Experiment - Acids & Alkali

Here's how to make an indicator that changes color according to the PH value of a substance. You will need:

• Fresh Red Cabbage
• A sharp knife
• A cutting board
• Hot tap water
• Seven clear plastic cups - please throw these away after use if you don't want to die by poisoning. (Advice from my bro:)
  
• Seven plastic spoons
• A large plastic bottle
• A range of household products:
  
• Strongly Acidic - powdered toilet cleaner or pineapple - i haven't tried pineapple but you can give it a go.
• Acidic - Lemonade, white wine or citric acid
  
• Weakly/Slightly acidic - cream of tartar
• Neutral - baby shampoo, water, Salt solution (mix salt in water) - you can do the same with sugar
• Weakly/Slightly basic- bicarbonate soda
• Basic/Alkaline- washing powder, milk of magnesia- or indigestion tablets
• Strongly basic/alkaline- dishwater liquid
• an adult to help you, of course this ruins all the fun but this activity requires the use of a knife, poisonous chemicals and hot water. Ask an adult to assist you. Always follow the safety advice on the products you are using.

Steps

1. Using a sharp knife and cutting board, finely slice three or four red cabbage leaves.
2. Place the cabbage leaves in the plastic bottle, half fill the bottle with hot water and screw the lid on tightly.
3. Shake the bottle for a few minutes until the water becomes a deep purple colour. Leave the solution to cool.
4. Strain the solution and add sufficient water to the solution to make about one litre.
5. In each of the cups, place a small amount of one of the above household substances in the following order: strongly acidic; acidic; slightly acidic; neutral; slightly basic; basic and strongly basic.
6. Now half fill each cup with the red cabbage water and stir the solution. If arranged in order, the jars should display a spectrum of colours from cherry red (strongly acidic), pink-red (acidic), lilac (slightly acidic), purple (neutral), blue (slightly basic), green (basic) and yellow (strongly basic).

What's happening

The things we eat and drink are all acidic, and the things we use for cleaning are basic. This is because basic substances taste unpleasant, but a cleaning agent usually needs to be basic to remove dirt and grease.

Substances that are acidic or basic make the eyes sting, so baby shampoo is made neutral. Pure water has a pH of seven and is regarded as neutral. Sugar and salt have a pH value of seven. Most cosmetics (especially cleansers) have their pH value written on the back. In my experience, Aloe Vera products are more likely to have given their pH value. These products, like the baby shampoo are neutral.

Acids

Acids are a very common group of chemical compounds, many of which occur naturally. Acids can be strong or weak.

Citric acid, which occurs naturally in lemons, is a weak acid. Hydrochloric acid (used for soldering) and sulfuric acid (battery acid) are very strong acids.

Bases

Bases are another group of chemical compounds that have different chemical properties from acids. Bases and Alkali are similar, however, Alkali is the name given to bases which dissolve in water. When bases and acids are added together, they will neutralise each other's properties. This process is called Neutralisation.

We describe whether things are acidic, basic or neutral by using a scale called the pH scale. The pH scale ranges from zero to 14. A substance with a pH of:

• 0 is a very strong acid
• 3 - 5 is a weak acid
• 7 is neutral
• 8 - 9 is a weak base
• 13 - 14 is a very strong base.

Acids and bases can be detected by a group of chemical compounds called acid-base indicators. One of the first known naturally occurring indicators was a type of lichen called litmus. (Lichens are plant-like growths that are often found on rocks and tree bark.) Litmus is a blue dye which is extracted from various species around the world (but mainly from Holland) and it turns red (around pH 4.5) in the presence of an acid or blue (around pH 8.3) with a base. Litmus is used to make Litmus paper which has the same effect. i.e.: Red Litmus paper turns blue in the presence of an acid. Blue Litmus paper turns red in the presence of a base. While most litmus is used to make litmus papers, some is used as a coloring for beverages.

Most indicators used today to detect acids and bases are man-made, such as universal indicator. However, many plant pigments, such as the red cabbage you used, contain chemicals that act as acid-base indicators.

lichen info: http://www.pharmainfo.net/reviews/natural-ph-indicators-review
experiment from: www.csiro.au



. xoxo
Snoozy

Centripetal Force vs. Centrifugal force

Centripetal force describes how a force acts when the object which the force is exerted on is traveling in circular motion. The Latin meaning for centripetal is towards the center because the force acts towards the center. For example: the centripetal force is present in Roller Coasters, when you go loop-the-loop.

The Centrifugal force is a virtual force. The Centrifugal force is merely the reaction of the Centripetal force. Sir Isaac Newtons' third law supports this theory:
For every force there is an equal and opposite force.
For example:
A carnival ride that spins around in a circle at a constant speed.

When moving fast, a large force is required to make you change
direction.  Your body wants to continue in a straight line.  The curved
wall gets in the way.  The wall pushes in against your body.  The "outward
force" is just your body trying to move in a straight line.  It is not a
force at all.  It is just your body resisting the effects of the forces
it feels.
info from:

• csiro science emails (SUBSCRIBE!)
  
• http://www.newton.dep.anl.gov/askasci/
  

               Hope this helped

xoxo
Snoozy