![ Energy profile diagram where the reactant energy level is at $50\text{ kJ/mol}$ , the peak of the curve is at $150\text{ kJ/mol}$ , and the product energy level is at $120\text{ kJ/mol}$ . ] Based on the diagram description, what is the value of the enthalpy change ( ${ \Delta H }$ )?

When considering the evaporation of sweat from a thermodynamic perspective, why does the skin feel cooler?

MYP MYP Chemistry Topic Endothermic and Exothermic Reactions Questionbank

Practice MYP MYP Chemistry Topic Endothermic and Exothermic Reactions with authentic exam-style questions for both SL and HL students. This question bank focuses on the exact syllabus content for Endothermic and Exothermic Reactions and mirrors Paper 1, 2 style where relevant.

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No energy is required to break bonds, and energy is only released during formation

The energy required to break bonds in the reactants is less than the energy released when forming bonds in the products

The energy required to break bonds in the reactants is greater than the energy released when forming bonds in the products

The energy required to break bonds is exactly equal to the energy released during formation

True

False

Evaporation is an exothermic process that lowers the local temperature

The sweat molecules release energy to the skin as they turn into a gas

The chemical bonds within the water molecules are being broken, which is exothermic

The liquid sweat absorbs heat energy from the skin to overcome attractive forces

$+70 \text{ kJ/mol}$

$+150 \text{ kJ/mol}$

$+100 \text{ kJ/mol}$

$-70 \text{ kJ/mol}$