is chewing food a chemical or physical reaction? why?

Question

australopithecus · Answer

http://chemwiki.ucdavis.edu/Analytical_Chemistry/Qualitative_Analysis/Chemical_Change_vs._Physical_Change this should help

thadyoung · Answer

Well, think about it. If you're eating, for example, a cracker that is well, solid, and you chew it, and if you follow the required amount of chews before you swallow, which is about 31 chews...
You will notice that the cracker that was once hard, has now become soft and moreso, liquidy. 
Why? Because the saliva in your mouth is dissolving the cracker. However, the cracker is still a cracker. If you spit it back out, you're going to have a cracker nonetheless. You're not going to somehow spit out a pizza. 

Does this help?

Chemical change means that two things must react to form a new molecule - e.g., iron and air  to form iron oxide
Physical change - no change in chemical composition, rather, a change in the shape - e.g., ice melting is a physical change.

ookawaiioo · Answer

Well, if you go into details..... I would have thought it was a chemical change. 

You have alpha-amylase in your mouth. It will breakdown the polysaccharides via glycosidic bonds.

thadyoung · Answer

Well, yes. If you go higher in biology and venture into biochemistry, you will see it's possible it to be a chemical change, however, for general purposes and high school level biology, I don't think they need to go that in depth.

ookawaiioo · Answer

^ Agreed.