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Secular Science Resources for Homeschoolers

High School Biology 04 – Cells

Students were asked to watch the following videos before class:

I also sent them the videos that I recommended to the middle school class.  Today’s lab was very similar to the middle school class as well but we pushed it a bit further.  Holt Biology has a lab, 3.2 Comparing Cells, you can download if you have their homeschool package with online resources.  This lab has students look at onion, celery, cheek cells and elodea under the microscope.  I didn’t have any elodea but I have a water feature (wine barrel with fountain) in our back yard which mosquito fish, algae and various microscopic critters call home, so students took sample of the algae and water instead.  Students found a couple of live critters amongst the algae which was pretty cool. Below is a photo of a dead water mite(?) amongst some algae.

We also spotted a copepod and some kind of microscopic worm.

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Copepod from backyard ‘pond’.
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Stained celery cells.  The stain was only absorbed by the cells on the edge of the sample

We didn’t actually see very much when looking at cheek cells. But below are some photos of red onion cells at different magnifications.

 

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Middle School Biology 03 – Cells

I sent links to The Wacky History of Cell Theory and the Amoeba Sisters video, Introduction to Cell, for kids to watch at home before class.

In class I did a short presentation on cells and cell theory, covering the same information that was in the videos but being a little more interactive.  I showed drawings of both a plant and animal cell and asked the students to spot the differences – plant cells usually have one large vacuole (for storage) while animal cells may have many small ones.  Students also spotted that the plant cell had chloroplasts – green organelles where photosynthesis takes place.  The last major difference is that plant cells have a rigid cell wall, not just a cell membrane.

IMG_8308Before students could look at cells under the microscope, they labeled the parts of a microscope on a page from the Cells Interactive Notebook by Getting Nerdy with Mel and Gerdy.  Students can either cut and paste the labels or write the answers in the boxes.

As students finished the worksheet and put it in their notebook, I gave them a handout on how to make a wet mount slide and how to look at it with a microscope.  Then they came up to the table with the microscopes and slides and tried their hand at making a very thin slice of cork, mounting it on a slide and observing it under the microscope.  The photo below was taken with my iPhone in a Carson Universal Smartphone optics adapter (there is a newer version available called the HookUpz 2.0 , though I’m thinking about trying this one by Celestron – I’ve heard its a bit more stable) and the microscope was on the lowest objective lens with a magnification of 40X.

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This isn’t too different from what Robert Hooke saw and published in Micrographia: or some Physiological Descriptions of Minute bodies made by Magnifying Glasses (1665).

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Students also made slides of small pieces of red onion. If they got a thin enough sample they can see individual cells as in the photo below which was taken at 100X.IMG_8217

To see the nucleus in the onion cells we stained one slide with methylene blue chloride.   Here’s a short video showing how to stain cells on a slide.

Below is a photo of stained red onion cells at 100X.  The dark oval in each cell is the nucleus. Its easiest to see in the lighter blue cells near the center of the photo.  IMG_8224

Students learned how to use a microscope, the names of the different parts of a microscope and got to see some real cells.  We had some extra time at the end of class so students looked at a few prepared slides of different plant parts, like bamboo stems, dandelion fluff and pollen.

IMG_8219I have a number of different microscopes but I’m really enjoying the convenience of the dual-head LED microscope that I bought this summer from Home Science Tools.  The dual-head lets two kids look at once, or I can look while a student is trying to focus, or we can set up a smart phone on one eye piece and take photos while still using the other one.

 

High School Biology 03 – Chemical Reactions

Students were told to watch Crash Course Biology #3 on biological molecules before coming to class.

There were two activities for this class, one was to build some biological molecules like glucose and amino acids using the snatoms and zometools and the second was to investigate a chemical reaction.   I have a MicroSnatoms kit and I love it for building IMG_8197molecules, but it can be tricky to build some of the bigger biological molecules without it falling apart.  The zometools can be frustrating at times since it can be hard to find the right hole in the ball to get the right angle and the bond parts have a tendency to break off in the balls, but being rigid does make it a bit easier to make the big molecules like the amino acids.   (Sidenote: I think the molecular mania set that I linked to above will suffice but I bought the Zometool STEAM kit many years ago when the homeschool buyers coop was having a deal for it and feel I’ve gotten my money’s worth since I’ve used it both biology and chemistry classes.  There are some geometry lessons that come with this as well, that I plan on using with my high schooler.)  Students used both sets to make various biological molecules while waiting their turn to do the chemical reaction lab.IMG_8191

The chemical reaction that we investigated was the decomposition of hydrogen peroxide into water and oxygen with the help of catalase, an enzyme found in liver.  This is lab 2.4 Chemical Reactions from the Holt Biology Homeschool package online resources.  We started by talking about the different things that can affect the rate of chemical reactions, like the temperature, the surface area of the catalyst and the pH of the environment.  Students chose a variable to test.  We had two groups do pH and one group tested the effect of temperature.   To measure how reactive the reaction was students measured the height of the foam/bubbles formed by the released oxygen.

Students placed 2 ml of hydrogen peroxide in each centrifuge tube – I like using these 50 ml centrifuge tubes for experiments because they stand up, they’re graduated so its easy to make measurements, their relatively cheap and they come with caps – though you don’t want to cap a tube with a reaction going on!  We used disposable graduated pipettes to transfer the 2 ml of hydrogen peroxide and the various other liquids.  Before class I prepared red cabbage indicator and 1.0 M solution of HCl and a 1.0 M solution of NaOH.  I had some 6.0 M solutions left over from previous chemistry classes so I just had to dilute them further to get 1.0 M solution, you’l only need a few ml of each.   Students testing the effect of pH used 5 centrifuge tubes and put in various amounts of the HCl, NaOH and distilled water to get a variety of pH levels ranging from 2 to 13.  To determine the pH of the solutions before adding the liver, students used pipettes to place 2 drops of each solution in a well plate with red cabbage indicator.  By comparing the color of the solution with a chart they were able to determine the pH level.DSCF1494The red cabbage indicator didn’t seem to work too well for the extreme bases so we pulled out some pH test paper to double check some of the pH levels.  When the solutions were ready students put a small piece of beef liver (found in freezer section of grocery store) in each tube and observed the reactions.  The reaction starts producing bubbles immediately and the pH has a definite effect on the amount of bubbles produced, with some tubes barely showing any foam (acids) while others producing up to 10 ml of bubbles.

IMG_8196For investigating the effect of temperature on the reaction, students took a small beaker of water and put crushed ice in it to bring the temperature down to 3 Celsius and put another beaker of water in the  microwave to heat it to 54 Celsius.  They had a third sample of room temperature water.  The students set up 3 tubes with hydrogen peroxide and added 2 ml of each water sample to a different tube.  It wasn’t a huge difference in reaction rate but the higher temperature did have slightly more bubbles so they decided to try one more at an even higher temperature, 70 Celsius, and indeed the reaction was more vigorous for the higher temperature (photo above).

This was a pretty simple lab with a very noticeable chemical reaction and if you don’t have HCl or NaOH available you can still do the experiment just using different temperatures or try changing the surface area by cutting up the liver into different size pieces.   If you use the HCl and NaOH make sure everyone wears safety goggles and gloves.

 

Middle School Biology 02 – Water

IMG_8178Today’s class was all about water and its properties.  We started by doing an interactive notebook activity about graduated cylinders that can be found in the Scientific Method part of the Life Science & Biology Interactive Notebook Bundle by Getting Nerdy with Mel and Gerdy on teacherpaypteachers.com.  Students cut out 6 different graduated cylinders and colored them in to show the right volume.  I had a small 10 ml graduated cylinder with some water in it that I passed around the class so the students could see how the top of the water is curved  forming what is called a meniscus.  The meniscus forms because of adhesion, water molecules are attracted to the sides of the graduated cylinder.

Here’s a great video on the properties of water by the Amoeba Sisters.  They have a whole series of videos for biology and I’l be posting a lot of them.

For the lab I bought Unique Properties of Water – Cohesion, Adhesion & More by Science Island on teacherspayteachers.  I had already done all of these experiments in one form or another, but this file was nicely formatted into 7 different stations that I could easily set up, along with explanations for every activity, so I went ahead and spent $4 to save myself some work.  The stations included floating paperclips on water, a density column, capillary action (water going up a paper towel), dissolving salt, how many drops of water can fit on a penny, etc.  The favorite activity was the milk rainbow, where

you pour just enough milk into a bowl to cover the bottom and then drop some food coloring in the milk.  Not much happening at this point, but when you take a Q-tip and dip it in dish soap and then touch the milk,  the surface becomes very active and you end up with a cool design.  This movement happens because the fat molecules in the milk are attracted to the soap molecules, while at the same time the soap is also weakening the surface tension of the milk allowing molecules to move more easily. Here’s a video from Steve Spangler that includes a description of why it works.

I made up my own interactive notebook activity for the properties of water and had students put it together after completing the labs.  I have a couple of Dinah Zike’s books on foldables so I grabbed the Big Book of Science and looked for something that would work. Then I made a page listing the properties of water in a big letters and a page with  photos depicting each property for the students to glue on each flap.

At the beginning of next week’s class we’l go through each property and I’l ask the students which water experiment goes with each property.   It was when we were working on putting the above flaps into the notebooks that I realized I had forgotten to do the high specific heat demo so I quickly pulled out my butane burner (a candle would have been better, burner was over kill) and blew up a couple of balloons, one with a bit of water inside.  I had the kids put on safety goggles since I intended on purposely blowing up balloons.  First you hold a ballon full of air over the flame and it pops pretty much immediately as the rubber melts quickly.  Then you hold the balloon with water in it – pour a tablespoon or 2 of water into the balloon before blowing it up.  When you hold this balloon over the heat source it does not pop!  The rubber does not melt because it takes a lot more energy to change the temperature of water than it does rubber and the water is keeping the rubber cool while it absorbs the heat!  The first time I tried to do this I had the burner turned up too hot so the balloon with water  popped fairly quickly.  Next time I’l just use a candle.  Here’s a video of Steve Spangler doing the same demo.

 

High School Biology 02 – Microscopic Measurements

Before coming to class students were asked to watch Crash Course Biology #1 and #2 and read Chapter 2 of Holt Biology.

The lab, measuring microscopic objects is from the Holt Biology homeschool package and can be found in the online teacher resources (Ch 1.4).  Students cut out a small lowercase letter ‘e’ from a newspaper and made a wet mount slide (placed it on a slide with a drop of water and then a cover slide over the top).  They observed the ‘e’ under a microscope at 40X, 100X and 400X magnification and recorded their observation by sketching what they saw through the eye piece and some took photos with their smart phones using a HookUpz mount by Carson.

 

The lab also asks students to use the translation stage to move the slide away from them and note the direction the image moves in the eye piece and likewise to move the slide to the right.

IMG_8049Students also measured the field of view by placing a transparent ruler under the objective in the microscope and measuring how many millimeters crossed the diameter of the field of view.  They did this at 40X and 100X.  We couldn’t do 400X because its less than 1 mm and its very hard to estimate a distance if you can’t see at least two lines on the ruler.  The lab then had students convert from millimeters to micrometers (microns) since those are the units commonly used for microscopic objects.

This lab is a nice introduction to how to use a microscope and now the students know the size of the field of view at different magnifications and can estimate the size of objects that they are looking at.

IMG_8081Near the end of class I handed out some biology doodle notes on the characteristics of life  that I downloaded for free from Science with Mrs Lau on  Teachers Pay Teachers.  This freebie has various versions of the notes from nearly blank to ones where the students just fill in a missing key words.  I also handed out a coloring page on the elements of life from The Biology Coloring Book that goes over the most abundant elements found in living organisms, hydrogen, oxygen, carbon, nitrogen, phosporus, calcium.

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