Which of the following is an indication that a substance has undergone a chemical change? A.
No new product has been formed.
B.
The color of the substance has not changed.
C.
The original constitute has not changed.
D.
The molecular structure has changed.

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

This classification of drug typically changes the brain's chemistry and reduces its ability to create its own endorphins.

Apump contains 0.5 l of air at 203 kpa.you draw back on the piston of the pump, expanding the volume until the pressure reads 50.8 kpa. what is the new volume of the air pump