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Why is Water Sticky?. Part 1 -- Investigating the Properties of Cohesion & Surface Tension. What are Hydrogen Bonds?. Weak chemical attractions between polar molecules
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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