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Draw a water molecule. Label the elements and the charges.

Draw a water molecule. Label the elements and the charges.

What is the chemical formula for water?

H2O Two hydrogen atoms and one oxygen atom

Why is water considered a polar molecule?

Because parts of the molecule have either a positive (+) or negative (-) charge

The oxygen and hydrogen are bonded because they share electrons, but they do not share them equally. So, the oxygen becomes slightly negative and the hydrogen is slightly positive.

What is a hydrogen bond?

An attraction between the hydrogen of one water molecule and the oxygen of a separate water molecule.

Hydrogen bonds are like a magnetic attraction- they do not involve shared electrons

Which has stronger hydrogen bonds- water or alcohol? How do you know?

Water has stronger hydrogen bonds More drops of water fit on a penny, because

they are better able to “hold on” to each other

Water needs to be at a higher temperature to boil because the hydrogen bonds are preventing the water molecules from increased movement

What is cohesion?

Cohesion is the attraction between two molecules that are the same (water to water)

Water is very cohesive because it has strong hydrogen bonds

What is heat capacity?

The ability to absorb heat energy without drastic changes in temperature.

What has a higher heat capacity- water or alcohol?

Water has a higher heat capacity. Alcohol boiled at a much lower

temperature, meaning it’s hydrogen bonds weren’t as strong

What is a solvent? Solute? Solution?

Solution: mixture of water and dissolved substances

Solute: the material that is being dissolved Solvent: the liquid that the solute is being

dissolved into

Solution: Salt water Solvent: Water Solute: Salt

What affect do dissolved solutes have on freezing temperature?

Dissolved solutes lower the freezing temperature of liquids

This is why salt water must be cooled to a much lower temperature in order to freeze that plain water

What is unique about water when it freezes?

It expands, causing ice to float Water is the only liquid that does this

Why is the layer of ice on top of lakes important?

It provides insulation for the water below

What is the pH of pure water?

7

What is the pH of an acid?

0-6.9 In other words, less than 7

What is the pH of a base?

7.1-14 In other words, greater than 7

Name three acidic foods

Lemon juice, coffee, sour candy Acidic foods taste tart or sour

Name three items that are bases

Bleach, ammonia, cleaner

How do you find the average of a set of numbers?

Add everything up, and divide the sum by the number of numbers

Average of 6, 10, and 5 6 + 10 + 5 = 21 21 / 3 = 7

What is the freezing point of pure water?

0°C

What is the boiling point of pure water?

100°C

What is a covalent bond?

A covalent bond connects two atoms by sharing an electron

The hydrogen is bonded to the oxygen (in the same molecule) through a covalent bond

Why is polarity important to life on earth?

Since water is polar, water can dissolve lots of substances

This is why water is called the universal solvent.

Why is cohesion important to life on earth?

Cohesion is responsible for surface tension, which allows certain organisms to float.

Why is adhesion important to life on earth?

Adhesion helps move water upwards through the stems of plants, since they don’t have any other way of moving the water against the force of gravity.

How is water’s heat capacity important to life on earth?

The water in our cells can absorb a lot of heat energy without killing our cells

Oceans can absorb a lot of heat energy from the sun without getting so hot that it kills all of the fish and other organisms.

Water Notes

Do Nows, PQQ’s and TOD’s

2.2 Worksheet

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