Acidity Tester Project


Engineers use robots to do tasks that might be harmful to humans. One common example is working with hazardous chemicals. A hazardous chemical is one that could cause a negative health effect, such as cancer, lung damage, skin irritation, or even death. If a mixture contains at least 1% of a known hazardous chemical, it is classified as a hazardous material. Consequently, many common household solutions, such as paints, cleaners, inks, and dyes can be considered hazardous. An acid is sometimes considered a hazardous chemical, because it can cause severe burns if it gets in your eyes, nose, or skin. Not all acids are hazardous, however. Some acids, such as vinegar and lemon juice, are used in cooking to give foods their distinctive flavor.

In this project, your challenge is to build a sensor-controlled robot to determine the acidity of a liquid. Your robot should be mobile, so that “hazardous” chemicals can be kept away from human operators. You will use a Vernier pH Sensor and a Vernier NXT Sensor Adapter connected to your NXT to test the acidity of several common household solutions. Solutions that are “acidic” will have a pH value between 0–7.


In this project, you will

  • Build a robot to find a cup and lower a probe.
  • Use the NXT to determine the pH value of a liquid.
  • Play a sound based on sensor data.

Sensors and Equipment

This project/activity requires each of the following Vernier sensors and equipment (unless otherwise noted):

Additional Requirements

You will also need NXT Sensor Adapter and a LEGO MINDSTORMS NXT robotics system.

Download Experiment Preview

The student-version preview includes:

  • Step-by-step instructions for computer-based data collection
  • List of materials and equipment

The preview does not include essential teacher information, safety tips, or sample data. We strongly recommend that you purchase the book for classroom use.

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Standards Correlations

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Experiment 3 from STEM with Vernier and LEGO MINDSTORMS NXT Lab Book

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Included in the Lab Book

Vernier lab books include a CD with word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.

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