The law of thermodynamics states that not all energy is used because

Answer : The second law of thermodynamics states that not all energy is used because some amount of energy disperses as a heat.

Explanation :

First law of thermodynamic : It states that the energy can not be created or destroyed, it can only change or transfer from one state to another state.

Second law of thermodynamics : It states that all the energy are not used in the reaction because some amount of the energy is lost in the form of heat. This lost heat energy is the unusable form of energy.

This lost heat energy causes an increase in the entropy of the universe. That means there is no energy transferred due to the loss of energy.

Third law of thermodynamic : It states that the entropy of the system access a constant value as the temperature access absolute zero.

Hence, the second law of thermodynamics states that not all energy is used because some amount of energy disperses as a heat.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

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