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Hello! I am teaching a lesson on float/sink for my first grade class. I know that my students don't need to be able to explain why an object floats or sinks but I'm not sure how in depth I need to go. Should I stop at 'this floats, this sinks' and show them the objects in a tub of water or should I go farther and try to explain because it is lighter/heavier than water?
Thanks All!
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Hi Joy!
I am a student at the University of Northern Iowa, something we discuss in a lot of our classes is explaining the 'why' to students. I think it is important to explain to students why things sink or float, but that is something that you can simplify. I would suggest refrain from using the phrase 'more dense' or 'less dense' I think students are going to grasp a better understanding of why things sink and float if they are given a little more information rather than 'because I said.' Giving students something to think about can allow them to create their own educated guess of future objects. For instance, you can give examples of objects which float and which sink and give an explaination (something simple) After, choose another object and allow them to choose if it would sink or float!
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Great question! Try ngss.nsta.org and search for lessons that address this. What does your standard say about addressing floating or sinking?
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I would suggest going a little farther and actually explaining why the object floats/sinks. If the students do not have an explanation, then they will assume that everything that looks like the items that sunk will sink and every item that looked like the item that was floating will float. It will allow the students to also apply the knowledge to other science concepts.
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It is important to explain to students why objects float or sink. below is a link with fun activities for objects that float or sink along with important vocabulary students should know:
https://easyscienceforkids.com/all-about-sink-and-float/
This website also has a video of “Why do things float?” followed by sink and float questions and answers section.
It is important that students have a good understanding of why objects float and sink by using different vocabulary and going more in-depth with the lesson. You could incorporate experiments for the students with a worksheet consisting of objects that sink and float have the students explain why. Then have a class discussion on the responses.
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I personally think its okay to just stop at showing them that it floats or sinks.
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I agree that density is a difficult concept for young children to understand, or even for adults to explain to ourselves, and it is not necessary to explain it in a beginning exploration of why objects float or sink. In addition to the relative density of the objects, the shape also plays a part in whether or not an object floats. Multiple experiences over time--days and weeks and months--will help children develop their ideas about what makes an object sink or float.
One misconception that people often hold is that heavy objects will sink. Involve children in comparing the weight of objects, either in their hands or using a balance. Choose objects that are small and lightweight but sink (small coin or stone) and some that are larger and heavier (orange or pumpkin) for children to compare and test for float-ability. Have them try two objects made of the same material but of different sizes--a small and a large block of wood. Test the objects yourself first! Each time they test an object, have children talk about the attributes of the object beforehand, including color, shape, size, weight, texture, and material. This will help them see that some attributes, such as color, are not related to whether or not the object floats.
Best wishes,
Peggy
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Excellent, Peggy! The misconceptions of 'heavy' or 'light' being the cause of bouyancy is probably the largest to overcome.
Near the end of your lessons I would perhaps even give them small squares of aluminum foil to rattle their brains! They might be able to float a small flat piece (surface tension), but roll it into a ball and it will will sink. Form it into a boat-like cup or box and they can float it! Pour water into the boat and it will sink! See if they make the connection between shape and sinking/floating. The explanation hurts many adult brains so you don't have to go there.
Good luck!
Gabe
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Hi Peggy. I taught in an alternative education school and it was always a challenge engaging the kids but these buoyancy activities were always successful: Gabe's aluminum boats are great. We had the kids measure out identical pieces of aluminum foil - index card size and had them make boats, set them afloat in a small aquarium and then had a contest to see how many pennies they could get in them before they would sink.
Floating paper clips. Yes it works but it's tricky. I usually used a fork under the paper clip to get it perfectly flat and with the least disturbance to the surface tension. If they look carefully, they can see the indentitation in the surface tension.
I introduced density as part of this activity using a digital scale and displacement and introduced Archimedes Principle.
We even compared the density of sea water and fresh water by making sea water using aquarium salt and coloring it with food coloring and introducing the colored salt water into the fresh water in the aquarium. It goes straight to the bottom and makes bands of water. You can even talk about how the oceans circulate nutrients because of the layering of different concentrations of salt.
We were pretty close to a small stream, so we also did a field trip and watched water striders 'walk' on the surface tension.
Best of luck!
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Hi James,
Those sound like great explorations for the upper elementary and middle school students.
Best wishes,
Peggy
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Thanks, Peggy. Believe me, they were fun for me, too.
jj
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Best part of teaching--sharing the joy and excitment of exploration with children of any age!
Peggy
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I think that it would be best to explain to them why things sink or float. The students will certainly be curious to why things sink or float whenever you show them. Answering the why will hopefully help satisfy your students curiousity!
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I would suggest going a little further and explaining the why part of the lesson. It is always good to explain 'why' to the students because although they may not ask you, they are always going to be curious. The why explanation also helps the students apply knowledge to other science concepts and other concepts in life.
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Please don't just explain to them - Too many of my high school kids want me to tell them the answer rather than do the experiment to figure it out themselves. (In other words, they don't want to *do* science.) Having them do the weight/ shape vs float experiment - with appropriate discussion - builds much stronger knowledge & science skills. (Full disclosure: Carefully leading discussions is hard & I'm still not great at it.)
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I agree. Let your students do the science and think aloud about the why. There are many good suggestions above in giving students different matierials and same materials, different sizes. I have had college students in chemistry who still are not comfortable with density-having the students participate in the activity of float/sink at first grade starts building a foundation of knowledge.
Perhaps have the students predict what will and won't sink prior to testing will increase engagement andd help students ask questions of their own when their predictions are 1. incorrect and 2. different from other students. Giving students the opportunity to drive the discussion, even at 1st grade helps build and maintain their curosity!
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