative charges.
what are the limitations of the particle model
-forces between the particles
-size of the particles
-space between particles
what is a molecule
made from two or more atoms joined together
what is inside an atom
protons- 1 +1
neutrons- 1 0
electron: 0.005 -1
mass number =
protons and neutrons
atomic number=
protons
number of neutrons
mass number-atomic number
what are isotopes
atoms with same number of protons and elctrons,but diff number of neutrons-meaning the mass number is different
what are ions
charged particles
formed when atoms lose or gain electrons in chemical reactions
Dalton in 1803
-solid sphere
-all atoms of an element are identical
-different elements contain different types of atom
JJ Thompson in 1897
-discovered the electron-found that beams of cathode rays changed direction in electric and magnetic fields.Concluded that cathode rays were actually tiny particles of negative charge and smaller than atoms
-atoms contained electrons
-atoms are neutral overall
-plum pudding model with a sphere of positive charge and electrons dotted around it
Rutherford in 1909
-sent alpha particles through thin gold foil.some deflected,indiacating some negative thing was there-a positively charged nucleus
-also suggetsed that outside the nuclues electrons orbit like planets in a solar system
Bohr in 1913
-used mathematical models to suggest electrons occupy fixed energy levels,or shells around the nuclues as he realised orbiting electrons would be attracted to positive nucleus and spiral inwards
