The Lemonade Clock

A variation of the lemon battery

This might be the most cliché experiment for science right after Elephant’s toothpaste. If you know how both works – congratulations, you are probably pretty nerdy. Honestly, I have seen both experiments and they are both incredibly entertaining. And since I got the Lemonade Clock for my birthday, I thought I’d show you this cool variation of the lemon battery. Especially since it does not only make a lightbulb light up but we can use the actual clock that comes with the materials of the Lemonade Clock Box.

Let’s take a look at the Lemonade Clock first, before I explain how the lemonade battery works. In the box, we have the following tools:
A plug-in plate with a digital clock, cups for liquids, fitting lids, two copper sheets, and two zinc sheets.

Materials in the box to build my own lemonade clock.
Filling the lemonade into the cups and clipping it onto the board.

After filling in the lemonade into the cups and securing the cups with the fitting lids, I can stick the copper sheets and the zinc sheets into the accurate slots. The lemonade acts as the electrolyte, the substance that is capable of transporting electric charge. When the electric wires are connected, the clock begins to work.

The clock works!

Zinc and copper act as electrodes in this battery model. As soon as they are emerged into the lemonade, the metal reacts with the acid from the lemonade. Zinc atoms dissolve into the lemonade as positively charged ions, leaving negatively charged electrons behind. These electrons are now free to move around in the metal.

Connecting the electric wires closes the electric curcuit. These freely moving electrons move from the zinc eletrode to the copper electrode and we have an electric current that runs the clock!

Do you see the bubbles? Not all of this is from the lemonade, some bubbles are hydrogen molecules that come from the reactions.

On the copper sheets, the zinc ions in the liquid react with the electrons there. This is why, with some time, there will be a zinc layer over copper sheets. The clock is reusable for some time when the copper sheets are cleaned with some sand paper from time to time.

Overall, this was a nice gift and I really enjoyed it. I had the thought of trying the lemon battery for some time now. Unfortunately, I don’t have galvanized nails at home and these are coated with zinc.

Explaining Molecular Biology using Blocks and Bricks

Guest post by Danny Ward

This is something new! I offered a fellow science communicator on Twitter to write a guest post for my blog and the only requirement I named him was to pick a subject of his choosing that either makes a cool experiment or has a suitable explanation for children and teens. And Danny had the perfect outreach activity in mind which he gladly explains in the following post. He studies how some micro-organisms are able infect things and how we can potentially stop them in the future. Check out his Twitter (@DannyJamesWard) or Instagram (@dannyjamesward) if you want to know more about his work!

Molecular biology is the study of the tiny bio-molecules which make us a cell. These often come in the form of DNA, RNA and proteins.
DNA and RNA act as the genetic instructions for a living thing and tell it how to look and function. These genetic instructions come in the form of a code. This code is turned in to proteins which are biological structures which make the genetic instructions a reality – they are what make up the living thing.

This is the case whether we are dealing with a tiny microscopic virus, a plant by the side of the road or a large elephant. All living things work with this basic system.
Communicating this in the form of a scientific outreach activity can be tough. There are a lot of abstract things that require a good imagination and mental visualisation to fully understand. We can’t see any of the things I just spoke about unless we’re using high-tech scientific instruments!

I was involved in a scientific outreach activity which aimed to visualise this process with a young target audience in mind of ages from 5 to 15 years old.
This activity used conventional building bricks and blocks not uncommonly found in your average toy box to build plants, incorporating the fundamentals of molecular biology.

Blocks and bricks like these can be used to explain molecular biology.
Picture by Danny Ward.

Participants would pick five coloured instruction cubes at random from a box. These cubes represented DNA as they served as the instructions. Based on what colours a child had picked up, and how many of each would lead to different plant building instructions. The child would use these instructions to build their own plant using building bricks.

Examples of such instructions included the following:

Do you have two red instruction cubes? Pick up 10 green bricks.
Do you have any brown instruction cubes? Add three leaves to your plant.
Do you not have a purple instruction cube? Build a really tall plant.
Do you have more than three different colours of instruction cubes? Add flowers to your plant.

Using these rules, children were then given the opportunity to build their plant.

Children build their own plants according to the instructions.
Picture by Danny Ward.

Following this, participants were then asked to pick up two environment cards. These were cards which had environmental conditions which would change the plant at the genetic level by changing the rules again. This helps to introduce the idea that DNA isn’t fixed, certain genes can respond to the environment and that the environment can impact how living things can look and function too.

Examples of environment cards included:

Cold, icy weather approaches. Remove all leaves.
The rain has come. Build your plant 5 bricks taller using only green bricks.
Its springtime, all the bumblebees have come out to say hello. Add 5 colourful flowers to your plant.

This activity helped to convey the idea that genetic instructions are what build living things like plants using proteins. These genetic instructions can lead to lots of variation. The environment can then add further variation. All participants started off with just five coloured instruction cubes, but ended up with final plants which all looked radically different to each other.

Participants were then able to showcase their plant creations. We had a plant garden which served as a museum-like display where all the final creations were put to show all the different kinds of plants which were created on the day.

The plant garden shows off all the different plants the children built.
Picture by Danny Ward.

The outreach activity was led by real molecular biology research scientists and so work on the concepts taught every day.

The kids seemed to really enjoy the activity and by the end of it, they had a good grasp on the concepts at hand. Many of those who took part, especially the younger children, had very limited exposure, if any, to molecular biology. Some people had heard of DNA before, but they didn’t know what it was or why it was important. I know I was the same when I was their age too, its often not fully taught until much later. By the end of the session, all who took part were familiar with the idea that DNA, a form of instructions which living things use are part of the reason why living things look the way that they do.

While this activity used plants as an example but there is no reason why it couldn’t be adapted in future to feature other living things instead. Build your own animal, build your own virus or even build your own person could all be possible using the instruction cube and building brick concept. Perhaps, for certain audiences, it could even be taken a step further. Maybe the idea of genetic inheritance or epigenetics could be introduced.

The nice part about this activity is that it looks like fun from a distance. This may seem trivial but for members of the general public walking past a stall in a busy environment, that initial draw to pull people in is so important. If a child sees other children having fun building with these bricks and learning from real scientist, they may very well want to join in. Had the stall instead been a few sheets of dense complex information printed out and left on the table explaining the same concepts without anyone there to talk to, I highly doubt many of people would have visited the stall and even fewer would have taken any new meaningful understanding away from that. The fact that it was hands-on, got people creative, taught people about cool new concepts they probably had never heard of before and then related this to the real world, I think is what helped to make it successful.

This article was written by Danny Ward, a molecular microbiology PhD student from Norwich, England.
Learn more about the author at

Polaris and Constellations

The STEM challenge by the ICSE

ICSE – what exactly is that? It stands for International Center of STEM Education and it’s based at the University of Education in Freiburg, Germany. The ICSE is an internationally connected research center with a special focus in practice-related research and its transfer into practice. I know this, because I work at the MaSDiV project which is affiliated with the ICSE. I’ll come back to that in another post because today I want to talk about the STEM challenge, the ICSE posed on Twitter.

STEM challenge posed by the ICSE. A great starting point to talk about seasons, constellations and the axial tilt.

Ultimately, this challenge can be separated into two questions:

1. Why does the North Star (or Polaris) stay in place?
2. Why do different stars appear with the seasons?

So let’s talk about these two phenomenon and at the end I want to discuss an implementation into physics or science lessons.

It seems like the North Star does barely move.

Over the course of the night, all stars rotate, except for the North Star. Polaris seems to stay at one point. Earth’s movement around its axis is the reason the sun and the stars rise and set each day. We notice Polaris because it’s an exceptionally bright star. It can be easily found every night, mostly because of its unique characteristic of almost staying in the same place the whole night. But why is that so?

Polaris is an exception in the night sky. The axis of Earth is tilted with an angle. And since the North Star lies almost exactly above the Earth’s axis, it’s like the hub of a wheel. And I say almost because as you can see in the picture above, even the North Star wobbles a little over the course of the night.

The axial tilt of the earth is the reason why the North Star appears to stay at one point in the Northern Hemisphere night sky.

Now that we’ve talked about the axial tilt and its consequence of the North Star seemingly staying in place, let’s discuss why different stars appear with the seasons. And with this I would really like to make an example of two constellations – the Lyra and Orion. Constellations are groups of stars that form an imaginary pattern. From the northern hemisphere, the Lyra or Orion are well seen either during Summer or during winter.

Seasonal change of constellations.
Graphic by Classzone

The reason for the seasonal change of the constellations is the movement of Earth around the sun:
In Northern hemisphere’s Summer, the nightsky faces towards constellations like Lyra. While in Winter, the daytime side of Earth faces the part of the sky containing Lyra, while constellations like Orion are visible at night.

My conclusion for this STEM challenge is its great opportunity to reflect on a phenomenon I grew up with. Real-life contexts need to be broken down into smaller questions, which is shown very well with this example.

I love the potential in this challenge. A lot of astronomy can be covered and explore going from here. For example, the formation of the seasons can be explored, since students already know about the axial tilt. With balls or oranges, this can even be transformed into hands-on, investigative activities. Students can directly transform their everyday observations and connect it to the content. I believe this is the core of great physics or science lessons because it makes the content instantly relevant for students. This could lead to a huge gain in motivation.

“Look – the paddle has a kink!” – Exploring Snell’s Law

Admittedly, I don’t have a paddle for this blog post. But I have a pen. That’s basically the same when it comes to optics. And today I did not only prepare one, but TWO experiments for exploring Snell’s Law. And they are great for younger students because they both seem like magic. And thank you to Mirjam (@fascinocean_kiel) and her great idea for this post – without her niece I wouldn’t have thought of how fascinating this phenomenon can be even for younger children.

Is this pen really broken? Where does the kink come from?

Instead of a pen, every straight object could do. A spoon, a straw, a ruler. Or even a paddle. This makes the experiment so great, because you can even explore it outdoors. And even though the explanation is a little hard to grasp, even young children notice this phenomenon. It’s not only a great opportunity to learn about the physics content but also about observation and inquiry. Which I absolutely adore about experiments.

The reason for the seemingly broken pen is because the light is refracted. And here are several concepts coming into the game:

First, the idea of seeing itself. The light coming from the light source in the room is reflected by the object it hits. The reflection happens in every possible direction and some of the reflected light reaches our eyes. This is how we eventually see anything in the world.
When light reaches our eyes, we still need to convert the information from our retina into an image. This happens in the brain. You might have heard how our brain turns the image around so that we don’t see the world upside down, because this is how the image gets projected onto the retina. Keep that in mind, that we still need our brains to see anything.

The second concept is the refraction. Light moves with a certain speed (the speed of light, you might have heard about that) but in other materials than air, it moves slower. Water is one of those materials. And with this slower speed comes the refraction. The other way around works the same – light coming out of the water into the air gets refracted as well.

Now let’s put these together: The light being reflected from the pen gets refracted when it passes from the water to the air. And now something interesting happens. Our brains cannot put together this concept of refraction. In our mind, we lengthen the light rays backwards in a straight line. And that is why the underwater part of the pan looks a little closer to the surface and the pen looks kinked. It isn’t really broken, it just appears closer.

Black lines represent the way the light travels after being reflected by the object. The dottet lines is how the brain makes up the image of it.

There is another really great experiment showing this phenomenon. And it might be even more magical than the seemingly broken pen. Take a look at the video and note your observation. How does this fit together with the explanation I just gave for the kink in the pen?

The coin is fixed with tape so it won’t move when I pour water into the cup.

Let’s take a closer look at what happens:

The coin is fixed with tape in the middle of the cup.
Now let’s move the cup until we don’t see the coin anymore.

Remember, I taped the coin to the bottom, so it’s really not floating. You can try yourself at home if you like!

And suddenly we can see the coin again. This is another example of refraction and optical lift of the object in the water.

This is no magic but simple physics. You can draw the light rays the same way I did for the pen. It’s like getting the ability to look around a corner. Isn’t that just amazing?

Hair and Walls and Static Electricity

If you have been following my blog, you might know already, that I love a good hands-on experiment served with the good ol’ inquiry. These static electricity experiments I’m going to explain are just that – prompted with a question, they awe students into wanting to inquiry the nature of hair standing to all sides, balloon floating on the ceiling and maybe even waterbending with a comb. So let’s dive into the physics behind these fascinating experiments.

Rubbing a balloon over your hair will most likely leave you with a hairstyle similar to Albert Einstein.

This experiment might be a tale as old as time but it almost every time catches childrens’ curiousity and interest. They just WANT to do it themselves. See how their hair stands apart. Laugh at each other. Maybe even try to put the balloon up to the ceiling or the wall. I know that I always did. And still do, as a matter of fact. But what exactly is happening when I rub the balloon over my head? Sometimes I can even hear a crackling, like electricity.

And it’s something like that. The phenomenon is called static electricity and it’s electrons moving somewhat freely in the material. When a rubber balloon is rubbed against human hair, electrons are transferred from the hair to the balloon, giving the balloon a negative charge, and leaving the hair with a positive charge. The hair is attracted to the balloon, because the materials have opposite charges. When the balloon is pulled away from the hair, the positive charge of the hair makes the hair stand out, because the positive charge on the individual hairs causes each hair to repel the other hairs. That’s why you end up looking a little like Albert Einstein.

And putting the (now negatively charged) balloon to a ceiling or a wall brings up the next question: How does the balloon stick to the wall or ceiling? There is no glue, no string and the wall is not positively charged like our hair is at the moment (still looking funny, huh?).

A balloon sticking to the ceiling. How does this even work?

This is where the scientific reasoning comes in. Remember how I said that electrons are moving somewhat freely in the material? That’s how they were able to transfer from our hair to the balloon anyway. And it’s the same in the ceiling or the wall. The negatively charged balloon repells the electrons (which are negative charges) in the wall, leaving only the positively charged ions (ions are charged atoms or molecules) behind. These are attracted to the negatively charged balloon but since the wall cannot move, the balloon simply sticks to the wall.

The negatively charged balloon repells the electrons in the wall, leaving only positive ions which attract the balloon and make it stick to the wall.

Over time, the electrons will wander from the balloon to the wall, making the balloon fall to the ground. It will not stick to the wall forever. But still, it makes for a great demonstration and since we can’t see what’s happening in the wall or ceiling, we need to induce what might happen from our previous experiments.

There are several more cool static electricity experiments like bending water with a balloon, using a Van de Graaff generator or demonstrating a jacob’s ladder and its spark gap. These take up a little more explaining than just simple positive and negative electrical charges but are worth a look at in science classrooms because they make for amazing demonstration experiments. Especially with regards of the simple static electricity experiments I just presented to you, the topic can be embedded as sort of a spiral curriculum and students can fall back on their knowledge on charges and static electricity.

Optics on surface waves – Caustics in the deep blue sea

On my trip to Cyprus for our project meeting, we got the chance to make a trip to the sear and network with members of a different project while spending some time on a boat. I noticed some very interesting and fascinating patterns on the sandy floor beneath and besides feeling the urge of jumping in and enjoying the sea, I obviously almost instantly started thinking about the physics behind the phenomenon. And realized once more how much awe the physics behind nature inspires in me.

Don’t you just want to jump into the water? Looking at the floor of the ocean, enjoying a nice breeze of warm air, this moment really felt like a holiday. I couldn’t help but forget that I was actually on a networking event at our current project meeting. Even though I live at the baltic sea, views like these are rare because the ocean floor gets easily stirred up and waters get muddy. A few shots and explanations on the wavewatching behind these are contributed by my friend Mirjam on her blog. I’d like to dig in a little into the optics behind what we see on the picture and talk about an implementation in the physics classroom:

Reflections of light on the ocean floor are visible when the water is really clear and the sun is bright. Wouldn’t you just love to take a swim?

The reason for the light spots on the ocean floor is a concentration of light because of the waves at the ocean surface. This phenomenon is called caustic and when you don’t have an ocean at hand, you can also see it in glasses or cups filled with a liquid. It’s a neat presentation of spherical abberation, a characteristics of the optical system to spread out light over some region of space rather than on a focused point. In cups it’s mostly the reflection of the light at the wall of the mug, in the water it’s the refraction that is the reason for the caustic. The following representation makes it a little clearer on the optical path of light.

Light rays are refracted at a water wave.
Rainald62 [CC BY 3.0 (

The phenomenon is another example of an every day life context, students can explore the physics behind. Implementation works best with an interactive geometry application like GeoGebra. With this, students can interactively work out the optical path of the light. Starting with the caustic in a circle (for example like a mug), students can work on the reflection of light in a concave mirror, draw the optical path and then continue to refraction and the more challenging form of a wave. In the end, students should be able to explain what causes caustics and draw the optical path of light being reflected in a concave mirror.

Caustics in a pool.

Even though waves are a little more challenging, students should be able to describe the optical path of light, explain the concentration of the light in some areas and therefore express qualitatively the caustics under water. I judge this context to be a demanding one, so reflection on mirrors and especially on concave mirrors as well as refraction of light into water should have been talked about before the exploration of the caustic. Especially since it’s an abberation, it’s a little harder to grasp for students, because they first need to understand that optical systems are not perfect like we assume they are everytime we draw optical paths through lenses or mirrors. Typical misconceptions can accur with either reflection or refraction. Nonetheless, this context-driven approach to caustics might shed some light on the matter.

Exploring the Optics of everyday gadgets

Who hasn’t seen the kids walking to school with their cute little warning stripes all over their jackets and backpacks. But why do gadgets like warning stripes or safety vests even light up, no matter from which direction the headlights come from? Obviously, there’s no mirror tied to the backpack or the vest but what is it? Here’s an idea on how students can explore the optics of safety vests and find out about a phenomenon called retro-reflection.

Safety vests are pretty common these days, mostly for construction worker or in the car. On backpacks or jackets, reflecting stripes can also be found.

Physically speaking, retro-reflection describes the way light is reflected right back at the light source, no matter the angle. If you recall your physics lessons in high school, this is only the case when the light shines upon a mirror when held exactly perpendicular to the mirror. So how come, these materials used for safety vests don’t reflect light the same way?

Students can be prompted to design their own safety vest with aluminum foil. It has the perfect reflective characteristics that can be used to produce individually designed safety vests for the students. This takes them some time and is a great way of then using that self-made product to compare with the real thing. Where exactly is the difference? Engaging questions could be “why wear a safety vest at all?” and let them describe the function of both the color (being seen in broad daylight) and the reflective stripes (being seen during the night). This ultimately leads to the question of why the stripes are so dark during the day. Wouldn’t that make them less visible compared to the bright neon color of the vest?

This almost certainly leads to the experiments in the dark. With flashlights in a darkened room, students are able to fully explore the phenomenon and compare it to their home-made vest. Spot on!

The reflective stripes of the vest are well visible when lighted by a flashlight.

Especially for bigger distances and lights closer to the eye, the effects of the safety vest’s reflective stripes becomes clear and well differentiated to the home-made aluminum vest. Students become certain, that the explanation can’t be simple reflection of the light. Letting students draw the lightpath might lead them into the right direction of understanding the textures of these retro-reflective materials.

One way to produce retro reflection is with layer of microscopically small spheres that are embedded into the stripes. These are as tiny as the hair can be thick, which means they are barely visible with the eyes. The reflection of light within these tiny spheres happens in such a way that they go nearly back in the same direction that they came from.

And by the way: cat’s eyes are also retro-reflectors. That’s why we see them so well in the dark when they appear in the headlights.