Based on the information provided, we can categorize the reactions and phenomena described into two categories: endothermic reactions and exothermic reactions.
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Left-side Graph - Endothermic Reactions:
- An endothermic reaction is characterized by the absorption of energy from the surroundings.
- Example: Ice from the freezer melting into water is an endothermic process because it absorbs heat from the surrounding environment (the kitchen floor) to change from solid to liquid.
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Right-side Graph - Exothermic Reactions:
- An exothermic reaction is characterized by the release of energy to the surroundings, usually in the form of heat.
- Example: The combustion reaction in a car where octane gas burns in the presence of oxygen is an exothermic reaction. It releases heat and energy, which can make the surroundings feel hot or warm.
Summary:
- Endothermic Reaction: Absorbs energy (Ice melting).
- Exothermic Reaction: Releases energy (Combustion of octane gas).
A system that "feels hot or warm" to the touch indicates that it likely has an exothermic reaction occurring.