Lecture 0: Some reminders

required knowledge

What is a physical change? Name two examples

change in state of matter

Melting

Dissolving

what is a chemical change?

= chemical reaction. Its the change of matter into a new kind of matter.

What is a compound?

matter composed of atoms of two or more elements combined in a fixed ratio

solution vs. suspension and colloids (dispersed systems)

Solutions - homogeneous fluid • dissolving agent: solvent (Lösemittel). • substance dissolved: solute (gelöster Stoff).

Suspensions - heterogeneous fluid • contains particles large enough for sedimentation.

Colloids (Kolloide) - dispersion • remain evenly distributed without settling • intermediate size (10-8 - 10-6 m); colloidal particles or colloids

Tyndall effect

distinguishes solution from colloidal dispersion

Beam of light if reflected then colloidal dispersion

collodial dispersion

dispersing medium gas:

gas

aerosol smoke/fog

dispersing medium liquid:

foam whipped cream gaseous particels in liquid

emulsion oil in water/mayonnaise

sol paint

dispersing medium solid:

solid foam Styrofoam

gel Butter

solid sol gravel