Science Investigative Project

Documentation of the experiment

Apparatus and materials

Apparatus and Materials used in the experiment

As presented in my report, the apparatus and materials used are:

·       ½ cup of flour

·       ½ cup of rice grains

·       ½ cup of sugar

·       ½ cup of fine salt

·       4 glass cups of the same kind

·       1 metal spoon

·       1 measuring cup

·       1 roll of tape

·       1 permanent marker

·       2 rulers

·       1 laptop with built-in microphone and Audacity (software) installed

Procedure of Experiment with images

Set-up

  

              Using tape, secure a ruler standing upright, perpendicular to the tabletop. 

 Mark a spot in front of the taped ruler.

            

                                                                                                                      

Place a glass cup such that the spoon will hit the glass cup  from the marked spot.

For my experiment, I placed the glass cup 12cm from the marked spot.

Mark the spot where the glass cup is as well.

                                    

Using a ruler, place the laptop 10cm away from the glass cup.
Open the software Audacity.

Conducting the experiment

1. Measure 1/2 cup of each substance and pour them into glass cups.

 

⬇

2. Start with one of the glass cups and place it over the marked spot in front of the ruler. For me, I started with the glass cup containing salt.

3.  With one hand, hold the spoon upright with the tip of the spoon touching the other marking, which is in front of the upright ruler. The tip of the spoon should be in contact with the marked spot at all times during the experiment.

4. With the other hand, press “Record” on Audacity.

The Audacity toolbar

\     5. Strike the rim of the glass cup briefly using the handle of the spoon before returning to the original starting position of 90°, while the hand keeps the tip at the tabletop. This is to minimize the amount of external force used when striking the glass cup, as it might affect the results of the experiment. Also, it ensures that the angle from which the glass cup is hit is constant.

      6. Strike the glass cup two more times in the same way used in Step 5. Pause for about 2 seconds between each striking.

      7. Press the “Stop Recording Button” on Audacity.

      8. Select “Split Stereo to Mono” in the drop-down menu on the left, and delete the one of the two tracks that has been split. 

      9. Mute the track that was just recorded so that the previous recording will not interfere with the ongoing recording.

    10. Repeat Steps 3-8 with the rest of the glass cups containing the different substances.

         

      Analysis of results

      Below are the results that I have obtained from my experiment. 

To get the value of the frequency and pitch produced from each strike, I used the "Analyse --> Plot Spectrum" function on Audacity. I first highlighted the part which I wanted to analyse. 

Sound waves produced when hitting the glass cup containing salt. 

Frequency analysis of the first hit on the container containing salt

As shown above, the peak frequency of this reading is 4946 Hz. I used the same method to obtain the frequency of the rest of the readings, including those of the other substances. 

This is the table of results: 

This is the graph that I have obtained from the readings: 

As shown above, the values of the readings for each substance are rather consistent except for the rice grains. The frequency produced by the fine sugar and salt are very similar to each other, which a difference of 32.4 Hz. This is because the particles of these two substances are of similar sizes. From left to right, the substances are arranged in ascending order of the particle sizes. 

Although the particles of the flour produced lower frequency than fine sugar and salt, which had larger particle sizes, the results generally show that the smaller the particle size, the higher the pitch produced, and the larger the particle size, the lower the pitch produced.

One reason that might cause the flour particles to produce a lower pitch than the fine sugar and salt is that the flour particles are more compact and are packed more closely with each other, such that they do not move individually, but as a cluster. An assumption of the Kinetic Particle Theory states that the heavier particles move slower than lighter particles. Moving as a cluster is heavier than moving as individual particles and as such, the vibrations are slower. Also, as the particles are more compact, there are lesser spaces for vibrations to take place, therefore producing lesser sound waves and a lower frequency produced. 

A possible explanation for the inconsistency of the readings of the frequency produced by the particles of rice, which are the rice grains, is that there might be human error when striking the glass. I might have changed one of the variables unknowingly, such as the angle in which the glass is struck from. This is the reason why I took three readings for each substance instead of just one, because this minimizes the human error in the experiment and makes the results more reliable. 

To conclude, my hypothesis is tested to be correct. I have proved that the smaller the particles are, the higher the pitch produced when the container holding them is hit.

Linking back to the problem, as the differences between the frequencies of pitch produced by the substances are greater than 7 Hz, it can be an applicable method for the blind to use in gauging the size of the particles, using my hypothesis which was tested true.

1    

4