Understand that chemical changes result in the formation of entirely new substances, using lime water and rusting as primary examples.
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Hook on bioluminescence as a chemical change.
The beautiful glow that fireflies produce at night is called bioluminescence. It is the fascinating result of a natural chemical change happening right inside their bodies, allowing them to produce brilliant light without any heat!
Hook introducing chemical changes via decaying fruit.
Imagine leaving a banana on the kitchen counter for a week. As the days pass, it develops dark brown spots, the skin softens, and it starts to give off a strong, sweet smell.
Where did this new smell and color come from?
Definition of chemical changes and the lime water test.
A chemical change occurs when one or more new substances are formed. This transformation is driven by a process called a chemical reaction.
Unlike physical changes (like melting ice), chemical changes are usually difficult or impossible to reverse.
Diagram of the carbon dioxide and lime water experiment.
Two connected test tubes. First tube has bubbling vinegar and baking soda. A bent delivery tube connects the top of the …
Fill in the missing terms in the chemical reactions.
Chemical equations help us easily track what substances are changing. In a common kitchen experiment, Vinegar + yields along with other substances. We can test for the presence of this gas using a specific indicator liquid. When the reaction Carbon dioxide + Lime water occurs, it produces + Water. Because this new substance is insoluble in water, it settles and creates a visible milky appearance.
Explanation of the rusting process of iron.
Not all chemical changes happen instantly like fizzing vinegar. Some chemical reactions, like rusting, take place over a long period of time.
When iron is left exposed to oxygen (from the air) and moisture (water), a gradual chemical reaction occurs.
Visual of rusted iron.
Highly detailed, realistic pile of old iron nails. They are heavily coated in a flaky, reddish-brown layer of rust (iron…