Why did the discovery of nuclear reactions cause the separate laws of conservation of matter and conservation of energy to be combined into the law of conservation of mass-energy?

Matter is not conserved in nuclear reactions because some of the matter is converted to energy.

Nuclear reactions happen too quickly for changes in energy to be measured.

Energy is conserved in nuclear reactions but not in chemical reactions.

Only particles that move at the speed of light can overcome the laws of conservation.

Question

Why did the discovery of nuclear reactions cause the separate laws of conservation of matter and conservation of energy to be combined into the law of conservation of mass-energy?

		
Matter is not conserved in nuclear reactions because some of the matter is converted to energy.
 		
Nuclear reactions happen too quickly for changes in energy to be measured.
 		
Energy is conserved in nuclear reactions but not in chemical reactions.
 		
Only particles that move at the speed of light can overcome the laws of conservation.

anonymous · Answer

Matter is not conserved in nuclear reactions because some of the matter is converted to energy.