Where does radioactivity come from? a. the nuclei of unstable isotopes b. physical changes in atoms c. chemical reactions d. the breaking of chemical bonds

Which is the layer underground where all empty spaces are filled with a combination of air and water ?

When the speed of the bottle is 2 m/s, the average maximum height of the beanbag is m.

1) which of the following is the best example of a physical change? a) sugar dissolving in tea b) firefly glowing 2) in the combustion of ethane, what is/are the reactants? c2h6 + o2 ==> co2 + h2o a) c2h6 and o2 b) co2 and c2h6