Mixtures: Characteristic Properties - Pre-requisite

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Students will be able to understand basic concepts of matter like mass, volume, and conservation of mass.

Big Idea

Matter can change shape (volume) but not amount (mass).

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Purpose of Lesson:

The purpose of this lesson is to reinforce with students the law of conservation of mass in a general way.  I used to do this day over a period of a week and have students write lab reports for each lab. This is no longer possible because of district constraints, but I have added a note in the mini- experiment section explaining this and attaching the labs if it is possible for you.  I run this as a center set-up and take two days to do this lesson.  The timing I use is below.

Day 1

Hook- 5min

Probe- 5 min

Intro- 7 min

Centers (2 rounds) 30 min

Closure- 3 min

Day 2

Intro 5 min

Probe- 5min

Centers (2 rounds) 30 min

Conclusion 10 min 

Closure 3min


Major Strategy to Watch for:

1) Center set-up- Using centers can compact the amount of time needed for labs as students work quickly at each setup.

2) Tree Map- Students make a tree map to store their information during a mini-lecture from me that summarizes the learning. 

Ready. Set. Engage!

5 minutes

Learning Goal: Understand important ideas about matter.

Opening Question: When you dissolve lemonade powder in water, what happens to it?  Would it weigh the same before an after?

Students record their opening question on their learning goal sheet and are ready to start class 3 min after the bell has rung.  I reward students who get started early with ROCK STAR SCIENTIST tickets.  

Follow the links to learn more about the beginning of class strategies and ROCK STAR scientist tickets

Probe: A Pre-assessment

5 minutes

I start each unit with a pre-assessment to open up the student thinking and help uncover misconceptions. This allows be to modify my teaching, compact curriculum, form appropriate groups, and measure growth. By far the best formative probes I've found are by Page Keeley. She's written several books of probes including Uncovering Student Ideas in Science Volume 1, 2, 3 and 4. 

The student who answered this probe is a little confused.  Her writing indicates that she might be willing to believe that the cookie has the same mass...but she continues to qualify that answer.  By looking at her probe, I believe she has a misconception about mass and is struggling to let go of it.  This lab day might be the experience she needs to gain a deeper understanding of mass.


5 minutes

This is a video of ice freezing.  I know that sounds about as interesting as watching paint dry...but it is surprisingly cool!  I introduce the video by stating that we are going to watch a video of water freezing and ask the students what they will expect to see.  I project the video on a whiteboard so that I can mark the place on the glass where the water was originally and students can see that the volume changes.  

When we are done with the video I ask the students questions, such as:

  • What happened to the volume of the water? (You have to tell me more than, "It's changed.")
  • Did the amount of water change? How do you know?
  • Do you think the mass of water changed? Why?

Center Mini-Experiments

60 minutes

Today's labs are going to be done in centers.   There are four centers.

1.  Lemonade stand-  Students use lemonade powder to observe dissolving and think about mass.

2. Crushed Ice- Students find the mass before and after ice melts and discuss whether there was a change in mass.

3. Clay Shapes- Students reshape clay three times to see whether reshaping changes the mass.

4. Chemical Reaction- Students react NAI and PbNO3 and see whether a chemical reaction effects the mass.  NOTE- be sure you know how to dispose of hazardous waste for this experiment.  If not you can use a you tube video instead.  See below

Students will use this tree map to record their data and observations at each center.  I like to give students 10-15 min at each center.  It is important to norm the students before sending them to the centers. I do this by drawing the students' attention to our center work norms and stressing that in centers we need to be focused on completing our work and doing our best thinking.  My center rules are;

1.  Follow the directions at each center exactly.  Don't add or leave anything out.

2.  Collaborate with the people in your group.

3.  Concentrate on learning.  

I also like to preview each of the centers before setting the students free.  This is important because it gives students a hook into each activity and provides clarity and direction.  A video of my intro on the centers is below and the power point is attached. 

Once the students are ready I assign them to centers through random selection.  I chose random groups today because it is nice for the students to get to work with new people and it isn't necessary for this activity to be grouped heterogeneously or homogeneously.  

While the students are working, I stay towards the middle of the room with the materials I need and keep a close eye on the activities going on.  I use an online timer on the board so that students can manage their time.  

**** Pacing note- In past years I have done each of these experiments on separate days, with students performing the experiments and writing up a lab report with a histogram.  I absolutely think this is a great way to learn conservation of mass, graphing, and lab procedure.  I no longer have time to do this because of district constraints, but I am including the lab write-ups that I have used.***

Important Concepts Mini-lecture

10 minutes

The purpose of this section is to tie the concepts of the min-labs together and allow the students to store their processing in a tree map.

I start this section by letting students first decompress the labs at their work tables.  These are the guiding questions that I ask students to use in their discussions.

1.  Go through each activity, describe it, and state the big idea.

2.  What did you learn about mass in these labs?

3.  The Law of Conservation of Mass states that matter can not be created or destroyed.  How do our activities support this statement.

Once the students have had a chance to talk, I put a completed tree map on the board and walk through the story line with the students.  I want them to see how mass stayed the same in each experiment even if the appearance of the matter changed.  A video of this mini lecture is below.  

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2 minutes

Closing Statement: "Today we looked at how matter can change shape, but no matter what happens to the volume, the mass stays the same.  This is one of the laws of nature, that matter cannot be created or destroyed."

Closing Question:  "One of the laws of nature is that Matter cannot be created or destroyed.  How do our experiments today support this law."  Complete the probe using this information. 

Below is an attached scan of a student probe.  

Closure depends greatly on timing and is not as easy to plan in advance as opening.  You can find more information about how I manage closure here.