Detailed Study Notes on Acids, Bases, and pH Levels

General Properties of Acids
- Acids are recognized by their sour taste. A primary example is the lemon, which contains citric acid ( $citronsyra$ ). This specific acid is what gives the fruit its characteristic sourness.
- Common household and industrial acids include:
- Acetic acid ( $ättiksyra$ ): Found in vinegar ( $ättika$ ), commonly used for pickling products like pickled cucumbers ( $ättiksgurka$ ).
- Carbonic acid ( $kolsyra$ ): Present in carbonated soft drinks ( $läskedrycker$ ).
- Food Additives: Acids are frequently found in candy and various food products. They serve a practical purpose in food preservation, helping products last longer.
General Properties of Bases
- Being basic ( $basiskt$ ) is the chemical opposite of being acidic.
- Unlike acidity, basicity is not defined primarily by a taste, although if tasted, a base may have a "soapy" flavor ( $tvålaktig$ ).
- Bases are physically identifiable by their texture; they feel slippery or "halt" when rubbed between the fingertips.
- Common examples of basic substances include:
- Soap ( $tvål$ )
- Toothpaste ( $tandkräm$ )
- Laundry detergent ( $tvättmedel$ )
- Shampoo ( $schampo$ )
- Bicarbonate ( $bikarbonat$ )
- Baking powder ( $bakpulver$ )

Corrosive Potential ( $Frätande$ )
- Both acids and bases can be highly corrosive. While substances used in school laboratories are typically diluted ( $utspädda$ ) with water to ensure safety, concentrated forms are dangerous.
- Strong Acids: Hydrochloric acid ( $HCl$ ) and Sulfuric acid ( $H_2SO_4$ ) are strong enough to corrode skin and burn holes through clothing.
- Strong Bases: Substances like lye ( $lut$ ) are also strongly corrosive. Lye includes products such as caustic soda ( $kaustiksoda$ ) and soft soap ( $såpa$ ), which are used as cleaning agents.
Safety Protocol
- If a corrosive substance comes into contact with the skin or eyes, it must be rinsed immediately with running water.
- The goal of rinsing is to dilute the concentration ( $koncentrationen$ ) or strength ( $styrkan$ ) of the chemical to minimize damage.

Definition of Indicators
- An indicator is a substance that changes color when it comes into contact with an acidic or basic solution. They are used to identify the chemical nature of a solution.
Natural Indicators
- Several substances found in nature react to changes in acidity/basicity, including:
- Red cabbage ( $rödkål$ )
- Blueberries ( $blåbär$ )
- Beets ( $rödbetor$ )
- Tea ( $te$ )
Laboratory Chemical Indicators
- Professional laboratories use synthetic indicators for more precise and reliable results.
- BTB (Bromothymol Blue):
- Turns red in very acidic solutions.
- Turns yellow in acidic solutions.
- Turns green in neutral solutions.
- Turns blue in basic solutions.
- Phenolphthalein ( $Fenolftalein$ ):
- This indicator only shows color in basic solutions, where it turns a distinct red-violet ( $rödviolett$ ).
- Litmus Paper ( $Lackmuspapper$ ):
- This turns blue when exposed to a base.

The pH Scale Structure
- The $pH$ scale determines the degree of acidity or basicity of a substance.
- Acidic: Substances with a $pH$ value below $7$ .
- Neutral: Substances with a $pH$ value of exactly $7$ . They are neither acidic nor basic.
- Basic: Substances with a $pH$ value above $7$ .
Reference Values for Common Substances
- Lemon: Approximately $pH\,2$ .
- Coca-Cola: Approximately $pH\,3$ . The acidity of this drink is high enough to potentially corrode tooth enamel.
- Coffee: $pH\,5$ .
- Milk: $pH\,6$ .
- Distilled Water ( $Destillerat vatten$ ): $pH\,7$ . It contains only water molecules and is strictly neutral.
- Tap Water ( $Kranvatten$ ): Usually slightly above $pH\,7$ .
- Soap: $pH\,9$ .
- Lye fish ( $Lutfisk$ ): A traditional dish with a very high basicity of approximately $pH\,12$ .
Measurement Tools
- pH Paper: Paper strips soaked in multiple indicators. When dipped in a solution, the color change is compared against a reference chart to determine the $pH$ .
- Digital pH Meter: A more modern tool involving a probe (stick) that is dipped into the solution. The exact numerical $pH$ value is then displayed on a digital screen.

Environmental Survival
- Correct $pH$ levels are essential for the functioning of living organisms.
- Soil $pH$ affects plant growth. For instance, the Rhododendron plant thrives specifically in acidic soil ( $sur\,jord$ ).
Human Physiology
- Different parts of the human body require specific $pH$ levels to function correctly:
- Stomach: Requires a high level of acidity, with a $pH$ of approximately $2$ .
- Skin: Maintains a slightly acidic environment with a $pH$ of roughly $5$ .
- Blood: Must remain slightly basic, with a value just above $pH\,7$ .