What are three main classifications of the elements

This chart represents the melting point of several substance. what besy explains the high melting point of the salt?

The clouds are grey and ground is wet. a quantitative b qualitative

The twister and runaway train are two coasters at the same amusement park. both coasters start at the same height. the coaster for the twister is twice the mass of the coaster for the runaway train. which roller coaster has greater gravitational potential energy at the start of the ride?