Which equation represents a physical change?

(1) H,0 (s) +6.01 kJH,0 (4)

(2) 2H, (g) +0,(g)--2H2O(g) + 483.6kJ

(3) H,(g) +12(g) + 53.0kJ →→ 2HI(g)

(4) N. (g) +20,(g) + 66.4k]— 2NO (9)

Select one:
a. reaction 1 only
b. reactions 1 &3
c. reactions 2&4
d. all reactions

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.

football

explanation:

because it is