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Properties of Water p. 53 in ILL
Water Water is an amazing substance with many unique properties and is vital for the survival of living things and necessary for many different functions on our planet. From moving chemicals around our bodies to keeping oceans liquid, the properties of water are very important.
Water Molecule • Structure of the water molecule is important because it helps explain water’s unique behavior • Molecules are made of two or more atoms bonded covalently • The water molecule is made of 2 Hydrogen atoms and 1 Oxygen atom = H2O
Water Moleculecontinued… • one positively charged side (hydrogen) • one negatively charged side (oxygen) • this attracts it to other molecules with a similar arrangement (opposites attract/likes repel) • it is especially attracted to other water molecules
Polarity polarity = an unequal sharing of electrons within a molecule causes strong attraction to similar substances water is polar because the electrons are pulled more towards the oxygen (--) side rather than the hydrogen (+) side does…thus making the molecule unbalanced/lopsided (this is due to oxygen’s high electronegativity) to feel more balanced it finds other polar substances to bond with water appears to be “sticky” or have magnetic properties…it is because of its polarity.
Hydrogen Bonding the polarity of the water molecule makes it want to bond the type of bond it uses to “stick” to itself or other molecules is a hydrogen bond – the hydrogen are bonding with other molecules form very easily yet they are not very strong… very little energy is needed to break hydrogen bonds
Adhesion and Cohesion • two ways water sticks to things • water sticking to water= cohesion • water is very attracted to itself and will come together whenever possible (ex: raindrops) • water sticking to other substances = adhesion • water likes other polar substances (ex: water sticking to a window)
1 Cohesion or Adhesion? 2 3 4
Surface Tension surface tension = due to bonds holding water molecules together (cohesion) there appears to be an “elastic film” around drops of water and over puddles, lakes, and ponds that requires energy to break through—the greater the amount of water, the greater force it imposes if acted upon Animals like the basilisk lizard and water strider use this “film” to their full advantage and can actually give the appearance of “walking on water” This plays an important role in how all liquids containing water behave
Capillary action capillary action = the tendency of a liquid to rise in narrow tubes or to be drawn into small openings such as those between grains of a rock. adhesion and cohesion allow this to happen Ex. plants using it to get water from their roots to their leaves, paper towels soaking up water, fountain pens
Universal Solvent • universal solvent = water dissolves more substances than any other liquid • Can it dissolve EVERYTHING in the universe? NO! Just more than other substances • water’s polarity and hydrogen bonding play a major role in making it able to dissolve so many polar things • Ex. dissolves glucose, oxygen and other nutrients in the blood
Specific Heat • specific heat = water absorbs and releases heat very slowly • Allows the temperature of lakes/oceans to change slowly, which protects marine life and Earth’s climate • Why?—because water has a very high specific heat…tons of energy is required to raise its temperature just 1°, so water temperatures do not fluctuate on our planet on a daily basis (land is the opposite)
Density • density of ice (0.92 g/mL) is less than that of water (1.0 g/mL) • one of the most important properties of water! • Frozen water - molecules align in a lattice-like pattern and leaves more space between the molecules than normal water • extra space makes it less dense • Water’s density + specific heat, allows ice to float on top of large bodies of water, preventing the rest of the water from freezing • it insulates water below it from the harsh temperatures above the ice. Marine and freshwater plants and animals are protected as a result.
Part Two- #1 • Why do rain drops form? A) Capillary Action B) Adhesion C) Infiltration D) Cohesion
Part Two- #2 • I’m like Saran Wrap, I give some organisms the ability to walk on water, and hydrogen bonding is very important to me. What am I? A) Skin B) Surface Tension C) Polarity D) All of the Above
Part Two- #3 • This unique property is responsible for ice’s ability to float on top of water. A) Weight B) Density C) Salinity D) Pressure
Part Two- #5 • What allows this droplet to form in the picture below? A) Surface Tension B) Adhesion C) Cohesion D) All of the above
Part Two- #6 • Due to water’s polarity, it A) will dissolve everything B) creates very strong hydrogen bonds C) takes a long time to heat up D) is considered lop-sided and attracts substances like itself easily
Part Two- #7 • What is demonstrated here? A) Capillary Action B) Polarity C) Surface Tension D) All of the above
