11-13 yrs old
14-18 yrs old
Identify when a chemical reaction has occurred and what elements, molecules or compounds were involved.
March 9, 2020
Elephant Toothpaste Demonstration Lesson
Defining Chemical Reactions, Video
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Elements consist of 1 type of atom and cannot be broken down into smaller components by chemical means.
Molecules consist of at least 2 atoms joined together with a chemical bond, for example two atoms of oxygen react with one another to from molecular oxygen (O2), and two hydrogen atoms react with an oxygen to form a molecule of water (H2O).
Compounds are molecules consisting of atoms of at least two different types of elements joined with chemical bonds. For example, water is a compound and it is also a molecule. A chemical reaction is needed to separate the elements in a compound or molecule.
Mixtures can be formed by intermingling compounds, molecules or elements. For example air is a mixture of gases (nitrogen, oxygen, carbon dioxide and water)
The parts of a mixture can be separated with a physical process.
Something might cause a mixture to react to form new compounds and molecules.
Students should use the compound creator to see what molecules they can make. They can be given chemical formula, without an explanation of what the formula will produce. Students can then use their new compounds to create new mixtures, particularly fertilizer, glow sticks and 'elephant's toothpaste'.
Students can discuss whether chemical reactions occur when the new items are used, and which parts react. For example elephants toothpaste is a mixture of hydrogen peroxide, potassium iodide and soap. The H2O2 decomposes to form H2O and O2. The potassium iodide is unchanged, but it catalyses (speeds up) the decomposition of the H2O2. The soap does no react either, but just captures the oxygen gas to make a foam.
Students should also be encouraged to think about the outcomes of the lesson 'chemistry all around us' and how the reactions, object and materials they discussed there might be categorized as elements, compounds or mixtures.
• Recognize and give examples of elements, compounds, molecules and mixtures
• Use Minecraft to provide examples of chemical reactions.
• Be able to recgonise the difference between a chemical and physical reaction.
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