Acid

The word acid comes from the Latin word acere, which means sour. In dilute concentrations acids are responsible for the sour taste of lemons, limes, vinegar and other substances. Hydrochloric acid is produced in your stomach to help digest food. Sulfuric acid is found in car batteries. Acids can conduct an electric current. Acids are also corrosive. When acids react with metals they form hydrogen gas. When an acid reacts with a carbonate it forms carbon dioxide, water, and a salt. Acids can cause skin to burn so you should be careful when handling acids Acids can be classified according to the number of hydrogen atoms available to react with a base and degree of ionization (how many of the available hydrogen atoms dissociate in water). A base is most commonly thought of as an aqueous substance that can accept hydrogen ions. Bases are also the oxides or hydroxides of metals. A soluble base is also often referred to as an alkali if hydroxide ions are involved. Indicators are very special chemicals; they will change color if you change the pH (by adding acid or alkali). |Indicator |pH |Color in Acid |Color in Alkali | | |7.0 |Red |Blue | |Litmus | | | | | |9.7 |Colorless |Red / Pink | |Phenolphthalein | | | | | |3.7 |Red |Yellow | |Methyl Orange | | | | | |4.0 |Yellow |Blue | |Bromophenol Blue | | | | PH is short for potentiometric hydrogen ion concentration. The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. The pH scale is logarithmic and as a result, each whole pH value below 7 is ten times more acidic than the next higher value. For example, pH 4 is ten times more acidic than pH 5 and 100 times (10 times 10) more acidic than pH 6. The same goes for pH values above 7, each of which is ten times more alkaline (another way to say basic) than the next lower whole value. For example, pH 10 is ten times more alkaline than pH 9 and 100 times (10 times 10) more alkaline than pH 8. Pure water is neutral. But when chemicals are mixed with water, the mixture can become either acidic or basic. Examples of acidic substances are vinegar and lemon juice. Lye, milk of magnesia, and ammonia are examples of basic substances. [pic] Neutralization is a chemical reaction where an acid and a base react to form water and a salt. The generic equation for a neutralization reaction is Acid + Base ---> Metallic Salt + Water. Often, neutralization reactions are exothermic, meaning they give out energy in the form of heat (the enthalpy of neutralization). An example of an endothermic neutralization is the reaction between baking soda and any weak acid, for example vinegar. Electrolyte is a "medical/scientific" term for salts, specifically ions. The term electrolyte means that this ion is electrically-charged and moves to either a negative (cathode) or positive (anode) electrode. Ions that move to the cathode are positively charged and ions that move to the anode are negatively charged. Electrolytes are important because they are what your cells (heart and muscle) use to maintain voltages across their cell membranes and to carry electrical impulses across themselves and to other cells. Your kidneys work to keep the electrolytes in your blood the same even when you have changes in your body. For example, when you exercise a lot, you lose electrolytes in your sweat. These electrolytes must be replaced to keep the electrolyte concentrations of your body fluids the same. Many sports drinks have sodium chloride or potassium chloride added to them to help replace the electrolytes. Strong electrolytes fall into three categories: strong acids, strong bases, and salts. The weak electrolytes include weak acids and weak bases. [pic] [pic]