Changes in Matter

Shea Ryan

Overview/rationale

In previous units, students learned properties of matter as well as how to measure these properties. This lesson module would fall near the beginning of the Changes in Matter unit. At this point, we would have already covered the states of matter and phase changes in detail. We focused on how this type of change between states is an example of a physical change. Therefore, in this module, I will introduce the concept of chemical changes. The world is filled with examples and evidence of physical and chemical changes; rock weathering is certainly one of them. I will share my experience at Petrified Forest National Park with my students to engage their interest. Then in order to reinforce their learning about physical and chemical changes, they will do a stations lab in which they look more closely at weathering. As an educator, I have noticed that students tend to show better understanding and retention of concepts when they are able to see how it plays out in the real world. That is the essence of this lesson module, which ties earth science to physical science.

Learning Goals

In this module, students will:

·  Know that there are two types of changes in matter – chemical (new substance formed) and physical (only appearance changes).

·  Know that complex interrelationships exist between Earth’s structure (landforms , rocks, minerals, soils) and natural processes over time that are constructive (mountain building, volcanic activity, deposition) and destructive (landslides, weathering, earthquakes, erosion) processes. (From CO Draft Science Standards May 2009)

Learning Objectives

By the end of this module, students will be able to:

·  Distinguish between physical and chemical changes.

·  Describe what a petroglyph is and identify factors that can impact them.

·  Collect data and draw conclusions from observations.

·  Observe and recognize different ways that rocks can weather and identify them as physical or chemical changes.

Lesson Sequence and overview

Lesson 1 – Introduction to chemical changes; compare to previous learning about physical changes

Lesson 2 – Petrified Forest National Park – Introduction to petroglyphs and weathering

Lesson 3 – Physical and chemical weathering of rocks

Lesson Details

Lesson 1

  1. Warm Up/Attention getter: I will show them a piece of modeling clay and ask for a volunteer to mold into their favorite animal. Once the creature has been created I will walk around and show everyone their masterpiece.

Me: “Think back to what you have learned about physical changes. What does it mean to change matter physically again?”

Random student: “It means that you only change its appearance but it is still the same substance.”

Me: “Excellent! Now can you suggest a way that I can change this animal sculpture physically?”

Student: “Pound it with something to change its shape” or “Rip it into tiny little pieces”

Me: “Get a load of this! S/He wants to pummel your adorable animal! You are absolutely right. Smashing it doesn’t change the fact that it is still a lump of clay. It’ll just look different. As long as it’s okay with ______, would you please do the honors?” (I hand the student a dictionary so they can use it to smash the figurine.)

Then I would tell them that there is another type of change in matter – one in which the type of substance does change. I have them think quietly and record ideas as to what they could do (hypothetically of course) to the clay to make it form a new substance altogether. After a few minutes, share ideas.

  1. The class will read a short passage together that describes chemical changes. We will take notes as a class.
  2. I will show them a video for a song about chemical changes on Teacher Tube. (It is an odd play on anime that I think is amusing.) Then I will show a very short clip showing how molecules behave during a physical and chemical change. This will serve as a reminder that new substances only form during chemical changes which happens at the molecular level.
  3. I will then pass out mini whiteboards and markers to each student so we can practice categorizing changes as chemical or physical. On the SmartBoard, I created a sorting activity entitled “Name That Change in Matter!”. In it, I give pictures and description of different changes in matter. They have to write which they think it is an example of on their individual whiteboards while I go around and check as well as help kids who are struggling.
  4. Exit Slip: Think of your favorite food and draw one way that you could change it physically and one way that you could change it chemically.


Lesson 2

  1. Warm-up: Students will walk in and see a Venn diagram on the board. They have to fill in similarities, differences, and examples of physical and chemical changes. I will ask students to write their ideas in the diagram on the board.
  2. After the warm up, I will tell them that such changes are affecting materials all around them. We have already explored phase changes and over the next couple of weeks we will look at chemical reactions. However, other examples also include anything from a crack in the sidewalk to a fault in a mountain. Weathering is this process when the form of rock or other materials is altered. To help all students (especially for students for whom English is a second language), I will share with them images of weathered rock and building materials. For each we will discuss whether they are examples of physical changes in appearance or if they are due to chemical reactions on the rock.
  3. After I feel that they have some sort of an understanding of weathering, I will tell them about my work with the RASI group this summer and show them the PowerPoint we made for the cohort meetings. As a class, we will brainstorm a list of factors that can make petroglyphs vulnerable to weathering and therefore damage.
  4. Exit Slip: For fun, students will have the last 10 minutes of class to create a “petroglyph” that would indicate something about their life – hobby, everyday activity, interests, food, family traditions, etc. I will post these in the hall and around the room.

Lesson 3 (2 class periods)

  1. Warm-up: Make a list of things you remember from yesterday’s class.
  2. Students will complete a stations lab in which they have the opportunity to see simulations of seven of the most common causes of weathering. The stations will be scattered around the room. The procedure and questions will be included on sheets at each station. They will have 10-15 minutes to complete each station and answer the questions in their lab notebooks. At the end of the second class period, I will organize the students into new groups to discuss the seven stations. Which activities demonstrated chemical weathering? Which showed physical weathering? How do they know? (One person from each original group will form a group with one student from each of the other groups. This way, students cannot rely on another group member to share their original group’s observations.)

The stations will be as follows:

Station 1 – Effect of Water on Iron-Rich Rocks

Station 2 – Effect of Freezing on Water

Station 3 – Effect of Water on Rocks

Station 4 – Effect of Acid Rain on Copper

Station 5 – Effect of Gravel on Sugar Cubes

Station 6 – Effect of Rock Size on Weathering Rate

Station 7 – Effect of Acid Rain on Limestone

Assessment

Students will be assessed multiple times throughout the module. Formative assessments include warm-ups, exit slips, the whiteboard activity, and their lab journals. Of course, I will also determine the extent of understanding by listening in on group discussions during the stations lab. I can then try to clarify misunderstandings during the post-lab discussion with the whole class. I will use a summative assessment to evaluate students’ mastery of the learning objectives for this module. The summative assessment will be a homework assignment in which they have to find and document three pieces of evidence of weathering- buildings, rock, etc. They must explain why it is an appropriate example and what kind it is.

Attachments:

·  PowerPoint containing images of different types of weathering

·  Stations Lab handout