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580302_ChemandPhysicalChanges_Q.docx2.zip580302_Chem and Physical Changes_Q.docx
Pre-Laboratory Questions
1. Explain the difference between a chemical change and a physical change.
2. List three examples of physical changes and three examples of chemical changes. Explain why these are chemical or physical changes.
Exploring Physical and Chemical Changes
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Laboratory Questions
In the following scenarios, tell whether the change being described is a physical or a chemical change, and explain the reasoning behind your answer.
1. A carbonated beverage container is opened, producing a fizzing sound and carbon dioxide (CO2) bubbles.
2. Dry ice (solid CO2) is taken from a freezer and placed in an ice bucket at room temperature. With time, the block decreases in size and is surrounded by a visible cloud.
3. A pastry chef adds a mixture of white vinegar (~5% acetic acid in water) and baking soda (sodium bicarbonate, NaHCO3) to the batter for a red velvet cake to create bubbles that make the cake rise.
4. A shiny, silvery iron nail turns reddish-brown when left exposed to the weather.
5. A chemical heat pack is manufactured by sealing water (H2O) and calcium chloride (CaCl2) in separate compartments of a container. When the two components are mixed, the CaCl2 dissolves in the water, producing a large amount of heat.
Discussion Questions
1. Draw a diagram depicting what happens to the atoms of elements or molecules of compounds when a chemical change occurs and when a physical change occurs. Explain how the changes differ.
2. Whereas there are some outward signs of a chemical change, many of these can be mimicked by physical changes (e.g., a change in color). What are some more reliable ways by which a chemical change can be distinguished from a physical change?
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