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Main Curriculum Tie:
Background For Teachers:
The two hydrogen atoms are connected to the oxygen at 105 degree angles which make one end of the water molecule slightly more negatively charged or positively charged than the other. This is an important property of water which makes it attract other substances carrying either a positive or negative charge. The attraction is effective with other water molecules as it is with other substances.
This attraction between a negative pole of one water molecule and a positive pole of another is due to a connection called HYDROGEN BONDING. (See overhead transparency.)
This type of bond is not as strong as the COVALENT BOND which keeps the oxygen connected to the hydrogen within a single water molecule.
The hydrogen (H) bonds formed between the positive and negative poles on water molecules cause surface tension and increases the bonds that must be broken before water can escape as steam when boiling.
SURFACE TENSION - Hydrogen bonds on the surface aren't equally surrounded as in the middle of a glass of water. So, the molecules are pulled into the middle and a rounded, skin-like effect is formed on the surface. The relationship between hydrogen bonding (polarity) and surface tension is illustrated by the transparency SURFACE TENSION found in the Resource section. The phenomenon of rain drops falling on a leaf or painted surface also illustrates surface tension. This characteristic of water allows of emulsions and foams to take place in food preparation.
HIGH BOILING AND FREEZING POINT - Water has a high freezing and boiling point because the molecules must break the H-bond and the atmospheric pressure before they can change from a liquid state to ice or steam.
Matter is composed of small particles called atoms, ions, and molecules. These particles are in constant motion and, therefore, the matter possesses a kind of energy called kinetic. In other words, the average kinetic energy of a group of particles determines the group's temperature. If heat is added to an object, the kinetic energy of its particles increase. The greater the average kinetic energy, the higher the temperature of the material.
Intended Learning Outcomes:
The students will participate in a PREASSESSMENT to access their knowledge of water by experimenting with surface tension, cohesion/adhesion, and temperature properties of water.
The students will perform an experiment to discover the amount of carbon dioxide in a bottle of carbonated beverage using the directions given in CARBON DIOXIDE IN SOFT DRINKS. They will record their observations on the worksheet CARBON DIOXIDE IN SOFT DRINKS - RECORD.
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