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# Month: March 2017

## James Lincoln Introduces us to PASCO’s new Modular Circuits Kits

James Lincoln (physicsvideos.com) introduces teaches to PASCO’s new Modular Circuits Kits at NSTA 2017.

## Test the Rainbow! Understanding pH

Students often struggle understanding pH. While we can tell them that it is a logarithmic function, students are more likely to associate “logs” with a calculator button or a piece of wood. So how do we get them to understand what the pH scale really means? Look for a lesson, instead of a pot of gold, at the end of a rainbow.

Let’s start with the acids. First have the students pour 10 mL of 0.1 M HCl into a test tube. Using graduated cylinders and pipets they can add 1 mL of that solution to another test tube with 9 mL of water making a 0.1 M solution. They should repeat the process of taking 1 mL of the previous solution and adding 9 mL of water until there are 5 solutions. They won’t know it, but they just performed a serial dilution. Now they can add some universal indictor to the solutions for a splash of colour.

Indicators are nice, but they really are just an indicator. In this case the indictor was not able to distinguish between the first four test tubes. (Note to self: get some new universal indicator!). Since the true colors aren’t shining through, it’s important to remember that to really understand pH, your students need to take actual pH measurements.

Now comes the pHun part! After recording the data for the solutions, it is important for students to try to make some meaning out of those measurements. Time to dust off those concentration calculation skills. They should be able to calculate the concentration, and write the concentration of the acids in scientific notation.

No need to travel somewhere over the rainbow, all your students need now are some good guiding questions and they should see that pH is primarily based on the negative exponent of the concentration of H+.  With this understanding, pH=-log[H+] can be something more powerful than just a formula to plug and chug in calculator.

You can even extend this activity to pOH and its relationship to pH if you drop the base. Following the same procedure, students can perform a serial dilution starting with a 0.1 M NaOH solution.

After this colourful and engaging activity with the Wireless pH sensor and some fresh universal indicator, your students will be able to find the rainbow connection:  a better understanding of the pH scale, what it means and how it’s measured.

It’s hard to believe that the end of the budget year is fast approaching.  If your department has unspent funds now is a great time to consider acquiring one or more of PASCO’s premier instructional apparatus.  The very popular featured products below are all in stock and can be shipped in time to make this year’s budget deadline.

1. Microwave Optics

The transmitter emits a large 3 cm wavelength that makes it easy for students to visualize and understand electromagnetic interactions. The system can be quickly adjusted with magnetic mounting components, rotatable transmitters and receivers and a Goniometer with rotatable arms featuring built-in degree and millimeter scales. Durably designed, the system will provide years of trouble free labs with components made of either cast-die aluminum or stainless steel.

WA-9314C (\$2995) – Basic System for investigation electromagnetic interactions

WA-9316A (\$3995) – Advanced System includes accessories for Brewster Angle and Bragg Diffraction experiments

### 2. Educational Spectrophotometer System

This very versatile system’s open design is ideal for education. When used with Capstone software, students can graph the spectral lines of gases; precisely measure the relationship between angle wave length and intensity; and analyze the transmission characteristics of filters and chemical solutions. The sensors can connect to PASCO’s full range of interfaces including the very affordable Wireless Airlink or the powerful 850 universal interface.

OS-8450 (\$1912) – Includes Light and Rotary Motion Sensors and Optics Bench

OS-8537 (\$1257) – Sensors and Optics Bench not included

### 3. Photoelectric Effect System

Planck’s constant is a central quantity in quantum mechanics and its discovery was one of the greatest breakthroughs in understanding the nature of light.   With this system your students will be able to perform the photoelectric experiment to determine Planck’s Constant to within 5%. Students will also be able to verify that stopping voltage is independent of intensity and find the characteristics of the photodiode. Can be used with the 850 Interface and Capstone software

SE-6614 (\$3156) – Basic System, includes Mercury Light Source with Hg tube

SE-6609 (\$5666) – Basic System plus DC Current Amplifier and DC Power Supply

### 4. Electron Charge-to-Mass Ratio System

This system reproduces J.J Thompson’s landmark experiment to calculate the charge-to-mass ratio of the electron. A very sharp and visible electron beam within the vacuum tube allows for its radius (R) to be easily measured using the built-in fluorescent scale. The system also provides a measurement for the accelerating potential (V) applied to the electron gun as well as the magnetic field (B) produced from applying a current to the Helmholtz coils. With these measurements students can then accurately calculate the electron’s charge to mass ratio using the formula e/m=2V/B2R2.

SE-9629 (\$6555) – Complete system with e/m tube and power supplies

## Introducing PASCO’s New Wireless CO2 Sensor

The ability to easily and affordably measure CO2 levels is great news for Biology and Environmental Science teachers.

PASCO’s new Wireless CO2 Sensor communicates directly with a wide range of Bluetooth equipped computers without requiring an expensive interface.

Ambient environmental Carbon Dioxide levels are typically very low. This means any experimental changes to CO2 levels tend to be significant in percentage terms providing convincing and reliable evidence of the phenomenon being studied.

Investigations based on the wireless CO2 sensors are easy to setup and they work.

Other opportunities for CO2 investigations include:

• Cell Respiration
• Photosynthesis
• Metabolism of cold blooded animals
• Enzyme activity
• Fermentation
• Indoor & Outdoor CO2 levels
• Pollution
• Decomposition

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