What can be interpreted if mass of product < mass of reactant?

[songoku]

TL;DR Summary

This learning material is high school level

Let say I have a nuclear reaction A + B $\rightarrow$ C + D where total mass of A + B is bigger than C + D. This will mean that there is some mass of A + B that is converted into energy,

If I have another reaction P + Q $\rightarrow$ X + Y where mass of X + Y is bigger than P + Q, what does this mean?

Can I just interpret that some of energy of P + Q (maybe KE) is converted into mass of X + Y?

Another question: is it possible that mass of products = mass of reactants?

Thanks

 

[mfb]

If I have another reaction P + Q $\rightarrow$ X + Y where mass of X + Y is bigger than P + Q, what does this mean?

Can I just interpret that some of energy of P + Q (maybe KE) is converted into mass of X + Y?

Yes, and kinetic energy is the only thing that's available normally.

If you measure precisely enough then different things will never have exactly the same mass, but of course you can have scattering, A+B $\rightarrow$ A+B.

 

[songoku]

Thank you very much mfb