shapes make a lot of difference shapes make a lot of difference!! why does “ice float on water”?

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Shapes Make A Lot of Difference

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Page 1: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Shapes Make A Lot of Difference

Page 2: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Shapes Make A Lot of Difference!!

Why does “ice float on water”?

Page 3: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Shape Makes A Lot of Difference

All these contain water. Why can water dissolve many things?

Page 4: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Shape Makes A Lot of Difference

Why can I swim in water on a hot summer day but cannot step on sand for long?

What has shape got to do with all these observations? Let’s see…..

Page 5: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water’s Chemical Structure

Each water molecule consists of 2 atoms of hydrogen atoms bonded to an atom of oxygen. The chemical formula of water is H2O.

H

H

O

H

HH

O

O

O

H

H H

Page 6: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water’s Chemical Structure

The oxygen atom attracts the electrons shared with hydrogen atoms more strongly to itself. In effect, each hydrogen atom acquires a partial (+) charge. Oxygen acquires a partial (-) charge.

Page 7: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water’s Chemical Structure

The uneven distribution of electrical charges makes water a polar molecule. The two O-H bonds make an angle of 104.5o between them giving the molecule a triangular shape.

HH

O

104.5o

104.5o

104.5o

HH

H H

O

O

Page 8: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water Forms Hydrogen Bonds

Water molecules are attracted to each other creating hydrogen bonds. The attraction of the oxygen of one molecule to the hydrogen of another molecule forms the hydrogen bond.

H

O

H-bond

Page 9: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

More hydrogen bonds are formed when water molecules move closer to one another.

Water Forms Hydrogen Bonds

H-bonds

H-bonds

Page 10: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

In solid water or ice, the molecules form themselves into a well-ordered crystalline structure (hexagon) held by hydrogen bonds.

Water Forms Hydrogen Bonds

H-bonds

Page 11: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water –The Unique Solvent

Our experiment showed that water can dissolve different kinds of solids like salt, sugar, lime, and chemical salts like potassium nitrate and lead nitrate.

salt

sugar

lime potassium nitrate

lead nitrate

Water and

Page 12: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water –The Unique Solvent

Not only solids, water can dissolve different kinds of liquids. It can dissolve alcohol, vinegar, lye, and muriatic acid. But, it cannot dissolve oil and gasoline.

alcohol vinega

r

muriatic acid lye

oil gasoline

Water and

Page 13: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water –The Unique Solvent

Even gases dissolve in water but to a very limited extent. The bubbles coming out of the test tubes are gases that were dissolved in water under pressure.

carbon dioxid

e

oxygen

sulfur dioxide

chlorine

Water and

Page 14: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water –The Unique Solvent

Here is a sample data gathered from a library research. It was found out that the solubility of many salts increases with increase in temperature.

SubstanceSolubility (g solute/100g water)

10oC 30oC 50oC

Lead nitrate 48.3 66.0 85.0

Sodium chloride 35.8 36.3 37.0

Potassium nitrate 20.9 45.8 85.5

Potassium dichromate

7.0 20.0 34.0

Page 15: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Solubility of Solutes at Varying Temperatures

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

10oC 30oC 50oC

Temperature

So

lub

ility

(g

so

lute

/ 1

00g

wat

er)

Lead Nitrate

SodiumChloridePotassiumNitratePotassiumDichromate

Water – The Unique SolventData has been translated into a bar graph to show the

comparative increase in solubility of the solutes at 10oC, 30oC, and 50oC.

Page 16: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water –The Unique Solvent

A bar graph of the data.

Solubilities of gases in water

0.000

2.000

4.000

6.000

8.000

1 0.000

1 2.000

1 4.000

1 6.000

1 8.000

Sul f ur dioxide Chlor ine Car bon dioxide Oxygen

Gases

Solu

bilit

ies

(g s

olut

e /

100g

wat

er) 10oC

30oC

50oC

Page 17: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water –The Unique Solvent

On the other hand, the solubility of many gases decreases with increase in temperature.

SubstanceSolubility (g solute/100g water)

10oC 30oC 50oC

Sulfur dioxide 16.210 7.800 0.393

Chlorine 0.997 0.572 0.393

Carbon dioxide 0.232 0.126 0.076

Oxygen 0.005 0.005 0.003

Page 18: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water – The Unique SolventData has been translated into a bar graph to show the

comparative increase in solubility of the gases at 10oC, 30oC, and 50oC.

Solubilities of gases in water

0.000

2.000

4.000

6.000

8.000

1 0.000

1 2.000

1 4.000

1 6.000

1 8.000

Sul f ur dioxide Chlor ine Car bon dioxide Oxygen

Gases

Solu

bilit

ies

(g s

olut

e /

100g

wat

er) 10oC

30oC

50oC

Page 19: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water – The Unique SolventData has been translated into a bar graph to show the

comparative increase in solubility of the gases at 10oC, 30oC, and 50oC.

Solubilities of gases in water

0.000

2.000

4.000

6.000

8.000

1 0.000

1 2.000

1 4.000

1 6.000

1 8.000

1 0oC 30oC 50oC

Temperature

Solu

bilit

ies

(g s

olut

e /

100g

wat

er)

SulfurdioxideChlorine

CarbondioxideOxygen

Page 20: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water –The Unique Solvent

The graph shows that …

1. In general, the solubility of a solid in water increases with increase in temperature. The degree of increment varies with the nature

of the solid.2. The increase in solubility of sodium

chloride is relatively small, thus, a temperature increase has a slight effect on the solubility of sodium chloride in water.

3. The increase in solubility of potassium nitrate is relatively large, thus a temperature increase has a large effect on the solubility of potassium nitrate in water.

Page 21: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water –The Unique Solvent

The graph shows that …

1. In general, the solubility of a gas in water decreases with increase in temperature. The decrease varies with the nature of the

solute.

3. The solubility of oxygen is very, very small (almost negligible) and seem unaffected by

an increase in temperature.

2. Sulfur dioxide has the highest solubility under the same temperature, and experience the greatest decrease in solubility when its temperature is increased.

Page 22: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water – The Unique Solvent

A sodium chloride unit (NaCl) consists of a sodium ion and a chloride ion.

What happens when NaCl is added to water?

Na+ Cl-

Page 23: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water – The Unique Solvent

Several sodium chloride (NaCl) units make up a sodium chloride crystal.

Na+ Cl-

NaCl

Page 24: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water – The Unique Solvent

Water exerts an attractive force on NaCl - with the Cl side attracted to the H of water and the Na side to the O of water.

Cl-

H

O

Na+

Page 25: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water – The Unique SolventThe attractive force is strong enough to break the bonds between Na+ and Cl- ions, and the ions break away from their positions in the crystal. They are quickly surrounded by the water molecules.

Page 26: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water – The Unique Solvent

The same thing happens when other ionic substances like potassium chloride, calcium chloride, sodium nitrate, and polar substances like alcohol, vinegar and muriatic acid dissolve in water.

KCl

K+

Cl-K+

K+

Cl-

Cl-

Page 27: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Water – The Unique Solvent

Write these:

1. Why is seawater salty? Where did the salts come from?

2. Water is a poor solvent to many nonpolar substances like oil and gasoline. They form layers with water usually occupying the lower layer. What is the effect of oil spills on rivers and lakes and the living things in it? 3. What is the effect of an increase in

temperature on the amount of dissolved oxygen in a river or lake?

Page 28: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Some Applications

The high solubility of alcohol in water makes possible

a)the preparation of wines, colognes,perfumes, rubbing alcohol, etc..

b) the rapid spread of ethyl alcohol (from alcoholic drinks) in the body because the body is made up of 75% water.

Page 29: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Some Applications

Fire caused by gasoline or oil cannot be put off by dousing it with water. Water will sink and formthe lower layer. The oil or gasoline will form the upper layer and spread out, exposing more of it to oxygen.

Page 30: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Some Applications

The low solubility of oxygen in water limits its presence in water. This dissolved oxygen is used by fish and other organisms in rivers, lakes, etc.in order to live.

Page 31: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Some Applications

An increase in temperature of the water will further reduce the dissolved oxygen, further lowering the available oxygen for these living things.

Page 32: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Some Applications

Rainwater dissolves certain gases in air as it falls to the ground, seas, and oceans. As it flows through soil and rock formations, it dissolves many mineral salts and carries with it countless bacteria.

Page 33: Shapes Make A Lot of Difference Shapes Make A Lot of Difference!! Why does “ice float on water”?

Well, these are all for today, class.

I hope you learned from the experiments we did and from the presentation.

Until our next meeting….. BYE!!