LESSON 20

Breaking Down a Compound

Review:

· Water has its own characteristic properties:

o Density

o Melting point

o Boiling point

o Produce solutions

o Pure substance

To be discovered:

1. Electrolysis will decompose water into hydrogen and oxygen.

2. Comparisons will be made of the physical and chemical properties of the reactant and the products of this reaction.

Background information on discovery info:

1. Electrochemistry began in the year 1800 by Alessandro Guiseppe.

a. He demonstrated that chemical reactions could produce electricity.

2. William Nicholson used a battery of the same design to pass an electric current through slightly acidified water to produce bubbles of gas.

3. Later, Johann Ritter was able to collect gases produced.

a. He identified them as hydrogen and oxygen, which were present in a ratio of 2:1.

4. Humphrey Davy constructed a battery with more than 250 plates for collecting elements produced when electricity was passes through liquids.

a. This battery isolated new elements:

i. Potassium

ii. Sodium

iii. Barium

iv. Strontium

v. Calcium

vi. Magnesium

Your notes:

1. electrolysis: the process of passing an electrical current through a liquid to decompose compounds into their constituent elements.

2. electrolyte: describes the solution or liquid that conducted the electricity. (How is it used in physiology?)

3. electrodes: rods that were placed in the electrolyte.

4. Compounds composed of pure substances can be decomposed by a chemical reaction and that elements are pure substances that cannot be decomposed.

5. Elements and compounds are pure substances.

6. The elements in compounds are combined in fixed proportions.