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.

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)

Cohesion or Adhesion?

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3 4

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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

Jesus Christ Lizard..mp4

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 ActionB) AdhesionC) InfiltrationD) 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) SkinB) Surface TensionC) PolarityD) All of the Above

Part Two- #3• This unique property is

responsible for ice’s ability to float on top of water.

A) WeightB) DensityC) SalinityD) Pressure

Part Two- #5

• What allows this droplet to form in the picture below?

A) Surface TensionB) AdhesionC) CohesionD) All of the above

Part Two- #6

• Due to water’s polarity, it

A) will dissolve everything B) creates very strong hydrogen bondsC) takes a long time to heat upD) is considered lop-sided and attracts substances like itself easily

Part Two- #7

• What is demonstrated here?

A) Capillary ActionB) PolarityC) Surface TensionD) All of the above