Select all that apply. if a substance is at its melting or boiling point, as the heat content of the sample of matter increases, a. its temperature increases b. the number of intermolecular bonds decreases c. the space between particles increases d. the particles move faster

All are correct.

1. Because when a substance is neither at its m.p nor at its b.p, it is not in a transitory state.

i.e, the heat is not latent and is being supplied to increase temperature.

2. No.of intermolecular bonds decreases, since some energy is supplied, bonds will break.

3. Space between particles will increase, since bond length increases.

Transition is Sold -> Liquid -> Gas

So increase in energy increases the space between particles.

4. Velocity of particles will increase, since intermolecular force of attraction decreases.

the answer is c.the valence of the atoms combine .