Urgent!
how does a model differ from a law or a theory?
a.
models are universal
c.
theories are only accurate under limited conditions
b.
models are for all situations
d.
models are only useful in limited situations

Which of the following is an indication that a substance has undergone a chemical change? a. no new product has been formed. b. the color of the substance has not changed. c. the original constitute has not changed. d. the molecular structure has changed.