Chapter+8 +Acids,+alkalis+and+salts


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Acids change litmus to a **__red__** colour. Acid particles make other particles change. Lots of acids become __dangerous__.  Uses:__Metal cleaner, Vitamin C__, Aspirin

 Alkalis make __litmus **blue**__**.** Alkalis have different active particles. Alkali particles taste bad. Lots of alkalis are also __dangerous.__ Uses: Oven __cleaner__ is a strong alkali. They are often used to destroy grease.

 The **pH** scale is used to measure acidity.  (pH - The power of hydrogen) Figure 1 on page 98
 * The pH scale & Universal Indicator ||
 * Universal Indicator (solution or paper) || The pH scale ||
 * Universal Indicator is a mixture of dyes that goes **different colours** according to **how concentrated** / **strong the acid or alkali** in a solution is. || The pH scale is a scale for measuring acidity. The pH number match to a colour chart of Universal Indicator. ||


 * **Acids** ||
 * Less dangerous acids || More dangerous acids ||

Table 1 on page.98 Examples of [|pH scale] from sciencebuddies.org
 * pH** is an abbreviation for "power of hydrogen" that indicates how acidic or alkaline a substance is.

An **acid** is a substance that donates hydrogen ions. Because of this, when an acid is dissolved in water, the balance between hydrogen ions (H+) and hydroxide ions (OH−) is shifted. Now there are more hydrogen ions (H+) than hydroxide ions (OH−) in the solution. This kind of solution is acidic. A **base** is a substance that accepts hydrogen ions. When a base is dissolved in water, the balance between hydrogen ions and hydroxide ions shifts the opposite way. Because the base "soaks up" hydrogen ions, the result is a solution with more hydroxide ions than hydrogen ions. This kind of solution is alkaline.

For each 1-unit change in pH, the hydrogen ion concentration changes ten-fold. Pure water has a neutral pH of 7. pH values lower than 7 are acidic, and pH values higher than 7 are alkaline (basic). Examples of substances with different pH values (Decelles, 2002; Environment Canada, 2002; EPA, date unknown).

[|pH scale] from sciencebuddies.org

Marking criteria on Safety symbols (poster) [|pH scale] from chemistry.about.com
 * || Strongly ||  || Mostly ||   || Weak ||   || Hardly ||   ||
 * || 5 || 4 ||  || 3 || 2 ||   || 1 ||
 * Visually pleasing ||  ||   ||   ||   ||   ||   ||
 * Shows adequate effort ||  ||   ||   ||   ||   ||   ||
 * Has clear safety message ||  ||   ||   ||   ||   ||   ||