30. “Lava lamp” (It is suitable for case-lessons “Oil in a salad and head”, “The fascinating world of volcanoes”).

The essence of the task: You will need salt, water, a cup of oil, few food colorings and a big transparent glass. The recommended time limit is 15 minutes. The algorithm of creation of the lamp:

• fill the glass by 2/3 with water;
• add oil into the glass (it will be floating on the surface of water, don’t stir it);
• add few drops of the coloring;
• slowly add 1 tea spoon of salt to the glass. The lamp is ready, now you can watch the “lava”!

Students have to explain what causes the “lamp” effect. (Salt and oil have different density and weight; when they are dissolved particles of salt “release” the drops of oil, which were previously “captured” by them).

OBJECTIVE: Practical mastering of scientific and educational information in physics and chemistry, gaining practical skills.