Exploring physical and chemical changes
Pre-Laboratory Questions
Explain the difference between a chemical change and a physical change.
List three examples of physical changes and three examples of chemical changes. Explain why these are chemical or physical changes.
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.
A carbonated beverage container is opened, producing a fizzing sound and carbon dioxide (CO2) bubbles.
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.
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.
A shiny, silvery iron nail turns reddish-brown when left exposed to the weather.
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.
General Lab Questions
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.
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?
