Transcript Chapter 9
WATER & WATER CONTENT TRIVIA Brazil is home to 18% of the world's available freshwater resources in its rivers, lakes and aquifers. Agriculture accounts for about 70% of all water use in the world. Americans drink an average of 30 gallons of bottled water per person each year (2010). In 1980 the average was about 1 1/2 gallons. There is no scientific basis to support the recommendation to drink 8 glasses of water a day. We probably need about that much water intake daily, but we get much of that from the food we eat. You can drink too much water. Drinking significantly more water than we need can lead to 'water intoxication,' which can lead to fatal cerebral and pulmonary edema. Some amateur marathon runners have died in this manner. http://search.yahoo.com/search;_ylt=A0oG7hJW5p xSKVkAGUJXNyoA?p=chemical+water+videos+&fr 2=sb-bot&fr=yfp-t-900-1&vm=r Chapter 9 Water – Part 2 Boiling and Condensing Boiling point – the temperature at which its vapor pressure equals the air pressure above the liquid. Water and Foods Water is the main ingredient in many foods. Water Content in Food Fruits, vegetables, & meats are 70 to 90% water. Free water Water that readily separates from foods that are sliced, diced Slice of bread gets crisp in the toaster as the heat evaporates the free water at the bread’s surface. Bound water Water that cannot be easily separated in food. Chemical group’s in a food’s molecules hold bound water tightly. Cannot react with other substances Freezes only at very low temperatures. Doesn’t evaporate. Ex: adding dry gelatin to water; water becomes bound. Water in Heat Transfer Acts as the medium for heat transfer. Example: Imagine heating a potato in a saucepan on a range top. The bottom of the potato would scorch before the rest of the vegetable cooks. By adding water it acts as the medium. Water as a Solvent Solvent – the substance that dissolves another substance. Solute – the substance that is dissolved. A substance that can be dissolved in another substance is said to be soluble. Solubility The maximum amount of solute that can dissolve in a given quantity of solvent at a given quantity of solvent at a specific temperature. Hard Water – water that contains calcium or magnesium ions. The metallic elements often dissolve in water as it passes through the ground. Water that doesn’t contain these metal ions is considered soft. Water and the Body Body weight equals about 50 to 65 percent water. Exact percentage depends on the amount of fat, bone, and muscle in the body. Water is obtained from two sources: food and liquid consumed and internal chemical reactions. Water helps your body maintain a constant temperature. Body temperature rises → you perspire → perspiration evaporates off your skin.