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physical v.s. chemical changes help pls


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#1 thorn_jac

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Posted 1 September 2008 - 03:46 PM

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 :confused:
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#2 insane_alien

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Posted 1 September 2008 - 03:59 PM

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.
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#3 DrP

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Posted 1 September 2008 - 04:03 PM

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.sciencefo...highlight=smell - where we discussed smells before.
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