WATER Most abundant liquid on the earth Chemical Formula: H 2 O Density: 1 g/mL Freezing Point: 0°C Boiling Point: 100°C One of the only substances whose solid form floats in its liquid form (Ice)
Rime of the Ancient Mariner by Samuel Coleridge “Water, water, everywhere, And all the boards did shrink; Water, water everywhere, Nor any drop to drink.”
FYI: Water Appx 70% of the human body is water The average human can drink about 3 gallons/12L of water a day The total amount of water on the earth is 326 cubic million miles of water More fresh water is stored underground in aquifers than above ground Drinking too much water too fast can lead to water intoxication, which causes the sodium in the blood to be diluted and causes an imbalance in the brain.
CHARACTERISTICS OF WATER Polar: Water is polar due to the high electronegativity of the oxygen atom. This causes the shared electrons to be closer to the oxygen atom, thus creating a polar bond. Thus the oxygen atom becomes slightly negative and the hydrogen atoms become slightly positive. (creating “poles”)
Bent Shape The bent shape of the water molecule is what actually makes water polar. The 2 lone pairs of electrons on oxygen and the 2 hydrogen atoms push as far apart as possible causing the water molecule to take on a bent shape. (104 degree bond angle between the H’s)
High Surface Tension Surface Tension: auf Deutsch: Wasserüberflaschungspannung Inward force that tends to minimize the surface area of a liquid Liquids with a high surface tension tend to form spherical droplets Surfactant: decreases a liquids surface tension: ex: soap
Cohesion/Adhesion/ Surface Tension Water: Too Stick or Not to Stick
Low Vapor Pressure Vapor Pressure: Caused by molecules that escape the surface of a liquid and enter the gas phase (in a closed container) vapor pressure
High Specific Heat Capacity Amount of energy (Joules) required to raise the temperature of 1 g of water 1°C Specific heat for water is: 4.184 J g °C
Advantages of a high specific heat: Helps prevent bodies of water from evaporating Helps prevent our bodies from burning up on the inside
Assorted Specific Heats SubstanceSpecific Heat J/g C Aluminum0.901 Copper0.384 Iron0.449 Sand0.835 Water4.184
High Heat of Vaporization Heat of Vaporization: the amount of energy needed to convert 1g of a substance from a liquid to a gas at the boiling point
High Boiling Point Boiling Point: temperature at which the vapor pressure of a liquid is just equal to the external pressure on the liquid The higher the altitude, the lower the temperature at which water boils. EX: Water boils at 72°C on Mt. Everest Pressure cookers can cook food at a temperature of 120°C therefore decreasing cooking time by 1/3.
Universal Solvent Water can dissolve many substances, including metals (turning iron into rust) Solvent: substance doing the dissolving Solute: substance being dissolved EX: salt water – Water is the solvent – Salt is the solute
Likes dissolve Likes Since water is polar, has a positive and negative end, it can dissolve other substances that are polar. Water can also dissolve ionic compounds, since they are made up of + and – ions Polar substances cannot dissolve nonpolar substances. (nonpolar, do not have a positive and negative end)