1. Calculate the gravitational force of the Earth on a 1-kg mass at the surface. The Earth
has a mass of 6 x 104 kg, and its radius is 6.4 x 109 m.

conduction is the transfer of thermal energy (heat in transfer) due to collisions between the molecules in the object. collisions between adjacent atoms and molecules transfer kinetic energy from the warmer to the cooler object. the objects must be in physical contact.

1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.