Unit 1 - Matter and Chemical Bonding Flashcards
(20 cards)
Uniform composition
same ratio all throughout
Homogenous mixture
- visibly indistinguishable components (has uniform composition)
- salt water
Heterogeneous mixture
- visibly distinguishable components
- oil and vinegar
Matter is categorized as ____ or _____
pure substances and mixtures
Pure substances can be categorized as ____ or ____
elements and compounds (can only be separated into its original elements through chemical reactions)
Mixtures can be categorized as ____ or ____
heterogeneous or homogenous
Methods of Separation
Distillation
Filtration
Centrifugation
Chromatography
Distillation
- Process that depends heavily on differences in volatility of component
- Ideal for separating liquids from solid in homogenous
- Good for separating 2 liquids with different boiling points
Filtration
- Separating solid from liquid in heterogeneous
- Can be carried out by gravity of partial vacuum
Centrifugation
- separation of insoluble materials from a liquid where normal filtration does not work
- Based on size, shape, density of particles, this viscosity of medium and speed of rotation
- Denser particles are forced to bottom and later one stay at the top when spun rapidly
Chromatography
- Separation method using mobile (solvent, gas or liquid) and stationary phase (solid)
- Component with a high affinity for mobile phase moves more quickly through the system
The word atom comes from the Greek word ____ meaning ____.
The word atom comes from the Greek word “__atomos__” meaning indivisible
Democritus and Leucippus
(460-370 B.C.)
Expressed the belief that matter is composed of very small, indivisible particles, atomos (later known as atoms). They had, however, no way of testing their ideas.
In___ an English scientist, ___ ___ formulated a precise definition of the indivisible building blocks of matter, which we call atoms.
In 1809 an English scientist, John Dalton formulated a precise definition of the indivisible building blocks of matter, which we call atoms.
Dalton’s Atomic Theory
- All matter is made up of small particle called atoms that can’t be broken further (not including subatomic particles)
- The atoms of one element must all have same mass and size. (doesn’t know about isotopes yet)
- atoms of different elements combine in whole # ratios to make compound (Law of definite proportion)
- In chemical reactions, atoms are not changed; rather, they are reorganized. (Law of conservation of mass).
Uniform Composition
Same ratio throughout
JJ Thomson’s Atomic Model (the plum pudding model)
- described composition of atom (late 19th to early 20th century)
- ray in cathode-ray tube was coming out from -ve side of conductor
- ray is beam of electrons
- assumed that electrons lay in a cloud of positively charged particles
Ernest Rutherford Atomic Model
1911
- decided to test Thomson’s model and shot alpha particles that are +vely charged at a thin gold sheet
- if it followed Thomson all the rays would shoot straight through
- many particles deflected at large angles
- reasoned that the angels were caused by a centre of concentrated positive charge that contains most of the atomic mass
alpha particle is nucleus (2n and 2p)
Neils Bohr Atomic Model
1913
- was Danish
- developed model for atom
- protons and neutrons form nucleus, not in it
- electrons are lighter than protons
- Coulombs charge of electron
- P+E have same magnitude but opposite, that’s why they are relative
Electron Cloud
electrons at different spots at different instances, can not follow path of electrons
