endothermic and exothermic reactions

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Endothermic & Exothermic :

Endothermic & Exothermic Chemical Reactions and Their Thermal Properties

Endothermic Reactions:

Endothermic Reactions The system gains energy in the form of heat. Absorbs E from the surroundings. Requires an input of energy in order to happen (react).

What Happens:

What Happens Energy is drawn from the surroundings (the environment). This fuels the start of the reaction.

Physical Properties:

Physical Properties Cold energy drawn into the system is taken from its surroundings. this is why it creates a “cold” feeling.

Chemical Properties:

Chemical Properties Hard to identify Monitor △T (change in temp.) Endothermic reactions will ALWAYS drop in temperature. (even if only a little)

Ways to Identify A Reaction:

Ways to Identify A Reaction Chemical and Physical Properties Is it cold? Was there a temperature change? What kind of energy is available? Using Calculations The △H for the reaction will be positive This means that the system has a positive energy change. (gaining energy)

Examples:

Examples Melting ice This is why it feels cold against your skin. It draws heat from your body This allows the ice to continue melting. You are part of the process!

Exothermic Reactions:

Exothermic Reactions The system loses energy in the form of heat. Loses E to the surroundings. Energy of the surroundings will increase.

What Happens:

What Happens Energy is given off to the environment. The reaction starts with more E than it ends with.

Physical Properties:

Physical Properties Energy given off can be: Heat energy (warm/hot) Light energy Sound energy All three (i.e.- an explosion)

Chemical Properties:

Chemical Properties Easier to identify Monitor △T (change in temp.) System and its surroundings Endothermic reactions will ALWAYS drop in temperature. (even if only a little)