Think About It Thursday: Why are Tears Salty?

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Almost every food item that we consume has some sort of salt in it. The sodium chloride (salt) gets dissolved by the body and ends up in your blood stream and tears!  Your blood contains a little less than 1 percent sodium chloride and your tears probably contain almost that much. Just for comparison, seawater contains about 3 percent sodium chloride. An adult body contains as much as 1 cup of salt at one time!

FUN Holiday Science – Poinsettia pH Paper!

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Many plants contain pigments that are responsive to changes in acidity. An example is the poinsettia plant, which has colored ‘flowers’ (really specialized leaves called bracts). Although poinsettias are perennials in warmer climates, most people are likely to see them used as a decorative houseplant over the winter holidays. You can extract the red pigment from deeply colored poinsettias and use it to make your own pH paper strips to test whether a liquid is an acid or a base.

Materials

  • poinsettia ‘flowers’
  • beaker or cup
  • hot plate or boiling water
  • scissors or a blender
  • filter paper or coffee filters
  • 0.1 M HCl
  • vinegar (dilute acetic acid)
  • baking soda solution (2 g / 200 mL water)
  • 0.1 M NaOH
How To Do It – 
1. Cut flower petals into strips or chop them in a blender. Place the cut pieces into a beaker or cup.
2. Add just enough water to cover the plant material. Simmer until the color is removed from the plant. (Personally, I would just microwave the chopped bracts with a little water for about a minute and allow the mixture to steep, like a tea.
3. Filter the liquid into another container, such as a petri dish. Discard the plant matter.
4. Saturate clean filter paper with the poinsettia solution. Allow the filter paper to dry. You can cut the colored paper with scissors to make pH test strips.
5. Use a dropper or toothpick to apply a little liquid to a test strip. The color range for acids and bases will depend on the particular plant. If you like, you can construct a chart of pH and colors using liquids with a known pH so that you can then test unknowns. Examples of acids include hydrochloric acid (HCl), vinegar, and lemon juice. Examples of bases include sodium or potassium hydroxide (NaOH or KOH) and baking soda solution.
6. Another way to use your pH paper is as a color-change paper. You can draw on pH paper using a toothpick or cotton swab that has been dipped in an acid or base.
Learn more about pH levels here :

Edible pH Indicators 

Chem4Kids.com – Reactions : Acids & Bases