Question

1. Which combinations of substances resulted in a chemical change?(no answer choices)

Answer 1

Explanation:

Chemical reaction -

The combination or reaction of two or more substance , which leads to any change in the temperature , evolution of gas , change in color . This type of reaction is called a chemical reaction ,

The example of chemical reaction is as follows -

H₂ ( g ) + O₂ ( g )   ----> H₂O ( l )

In the above reaction , two gases combines together to form a completely new substance with different chemical and physical properties .

Hence , it is a chemical reaction .

Answer 2

All chemical reaction between substances results into a chemical change. When two substances just like HCL and NaOH reacts with each other, NaCl means Sodium Chloride salt is formed.  

The phenomenon like change in color, change in temperature, release of gas etc when happens ,then it means chemical change has been occurred. e.g

HCl +NaOH ----> NaCl +H2O.