Why is Water Sticky? Part 1 -- Investigating the Properties of Cohesion & Surface Tension

What are Hydrogen Bonds? Weak chemical attractions between polar molecules Polar molecules: have an uneven distribution of electrical charge; one end is positive and the other end is negative (like a battery) Water molecules are polar The blue “Mickey Mouse ears” represent Hydrogen atoms (negatively charged) The red “Mickey Mouse head” represents an Oxygen atom (positively charged) The blue end of one water molecule is attracted to the red end of another, forming a hydrogen bond

What is Cohesion? Since water is polar, it bonds (sticks) to itself Many water molecules “stick” together to form drops This is referred to as cohesion Cohesion: an attraction between substances of the same kind

Why can some insects walk on water? Cohesion causes surface tension Surface tension: cohesion of water molecules at the surface of a body of water Due to surface tension, some things can “float” on water Allows water striders to “skate” across the top of water