Endothermic processes absorb energy from surroundings

Steps:

• Define endothermic: chemical reactions that absorb heat or energy, increasing system energy.
• Identify endothermic processes: photosynthesis absorbs light to form glucose; cracking absorbs heat to break hydrocarbon bonds.
• Eliminate exothermic processes: combustion releases heat via oxidation; fermentation releases energy in anaerobic breakdown; respiration releases energy to form ATP.
• Select option pairing two endothermic processes: cracking and photosynthesis.

Why C is correct:

• Both absorb energy per thermodynamics: photosynthesis follows ΔH > 0 for 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂; cracking requires heat input (ΔH > 0) to cleave C-C bonds.

Why the others are wrong:

• A: Combustion is exothermic (ΔH < 0), releasing heat.
• B: Fermentation is exothermic, producing heat and ATP.
• D: Respiration is exothermic (ΔH < 0), liberating energy.

Final answer: C