Mixtures: Characteristic Properties - Discovery

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Students will be able to learn foundational vocabulary about characteristic properties and gain an interest in identifying substances.

Big Idea

Substances have characteristic properties that can be used to identify them.

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Purpose of Lesson:

 The purpose of this lesson is to give students an opportunity to experiment with different properties and using properties to identify substances.  Also, students will be doing a group writing for a peer audience.


Major Strategies to Watch for:

1)  Team writing-  Students will be writing predictions and conclusions as a team today and assessing the other conclusions to decide what makes a good piece of science writing. 

Ready. Set. Engage!

5 minutes

Learning Goal: Discover some properties of substances that can be used to sort and identify them. 

Opening Challenge: Two crowns are put before a king of Greece. One of them is pure gold, the other is made of a cheaper material, made to look like gold.  Without harming the crowns how could we tell which was which?

Problem of the day:  Put containers of flour, sugar, and corn starch on the table.  The question to the kids is, "How can you tell flour, sugar, and corn starch without tasting them?"  

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


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 such as Uncovering Student Ideas in Science Volume 1,2,3 and 4. In this prompt, "Is it matter" the probe is trying to uncover student beliefs about matter.  

What's really interesting about this student response is that the student definitely has some misconceptions that came out in the probe.  She lists dust, Jupiter, and atoms as matter but does not mark oxygen or steam.  My guess would be that this student has a common misbelief that gas is not made out matter. During this unit it will be important to give the students some tangible evidence about gas and matter.

Discovery Activity

10 minutes

Problem of the day:  Put containers of flour, sugar, salt, and corn starch on the table.  The question to the kids is, "How can you tell flour, sugar, and corn starch without tasting them?" 

Observation - I give the students the four powders and a magnifying lens.  I ask the students to use their observational skills to try to predict which powder is which. This is a very engaging and interesting experiment for students to do. I like to walk around and listen to their conversations and also make note of the different observations I hear them making.

Mini-lesson - Once the students have had 5 minutes to talk and think, I bring the class back together and write up what I heard them say. My goal of this mini lesson is to get to the idea of properties. I want the students to understand that all substances have different properties that can be used to identify them. I finish this out by stating that this task is difficult because all the powders share the same color (white). That means we are going to have to look at DIFFERENT properties that could be used to tell them apart.  .  

Prediction - I tell the students that they are working as a team today.  That means they will come up with 1 prediction for their team and 1 conclusion. I'm choosing to use the strategy of group writing as a scaffold for students that are still struggling and to put some peer accountability in place for the students that are proficient. I like to use miniature white boards. I put one whiteboard and one marker on the tables and ask students to write a GREAT prediction together. I walk around and listen to the conversations they are having as a table. If I see the point in stepping in to correct structure or format of the prediction I do.  

Experiment - Now, I give the students water, cups, and stir rods and tell them that they have time to experiment now and see if they can get evidence to support their predictions. The students start adding water to the cups and the substances and watching what happens. Generally there is enough background knowledge at the tables to be able to make some conclusions about each substance.

Conclusion - Once the students have completed their experiments, I tell them that they are going to write their conclusion together and that it will be displayed to the class.  

I make sure that the anchor chart with our sentence starters is visible and then give the students 5 minutes to write.

In this lab we found...

We know this because...

This makes sense because...

Evaluation - The students put the conclusions on the mini-white boards and then I have them bring the white boards up to the front of the room. We do a gallery walk looking at the different conclusions. I ask the teams to pick the conclusion that they think is the best. Once the students are back in their seats, I ask the students to share which conclusions they liked the best and what made those conclusions better than others. This practice of reading other conclusions and justifying what makes a good conclusion is a great strategy for increasing the students ability and motivation to write well.   

Vocabulary Discussion

15 minutes

Now that students are excited to learn about mixtures and know what they are going to learn about, it is a perfect time to introduce some vocabulary words.  I use a multimodality strategy to introduce only about five to seven words, and do this in collaborative groups of four with each person having an assigned job.  

1- Word person- states what they already know about the word or what the word means to them.

2- Image person- States what they think about the picture and what it means to them.  

3- Definition person- Reads the definition and states what it means to them.

4- Sentence Person- Reads the sentence and states what it means to them.  

I project the presentation on the board or put individual copies at the desks.  

I use a timer and a bell.  Each person gets 15 sec for their role.  In the beginning of the activity the students need to be trained on what to do and it helps to give them some sentence starters, like "This means..."  "When I hear this I think..."

After each person has rotated through their roles for the first word, I give the students 1-2 min of independent time to make their TIP charts (Term, Information, Picture) for that term. Then we move on as a class to the next term.  Later in the year, when students are familiar with the process this can be released to them to manage their time.  But in the beginning I manage the time to keep the class on track.

This work has meaning and purpose. Students keep these homemade glossaries in their folders and can use them on all the work we do in class including tests and quizzes.  This is a great resource for them to use the rest of the year!

Below is a picture of the slide for the word CHARACTERISTIC PROPERTY and a video of two student discussions.



2 minutes

Closing Statement: "Today we looked at properties that we would use to identify different substances. Next we will be exploring these properties in more depth."

Closing Question:  "How many pieces of evidence would you need to have to be SURE that the white powder is sugar instead of salt?  What would finally prove it to you?"

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.