This experience illustrates the basic techniques to measure the mass of different types of solids, both in full -fit and powdered, using a three -plague balance, a classic laboratory instrument.
The objective is to learn to weigh substances precisely and to understand the importance of precision in scientific measures.
This section establishes the fundamental steps to properly use a three-plague balance, including initial calibration, the positioning of the object on the tray, and the adjustment of the cursors to obtain precise reading of the mass.
The addition of the masses indicated by the sliders makes it possible to determine the total mass of the object.
Measure the mass of a whole solid: This process implies the use of a weighing nacelle to measure the mass of whole solids, such as magnesium ribbons.
The procedure details how to adjust the scale, weigh the nacelle alone, then weigh again with the magnesium ribbons, allowing to calculate the mass of the ribbons by subtracting the mass of the empty nacelle from the total mass.
Measure the mass of a solid powder: This part focuses on the measurement of the mass of a solid powder, such as magnesium oxide. The method consists in using a spatula to transfer a specific amount of powder in the nacelle, weigh the whole, and calculate the mass of the powder by performing the appropriate subtraction.
Educational Goals
Learn to use a triple beam balance: Understanding the operation and steps necessary to obtain a precise measurement of the mass.
Develop skills with precise measurement: exercise to weigh objects of different forms and sizes, as well as powdered substances, which is essential in many scientific procedures.
Understanding the importance of precision: recognizing the importance of precisely measuring the mass in scientific experiences to guarantee the reliability and validity of the results.
In summary, this experience teaches fundamental laboratory skills, essential for the realization of precise and reproducible experiences in science, by emphasizing the exact measure of the mass of solids in different states.
Protocol
General procedure
1) Ensure the balance sliders are at zero and the platform is clean.
2) Check that the needle points to zero. If the needle is not aligned with the zero point, calibrate the balance using the adjustment screw.
3) Place the object to be weighed on the balance platform.
4) Move the slider of the larger scale until the needle is lower than the zero point.
5) Move the slider back one notch to the left so that the needle is above the zero point.
6) Repeat steps 4 and 5 with the second slider.
7) Move the slider of the smaller scale until the needle is perfectly aligned with the zero point.
8) Add the mass of the sliders to find the mass of the object.
Measuring the mass of a solid object
1) Adjust the level of the balance using the adjustment screw.
2) Weigh the weighing boat using the balance.
3) Place all the pieces of CaCO3 into the boat on the balance platform using tweezers. (Reminder : To use the tweezer in hand tracking mode, once the interactive object is picked up, join the thumb and index finger to activate the object’s interaction.)
4) Weigh the boat and the pieces.
5) Calculate the mass of the substance as follows: mass of the container and substance – mass of the empty container.
6) Remove the pieces of CaCO3 from the boat.
Measuring the mass of a powdered solid
1) Take 5 mL of CaCO3 powder using the large spatula and place it in the boat.
2) Weigh the boat and the CaCO3 powder.
3) Calculate the mass of the substance as follows: mass of the container and substance – mass of the empty container.
4) Remove the boat from the balance platform.
5) Remove the CaCO3 powder from the boat.
6) Reset the balance sliders to zero.
Anticipated Outcomes
This is a practical session to familiarize yourself with the use of the triple beam balance.
The 5 pieces of CaCO₃ will weigh 5 × 2.9 g = 14.5 g.
5 mL of CaCO₃ will weigh 13.55 g.
Summary of Assignment by Grade Range
Grades 3-5 (Ages 8-10)
- Focus: Basic operation of a triple beam balance and simple measurement tasks.
- Activities: Using balance to measure small objects, discussing the importance of precision in basic terms.
Grades 6-8 (Ages 11-13)
- Focus: Detailed understanding of balance operation and more complex measurement tasks.
- Activities: Measuring a variety of objects, including powders, discussing the role of precision in scientific results.
Grades 9-12 (Ages 14-18)
- Focus: Mastery of balance operation, advanced measurement tasks, and deep understanding of precision in scientific research.
- Activities: Precise measurement of complex objects, in-depth discussions on the impact of precision on scientific reliability and validity.
Laboratory essentials
Instruments
Spatulas
Triple beam balance
Tweezers
Products
Calcium carbonate (pieces)
Calcium carbonate (powder)