Question

List any four observations which help us to determine whether a chemical reaction has taken place.

Answer 1

Hey mate,

The 4 observations are:-

1. Change in colour (Bromine and ethene)

Br2+C2H4 = CHBrCHBr

2. Formation of a preciptate (AgNO3 and NaCl)

AgNO3+NaCl = AgCl+NaNO3

3. Temperature change

4. Change of smell

Hope it helps!

Answer 2

Explanation:

the top answer is the best