S.1.1 Introduction to particulate state of matter

properties of elements

1. one type of atoms

2. represented by chemical signals

3. cannot be broken down

element

the simplest form of matter that cannot be broken down into simpler substances by any means

compound

substance formed when two or more elements chemically bond in fixed proportions,

properties of compounds

1. have a fixed chemical formula

2. their properties differ from the elements they are made of

3. can only be separeted into their elements through chemical reactions

mixture

contains two or more elements, compounds or both that are physically combined but not chemically bonded

key properties of mixtures

1. components are not chemically bonded

2. they can be separated by physical methods

3. composition can vary

homogenous mixture

uniform composition throught (saltwater, air)

Heterogenous mixture

non uniform composition (oil and water, sand and water)

pure substance

consists only of one type of particle with a fixed composition and uniform properties througt

Separatng techniques of mixtures

1. filtration

2. distilation

3. recryatalization

4. evaporation

5. chromatography

filtration

used to separate insoluble solids from liquids exsand from water using paper filter.

1. pour the mixture through a funnel lined with filter paper

2. the liquid (filtrate) passes through, leaving the soid (residue) behind

recrystalization

exploits differences in solubility ex. puryfing sugar from an impure sample

1. a soluble substance is dissolved in hot solvent

2. as the solution cools crystals form and can be separated by filtration

evaporation

removes a liquid from a solution by heating it, leaving behined the disolved solid ex. salt can be obtained from saltwater by evaporating the water

distilation

separates two or more liquits with different boiling points, the liquid wih the lower boiling point evaporates first, is condensed and collected

paper chromatography

technique used to separate the components of a mixture based on differences in their solubility and polarity

1. small drop of mixture is placed neer the bottom of the strip of paper

2. paper is suspended in the solvent with the spot above solvent level

3. as the solvent moves upward by capilary actio, it dissolves the solutes in the mixture.

4. components that are more soluble travel further

factors affecting separation

1. polarity- polar solutes dissolve better in polar, non polar in non polar

2. solubility- higher solubility in the solvent results in faster movement along the paper

3. molecular size- smaller molecules travel faster that larger ones

retention factor

ratio between the distance traveled by a solute and the solvent front

Rf=distance traveled by solute/ distance traveled by solvent font.

solid

particles are tightly packed in a fixed arrangement, they vibrate in place but do not move freely, shape and volume fixed

liquids

particles close together but not in a fixed arrangement, this allows them to flow and take shape of the container while maintaining constant volume

gas

particles are far apart and move freely in all directions. gases expand to fill the shape and volume of their container

changes of state

1. occur when substance absorbs aor releases thermal energy

2. chemical composition remains unchanged but physial changes occur

3. energy involves affects potential energy not their temperature

melting

solid to liquid

solid absorbs thermal energy and particles gain potential energy and vibrate more vigourously and eventually gaining enough energy to break free from their fixed positions

freezing

liquid to solid

when liquid loses thermal energy and as the particles release potential energy they slow down and arrange themselves into a fixed, structured lattice

evaporation

liquid to gas

when a liquid absorbs thermal energy its particles gain potential energy to overcome intermolecula forces

1. evaporation- only at the surface of the liquid at any temperature when particles neer the surface absorb enough energy to escape

2. boiling0 through the entire liquid at a specific temperature where particles gain enough energy to break free

condensation

gas to liquid

when gas looses thermal energy causing particles to release potential energy and slow down, as a result intermolecular forces draw the particles together forming a liquid

sublimation

solid to gas

when a solid absrobs thermal energy so rapidly that its particles gain enough potential energy to breal free directly into gas phase (dry ice)

deposition

gas to solid

occurs when a gas loses thermal energy, and its particles release potential energy so quickly that they transition directly into solid

endothermic process

thermal energy is absorbed from surroundings increasing potential energy of particles (melting, vaporisation and sublimation)

exothermic processes

thermal energy is released t o the surroundings as particles lose potential energy (freezing, condenation, deposition)

temperature

direct measure of the average kinetic energy of the particles in a substance

kelvin and average kinetic energy

relationship between them is proportional

expansion or contraction of matter

expansion- as particles gain kinetic energy they move more vigorously and occupy more space

contraction- when particles lose energy they slow down and take up less space

changes in physical state tied to energy of particles

melting, boiling, freezing

Phase change

during a phase change energy is transfererd but does not result in a temperature change, instead energy is used to break from intermolecular forces altering the state of the substance

key energy changes

1. melting- energy is absorbed to break the bonds holding particles in a fixed structure

2. freezing- energy is released as particles lose kinetic energy, forming stronger intermolecular bonds

3. boiling- energy is absorbes to overcome attractive forces, allowing particles to move freely as a gas

4. condensation- energy is released as particles slow down and intermolecular forces pulls them closer together

latent heat

the energy added or removed that affects the potential energy of the particles not their kinetic energy

heat

heat is the total energy transferred due to a temperature difference, related to both the kinetic energy and the number of particles in a substance. It depends on mass and is measured in joules