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What is the effect of a negative ΔH on a reaction?
The reaction is exothermic, releasing heat to the surroundings.
What is the effect of a positive ΔH on a reaction?
The reaction is endothermic, absorbing heat from the surroundings.
What happens to the temperature of the surroundings during an exothermic phase change?
The temperature of the surroundings increases as heat is released.
What happens to the temperature of the surroundings during an endothermic phase change?
The temperature of the surroundings decreases as heat is absorbed.
What is Activation Energy (Ea)?
The minimum energy required to start a chemical reaction.
Define Enthalpy (ΔH).
A measure of the heat energy exchanged in a reaction at constant pressure; ΔH = H(products) - H(reactants).
What is an exothermic reaction?
A reaction that releases energy, resulting in products having lower energy than reactants (ΔH < 0).
What is an endothermic reaction?
A reaction that absorbs energy, resulting in products having higher energy than reactants (ΔH > 0).
Define the term 'activated complex'.
An unstable intermediate state at the peak of the energy diagram.
What is latent heat?
The heat absorbed or released during a phase change at constant temperature.
What are the key differences between exothermic and endothermic reactions?
Exothermic: Releases heat, ΔH < 0, products have lower energy. Endothermic: Absorbs heat, ΔH > 0, products have higher energy.
How do energy diagrams differ for exothermic vs. endothermic reactions?
Exothermic: Downward slope from reactants to products. Endothermic: Upward slope from reactants to products.