Exothermic and Endothermic Reactions

This chemistry lesson focuses on two IBMC questions from past papers, exploring exothermic and endothermic reactions. The instructor defines these reactions, discusses key reactions in the Topic 5 SL syllabus, and analyzes multiple choice options using energy diagrams. The lesson concludes with explanations of the correct answers.

What is the main focus of the IBMC questions discussed in the lesson?

• Organic chemistry reactions

• Exothermic and endothermic reactions

• Periodic table trends

• Chemical bonding

Which of the following is a characteristic of exothermic reactions?

• They absorb heat from the surroundings.

• They have a positive enthalpy change.

• They require energy input to proceed.

• They release heat to the surroundings.

What happens to energy during an exothermic reaction?

• It is released to the surroundings.

• It is converted to mass.

• It remains constant.

• It is absorbed from the surroundings.

Which reaction is always exothermic?

• Neutralization

• Photosynthesis

• Decomposition

• Electrolysis

What type of reaction is the combustion of methane?

• Neither

• Exothermic

• Endothermic

• Both

Why is the decomposition of calcium carbonate considered endothermic?

• It occurs spontaneously at room temperature.

• It forms a stable compound.

• It releases energy to the surroundings.

• It requires energy to break chemical bonds.

Which of the following is an example of a physical change that is exothermic?

• Sublimation of dry ice

• Boiling water

• Freezing water

• Melting ice

What is the enthalpy change sign for an endothermic reaction?

• Negative

• Positive

• Zero

• Variable

Which process involves a negative enthalpy change?

• Photosynthesis

• Melting of ice

• Combustion of a fuel

• Evaporation of water

Which of the following reactions is not exothermic?

• Decomposition of calcium carbonate

• Neutralization of an acid and base

• Formation of water from hydrogen and oxygen

• Combustion of methane