Simple lab using markers, water, jelly jar, and coffee filter paper. (You can use rubbing alcohol instead of water, results are similar). Shows how you can physically separate a mixture, as well as demonstrate capillary action.
Tag Archives: mixtures
Hot and Cold Water: Mixing
Tried this demonstration at home before I try it in the classroom. It shows how hot and cold water can both mix or not mix together. I used blue food coloring for cold water and yellow food coloring for hot water (didn’t have red handy at home, but will use red at school). It also demonstrates a great surface tension trick with the upside down jar of water and a playing card. I use playing cards b/c the waxy surface works best for either demo. (I used old glass jelly jars, we go through a lot of jelly at my house. I run them in the dishwasher and save them for science experiments.)
For this demo, I am not going to tell the kids that I am using cold and hot water. Want to see if they can figure it out 
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When the cold blue water is on the top, and the hot yellow water in on the bottom, as soon as you pull the card away, they mix and the water turns green in both jars. (purple if you use red). When the cold water is on the bottom, and the hot water is on the top, when you take the card away, it does NOT mix like before. there may be a small zone of mixing where the two meet. Great discussion about density and the effects of temperature on the movement of the water particles.
It is a pretty cool trick and I think the kids will love it when they see it, only b/c it is so unexpected for them .
For more information, check out this website: http://www.exploratorium.edu/science_explorer/watertrick.html
Chromatography
Just wanted to post this quickly. We completed a chromatography lab using coffee filter paper and washable markers. We were able to show how to physically separate a mixture. Each student received one piece of filter paper with a black marker spot on it. Since I only had one black marker, I prepared all the filter papers. It was easy and quick to do, I could prepare three at a time, the marker bleeds through from the top layer. I wanted to use the black as a control so that all the students could have a reference. Each student then chose two colors to place next to the black dot.
You can use water if you don’t have rubbing alcohol, it doesn’t really change the results much. Each student had a paper cup and poured in about 15 mL of water, it didn’t have to be exact. They slowly placed their filter paper into the cup, being careful not to let the paper fall into the cup. It contaminates the water and the student will have to start all over again with a new piece and clean water. I also showed them how to fold over the top of the paper over the lip of the cup to help it stay in place.
Students were to represent what their filter paper looked like in their lab sheet and make observations. Once they were done, we let the papers dry (have students write their names in pencil at the top of the filter paper) and then attached it into their notebooks. Analysis questions were written into the right page of their notebook.
Handout:
Rainbow Lab
One of my favorite activities is the Rainbow Lab. This is a great activity for practicing their measurement skills, ability to follow directions, precision, working as a group, following correct lab procedures, equipment use and identification, solutions, mixtures, physical changes, problem solving, etc… It’s chock-full of stuff.
What I also love about this lab is the importance of not fudging your data, and reporting what actually happened in the lab, not what you think should have happened, or covering up “mistakes”. If one of your lab partners spilled the yellow, you have to account for the loss of the yellow in your data, how it affected your measurements, etc. What do we do if someone breaks a test tube? What if I spilled something onto my clothes or skin? How can I avoid contamination of my colors when using only one graduated cylinder?
To set up this lab, I use a concentration of 5 drops of food coloring per 100 mL of water. Each group gets one set of test tubes, a beaker for waste water, a beaker of clean water, a pipette, 25 mL graduated cylinder, 3 flasks, and stoppers. The stoppers are important because if a group does not finish the experiment in one class and has to continue the next day, it prevents evaporation – which would alter their data.
Before I start a lab, we always meet as a group, usually around a table with one set-up. I explained the lab, and talked about what a solution is, and what the solutes and solvents were for this lab. We talked about how this was a homogeneous solution, the food coloring does not settle out over time.
I stress the importance of avoiding contamination, or the “Big C”. We don’t want colors mixing together and making muddy colors. I show them how to rinse out their graduated cylinder between measurements, and dumping the “dirty” water into the waste water beaker. I show them how to twist the graduated cylinder as they pour, this cleans the sides of any food coloring residue. I also reminded them about the meniscus when reading measurements.
When completed, the measurements for each test tube should read A-F: 10, 11, 10, 11, 10, 11 with a total of 63 mL. They also have to account for having more or less than 63 mL, where did the extra volume come from if they went over? Where did it go if they were short?
I don’t tell the kids how much they should have had until the next day, when we go over the analysis questions.
Handout:
- Rainbow Lab- updated for the interactive notebook
Lego Lab
To continue our exploration of elements, compounds, and mixtures, I set up an activity using Legos to model and further explore this concept. Each group of two students received 12 Legos in a quart sized baggie with 3 different colors, 4 pieces of each color. I explained how each Lego represents one atom. Just like real atoms, some Legos were bigger than others. Each color represented an atom of a different element. We reviewed the definitions for compounds and mixtures before we started the activity.
What I really liked about this activity was that it took an abstract concept and made it concrete for them, they could handle the Legos, see the different colors, they could see how elements create compounds, snapping the Legos together represented chemical bonds, and so forth. You could see the “a-ha” moments. The kids also had fun playing with the Legos. One boy made a little robot and asked – “Is this a compound?” And I asked, “Does it have 2 or more different elements bonded together?” And he said ”Yes!”, and I said, “Well, then it’s a compound! Good job!”
After the activity, to reinforce the concepts, I had a cut’n paste activity and review sheet. They had to have the cut’n paste checked before they glued it in. To borrow a quote from wood shop, I ask them to “dry fit” the pieces before they glued anything.
Handouts:
Elements, Compounds, & Mixtures Notes/PPT Activity
I wanted to make my power point presentation an interactive and fun activity that would allow the kids to practice categorizing elements, compounds, and mixtures. We have been talking about properties of matter for a while and we are now starting to get into the meat of Chemistry with an introduction to how matter is classified. Soon we will explore elements and compounds in more depth.
Using the power point, we had a class discussion to introduce the topic. We went through the first few slides together. Each lab table was then given a set of large 4×6 index cards that are multicolored, each index card was two-toned, green on the front, red on the back, and blue on the front, and yellow on the back. The “E” stood for element, “C” for compound, “M” for mixture, and “?” for if they were not sure and could not decide. Groups of 3-4 worked well for this activity. I gave the index cards to two students in each group and they were in charge of holding the card up to show their answer.
I showed the first picture, and as a group, they had to decide if the item shown was made of an element, compound, or mixture. Once they decided on an answer, they were to hold up the corresponding card. Once everyone picked an answer, I revealed the correct answer and discussed why that item was an element, compound, or mixture. We didn’t keep score, but they were happy if they got an answer correct. The kids were very engaged and it was a simple way to make a power point presentation a little more interactive. We would then write down the answer into their notes under the corresponding column so they can see how the items are categorized.
After the ppt, we did the concept map together. I broke it into 1-2 minute chunks of time where they had to determine what went on the first level, then we would go over the answer. Another 1-2 minutes to decide what went on the second level, then discussed the answer, and so forth down the line until all the words were used from the word bank. This was a good closure activity to process the information from their notes and the activity.
Handouts/Resources:
