1. The chemical formula for water is H₂O.
2. A water molecule model consists of one oxygen atom (O) bonded to two hydrogen atoms (H). The oxygen atom has a partial negative charge (δ⁻) and each hydrogen atom has a partial positive charge (δ⁺). Electrons are shared unequally, with more electron density around the oxygen atom, creating a bent molecular shape.
3. A solution is a homogeneous mixture composed of two or more substances. The solute is the substance that dissolves, and the solvent is the substance in which the solute dissolves. For example, in saltwater, salt is the solute and water is the solvent.
4. A water molecule is like a magnet because it is polar—it has a partial negative charge on the oxygen end and partial positive charges on the hydrogen ends. This polarity allows water molecules to attract each other and other polar substances, similar to how opposite poles of magnets attract.
5. Cohesion causes surface tension in water. Cohesion is the attraction between like molecules—in this case, water molecules. At the surface, water molecules are pulled inward by neighboring molecules, creating a “skin” or tension that resists external force.
6. An example of surface tension observed in nature is water striders walking on the surface of ponds without sinking. Their weight is supported by the cohesive forces between water molecules at the surface.
7. Cohesion is the attraction between molecules of the same substance. Example: Water droplets form beads on a waxed car surface because water molecules stick to each other.
8. Adhesion is the attraction between molecules of different substances. Example: Water climbs up the walls of a glass tube (capillary action) because water molecules are attracted to the glass surface.
Parent Tip: Review the logic above to help your child master the concept of properties of water worksheet answer key.
