Students will continue their observations from demonstrations set up the day before in Day 1 of this lesson plan.

Students will understand some of the weathering processes that influence the shape of the earth's crust.

5 minutes

**Review**

Gather students together in the gathering area. Ask students to share out their observations from the three demonstrations they completed in the previous lesson. Remind them that they were:

- Students filled an aluminum can and froze it over night. Remember, at this point, students have not seen the frozen can; they only observed the water as they filled the can.
- Students placed limestone in a cup of vinegar. Students made some immediate observations, but left the rock in the vinegar overnight and have not yet made additional observations.
- Students inscribed on a piece of sidewalk chalk, placed it in a baggie of sand, and shook the baggie. Students observed that the chalk inscription was dulled or removed as a result of the sand rubbing against it.

**Preview**

At this point, students are really wanting to see what happened to the can and the rocks in vinegar and are getting restless. Tell them that they will be making more observations today and coming up with some conclusions about weathering processes based on their observations.

I remind students over and over, that they cannot overdo the observations, but they can make too few. It is difficult to make conclusions about anything without enough evidence. The observations they made in the previous lesson and the observations they make in this lesson, will provide the basis for them to make some conclusions about weathering. I make the comparison to being a detective. Students need to gather clues from their demonstrations in order to make statements about how these processes work in the real world. To further my detective metaphor I hand out hand lenses to students to assist in their observations.

5 minutes

At this point, I ask students to go to their desks and look at their observations on the left side of their notebooks. I ask them to think about any questions they might have that they could answer during today’s lesson. I ask them to write those questions down at the bottom of the left hand page, under their observation sheets from the last lesson. I give students just a couple of minutes to read through their work and write a question. I then have them share with a shoulder partner, what their questions might be. I do not let students discuss answers at this point. This is just a time for sharing questions and stimulating thought.

20 minutes

Students come back together and find their partner from the previous lesson. I ask students to return to the same spot as they had worked, the previous lesson and I hand out the frozen cans. One partner retrieves the limestone and vinegar as well. Students take about 10 minutes to make their observations, first of the can, and then of the limestone. Students may see that the can has cracked or ripped open as a result of the increasing volume of the ice. They may also observe that the ice came up through the mouth of the can, despite the water being below the level of the mouth the previous day. Remind students to just make observations, not make conclusions.

Students may observe that the limestone chunk has reduced in size. They may observe that there are powdery deposits on the bottom of the cup.

After students have had a few moments to make their observations, call them back to the gathering area to talk about visual observations. So far, students have made written observations, now they will make a visual observation. Show students how to look through the hand lens at the limestone or the deposits. Show students that they can draw a circle and draw an enlarged picture of what they observe. I talk about the added details that I can see on the limestone chunk. I can see the jagged edges that the vinegar has created. I can see that the limestone deposits on the bottom of the cup, are granular. I show students how they can enhance their written observations and create visual observations to remind them later of what they saw. I have to have the discussion with students, that drawing observations and diagrams in science is not an art project. There is no creative license in these drawings. Students need to be as accurate as possible in their drawings. If they are coloring them, the colors need to be as close as possible, to what is observed.

Student pairs then return to their partnerships and complete an enlarged drawing from their hand lens. One partner can hold the lens while the other draws, and vice versa.

Once students have completed their drawings, gather them back together to discuss their findings.

15 minutes

Have students look back at their water and ice observations. Have them share out what they observed and ask them what they think water might do to a rock if it froze in a crevice. Students will brainstorm that, depending on the kind of rock, or how broken it was, the rock might crack further, or even break apart. Talk with students, about how mountains can be broken into boulders, can be broken into rocks, can be broken into small stones over time, through the freezing and melting of water. I tell students that there are two different types of weathering that we are exploring here: mechanical and chemical weathering. I ask them which kind they think the water weathering is. It is mechanical.

Move on to the limestone and vinegar. Have students share their observations and relate how this might work in the natural world in terms of weathering. Different natural substances mix with water and create acidic or basic solutions. These different solutions react differently on rock and dissolve them, weakening them, and finally destroying the rock. I ask students to classify this type of weathering – it is chemical.

Finally, ask students how they think the sand demonstration shows how weathering of this kind might occur in the natural environment. Ask students if they have ever been in a wind or sand storm and how that feels on their bodies. Have students relate this to the natural weathering process. Students classify this as mechanical weathering.

During this time, students can take notes in their notebooks as we are talking. They can add information they may have missed and they can write any questions they may have.

5 minutes

At this point students have constructed their own understanding of mechanical and chemical weathering. I ask them to go back to their seats and write their own definition of mechanical and chemical weathering. I ask them to share with a shoulder partner and then refine their definitions. The formal definitions will be explored in a different lesson.

5 minutes

At this point students have constructed their own understanding of mechanical and chemical weathering. I ask them to go back to their seats and write their own definition of mechanical and chemical weathering. I ask them to share with a shoulder partner and then refine their definitions. The formal definitions will be explored in a different lesson.