Five mixes of everyday materials fill the results table on this 4-page 5th grade investigation: salt and water, baking soda and vinegar, sand and water, milk and lemon juice, and sugar and iced tea. Each row gives the observations, and students write Yes or No for a new substance, name the change as physical or chemical and give evidence. Part 2 asks three follow-up questions, including how to get the salt back. It fits NGSS 5-PS1-4, and pages 3 and 4 are the answer key.
5-PS1-4
“Conduct an investigation to determine whether the mixing of two or more substances results in new substances.”
Students work from recorded observations of five mixes and decide which ones made a new substance, so they analyze the results of an investigation instead of running one.
A five-row table with each mix and its observations, for example fizzing, bubbles of gas and a colder cup for baking soda and vinegar. Students fill in two blank columns, New substance? and Evidence.
Three written answers: which mixes made a new substance, how you could get the salt back from the salt and water mix, and why dissolving sugar in iced tea is not a chemical change.
The completed table with a Yes or No, the type of change and a sentence of evidence for each mix, then model answers for the three questions.
Run it for real
Mix two or three of the pairs in clear cups first and let students write their own observations. Salt and water and baking soda and vinegar are the easiest to set up.
Model one row
Fill in one row on the board before students start. The evidence cell is small, so steer them to a short phrase such as gas bubbles or salt can be evaporated back.
Salt back question
Pair question 2 with a dish of salt water left on a windowsill. Students watch the salt return, which shows that dissolving does not make a new substance.
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