Physical Properties and Changes in Nature

Before diving into my chemistry unit, I always felt that it was really important for students to have a strong understanding of physical properties and physical changes.

For example, physical changes are much more than just tearing paper or crushing cans. Processes like weather, ocean currents and rock erosion literally depend on physical changes. Also, giving students the chance to measure physical properties helps them get comfortable with concepts like mass, volume, and density - topics found in almost every field of science! 

Here are a couple creative lesson ideas to get your students appreciating how physical changes shape our natural world. 🌍 

⚗️Changing the density of water: When introducing density to middle schoolers, tossing random items into a tub of water always makes a splash. The only thing is, most of the water on our planet is not fresh! 

It could be worthwhile for students to explore how creating saltwater mixtures impacts the density of the liquid. If students took an item that mostly floats in freshwater, like a small pumpkin, and dumped it into a container of salt water, what differences would they see?

Could students model how a boat might behave in freshwater, brackish water, and the super salty water of the Arctic Ocean? If students had beakers filled with 100 mL of water and dissolved varying amounts of salt into each, could they manually calculate the densities of each liquid? Having some salt, water, and a stirring rod can be the start of some great investigations!

⚗️Observing the effects of temperature changes:

Students can observe how changing the temperature of liquid water can have some pretty dramatic effects. One idea is to take two beakers of room temperature water. Students can add 50 mL of very cold water, ed blue, to one beaker and 50 mL of very hot water, dyed red, to the other. How do these systems compare?

You could extend this concept out to some real world examples too. In one example, scientists say that warmer surface ocean temperatures are not good for ocean currents. In another example, when the nights get cool near a pond or lake, the water body starts to circulate, churning up nutrients from the bottom. Students can research these phenomena and draw some great conclusions about the importance of physical changes to currents.

Here's something I've noticed: it's usually when they're learning about phase changes that students realize the convenience of reading temperatures in degrees Celsius. Water freezes at 0 and boils at 100 - how easy is that to remember?!

⚗️Geology connections: I recently read an article where students looked at how the shape and position of Niagara Falls has changed over time. How is it possible that the largest waterfall in North America could move?!

Turns out, the rock structure beneath the falls is experiencing all sorts of physical changes on a constant basis. This includes rocks breaking in the freeze/thaw cycle or the weathering of materials because of the flow of water. 

With a few simple materials, students can model this weathering process.

• First, put students into groups and give each group a set of materials in which some of the materials will dissolve in water (sugar cubes, chalk, salt, etc.). The other materials should be rocks or gravel that will not dissolve.
• Have students stack the materials in a plastic container to make a "landform" that they think will hold out against running water. They have to use all the materials, though - including the ones that dissolve!
• Next, have students guess how many beakers of water the structure will withstand being poured over it before it collapses.
• Finally, have the students pour water onto the structure (the container should be big enough to catch the water). How close were their guesses? Which structures lasted the longest, and why? Students will start to see how physical changes and gravity can change a massive land feature over time. 

Hope some of these ideas inspire you! Physical changes may seem simple, but they have a huge impact on our surroundings!

If you're looking for some resources on physical and chemical changes with minimal prep, check out these activities:

🧪 Physical and Chemical Changes Complete Lesson Plan

🧪 Physical and Chemical Changes Escape Room

🧪 Physical and Chemical Changes Reading Comprehension

🧪 Physical and Chemical Changes Writing Prompt

🧪 Physical and Chemical Changes Station Lab

🧪 Physical and Chemical Changes Amazing Anchor Phenomenon