"Changes of Water" The most common liquid - water PPT courseware 2

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"Changes of Water" The most common liquid - water PPT courseware 2

1. Three state changes of water

ice→water→water vapor

2. Electrolysis of water experiment

What happens in the buret connected to the two poles of the power supply?

[Phenomena 1] Colorless bubbles are produced at both poles.

[Phenomena 2] The volume ratio of the gas generated by the positive electrode and the negative electrode is about 1:2

[Phenomena 3] The gas produced by the positive electrode can re-ignite the wood strips with sparks; the gas produced by the negative electrode can burn, and the flame will be light blue.

[Conclusion] The gas produced by the positive electrode can re-ignite the wood strips with sparks, which is oxygen; the gas produced by the negative electrode can burn, and the flame is light blue, which is hydrogen.

3. Properties of Hydrogen

Physical properties: Hydrogen is a colorless, odorless, and insoluble gas. (Hydrogen is the lightest gas)

Chemical properties: Flammability

When hydrogen burns in the air, the flame appears light blue. A dry, cold beaker is placed above the flame, and colorless droplets are formed on the inner wall of the beaker.

hydrogen + oxygen → water

[Note] Pure hydrogen will burn quietly when ignited, but hydrogen mixed with a certain amount of air or oxygen will explode when ignited, so the purity of the hydrogen must be checked before igniting the hydrogen.

How to test the purity of hydrogen

A sharp popping sound indicates impurity, while a quiet sound indicates purer hydrogen.

1. Is hydrogen gas that has been tested not to explode necessarily pure hydrogen gas?

2. How many elements are hydrogen and oxygen composed of? How many elements are water and carbon dioxide made of?

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Update Time: 2024-11-29

This template belongs to Chemistry courseware Beijing Curriculum Reform Edition Ninth Grade Chemistry Volume 1 industry PPT template

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