Which two observations below can be evidence that a chemical change has occurred
a. production of bubbles (a gas)
b. melting
c. vaporization
d. production of heat

Answer is: osmotic pressure.

The direction of osmotic pressure is always from the side with the lower concentration of solute to the side with the higher concentration, in this example, from solution b (5% glucose) to solution b (25% glucose).

Osmotic pressure, alongside the vapor pressure depression, freezing point depression and the boiling point elevation are the colligative properties od solution.