Taste and Sense of Taste

Tasting and Sense of Taste

• Our tongue has small, round bumps called papillae, which contain taste buds.
• Taste buds have sensitive hairs that detect chemicals in food, which are dissolved in saliva.
• These chemicals stimulate the hairs, sending signals to the brain, allowing us to experience the sensation of taste.
• We have over 10,000 taste buds in our mouth, including on the roof of our mouth.
• Our tongue can only sense four flavors: sweet, sour, salt, and bitter.

Sense of Taste for Protection

• Our sense of taste protects us from poisoning by helping us avoid food with strong bitter or sour tastes.
• "Bitter" is the basic taste that our tongues are most sensitive to.
• Spoiled food often tastes sour and has a bad smell, which helps us avoid it.

Properties of Acids

• Acids have common properties, including:
  • Tasting sour
  • Feeling rough between fingers
  • Being corrosive
  • Making bases lose their basic character
  • Turning blue litmus red
• Examples of acids include orange juice, vinegar, lemon juice, citric acid, and gastric acid.

Laboratory Acids and Safe Acids

• Concentrated hydrochloric acid is very corrosive and dangerous.
• Laboratory acids must be handled carefully.
• Our stomach contains hydrochloric acid (HCl), which helps break down food for digestion.
• Not all acids are corrosive or dangerous, e.g., ascorbic acid (vitamin C) and acetic acid (found in vinegar).

Properties of Bases

• Bases have common properties, including:
  • Tasting bitter
  • Feeling slippery between fingers
  • Being corrosive
  • Making acids lose their acidic character
  • Turning red litmus blue
• Examples of bases include baking soda, soap, bleach, and ammonia solution.

Laboratory Bases and Neutral Substances

• Sodium hydroxide (NaOH) is a strong base used in laboratories.
• Neutral substances are neither acids nor bases, and examples include water, table salt, sugar solution, and cooking oil.

pH and Acid-Base Indicators

• pH is a measure of the acidity or basicity of a substance.
• Acid-base indicators are substances that change color when an acid or a base is added to them.
• Litmus paper is an example of an acid-base indicator, and it changes color depending on whether it's in an acid, base, or neutral substance.

Litmus Test

• Red litmus paper stays red in an acid or neutral substance, and turns blue in a base.
• Blue litmus paper stays blue in a neutral substance or base, and turns red in an acid.
• The litmus test helps determine whether a substance is an acid or a base.