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Mystery Powder Investigation

Mystery time! Can you figure out what the four white substances are? This lesson can be used to show properties of difference substances or demonstrate differences between chemical and physical changes. Or it can just be for fun!

 

Lesson introduction:

I introduced this investigation to students after discussing chemical and physical properties of substances. For a “warm-up” I asked the students if they would ever accidentally mistake glue for milk. “Gross!” seemed to be the normal response. However, they easily listed several reasons – color, viscosity, density – it was clear which liquid students could drink. I even showed students what happens when you mix vinegar with both. Again, they were grossed out by the curdling milk.

Powder Investigation Set Up

Before class, I prepared the lab for the students. Containers A, B, C, D were filled with a different white powder. I also included a magnifying glass, beakers of water and vinegar and an eye dropper in their lab baskets. Sheets of foil were ready for them to use as “plates” or testing stations for their powders as well. I do use iodine, because this makes a chemical reaction with one of the powders, but I don’t let any of the students handle it. and we put any iodine mixture in separate spaces.

Materials used

I placed cornstarch in container A, salt in container B, baking soda in container C and sugar in container D. Feel free to use other white substances (safe ones please!), but I chose these four because I had them available in my classroom, and they are “safe” to use. Remember… middle schoolers want to eat everything. I’m not going to use things that might put them in danger! Each substance also has a unique reaction to at least one of the tests that students can choose from. Cornstarch changes the color of iodine, salt has crystal-like particles, baking soda fizzes with vinegar, and sugar tastes sweet!

Time to test!

Students test a powder by mixing vinegar and watching for changes that occur!

I let students choose which tests they would like to do with the substances. This includes mixing the substances with water, vinegar, or iodine, feeling the textures of each, using the magnifying glasses to observe the particles, and of course, the taste test (but I make them wait to do this last so it is not a giveaway!)

It is important to emphasize where students may see chemical changes happening. I ask the students these questions:

Are there bubbles?

Was there a color change?

Did something new form?

Can you get the substances back?

While testing, students fill out a chart like this: MysteryPowders. A “P” is placed in the blank if a physical change occurs and a “C” for any chemical changes.

Mystery Solved!

At the end of the time, I do tell the students what each of the substances were and they are excited whenever they guessed correctly!

Have fun investigating!

 

Density Rainbow – Using Colored Liquids to Explore Density

 

Density can be a tricky topic to teach. Students usually understand the concept of mass. They can feel the difference in something that is more massive (or heavy) than something else. Volume can be shown easily — which one is bigger? What takes up more space? When you put mass and volume together, sometimes students get mixed up. Does heavy always mean dense? Does little mean it will be less dense?

I have a fun activity that addresses some of these possible misconceptions. It uses simple materials and the results turn out beautifully (if students do the lab correctly!).

The set up:

This activity can be used before introducing density as an inquiry activity, or it can be used as a culminating activity. Since my sixth grade students have worked with density here and there, I incorporate the lab after our official density lesson. In the days before, we work on understanding what makes something dense, students practice calculating density and we may even play a few rounds of “Sink or Float.” (This is SO easy for any grade level and students love it! You can either do it as a demonstration, or have small groups do it. Just get a beaker filled with water and random items from the classroom and students must predict whether it will sink or float when dropped in the water!)

Density Rainbow

In the Density Rainbow activity, students find the density of five different liquids and pour them one at a time into a 100mL graduated cylinder. If the students are careful with their pouring, the result is a beautifully layered, colorful cylinder!

Before measuring a liquid, students predict where in the layer it will go. On the top? Bottom? Somewhere in the middle? Because I want to include the math, I make students find the mass and volume (about 15mL) of each liquid, and then calculate the density. Most students see the connection between the numbers they are getting and where the liquid will end up. The higher the density, the lower it will go in the cylinder.

Make sure you tell the students to pour each new liquid carefully! Tilt each cylinder and pour the liquid down the side of the 100mL cylinder SLOWLY! This is especially important with the rubbing alcohol. If students splash, the colors will get mixed and the final result won’t be as pretty.

Here are the liquids I use:

The liquids ready to go!
  • A) Water with green food coloring
  • B) Vegetable oil (no food coloring necessary – it won’t mix well anyway!)
  • C) Blue dish soap (you can use any color of dish soap you would like, but I like the blue best!
  • D) Corn syrup with purple food coloring (this gets very thick and sticky!
  • E) Rubbing alcohol with red food coloring.
I label all the cups so students know what liquid to use when.

Condiment cups are also extremely helpful in this activity. I can prep this lab the day before, pop the lids on all the liquids and not worry about spilling or evaporating. You can find the cups most grocery store in the paper goods aisle. If you have a Gordon Foods nearby, they have huge packs of them too!

The final product!

If you would like to use the handout that I do, here it is: Densityrainbow.doc

Notes and extensions:

Because I have students find the mass, they must first find the mass of the empty graduated cylinder they use to measure with. I am always double checking that they are subtracting the mass of the empty cylinder from the mass of the liquid plus the cylinder. If they don’t do this, their calculated density will be off!

Another extension I do is have the students change the volume and predict if the layers will still be the same. If we used 30 mL of vegetable oil and only 10 mL of water, what will happen? We do this as a group and it leads to the discussion of why adding MORE liquid does not change the density. A few of my quicker students pick up on the fact that when you increase volume, you are also increasing mass, so the density will be the same!

Have fun adding some color to your classroom! If you have any other ways you like to teach density, share them! I love introducing new activities to my classroom repertoire!

Cookie Dough Brownies

These brownies have a special place in my heart. The first time I tried making these, I was trying to impress a guy. It was the summer between my sophomore and junior year of college. My life long friend had roomed with “this guy” for the past year. Since we were all at the same school and hung out all the time, we had sort of ended the year with the possibility of getting to know each other more… whatever that meant! Anyway, classes were out for the summer and “this guy” was in town for a visit. The plan was for the two boys (my friend and “this guy”) to come over to my parents house to hang out before we met others to play frisbee golf. (Side note: I used to love playing frisbee golf but I was terrible at it!).

Of course I needed to make a snack.  I started searching all over the internet for ideas. Mind you, this was before Pinterest. Not much before, but all the same, no Pinterest. I don’t even know how to do anything without Pinterest anymore! But, I was in luck that day because I stumbled upon these doozies. Brownies, cookie dough, and chocolate. Um… yes? I also happened to know that cookie dough was an absolute favorite treat for one particular guy. Winning.

I made these brownies, served them, and loved them. Both boys asked for seconds. I was successful in my attempt to impress! In fact, fast forward three years and I married “this guy”. (Another side note: that friend ended up marrying MY college roommate. Isn’t it funny how life works out?) So ladies, try making these for that special someone in your life! Who knows what will happen!

Before getting on with the recipe, I must warn you: these brownies will kill any sort of diet you may be on! They are not meant to be healthy, but they are meant to be delicious. I typically make these as a special treat for get togethers or a special event.. Not just when they are going to sit around the house, because I would eat them all. The. Entire. Pan.

These start with your favorite brownie recipe. I start with a brownie mix (why go through the effort of brownies from scratch when I actually REALLY enjoy brownies from boxed mixes), but you can definitely make them from scratch if that is how you roll. Prepare these according to the directions and allow to cool to room temperature.

While you are waiting, you start the cookie dough. Mix the flour, butter, sugars, milk and vanilla together until smooth. Notice there are no eggs in here, so no worries about getting sick. Once the brownies are cooled, use a spatula to smooth the cookie dough over the brownies.

Finally, you melt the chocolate chips and oil. I usually use the microwave and stop every 20-30 seconds to stir. Once all the chips are melted, pour the chocolate over the cookie dough layer and smooth with a spatula. Place the brownies in the refrigerator to chill.

Before serving, let the brownies sit out for 5-10 minutes so the chocolate isn’t rock hard, however they should be stored in the refrigerator.

This recipe is for an 8×8 batch of brownies. If you would like a 9×13, just double the cookie dough and chocolate ingredients!

 

Cookie Dough Brownies
Ingredients
For Brownies:

  1 box brownie mix (8×8 or 9×9 pan size)**

            **If you want to do a 9×13 size, you can double the cookie dough and chocolate layer recipes!)

For Cookie Dough Layer:

½ Cup butter

½ cup brown sugar

¼ cup sugar

2 Tablespoons milk

1 teaspoon vanilla

1 cup flour

For chocolate topping:

1 cup chocolate chips

1 Tablespoon vegetable oil

Directions

Bake the brownies as directed on the box. Allow them to cool.

Cream butter and sugars together with a mixer. Add in the milk and vanilla.

Add the flour a little bit at a time and mix until well blended.

Spread the mixture over the cooled brownies

Mix the chocolate chips and vegetable oil in a microwavable bowl. Heat in microwave for 30 seconds at a time, mixing in between until the chocolate is melted.

Spread the melted chocolate over the cookie dough layer. Let the layer cool and harden.

 

Store in the refrigerator.

Gummy Bear Osmosis


I love working with food whenever I can in my science classroom. And I especially like using candy. You pull out a single M&M, and all eyes are on you. When you tell them they will be using any type of candy to do a lab experiment, they can’t wait to get started. Obviously, the first question I get is “Can we eat this?” Now, I’ve taught middle school students awhile now so I am extremely aware of the fact that even if I say “No,” students will still sneak in a lick or nibble! I’ve learned to keep a few extra samples of whatever food I’m using so at the end of class, students can get their candy fix!

In my seventh grade class, we have been discussing cells and how materials move in and out of the cell membrane through passive transport. This leads to discussing the concepts of diffusion and osmosis. When I found a lab that used candy to demonstrate the concept of osmosis, I knew it was a winner! I have been using a lab I found on this blog which is site that has many other resources and great ideas for teaching science. The link to the pdf file which I have used and adapted from year to year is linked below.

Day One

The lab must be done in two days. First, students will take a gummy bear and measure the height, width and mass. Next, the gummy bear is placed in a beaker of distilled water overnight. It’s always amusing to hear the predictions of what will happen. Without fail, I get at least one prediction of “It’s gonna explode!” What is it with science class and students’ expectations of exploding objects??

Students use electronic scales to find mass
I love using the triple-beam balance and so do the students!
Day Two

The students come in super excited to check out their bear the next day. Of course, half the groups have named their little gelatin blobs and are thrilled/mortified to see that their gummy babies grew overnight! Students check the height, mass and width again and find the percent change. (Always love the math tie in!) A graph is made and written responses are required. Then at least one student in every group tries to slurp down the bear or the water left behind. Disgusting, but amusing. (And don’t worry, I do not promote this, but it’s not worth fighting. I just make sure the beakers are clean and safe!)

While groups are working, I try to connect with them to see why they think the gummy bear grew to the size it did. Most students have no issue seeing the connection to osmosis! (Let’s be honest… there are always one or two that still remain oblivious to the fact that we science teachers DO have reasons for activities we choose to do in the classroom!) Other questions that can be used to dig deeper are:

“If we left the gummy bear in the beaker another night, would it continue to grow even bigger?”
“What might happen if the bear was left in salt water?”
“How might we make this process faster or slower?”

If you were to do a little google search on Gummy Bear Osmosis you can find many ideas and variations of how this may work in your classroom! This is the lab I’ve used and I encourage you to use it and check out the science blog here too! Thanks to “Mr. Poach” for creating this awesome lab packet! Happy diffusing!!