- Mixture: 2 or more pure substances, X chemically combined together

    -     Element + Element

    -     Element + Compound

   -      Compound + Compound

	Solid	Liquid	Gas
Arrangement of particles	- Tightly packed - Fixed pattern	- Fairly tightly packed - X fixed pattern	- Wildly separated - X fixed pattern
Motions of particles	- X move freely - Vibrate in fixed position	Move Freely	- Move freely - Great speed
Kinetic energy	Low	Moderate	High
Shape	Fixed	X fixed	- X fixed - Completely filled up with container
Volume	Fixed	Fixed	- X fixed - Change greatly with temp. & Pressure
Ease of compression	Almost incompressible	Difficult	Easy
Density	High	Medium	Low

下面的東西略懂便行, 不用刻意去背

Gas	Proportion
Nitrogen	78%
Oxygen	21%
Other gases	1% Noble gases (0.93%), CO2 (0.03%), varying amount of water vapour

Separation of Oxygen & Nitrogen (詳圖請看書P.57)

1.          Liquefy air by repeating cooling, compression & expanding cycles

2.          Fractional distillation of liquefied air

3.          Pump air into the fraction column, and then warm up slowly

***Nitrogen boils at - 196℃, Oxygen boils at -183℃***

n          Test for Oxygen: Glowing split

u        Relights immediately

n          Extraction of common salt

u        Evaporation

u        先filtration, 再Crystallization