Gases & Just how much water exists on Earth?

After our cloud in a bottle demonstration and discussions of the water cycle, students seemed to want to dive deeper into understanding water vapor and gases in general. This is an awesome initiative for a mixed age group of K-2nd graders. In looking into possible hands-on experiments for them to try, I found an easy and fun demonstration that uses the some of the same inexpensive materials we still had from our previous lesson. We used three empty plastic soda bottles filled about half way with warm water and several tablespoons of yeast. To turn it into an experiment rather than a demonstration, we fed each bottle of yeast/water with different nutrients: sugar, flour, or nothing at all. We placed thin walled balloons over the opening and waited. We all made predictions about which bottle would start to inflate the balloon first. The students had just recently baked pretzels with their teachers so we talked about how long they had waited for the dough to rise and what each of the ingredients were in that case.

We were very excited to see the balloons expand ever so slightly (in two of the three bottles) as we swirled the bottles to mix the bubbling yeast, sugar, and warm water. Some of our discussion as we waited included answering:

1. What caused the balloon to inflate?

2. What was the purpose of the balloon?

3. Which nutrient resulted in the best yeast growth? The most gas?

4. Do yeast require a food source to grow?

5. How does this relate to water vapor?

The following week we began by talking about percentages. We "made" a pizza (colored drawing on the board) and divided it up into quadrants - based on specific toppings that each of the students requested: plain cheese, or veggies with cheese, or meat with cheese, or no-cheese at all. Together we figured out the percentage of each favorite topping type on our pie and accordingly divided it up among the students. 

This provided us with a relatively standard starting point from which all students could move into a discussion of the overall water (percentages of: salt, fresh, frozen, potable) on our planet. Estimated at 97% ocean, 3% fresh water. 

To demonstrate we first filled a large graduated cylinder with 1000mL of water, this to represent all the water (in all forms) on the planet. Then we poured off 30mL of water into another cylinder, or 3% of the total water to represent earths fresh water. To the remaining 970mL we added salt, to represent the ocean, 97% undrinkable water. 

Next, using our globe, we asked the students what they noticed about the earth's poles...they are covered in snow! Almost 80% of the earth's fresh water is frozen in ice caps and glaciers. So we poured 6mL, from our 30mL of all fresh water, into another glass to represent non-frozen water. 

Using an eyedropper the students then removed a single drop of fresh water (from our 6mL) into a drinking glass, finally to represent clean, fresh, non-polluted water, 0.003% of the total! 

Students concluded that a very small amount of water is available to humans, but we stressed that this single drop is just a representation of the larger volume of water available to us on a global scale, remember we started with a pretend volume, 1000mL -- scientists estimate that there are over 300 million trillion gallons of water (in all forms) on earth, an inconceivable amount to picture even for an adult!

The water cycle

Last week we began talking about the water cycle, particularly as it relates to cloud formation. The students brought up many excellent questions for us to explore as we begin our spring semester on the topic of water. Here are just a few:

·      How are clouds made?

·      How is water made?

·      How does water get clean?

·      How does water evaporate? What is evaporation?

·      What is water vapor?

·      How does water get in the pond?

·      How does water stay in a pond?

·      How and when does rain happen?

·      How can animals live in water?

·      Why do we need water?

I was also thrilled to hear they were thinking about experiments that they want to try:

·      Will snow melt faster in the sun or shade?

·      Where is the best spot to collect the most water?

·      How long does it take water to evaporate?

·      Will snow melt faster than ice?

·      Which melts faster when you add water to it, ice or snow?

·      What melts faster, packed or unpacked snow? 

In order to introduce the water cycle we drew a circular diagram with arrows depicting land with a pool of water (rivers, ocean, lakes), the sun and clouds, and from the clouds, rain drops. The students were already aware of the terms: collection,  precipitation, condensation, and evaporation but not precisely what they meant. So we decided to go through each of the cycle terms together. 

For visualizing evaporation we each put a small squeeze of hand sanitizer onto our hands and talked about how it felt: "wet, squishy, sticky, cold". Then some of us waved our hands through the air to simulate wind and students described how our hands felt: "dry!". They decided that the hand sanitizer had evaporated from their hands. And we talked about how the sun does a similar process, as it warms the water that is collected on the land (in our rivers, oceans, lakes) it causes some portion of the water to evaporate and that means that water vapor - gas that we can't see - is able to rise up into the sky.  So what happens to water vapor as it rises into the atmosphere, I asked them. At a certain level in the sky the air temperature changes (many students were familiar with this thanks to being well-seasoned travelers; having seen water condensation on the windows of an airplane in flight) and at that high altitude, those vapors turn into tiny water droplets (and with dust) collect to form clouds. 

This came back to one of their original questions - How and when does rain happen? We talked about how on some days it is cloudy but also sunny and the shape and color of those clouds may appear fluffy and white, while on other days, clouds may appear quite grey even black.  Intuitively is seemed, they decided that on the grey-cloud days it was more likely to rain. I explained that as the clouds get more and more full of tiny droplets of water, they may appear grey at the bottom, at some point the cloud can't hold anymore water droplets, and it rains (thank you gravity). 

In order to visualize condensation we ventured to carry out by now universally famous, Make a Cloud in a Bottle Experiment. For those who are not familiar, we poured a small amount of warm water into a 2 liter plastic bottle and, in order to produce dust debris, we lit a match and let the particles/smoke fall into the bottle. We quickly closed the bottle off with the cap and began squeezing the bottle in the middle. By adding particles such as smoke and by squeezing the bottle we caused the air pressure to drop, and created a cloud!

Finally we made our way out to a nearby field with our clipboards, paper, and pencils, to look at the sky. We were lucky to find, on that chilly but beautiful winter morning, the sky was absolutely full of clouds. The color and shape of the clouds varied widely across the sky. 

One second grader knew the names of all the different types of clouds and he wrote down every name and definition. Many students actually sketched the clouds they saw, some chose those in the distance while others picked clouds right overhead. 

Here is a Kindergartner working on her sketch.

They made special care of the shading - for grey clouds that looked to be just about to empty on us, they used darkened pencil marks. 

Next week we plan to talk more in depth about gases that we cannot see and we have a very cool experiment that will help us to visualize water vapor.

Metamorphosis and life cycles

This week we began looking at the fruit fly life cycle. I brought several vials and bottles each containing eggs, larvae, pupae, or adults. Students used magnifying glasses to identify each of the life cycle stages and to also draw pictures of what they noticed about adult fruit flies. (The drawing to the right was done by a kindergartner who attempted to make careful note of the number of legs and the eye color of her chosen fruit fly.) We talked about many different types of organisms that undergo metamorphosis including: insects, amphibians, fish, and plants. The students are excited to track the timing of the fruit fly life cycle in their classroom. They will recording the different transitions that they notice in the vials, from egg to adulthood in about 2 weeks time!

Predator-prey board game

Last week we played a modified chutes and ladders game. I based it on the owl food web. As the students rolled dice and moved their pieces along the board, their goal was to reach the owl at the top of the food web.

If a piece landed on a picture-square (rather than a number-square), students read aloud from a "predator-prey" card that matched the image. Our cards held interesting facts about "who-eats-who?" depicting the plant or animal on the square and explaining how each member of the web fit together. Along the way students landed on different organisms that are linked to the barn owl's diet, sometimes their landing on a square involved skipping ahead - ladders - other times they landed on a chute and had to move their piece back down the food web. I was thrilled that the lesson kept them all engaged for the entire science period!

The owl food web

We've been busy the last few weeks! After having fun with bar graphs - plotting all the different bird species who have been visiting our feeders so far this winter, students compared time of day (and temperature outside) with number of visitors seen at the feeders (morning vs. afternoon sightings) - we moved onto several exciting lessons on owls. We read a beautiful book about barn owls and then, working in pairs, dissected our own large owl pellets. The trick was to dissect slowly and patiently, the students did a fantastic job and were richly rewarded with several identifiable skeletons from voles and shrews. The lesson went better than I could have hoped, a couple students even decided to skip outside time in order to keep at the dissection! They were careful and attentive, and equally thrilled with finding a skull as they were with finding a tibia or a clump of fur.

Our lead teacher assembled a poster of some of the skeletal remains and she included several gorgeous owl drawings made by students.

During one of our next science lessons, we talked about ecosystems and the interconnections between climate, plants, animals, and microbes, with particular attention to the owl food web. Students were especially interested in the fact the weather patterns that effect conditions of plants, grass, roots, and seeds, in turn help to determine the health of the soil: balance of microbes, earthworms and insects living in the ground. They began to see the interconnectedness of food resources: that voles eat plants, grains, seeds, vegetation, tree bark and roots, while shrews eat voles (as well as worms, insects, snails, fungi, and other small mammals) and from our first hand experience with pellet dissections, they told me that owls eat shrews and voles! Students got so much out of the barn owl pellets, it was a great way for us to review concepts we have been working on this fall and winter - habitat and environment - as well as for introducing them to the communities of decomposers, producers, and consumers that contribute to food chains and food webs.

Birding Basics

We have been diligently watching our feeders every Thursday and Friday for the past two weeks.  Along with noting weather conditions each day, the children have decided to perform their feeder observations at different times of the school day.  On one day they make observations for fifteen minutes in the morning while on the other day they watch for fifteen minutes in the afternoon.  They are interested in seeing whether or not time of day plays a role in the total visitor numbers and/or in the types of bird species who stop by. Many students are now adeptly calling out the species names without identification guides. Others are starting to be able to carefully track the actual visitor number from each species (without counting the same bird over and over during a given observation period).  It has been absolutely amazing to see the students' knowledge repertoire and critical observation skills developing so rapidly.  Even asking about why some bird species might prefer to feed off the fallen seeds (Junco) while other visitors swoop in quickly, nervously snagging a snack before taking it away to a higher branch to enjoy (Black-capped chickadee).

Along the way, in order to sculpt our noticing skills further, we have spent a fair amount of time describing and drawing what we see.  Paying particular attention to the diversity of plumage, markings, and assorted morphology -- characteristics that eventually lead us to key into which bird species we happen to be looking at.  By taking the time to draw and accurately color-in some common bird species on work sheets, the students are using identification guides and colored pencils to try and make precise renderings of our avian visitors.  Current favorites are the Northern Cardinal and the Blue Jay.

Up next, we will begin to talk about the different ways that scientists plot data.  We will learn how to visualize our raw data (by making graphs of our collected observations) and the ways that plots help us to look for patterns in our data.  The students will begin to make their own bar graphs, line graphs, and pie charts of the different species that we have seen. They will continue to hypothesize and to ask whether temperature, time of day, type of seeds, or placement of feeder plays a role in bird visitation frequency or in a given species being attracted to our offerings.  Ultimately, students will be introduced to concepts of variables (noun), and to begin to consider the difference between independent and dependent variables.

I look forward to showing you the graphs that they choose to create!

Bird Watch

Birches School students are so excited to be starting our project feederwatch.  As citizen scientists collecting data for Cornell Lab of Ornithology, we have chosen our winter count site.  Just beside the school building we will place three feeders. We plan to observe the bird-feeders for about fifteen minutes a day on Thursday and Friday each week that school is in session.  Students have already decided that they would like to offer a least two different seed types to our avian visitors, they would like to test whether different bird species have specific seed preferences.  We are learning to use tally sheets and to accurately record data just as scientists do.  Students will record the time of day we performed the watch and the length of time on a given day that we spent counting the birds in our feeder area.  They will document the daylight temperature extremes for each count day, the type/if any of precipitation, and the total depth of ice or snow cover during a given two-day count session.  Students will identify and report the highest number of each bird species that they see at one time.  Students will also have the opportunity to fill in paper data booklets and to participate in the online data entry of their recordings and to report rare, sick, or unusual bird sitings.  I look forward to updating you on their progress as we go!