if i change my front sprocket on tooth down, will the length of my chain change?

 

Lenght of cain won't change it will stay the same length as it was before but you will find that you have more travel on the adjuster to get the correct tension. I understand what you mean really about the length, sometimes you might have to remove a link depending on the age of chain,
If I was you I would replace the chain with sprockets anyway