Substances’ properties and reactions.
Properties to identify a substance:
- intensive: independent of amount (color of gold)
- extensive: depend on amount. (the quantity of gold in a sample)
- chemical: behavior in a chemical reaction
- physical: melting and boiling point
by measuring its properties and comparing them with the properties for known substances.
The law of conservation of mass.
Physical:
- density
- solubility (saturated, unsaturated)
- Color; absorption spectrum
Elements
to get: heating red mineral cinnabar (process)
| Properties | Uses |
| high density liquid | barometer, manometer |
| can dissolve many mental, forming solutions (amalgams) | a silver-mercury-tin amalgam in teethfillng |
exist: combined form in clays and rocks.
Process to obtain the element: Hall and Herroult process extracting Al from bauxite.
| Properties | Uses |
Compounds
have fixed compositions
elements don’t keep their original form.
methods to resolve compounds into their elements:
- heating
- electrolysis
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Mixtures
no fixed compositions.
each substances (either elements or compounds) remains its chemical identity.
- Homogeneous: solution = solvent + solutes (brass)
- Heterogeneous: rocks
methods to separate mixtures to get elements or compounds:
- Ho solid-liquid mixture – distillation
- He solid-liquid mixture – filteration
- chromatography: due to different solubility and/or absorption (gas-liquid chromatography: car exhaust test or drug test. )
Measurements
- length
- volume
- mass
- temperature
Uncertainties in measurements: significant figures (*/; +-)
scientific notation
round off
A number that is spelled out (parameters and prefix independent variable) does not affect the number of significant figures.