Introduction to Measurement
Learning Outcomes
- Identify and use common equipment and measuring devices in the chemistry laboratory.
- Properly record experimental data including the precision appropriate to the measuring devices used.
- Properly make measurements of length.
- Express measured quantities in a way that correctly shows the uncertainties of the measurements.
- Investigate how to increase the number of significant figures in measured and calculated quantities by properly using measuring devices.
Measurement uncertainty refers to the doubt that exists about the exactness of a measurement. Different devices, such as rulers, thermometers, and balances, have different degrees of uncertainty depending on their design, precision, and calibration. For example, a digital balance may have a higher uncertainty than a mechanical one, allowing for more precise measurements. Learning to account for and express these uncertainties is key to providing a true representation of the data collected.
In addition to uncertainty, it is crucial to use significant figures correctly. Significant figures convey not only the precision of the measurement but also the confidence we have in the data. By following the rules of significant figures, scientists can ensure that the results of calculations derived from measurements do not suggest a greater level of accuracy than is possible based on the initial measurements. For instance, when multiplying or dividing measurements, the result should reflect the least number of significant figures among the values used.
One of the goals of this lab is to explore how different devices with varying uncertainties impact the precision of measurements. You will investigate how to apply the rules of significant figures in representing measured and calculated values. By using various instruments, you will also learn how to maximize the number of significant figures reported, allowing for more precise data collection.
In addition to making measurements, you will calculate the area and perimeter of various objects. For example, for a rectangular object, the area of is equal to the product of the width and length (area = w x l). The perimeter is equal to the sum of the four sides (perimeter = w + w + l + l). In this procedure, you will measure the length and width of four different objects using two rulers with different measuring uncertainties. To calculate areas, you will have to multiply measured quantities according to the specified formula. The product should be expressed using the correct number of significant figures. Multiplication rules dictate that the product should be reported to the least number of significant figures. To calculate perimeters, you will add a series of measured quantities. The sum should be expressed using the correct number of decimal places. Addition rules dictate that the sum should be reported to the least number of decimal places.
