Here's why:

Carbon Dioxide (CO₂)

* Structure: CO₂ has a linear structure. The carbon atom is in the center, and the two oxygen atoms are on either side.

* Electronegativity: Oxygen is more electronegative than carbon. This means oxygen atoms attract electrons more strongly, creating a slight negative charge around the oxygen atoms and a slight positive charge around the carbon atom.

* Symmetry: The two oxygen atoms pull the electrons equally in opposite directions. This creates a symmetrical distribution of charge, and the molecule has no net dipole moment. Therefore, CO₂ is considered non-polar.

Water (H₂O)

* Structure: Water has a bent or V-shaped structure. The oxygen atom is in the center, with two hydrogen atoms at an angle.

* Electronegativity: Oxygen is more electronegative than hydrogen. This creates a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms.

* Asymmetry: The bent structure and the unequal distribution of charge mean that the two hydrogen atoms don't cancel out the oxygen's negative charge. This results in a net dipole moment, making water a polar molecule.

In summary:

* CO₂ is non-polar due to its linear structure and symmetrical distribution of charge.

* H₂O is polar due to its bent structure and unequal distribution of charge, creating a net dipole moment.