The pipette used had following markings 25m/s, green line, Ex,20°C,15seconds. explain meaning of these marking​

4hours and 17 mins i think

Yes, endothermic means it turns cold. and some chemical changes include change of tempature.

12 is probably the typical age for a first kiss but i think its to young.

You would be correct, boiling water does disinfect contamination.    the property of disinfecting means to kill  germs, bacteria and other pathogens or contamination  that might cause an infection or cause a person to become sickly. a couple methods of disinfecting are using soap, other cleaning supplies or by simply "boiling" the contaminate.  the reason why boiling water disinfects certain attributes is because some cells cannot survive the heat and pressure.