According to the principle of energy conservation, when a piston in an

According to the principle of energy conservation, when a piston in an automobile engine compresses the gas in a cylinder, which of the following must occur ?

Kinetic energy of gas must increase

The gas must undergo a change of state

The gas must undergo a chemical change

None of the above

Answer is Right!

Answer is Wrong!

This question was previously asked in

UPSC CAPF – 2014

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When a piston compresses the gas in a cylinder, work is done on the gas. According to the principle of energy conservation (specifically the First Law of Thermodynamics), this work done on the gas increases its internal energy. For an ideal gas, internal energy is directly related to its temperature, and temperature is a measure of the average kinetic energy of the gas molecules. Therefore, the kinetic energy of the gas must increase.

Work done *on* a system (like compressing gas) increases its internal energy. Increased internal energy in a gas manifests as increased temperature and thus increased average kinetic energy of the molecules.

Compression can lead to a change of state or chemical change under specific conditions (e.g., if the pressure and temperature exceed certain thresholds, or if the compression causes ignition in a fuel mixture). However, an increase in internal energy and kinetic energy is a direct and necessary consequence of work being done *on* the gas during compression, based purely on the principle of energy conservation.

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