We’re going to continue our adventure in biology with this next set of videos and experiments. The materials you need for this set is already included in the shopping list on the original page (Part 1). If you need to jump to the next section, please use the links below:

Lesson 24: How to Use a Microscope
Lesson 25: Microscope Optics
Lesson 26: Learning How to Work with a Microscope
Lesson 27: Preparing a Dry Mount Slide
Lesson 28: Microscope Drawing
Lesson 29: Preparing a Wet Mount
Lesson 30: Preparing to Stain
Lesson 31: Heat Fixes
Lesson 32: Scientific Method
Lesson 33: Biology Teleclass Replay
Lesson 34: Finale!

Quick Links:
Biology Part 1
Biology Part 2

[am4show have=’p155;’ guest_error=’Guest error message’ user_error=’User error message’ ]

Lesson 24: How to Use a Microscope

Welcome to the section on microscopes! We’re going to learn how to use our microscope to make things appear larger so we can study them more easily. If you’ve ever wondered what you’re eating for dinner, how many toes ants have, or if caterpillars have armpits, then this is the lab for you. How to the lenses work to make objects larger? We’re going to take a closer look at optics, magnification, lenses, and how to draw what you see with this lesson.

The compound microscope is a set of lenses stacked so they work together to make things look bigger. For example, if you’re using a 10x eyepiece (where your eye looks into) and a 40x objective (the lens near the slide), then you’re using a 400x power setting. You use a dry to get your specimens ready for viewing.

Materials

microscope (need a recommendation?)
slides
coverslips
tape
a penny
the letter “e”
scissors
an object to dry mount, such as a strand of hair

Nose? Objective? Stage? What kind of class is this? Well, some of the names may sound a bit odd, but this video will show you what they are and how they are used. As you watch the video, touch the corresponding part of your microscope to get a feel for how it works.

NOTE: Be very careful NOT to raise the stage too high or you’ll crack the objective lens! Always leave a space between the stage and the lens!! Anytime you use the coarse adjustment knob, always look at the stage itself, NOT through the eyepiece (for this very reason). When you use the fine adjustment knob, that’s when you look through the eyepiece.

1. After you’ve learned the different parts of the microscope, swing around and teach it to a nearby grown-up to test your knowledge. See if you can find all these parts: eyepiece, base (legs), objective lens, eyepiece, diaphragm (or iris), stage, fine and coarse adjustment knobs, mirror/lamp, nose.

2. Show your grown-up which parts never to touch with your fingers.

3. What’s the proper way to use the coarse adjustment knob so you don’t crack the objective lens?

Care and Cleaning

1. Pick up the microscope with two hands. Always grab the arm with one hand and the legs (base) with the other.

2. Don’t touch the lenses with your fingers. The oil on your fingers will smudge and etch the lenses. Use an optical wipe if you must clean the lenses. Steer clear of toilet paper and paper towels – they will scratch your lenses.

3. When you’re done with your scope for the day, reset it so that it’s on the lowest power of magnification and lower the stage to the lowest position. Cover it with your dust cover or place it in its case.

Lesson 25: Microscope Optics

How do the lenses work to make objects larger? We’re going to take a closer look at optics, magnification, lenses, and how to draw what you see with this lesson.

Lesson 26: Learning How to Work with a Microscope

Do how do you use this microscope thing, anyway? Here’s how you prepare, look, and adjust so you can get a great view of the micro world. First, download the worksheet that goes with this lab (and a couple other labs on this page).

1. Carefully cut a single letter (like an “a” or “e”) from a printed piece of paper (newspaper works well).

2. Use your tweezers to place the small letter on a slide and place a coverslip over it (be careful with these – they are thin pieces of glass that break easily!) If your letter slides around, add a drop of water and it should stick to the slide.

3. Lower the stage to the lowest setting using the coarse adjustment knob (look at the stage when you do this, not through the eyepiece).

4. Place your slide in the stage clips.

5. Turn the diaphragm to the largest hole setting (open the iris all the way).

6. Move the nose so that the lowest power objective lens is the one you’re using.

7. Bring the stage up halfway and peek through the eyepiece.

8. If you’re using a mirror, rotate the mirror as you look through the eyepiece until you find the brightest spot. You’ll probably only see a fuzzy patch, but you should be able to tell bright from dim at this point.

9. Use the coarse adjust to move the stage slowly up to bring it into rough focus. If you’ve lowered the stage all the way in step 7, you’ll see it pop into focus easily. (Be careful you don’t ram the stage into the lens!)

10. Use the fine adjust to bring it into sharp focus. What do you see?

Lesson 27: Preparing a Dry Mount Slide

This is simplest form of slide preparation! All you need to do is place it on the slide, use a coverslip (and you don’t even have to do that if it’s too bumpy), and take a look through the eyepiece. No water, stains, or glue required.

You know that this is the mount type you need when your specimen doesn’t require water to live. Good examples of things you can try are cloth fibers (the image here is of cotton thread at 40X magnification), wool, human hair, salt, and sugar. It’s especially fun to mix up salt and sugar first, and then look at it under the scope to see if you can tell the difference.

1. Pull a hair from your head and lay it on a slide. If it’s super-curly, use a bit of tape at either end, stretching it along the length of the slide. Keep the tape near the ends so it doesn’t come into your field of view when you look through the microscope.

2. Lower the stage to the lowest setting and rotate the nose piece to the lowest magnification power.

3. Place the slide on the stage in your clips.

4. Focus the hair by looking through the eyepiece and slowly turning the coarse adjustment knob. When you’re close to focus, switch to the fine adjustment knob until it pops into sharp view.

5. Open your science notebook and draw a circle. Sketch what you see (don’t forget the title and mag power!)

6. When you’re done, lower the stage all the way and insert a new slide… and repeat. Find at least six things to look at. We’re not only learning how to look and draw, but hammering a habit of how to handle the scope properly, so do as many as you can find.

Don’t forget to check the windowsills for interesting bits. Use baby food jars or film canisters to collect your specimens in and keep them safe until you need them.

TIP: If you want to keep your specimen on the slide for a couple of months, use a drop of super glue and lay a coverslip down on top, pressing gently using a toothpick (not your fingers) to get the air bubbles out. Let dry.

Lesson 28: Microscope Drawing

Learning to sketch what you see is important so that the view is useful to more than just you. Here’s the easy way to do it: get a water glass and trace around the rim on a sheet of paper with your pencil. This gives you a nice, large circle that represents your scope’s field of view (what you see when you look into the microscope). Now you’re ready for the next step:

1. Draw a picture of that the letter looks like under the lowest power setting in your first circle and label it ‘right side up’. Then give the slide a half turn and draw another picture in a new circle. Label this one ‘upside-down’.

2. If you’re using a mechanical stage (which we highly recommend), twist one of the knobs so that the slide physically moves to the right as you look from the side (not through the eyepiece) of the microscope. If you’re using stage clips, just nudge the slide to the right with your finger. Now peek through the eyepiece as you move the slide to the right – which way does your letter move?

3. Now do the same for the other direction – make the slide move toward you. Which way does the letter appear to move when you look through the eyepiece?

4. What effect do the two lenses have on the letter image as you move it around?

Look back at your two drawings above. Let’s make them so they are totally useful, the way scientists label their own sketches. We’re going to add a border, title, power of magnification, and more to get you in the habit of labeling correctly. Here’s how you do it:

Border You need to frame the picture so the person looking at it knows where the image starts and ends. Use a water glass to help make a perfect circle every time. When I sketch at the scope, I’ll fill an entire page with circles before I start so I can quickly move from image to image as I switch slides.

Title What IS it? Paramecia, goat boogers, or just a dirty slide? Let everyone (including you!) know what it is by writing exactly what it is. You can use bold lettering or underline to keep it separate from any notes you take nearby.

Magnification Power This is particularly useful for later, if you need to come back and reference the image. You’ll be quickly and easily able to duplicate your own experiment again and again, because you know how it was done.

Proportions This is where you need to draw only what you see. Don’t make the image larger or smaller – just draw exactly what you see. If it’s got three legs and is squished in the upper right corner, then draw that. Most people draw their image smaller than it really is when viewed through the eyepiece. If it helps, mentally divide the circle into four quarters and look at each quarter-circle and make it as close to what you see as you can.

Lesson 29: Preparing a Wet Mount

Anytime you have a specimen that needs water to live, you’ll need to prepare a wet mount slide. This is especially useful for looking at pond water (or scum), plants, protists (single-cell animals), mold, etc. If your critter is hard to see, you can use a dye to make it easier to view.

Some specimens need water to live, so you’ll need to keep them moist with a wet mount slide. When you keep your specimen alive in their environment, you not only get to observe it, but also how it eats, lives, breathes, and interacts in its environment. If your critter is hard to see, you can use a dye such as iodine to stain the cell and bring out its structure, making it easier to view. Be sure to download the worksheet that goes with this lab.

Materials

20mL sample of pond water
microscope
slides
cover slips
tweezers
medicine dropper (disposable)
a translucent specimen, such as a piece of onion and elodea leaf
iodine (you can use regular, non-clear iodine from the drug store)
Protoslo (optional)

1. Place a slide on the table.

2. Fill the eyedropper with pond water and place a drop on the slide.

3. Place the edge of the cover slip on the pond water drop, holding the other edge up at an angle. Slowly lower the end down so that the drop spreads out. You want a very thin film to lay on the slide without any air bubbles or excess water squirting out. If you go have bubbles, gently press down on the cover slip to squish them out or start over.

4. Take time practicing this – you want the water only under the coverslip. Dab away excess water that’s not under the slide with a paper towel.

5. Lower the stage to the lowest setting and rotate the nose piece to the lowest magnification power.

6. Place the slide on the stage in your clips.

7. Focus by looking through the eyepiece and slowly turning the coarse adjustment knob. When you’re close to focus, switch to the fine adjustment knob until it pops into sharp view.

8. Adjust the light level to get the greatest contrast so you can see better.

9. Move the slide around (this is where a mechanical stage is wonderful to have) until you spot something interesting. Place it in the center of your field of view, and switch magnification power to find a great view (not too close, not to far away). Adjust your focus as needed.

8. Open your science notebook and draw a circle. Sketch what you see (don’t forget the title and mag power!)

9. When you’re done, lower the stage all the way and insert a new slide… and repeat. Find at least six things to look at. We’re not only learning how to look and draw, but hammering a habit of how to handle the scope properly, so do as many as you can find.

NOTE: If the critters you’re looking at move too fast, add a drop of Protoslo to the edge of your slide to slow them down (by numbing them). The Protoslo will work its way under the cover slip.

Lesson 30: Preparing to Stain

If your critter is hard to see, you can use a dye to bring out the cell structure and make it easier to view. There are lots of different types of stains, depending on what you’re looking at.

The procedure is simple, although kids will probably stain not only their specimens, but the table and their fingers, too. Protect your surfaces with a plastic tablecloth and use gloves if you want to.

We’re going to use an iodine stain, which is used in chemistry as an indicator (it turns dark blue) for starch. This makes iodine a good choice when looking at plants. You can also use Lugol’s Stain, which also reacts with starch and will turn your specimen black to make the cell nuclei visible. Methylene blue is a good choice for looking at animal cells, blood, and tissues.

In addition to your specimen, you’ll need to get out your slides, microscope, cover slips, eye dropper, tweezers, iodine (you can use regular, non-clear iodine from the drug store), and a scrap of onion. If you can find an elodea leaf, add it to your pile (check with your local garden store). If you haven’t already, be sure to download the worksheet that goes with this lab (and the previous one on wet mounts).

Here’s what you do:

1. Place a slide on the table.

2. Fill the eyedropper with pond water and place a drop on the slide.

4. Take time practicing this – you want the water only under the coverslip. Dab away excess water that’s not under the slide with a paper towel.

5. Lower the stage to the lowest setting and rotate the nose piece to the lowest magnification power.

6. Place the slide on the stage in your clips.

7. Focus by looking through the eyepiece and slowly turning the coarse adjustment knob. When you’re close to focus, switch to the fine adjustment knob until it pops into sharp view.

8. Adjust the light level to get the greatest contrast so you can see better.

8. Open your science notebook and draw a circle. Sketch what you see (don’t forget the title and mag power!)

NOTE: If the critters you’re looking at move too fast, add a drop of Protoslo to the edge of your slide to slow them down (by numbing them). The Protoslo will work its way under the cover slip.

Lesson 31: Heat Fixes

If you tried looking at animal cells already, you know that they wiggle and squirm all over the place. And if you tried looking when using the staining technique, you know it only makes things worse. The heat fix technique is the one you want to use to nail your specimen to the slide and also stain it to bring out the cell structure and nuclei. This is the way scientists can look at things like bacteria.

Heat fixes are used when the specimens move all over the place when stained, like yeast. By drying out the specimen and fixing it to the slide, you can easily stain it several times to bring out the contrast and view the structure. Click here to download the worksheet that goes with this lab.

Materials

- microscope
- slides
- cover slips
- eyedropper
- toothpicks or tweezers
- candle and matches (with adult help)
- stain (you can use regular iodine or Lugol’s Stain)
- sugar
- yeast
- container to mix your specimen in

1. Fill your container with warm water. Add about a tablespoon of yeast (one packet is enough) along with a teaspoon of sugar. The warm water activates the yeast and the sugar feeds it. You should see a foam top form in about 10 minutes.

2. Using your eyedropper, grab a bit of your sample (you want the liquid, not the foam) and place a drop on a fresh slide. Spread the drop out with a toothpick. You want to smear it into a thin layer.

3. Light the candle (with adult help). Heat the slide in the flame by gently waving it back and forth. Don’t stop it in the flame, or you’ll get black soot on the underside of the slide and possibly crack it because the glass heats up and expands too fast. You also don’t want to cook the yeast, as it will destroy what you want to look at. Just wave it around to evaporate the water.

4. Add a drop of iodine (or stain) to the slide. Wait 15 seconds.

5. Rinse it under water. (You can optionally stain it again if you find it’s particularly difficult to see your specimen, but make sure to look at it first before repeat staining.)

6. Place a drop of water (use a clean eyedropper) on the specimen and add the cover slip.

7. Lower the stage to the lowest setting and rotate the nose piece to the lowest magnification power.

8. Place the slide on the stage in your clips.

9. Focus by looking through the eyepiece and slowly turning the coarse adjustment knob. When you’re close to focus, switch to the fine adjustment knob until it pops into sharp view.

10. Adjust the light level to get the greatest contrast so you can see better.

11. Move the slide around (this is where a mechanical stage is wonderful to have) until you spot something interesting. Place it in the center of your field of view, and switch magnification power to find a great view (not too close, not to far away). Adjust your focus as needed.

12. Open your science notebook and draw a circle. Sketch what you see (don’t forget the title and mag power!)

NOTE: What other things can you look at? You can scrape the inside of your cheek with a toothpick and smear it on a fresh slide, take a mold sample from last week’s leftovers in the fridge, or…? Have fun!

Lesson 32: Scientific Method

One of the problems kids have is how to experiment with their great ideas without getting lost in the jumble of results. So often students will not have any clear ideas about what change caused which effect in their results!

They also have trouble communicating their ideas in a way that not only makes sense, but also is acceptable by science fairs or other technical competitions designed to get kids thinking like a real scientist. Kids constantly struggle to apply the scientific method to their science project in school, for scout badges, or any other type of report where it’s important that other folks know and understand their work.

In this video, I am going to walk you through all the steps of the scientific method by just doing it so you can really see it in action. I’ve taken an everyday topic in alternative energy and applied the scientific method to get a real answer to my question about solar cells.

The scientific method is widely used by formal science academia as well as scientific researchers. For most people, it’s a real jump to figure out not only how to do a decent project, but also how to go about formulating a scientific question and investigate answers methodically like a real scientist. Presenting the results in a meaningful way via “exhibit board”… well, that’s just more of a stretch that most kids just aren’t ready for. There isn’t a whole lot of useful information available on how to do it by the people who really know how.

Lesson 33: Biology Teleclass Replay

Did you participate in the Biology Teleclass Webinar? Here’s the recording from our class together:

Lesson 34: Biology Teleclass Replay

Going Further

If you’ve enjoyed the content and would like to continue your studies, including doing a full microscope study course, learning about the different species on our planet (including human anatomy), join me in my online science course which covers these topics in biology (and much, much more!) You can try e-Science for $1 by clicking here.

[/am4show]