Acids and Alkalis

One of the ways to describe a substance is to say if they are acids or alkalis.  We decided to test different substances to determine how acidic or alkali a substance is.

Materials:
red cabbage
cooking pot
small containers with lids
funnel
eye dropper
coffee filter
various liquids to test - lemon juice, liquid soap, water, vinegar, milk, washing soda

Procedure:
Cut cabbage into small pieces.  Put in saucepan and add enough water to cover the cabbage.  Bring to a boil.  Turn off heat and let stand for about an hour.  Drain off cabbage juice into a jar.  Dip strips of coffee filter into the juice and let dry.  This will be the indicator paper.

Fill labeled containers with different substances to about 3/4ths full.  Dip strips into liquid, or use eye dropper to put liquid on strips.

The indicator reacts with the liquid and changes color according to the acidic or alkali level.  If the liquid is an acid, the paper will turn red or pink,  If the liquid is an alkali, the paper will burn blue or green.  Yellow indicates a neutral substance.

We also poured cabbage juice into the jars.  This made it easier for the students to see and compare the colors.

We had also used full sized coffee filters that were dipped with cabbage juice and made a picture by using a small paint brush to create a picture with different colors.

Chemical Changes

So much fun!  This activity is done after reading about states of matter, physical and chemical changes.
Before doing any experiments, we review our safety standards and decided that this was a 6.  It is glue and will make a horrible mess with fabric, as well as your hair.  So, roll up your sleeves and tie back your hair!


GAK - from Steve Spangler's Science

1tbs Borax laundry booster (found at Target)
50mL warm water
mix until Borax is dissolved

In large zip lock bag mix
1 bottle 8oz glue
200mL water
food coloring

Add Borax mixture to glue mixture

Knead with hands until it forms a lump.  Keep mixing until there isn't water left.  It will feel like smooshing grapes.

The students then explore the properties of GAK.  We listed the solid and liquid properties and discussed what the students thought it was.

We looked up information about polymers and non-Newtonian substances.
We also discussed the effects of pressure.