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# The pH Scale The pH scale measures the acidity or alkalinity of a substance. * **Acids:** Located on the left side of the scale, they range from red to green. * **Neutral substances:** Located in the center of the scale (pH 7), they turn jade green. * **Alkalis (bases):** Located on the right s...

# The pH Scale The pH scale measures the acidity or alkalinity of a substance. * **Acids:** Located on the left side of the scale, they range from red to green. * **Neutral substances:** Located in the center of the scale (pH 7), they turn jade green. * **Alkalis (bases):** Located on the right side of the scale, they range from light blue to purple. # Testing Oxides This section describes how oxides react with water, and whether they form acids or bases. A table is presented with the following information for different oxides: | Name of Oxide | Formula | Type of Oxide (metal or non-metal) | PH | Testing in water (observations after adding the oxide to water) | Conclusion/ Acid or Alkali | |---|---|---|---|---|---| | Magnesium oxide | MgO | Metal | Neutral | Likely no visible change | Likely no change or weakly alkali | | Sodium oxide | Na₂O | Metal | Alkaline | May form a base reaction in water | Likely produces an alkali | | Carbon dioxide | CO₂ | Non-metal | Acidic | May form an acid reaction in water | Likely produces an acid | | Sulfur dioxide | SO₂ | Non-metal | Acidic | May form an acid reaction in water | Likely produces an acid | | Nitrogen dioxide | NO₂ | Non-metal | Acidic | May form an acid reaction in water | Likely produces an acid | **Conclusion:** Soluble metal oxides form alkaline solutions in water. Soluble non-metal oxides form acidic solutions in water.