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Title: Electrolysis of Water
Principles Investigated:
Electrolysis
Chemical Bonds
Standards:
MS-PS1. B Chemical Reactions. How do substances combine or change (react) to make new substances? How does one characterize and explain these reactions and make predictions about them?
MS-PS1-2 Chemical reactions. Analyze and interpret data on the properties of a substance before and after the substances interact to determine if a chemical reaction has occurred.
Materials:
- One 250 mL beaker two
- 25 mL test tubes, two
- 25cm copper wires wrapped in electric tape except for 5cm on one end ( for wire/electrodes),
-seven 9volt batteries joined together
- filtered water
- baking soda (or salt)
Procedure:
1) Join seven 9 volt batteries together negatives to positives (4 on the bottom 3 on top and set aside- you could use 1 but more should increase reaction time).
2) Fill the beaker with 250 mL of water.
3) Add 3 tsp baking soda, stir until dissolved.
4) Pour the saltwater solution into test tubes to the brim one at a time. Place thumb over top and invert into the water of the beaker trying to keep all air out.
5) Make a ‘hook’ with each copper wire and tape wire with electrical tape to prevent gas formation outside of test tubes. Place wire hooks inside each test tube being careful not let any air in.
6) Then attach one wire to positive and the other one to negative. Do not allow wires to touch each other.
7) Let 1 test tube fill almost all the way with gas and disconnect wires from the battery.
8) Write observations. Answer Questions. Draw conclusions.
Student Prior Knowledge: Atoms, elements, periodic table, States of Matter, Molecules and Mixtures, Polar and nonpolar molecules, chemical change, and starting to learn about chemical formulas.
Explanation: We want to separate the atoms in water H2O to make H2 and O2 gas. This is not a normal reaction that happens in nature so we add electric energy to break their chemical bonds and create O2 and H2 gas. Running electricity through a substance that is liquid or molten is called ‘Electrolysis’. Scientists use it to separate compounds chemically. Here we used the addition of salt to increase the rate of results by adding more charged ions but we won’t focus on the salt or ions in this lesson. Mainly I want to teach about the principles: electrolysis, and how to separate water into hydrogen and oxygen gas.
Questions & Answers:
What elements make a water molecule? 2 Hydrogen and 1 Oxygen.
How does the electricity split the molecule? It adds more energy to break the bonds because the positive and negative electrodes pull the water molecule apart.
Applications to Everyday Life: Use to get chlorine for cleaning, Hydrogen for alternative energy
Resources:
Elemental Science, Logic Stage Teacher Textbook for Chemistry
From YouTube:
- water electrolysis by science fix
and
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