☰ Contents · Natural science

Lithosphere, volcanoes and hydrosphere

Lessons 46–48 · 3 lessons · K. T. Suyarov, Z. B. Sangirova, M. T. Umaraliyeva, S. G‘. Xasanova, M. K. Yuldasheva, D. T. Hasanova. Natural Science, Grade 6 (new edition). Republican Education Centre, 2022
47

Practical: Making a volcano model

Textbook, p. 107
GoalBuild a volcano model safely, state the difference between magma and lava, and judge how the model differs from a real volcano.
New words
lava (molten rock on the surface) · lavacrater · krater (vulqon og‘zi)vent / volcanic conduit · vulqon kanalivolcanic ash · kul
Explanation

A volcano is an opening in the crust through which hot molten rock, gases and ash erupt. Molten rock underground is magma; once it reaches the surface it is lava. Gases dissolved in the magma push it upward, like the fizz that bursts out when you open a shaken fizzy drink. In the model we show this with baking soda (sodium bicarbonate) and vinegar: they react to form carbon dioxide gas (CO2) and the foam overflows the crater. The model does not show the heat or the melting of rock, only the overflow driven by gas. Real volcanoes are dangerous: ash, gas and scorching lava spread when they erupt.

Worked examples
The model uses 4 teaspoons of baking soda, a little food colouring and vinegar: as soon as vinegar meets the soda, the “lava” froths over. This is a chemical change because a new substance (a gas) forms.
Magma is underground, lava is on the surface. So the hot liquid rock flowing out is “lava” and the source beneath it is “magma”.
Class activity

Build the volcano on a dry tray or dish. Put soda and colouring into the small cup, then, with an adult supervising, pour in vinegar slowly. Safety: wear eye protection (goggles); work on a tray or outdoors; do not taste soda or vinegar and if either gets in the eyes rinse at once with clean water; ask an adult’s permission; stand back during the eruption; wash hands afterwards. No hot materials are used in this model.

Practice
1
Explain the difference between magma and lava.
2
Which gas is released when soda reacts with vinegar?
3
How many teaspoons of soda are needed to prepare the 4-teaspoon portion 3 times?
4
How does the model differ from a real volcano and why does it matter?