AL chem:distinguish 4 species

cornstarch is 粟粉, composed of starch (polysaccharide), is organic and insoluble in water. decomposes (chars) under strong heating.

finely ground sugar is 幼砂糖, composed of sucrose (C12H22O11, disaccharide), is organic and soluble in water. melts, decomposes and chars under strong heating.

plastic of paris is 熟石膏, inorganic and does not char under strong heating ---- though it loses the water of crystallization.

baking soda is soluble inorganic compound. decomposes under heatign to give sodium carbonate and CO2.


Now you can see one pair is soluble; another pair chars under heating.
a: soluble and chars
b: soluble and does not char
c: insoluble and chars
d: insoluble and does not char

easy to distinguish?

Corn starch isa polymer, so it doesn't have an exact formula, maybe it's
圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701103190028213873391850.jpg
, n is very large integer (I just look it up on the net, I'm not sure if it's correct)


Finely ground sugar, is it table sugar , glucose or else?
If it's table sugar, usually it's talking about sucrose , with formula
圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701103190028213873391851.jpg
;
if it's talking about glucose , of course it's
圖片參考：http://imgcld.yimg.com/8/n/HA00656648/o/701103190028213873391862.jpg

(You yourself have to determine.)




What 特性 you want to talk about?
(I just list out some common)
Physical
soft compare to mortar and cement , quite high melting point , slightly soluble in water ...
Chemical
Corrode by acid(not sure)
when added to water, plaster of Paris forms a hard mass used in making plaster casts, quick-setting cements, molds, wall board...