Category: STEM

March 2019, 2:00 pm

There was a day in March where we had an experiment. The experiment about acid, an ionic compound that produces positive hydrogen ions (H+) when dissolved in water and base, an ionic compound that produces negative hydroxide ions (OH-) when dissolved in water. It was the day where we understand more about these two substances.

That day we were instructed to pour 20 milliliters of each solution into each cup. Those solutions were lemon juice, vinegar, sprite, water, toothpaste (with water solution), baking soda (with water solution), and bleach. We were told that these solutions represent different pH levels. 

Later on, we poured the red cabbage indicator into each solution’s cup. Then we noticed the changes in color. 

The clear sprite has turned into light red. The light blue toothpaste solution has turned into light purple. The other solutions also changed colors. 

The final step that we did was to combine those solutions that were mixed with the indicator, together. We blended lemon juice with bleach, baking soda solution with vinegar and sprite with toothpaste solution. The result that we got was that they changed colors again. 

 

The red lemon juice solution and light yellow bleach solution has turned into a red solution. This is because the solution has more acid than the base. 

 

 

 

We were then asked to write a theory about this experiment and this is what I’ve written. 

The reaction of acid and base is called neutralization where the products are water and salt. This neutralization helps to balance the solution but it depends on the concentrations of the acid and base in the solution. If you mix a high acid with a high base, it will produce water and salt and the solution will more likely to become neutral. If you mix a high base with a low acid or a low base with high acid, the solution won’t balance but it still produces water and salt. However, it will also contain a higher concentration of one side because of the leftover acid or base which makes it still be acidic or basic. 

The Experiment has End!

Six Simple Machines

 

Inclined Plane

A type of simple machine that uses for moving things upward or downward.

 

 

Lever

A type of simple machine that the force is applied at a point that gives the output at another point. Ex: scissors, etc

Wheel and Axle

A type of simple machine that consists of two circular objects with an axle in the middle which usually is used to move an object.

 

Wedge

A type of simple machine that is used to split and cut things. 

 

 

 

 

Pulley

A type of simple machine that consists of a wheel and string attached to it. Usually, it is used to lift things up. 

 

 

 

 

Screw

A type of simple machine that the inclined plane is wrapped spirally around a shaft. 

 

 

 

Mango Picker

Just by seeing the name, we know that the Mango Picker is used to pick up mangoes but for a long distance without having to carry a heavy dustpan that is full of mangoes with you while collecting them. It is a compound machine that composes of three different types of simple machine which are wheel & axle, lever, and inclined plane. This Mango Picker project was inspired by the situation in our school where there are full of mango trees and those mangoes are falling down every day. We always have to collect those mangoes and put them in the dustpan. After the dustpan is full, we have to throw them into the trash bin which is at least three meters far from each other. We have to repeat this process, again and again, several times until all the mangoes are being collected. It is really tiring to keep doing that because when the dustpan is filled up, it is heavy due to the weight of the mangoes. Therefore, our team has come up with the idea of creating this Mango Picker. The Mango Picker uses wheels to reduce the force that is needed to move the dustpan and the inclined plane which make the mango rolls down into the box. It uses the lever to help the mango moving too. We have created a prototype that is made out of papers and bottle caps. In overall, I think that this project is really fascinating and educational but also at the same time it is fun to learn. 

Instructions:

1. Get a half-full jar of hot water
2. Add as much sugar to the water
3. Mix them well together
4. Add food coloring and then stir them (Optional)
5. Put a stick into the jar or tight a string to a stick and put it into the jar
6. Wait until it forms crystals

To make rock candy, we need to add more sugar than the water can dissolve at room temperature. Because temperature affects the dissolving process. The higher the temperature is, the more solute can dissolve in the solvent. In this case, we need a greater salute so that the solvent can’t dissolve more solute, to create a saturated solution. As the saturated solution started to cool down, it becomes a supersaturated solution which the solution contains more solute than what the solvent can dissolve. A supersaturated solution is unstable and the sugar will come out of the solution to form a crystal in which a process called precipitation. The other process is called evaporation in which the water evaporates that will make the solution more saturated. When the solution becomes more and more saturated, the sugar will come out of the solution to form a crystal. We put the string or the stick to provide a surface for the crystal to form.

Our topic for STEM on the second round was Chemical Bond. There are three different types of chemical bonds but we just focused on two of them which are covalent bond and ionic bond.