1 Go to Phone or Phone Settings and select Calls or Incoming Calls.. 2  Press Blocked Callers, Blacklist, Unwanted Calls, or another similarly named option menu. 3  Your contact list or phone book will appear; choose the name you wish to block, or manually enter the phone number you wish to block.ress the menu button on your phone, then go to Settings.. 1  Go to Phone or Phone Settings and select Calls or Incoming Calls.. 2  Press Blocked Callers, Blacklist, Unwanted Calls, or another similarly named option menu.
An energy profile of an exothermic reaction. by definition the enthalpy change has a negative value: in an exothermic reaction, gives a negative value for Î´H, since a larger value (the energy released in the reaction) is subtracted from a smaller value (the energy used for the reaction). For example, when hydrogen burns:
Exothermic reactions transfer energy to the surroundings. Endothermic reactions take in energy from the surroundings. Reversible reactions are where the products can react to remake the original reactants. If the forward reaction is exothermic, the reverse reaction is endothermic. Exothermic and endothermic reactions When a chemical reaction occurs, energy is transferred to, or from, the surroundings - and there is often a temperature change. For example, when a bonfire burns it transfers heat energy to the surroundings.