What is the purpose of the universal indicator? how does it indicate a chemical reaction? does the indicator give any particular indication dor exothermic or endothermic reactions?

The purpose of an universal indicator is to test wether a solution is acid or if its a base. It changes colors according to the PH's. It helps a lot in the indication of a chemical reaction because it can say if each component loses or gains protons depending upon the acidity or basicity of the solution being tested.An universal indicator can say if a determined solution proves to be endothermic or exothermic. If the solution is not tested as acid or base then we cannot knwo if there will be an endothermic reaction or an exhotermic one

16- counting by fours

What are the options? physical property can be color, smell, opacity, viscosity, density, infra red spectrum, melting and boiling points, attraction and repulson to magnets, etc.