Science Class During the Past Couple of Weeks

 During the past two weeks of school, I built an electric motor and reviewed the first eight electricity goals. An electric motor transforms electric energy into mechanical energy.  In order to build it, you will need the following materials: 

- An alkaline battery type D

- Tape

- Two paper clips (the larger the better)

- A rectangular magnet (such as those used in refrigerators) 

- A toilet paper tube (with a small diameter)

- Thick enameled copper wire

- Sandpaper

- Optional: glue, small block of wood for the base

Instructions:

1.      Roll the copper wire around the carton tube, 10 0r more times (in parallel coils), leaving at least 5cm from each unwound ends and PERFECTLY strait. Remove the tube since it is only used to build the coil. The wire can also be rolled around any other cylindrical objects. For example, the “D” type battery itself.

The ends must match. In other words, they must face each other since they are the shafts of our motor. You can either use a drop of glue between each turn or give two turns to the wire of the ends from the coil to prevent its distortion.

2.     Using the sandpaper, completely remove the enamel of the wire of one of the ends of the coil. Leave at least 1 cm without sanding, the part that is closest to the coil.

3.     Place the coil on a flat surface and sand the other end of the wire. Again, leave at least 1 cm without sanding, the part closest to the coil.

4.     Fasten the magnet to one side of the battery by using glue.

5.     Using the paper clips, leave two hooks on each end having between them an angle of 90 degrees. Flat pliers or with a fine tip can be very useful.

6.     Use the tape to fasten a paper clip to each end of the battery, placing the ends on the same side of the magnet.

7.      Hang the coil on the free ends of the clips. If the coil doesn’t spin, immediately you should slightly help it.

Explanation:

When we place the coil on the ends of the clips, we close the circuit so that a magnetic field is induced in each of the turns of the coil. The electric current is generated by the battery. Anyways, the electric field faces the magnet itself, originating the rotation of the coil.  The coil will stop spinning when the electric current stops to flow. In other words, when the battery runs out since the wire is only sanded by one side of one of the ends of the wire and a static equilibrium of the whole will never be achieved.  If both sides were sanded, equilibrium between the electric fields would be produced, generating no movement.

If the motor doesn't work, make sure that the clips are making contact with the poles of the battery, that their surfaces are well sanded, or change the lateral position of the magnet. These were some of the factors of why my motor didn't work. 


*I couldn't post any images of my motor since it didn't work and I undid it before my teacher told me to provide an image of it in my post.  

Reviewing Electricity Goals:

            Building the motor introduced me to a new topic: Electricity. Later on, we reviewed some concepts from 7^th grade about the same topic. There were a total of eight goals we reviewed which are listed as follows:

1.      I can explain how electric charges interact

2.     I can give examples of how charges can be transferred between materials and explain them.

3.     I can explain how an electric current is produced

4.     I can compare conductors with insulators

5.     I can explain how resistance affects current

6.     I can use Ohm’s law to calculate resistance, current or voltage.

7.      I can build series and parallel circuits and describe its parts.

8.     I can explain the relationship between power, voltage and current.

There are three types of electric charges: protons (+), electrons (-), and neutrons (o).  The relationship between them is simple: opposites attract and likes repel.

Charges can be transferred from one object to another by three methods. One of them is charging by friction, the transfer of electrons from one uncharged object to another by rubbing. The second method is charging by conduction, the transfer of electrons from a charged object to another by direct contact. The third way is charging by induction, the movement of electrons from a part of an object to another which is caused by the electric field of a second object.

charging by friction

http://media.ehs.uen.org/html/PhysicsQ3/Charging_by_Friction_01/charging.jpg

charging by induction

http://media.ehs.uen.org/html/PhysicsQ3/Conduction_and_Induction_01/induction1.jpg

charging by conduction

http://media.ehs.uen.org/html/PhysicsQ3/Conduction_and_Induction_01/conduction.jpg

  












An electric current is the continuous flow of electrons. It is produced by the continuous flow of charges from one place to another.  In the following image of a car circuit, a simulation of what happens inside an current is present. The car circuit represents an electric current itself while the flowing charges are being represented by the cars. 
Furthermore, there are four factors that determine resistance: type of material the wire is made, temperature, diameter and length of the wire. The type of material the wire is made of refers to whether it is a conductor or an insulator. If the wire is an insulator, it will make it difficult for electrons to move through the current since it has tightly held electrons. In other words, it has more resistance. If the wire is a conductor, it will make it easier for electrons to flow through the current since it has loosely held electrons. It has less resistance. The second factor is temperature. As temperature increases, the resistance of the wire increases too. In contrast, as the temperature decreases, the resistance of the wire does as well. The third factor includes the length of the wire. A short wire has less resistance than a long wire. Lastly, the fourth factor that determines resistance is the diameter of the wire. A wide wire has less resistance than a narrow wire. 

http://www.woodentoys123.com/products/race-car-circuit-toy-1.jpg

Conductors and insulators are different groups of materials. Insulators are materials through which charges can’t flow easily. Conductors are the opposite, they are materials through which charges can flow easily and are used to carry charge, and they have less resistance. 

https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDwd3i-xchUbhPD3coK289Tcbhyphenhyphen8bHxMn3Aqh-ufmQoPp4-Xz8Q8tskGow-3aYt0tjB0tP84-vNkUAXksfDTFkqhpyPiL6-rHVzigF_-L6x-W58HNUEjaJdAhKpavmFayX-VQ1s3L279I/s1600/IMG_1872.JPG

Resistance is the measure of how difficult it is for charges to flow through a material. When resistance increases, the current decreases. There are four factors that determine resistance: the type of material, length of the wire, diameter of the wire, and temperature.

Ohm’s law is used to calculate resistance, current or voltage. The equation is resistance equals voltage divided by current (R=V/C).  When resistance increase and current remains the same, voltage increases. On the other hand, when resistance decreases and voltage remains the same, current decreases.

http://www.hondaforeman.com/attachments/how/7309d1318956570-electrical-system-explained-how-500px-ohms-law-triangle.jpg

There are two types of circuits: parallel and series. A parallel circuit has several paths while a series circuit has only one. The different parts of a circuit are the energy source, resistors, and a switch. The energy source is what makes charges move around the circuit. A resistor resists the flow of an electric current. The switch is used to open and close the circuit.

Another essential formula in electricity is P=VI, which represents the relationship between power, voltage and current. P represents power, V represents voltage, and I represents current. Power is the rate where one type of energy is transformed into another. 

http://www.sengpielaudio.com/FormulaPower01.gif

Self-Reflection:

In my opinion, building an electric motor helped me visualize how it works more easily. It was a more didactic and entertaining way of learning instead of just reading the book. Same thing goes with the goals. By performing different types of activities to learn, it helps maintain the concepts in my mind without the need of memorizing it. 

Electricity Quiz!!

It´s quiz time! Please take the quiz at the bottom, it will only take a minute to complete. 

Good Luck!

Cells Summative Assessment

During the past weeks, I have been working on a cell summative assessment.  Its purpose was to give our science teacher a tool that could be used with the students. The project could be a comic book, storybook, newspaper, game, song, talk show, etc. I decided to write a song.

  My initial plan was to create a website, which didn´t work at all due to a few technical problems. I gave up with 6 days remaining!! I couldn´t decide which project was more suitable for me until the weekend was left. So, I thought writing a song wouldn´t take me much time. Though, I was wrong. Writing the lyrics took me a whole day. Still, I hadn´t finish the entire project. My teacher requested a video which explained my work. Yet, what would I explain if it was a simple song about cell division? Ms. took this into consideration and told me to record it!?! I almost passed out but I had no choice. Despite the fact of my voice, practicing the song helped me remember each step of the cell division process without studying!

At the end comes my self-evaluation. Since I only worked on my project during the last weekend, the quality of it isn´t the most favorable. At least, it became a more interacting and fun way of learning science. The lyrics are provided below so feel free to check it out.

Lyrics:

How do Cells Divide

Ohh

How do cells divide, over and over again

A message to the man ohhh

The sequence of events, preparing to divide

Into two new cells

Let’s Go!!

Yeah, you listening now

 At interphase the cell grows to its mature size

 The cell makes an exact copy of the DNA

 At the end it has two equal sets of DNA

 Preparation in cell division beginns ahaa

 Produces structures that will be used ahaaa

 The next event of the cell cycle is prophase

 Chromatin in the nucleus condenses to form chromosomes

 The pairs of centrioles, move to opposed sides

 Spindle fibers form, a bridge from the end- sides

 The nuclear envelope breaks down

 Then is metaphase, chromosomes line up in the center of the cell

 Each attaches to spindle fibers at its centromere

 Stop making this so hard for me, damn

 I used to be a kid that couldn´t solve this out

 That’s why you have to keep singing till you understand

Ohh

How do cells divide, over and over again

A message to the man ohhh

The sequence of events, preparing to divide

Into two new cells

Yeah, anaphase is next

Two chromatids split becoming two new chromosomes

The new chromosomes

Begin moving to the opposed ends of the cell

It stretches out as the opposite ends are pushed apart

At the end, each pole has a complete pile of chromosomes

 At telophase, chromosomes begin to stretch out and lose

 Mate, now my song would leave them amazed

Great, it feels like a hard time fading out

Since the day I thought of that cunning plan

But I´m missing something I try to remember

Which belong to this song, the final stage!

It’s Cytokinesis, where the cell splits in half

Each ending with alike sets of chromosomes

 Everyone’s a kid that couldn´t solve this out

 You just gotta keep singing till you understand

How do cells divide, over and over again

A message to the man ohhh

The sequence of events, preparing to divide

Into two new cells

Ohh (4x) Interphase

Ohh (4x) Prophase

Ohh (4x) Metaphase

Ohh (4x) Anaphase

Ohh (4x) Telophase

Ohh (4x) Cytokinesis

I know how cells divide, over and over again

A message to the man ohhh

The sequence of events, preparing to divide

Into two new cells 

Egg Lab

Since it is difficult to see when osmosis is happening in cells due to the small size, in my science class we simulated what happens in a cell by using an egg. The egg may not be a single cell though; its membrane is selectively permeable, being a good model to show some basic osmotic effects in animal tissue.  Our aim was to investigate the effect of different solutions on an egg´s mass and volume.  For this experiment the class was split into groups of three. My group chose to use alcohol and salty water 20% solution. The goal of our experiment is to investigate the effect of different solutions on an egg´s mass and volume. At the beginning of the investigation, my group was asked to predict the possible effect. We predicted both eggs, either submerged in salty water 20% solution or alcohol, were going to dehydrate.

Before even starting the egg lab, all eggs spent two days in vinegar in order for the shells to dissolve. After the egg had no shell, my group was free to start the experiment. We measure each of the eggs mass, circumference, and solution filling each cup where the eggs were going to be submerged. Though, how were we going to differ each the second day? We named both eggs! The one in alcohol was named Stuart and the egg in salty water 20% solution, Steven. On the second and third day, we performed the same procedure: measuring the mass, circumference, and solution that was left inside cup from each egg. The average from my results and another group are recorded below. 

Average of Alcohol Solution Effects

Average of Salty Water 20%  Effects

Observations:

- the egg in alcohol got more yellow and lighter each day

- the egg in salty water 20% solution got whiter and heavier each day

- remaining solution decreased in both cups 

-when the egg in alcohol was opened, it looked like a boiled egg

- when the egg in salty water was opened, it exploded and scattered with a single touch

Conclusion and Analysis:

At the end of the experiment, my group had to summarize and analyze the experiment with our knowledge of osmosis. For the egg submerged in alcohol we concluded that there was a larger amount of water inside the egg than outside. This is when osmosis shows up. Since there was a higher concentration of water inside the egg, some H2O molecules went outside to keep balance. The reason the egg got smaller because it lost liquid. Though, how could the remaining solution in the cup be less if water was added to the total of 80ml (already outside the egg). Actually, alcohol evaporates really fast, a possible reason the remaining amount of alcohol reduced from 80ml to 68.5 and eventually until 59ml. At the end, our prediction was right, the egg did dehydrate since it got small and had a dry texture. 

On the other hand, the egg in salty water 20% solution, didn´t meet our expectations. My group thought it was going to dehydrate, supposed to decrease in mass and circumference. Though, the results were totally the opposite: the egg got heavier and larger. As a whole, my group concluded this happened due to the possible lower amount of water inside the cell, which lets the outside environment to send water particles to the inside of the cell. This reflects the enlargement of the egg since it was full of water. The most noticeable part where this effect happened is from the abrupt reduction of solution outside the egg between day 1 and day 2. It decreased from 80ml (what we started with) to 67ml. 

Possible Sources of Errors:


-Procedure: Pouring different amounts of the chosen solution. This may have been one of the causes why results varied a lot. Some groups submerged their eggs in a total of 100ml from their solution. Though, the cups where the eggs were being placed had a small space for the egg to fit. This didn´t let enough space for the primarily requested 100ml of solution. As a result, some of the liquid spilled due to the lack of room. The reason groups ended with various amounts of liquid, affecting the average. 
-Equipment:

String used to measure the eggs´ circumference could be easily stretched. Instead, a retractable tape measure could´ve been used. While you surround the tape around the egg, at the same time you are measuring the circumference. Helping you save some time. 

What have I learned?

Sincerely, the experiment was not a way of studying osmosis yet to review it. Osmosis is the movement of water molecules from a high concentrated area to low. This reflects what happened in the experiment. The center of the egg (yolk) contains protein and water. While, let´s say salty water contains salt and water. Osmosis may happen due to the fact that there are more water molecules in the yolk than in the solution (salty water). So, eventually water molecules move from the inside to the outside to keep balance. 

Team Evaluation:


In my opinion, my team worked efficiently all classes. While one member measured the circumference from one of the eggs, the other measured the mass from the other egg, while I placed the remaining liquid from the cup in the graduated cylinder to measure the solution that was left. We never got distracted by others. I very much appreciated the help from my group since it contributed in my understanding of osmosis. 

Cell Membrane

The simple facts students normally study about the cell membrane is that it´s made of fat and used for protection. If we were to see from a molecules´ point of view, what would happen inside the cell membrane? Actually, if we get through the cell membrane since it is selectively permeable, we could go through by either passive or active transport.   Through passive transport, substance can cross the cell membrane without using cellular energy. In other words, the cell doesn´t need to use its own energy.  On the other hand, active transport requires the cell to use its own energy in order to get through the cell membrane. Below, there´s an informative video I found which explains more clearly what I roughly explained.