Endothermic and Exothermic Reactions Explained Through Potential Energy Diagrams

The video explains endothermic and exothermic reactions, focusing on enthalpy changes and potential energy diagrams. It discusses how catalysts affect reaction speed by lowering activation energy. Multi-step reactions are analyzed to identify slow and fast steps. The video also covers enthalpy changes during phase transitions, such as melting and freezing.

What is the enthalpy change for an endothermic reaction?

• Positive

• Variable

• Zero

• Negative

In an exothermic reaction, what happens to the heat energy?

• It is absorbed by the system

• It is released by the system

• It remains constant

• It is converted to work

What does the y-axis represent in a potential energy diagram?

• Pressure

• Temperature

• Potential energy of the system

• Reaction time

How does a catalyst affect the activation energy of a reaction?

• Has no effect

• Decreases it

• Increases it

• Doubles it

What is the effect of a catalyst on the speed of a reaction?

• No effect on speed

• Stops the reaction

• Increases the speed

• Decreases the speed

In a multi-step reaction, which step is considered the slow step?

• The step with the highest transition state energy

• The last step

• The step with the lowest transition state energy

• The first step

What type of process is melting ice?

• Adiabatic

• Exothermic

• Endothermic

• Isothermal

Which phase change is an example of an exothermic process?

• Melting

• Vaporization

• Sublimation

• Condensation

What is the enthalpy change when a liquid turns into a gas?

• Variable

• Zero

• Negative

• Positive

What is the process called when a gas turns directly into a solid?

• Condensation

• Deposition

• Freezing

• Sublimation