What is chemical change

Which class of molecules functions as chemical signals? hormones water carbohydrates proteins

Ants live on acacia trees in south america. the ants feed on sugars secreted by the trees. the trees provide room for the ants to live. the ants sting any other insect or animal that comes to eat the trees. what type of relationship is this?

Light waves can move through , but they travel fastest when they move through a(n) .