Why does the worksheet classify wood and sodium chloride as mixtures?

[Imparcticle]

A mixture is defined as 2 substances that are arbitirarily combined. They are either homogenous or heterogenous.

A substance is defined as being homogenous and has definite, fixed composition that is NOT arbitrary.

On some classwork we did, this following was stated as being true:

wood is a...answer: mixture

sodium chloride is a... answer: mixture

I disagree; wood is a substance because it has a fixed composition by definition. And since sodium chloride is a compound, it is not a mixture either; it is a substance.
the choices for classification on the worksheet was "mixture" or "substance".
I am confused...please help.

thanx

 

[Pengwuino]

Wood is not a substance. There is no chemical compound that can be called "wood". A wood is a large mixture of various chemicals and compounds.

 

[Imparcticle]

thank you!

How about sodium chloride then? it is a substance?

 

[Pengwuino]

Yes.. its ordinary table salt.

 

[Cosmo16]

Think of it this way, a substance can not be physicly broken down into somthing else.

A mixture can be physicly separated (Like filtering a mixture)