physical v.s. chemical changes help pls

[thorn_jac]

1. when placed in H2O, a sodium pellet catches on fire as hydrogen gas is liberated and sodium hydroxide forms.

i put chemical change

 

2. evaporation

i put physical change

 

3.pancakes cooking on a griddle

i put physical change

 

4. A tire is inflated with air

i put physical

 

5. luster

i put chemical property

 

6. odor

i put physical property

 

please help

[insane_alien]

3 5 and 6 are wrong.

 

the process of cooking anything causes a lot of complex chemical reactions to occur. most aren't noticable and merely result in a slight augmentation of the flavour, the most obvious reaction in pancakes is that they become solid. this is due to proteins breaking down and sticking to each other.

 

luster is a physical property its to do with the physical characteristics of the electron shells in the atoms.

 

odour is the detection of chemicals in the nose. this is achieved by a reaction and is hence a chemical property rather than a physical one.

[DrP]

Was about to say the same thing before IA beat me to it. Cooking causes a chemical change. Lustre is physical (how shiny). Smells are chemical - I was was going to give you this: http://www.scienceforums.net/forum/showthread.php?t=33167&highlight=smell - where we discussed smells before.