Which describes what happens when fuel is ignited in a heat engine?
a.chemical energy is converted into thermal energy
b.thermal energy is converted into solar energy.
c.solar energy is converted into chemical energy
d.thermal energy is converted into chemical energy.

Chemical energy is converted into thermal energy

Explanation:

Chemical energy is the energy stored in the bonds of molecules.

Thermal energy is the energy possessed by a body by virtue of its temperature.

Solar energy is the energy that can be reflected by the sun through electrical or magnetic waves traveling through space.

According to law of conservation of energy, energy remains conserved. It only transforms from one form to another.

When fuel is ignited in the engine, the chemical energy stored in the bonds of fuel converts to thermal energy which is the energy possessed by an object by virtue of temperature and thus the engine gets hot.

A.Chemical energy is converted into thermal energy

Explanation:

here when fuel ignition takes place then then the energy is released due to breaking of bonds of the given chemical present in the fuel

This energy is termed as thermal energy and it is used to give output useful work to the shaft so that it can rotate the wheel

So overall this is the conversion of the chemical energy to thermal energy which can be used further as useful work of the engine.

So correct answer will be

A.Chemical energy is converted into thermal energy

The correct answer is:

B.  Radioisotopes used as tracers in industry