Is a marshmallow turning black when toasted a physical or chemical change?

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

Asolution contains 225 g of sodium chloride, nacl, dissolved in enough water to make a 0.25 l of solution. what is the molarity of the solution?

Why is the bond angle in a water molecule less than the bond angle of methane? a. the central oxygen atom in water has two lone pairs of electrons, whereas the central carbon atom in methane has no lone pairs. b. the central hydrogen atom in water has one lone pair of electrons, whereas the central carbon atom in methane has two lone pairs. c. the central oxygen atom in water has four lone pairs of electrons, whereas the central carbon atom in methane has only one lone pair. d. the central oxygen atom exerts more repulsive force on surrounding atoms than the central carbon atom in methane does. reset next