Which can happen during a physical change?
a. the molecules in a substance react with other molecules.
b. the molecules in a substance are destroyed.
c. molecules can move more rapidly and freely and change states.
d. the molecules in a substance break into smaller molecules

In positive numbers less than 1, the zeros between the decimal point and a non-zero number are blank significant

When electrons are added to the outermost shell of a carbon atom, it forms--an anion that has a larger anion that has a smaller cation that has a larger cation that has a smaller radius.

A47.2 g block of copper whose temperature is 480 k is placed in an insulating box with a 91.8 g block of lead whose temperature is 200 k. (a) what is the equilibrium temperature of the two-block system? (b) what is the change in the internal energy of the two-block system between the initial state and the equilibrium state? (c) what is the change in the entropy of the two-block system? the heat capacities of copper and lead are 386 j/kg·k and 128 j/kg·k, respectively.