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
Basic principles
1) Before performing a weighing, it is necessary to ensure that the balance’s cursors are at zero and that the pan is clean.
2) Check that the black arrow located on the right side of the scale points to the zero mark (small horizontal black line). If the arrow is not aligned with the zero mark, calibrate the scale using the small adjustment screw located on the left side of the scale under the platform.
3) Place the object to be weighed on the balance pan.
4) To determine the weight of the object, you will need to move one or more of the sliders on the three available scales (using the small red arrows) until the black arrow on the right side of the balance is perfectly aligned with the zero point.
5) You will then only have to add the mass of the sliders to find the mass of the object.
Measure the mass of a whole solid
1) Adjust the level of the balance using the adjustment screw.
2) Weigh the weighing boat using the balance.
3) Place all the magnesium ribbons into the boat on the balance pan using the tweezers.
4) Weigh the basket and the ribbons.
5) Calculate the mass of the substance as follows: mass of the container and the substance – mass of the empty container.
6) Remove the magnesium ribbons from the basket.
Measure the mass of a solid in powder form.
1) Take 5 mL of magnesium oxide powder using the large spatula and place it in the boat.
2) Weigh the boat and the magnesium oxide powder.
3) Calculate the mass of the substance as follows: mass of the container and the substance – mass of the empty container.
4) Remove the pan from the balance platform.
5) Remove the magnesium oxide powder from the boat.
6) Reset the balance cursors to zero.
Anticipated Outcomes
- The substances are Mg(s) in ribbons and MgO(s) in powder.
- 1 ribbon of Mg weights 0.55g. There are 5 pieces in the container; therefore weigh 2.75g.
- Mg(s) in powder has a density of 3.58g/mL.
- 5 mL of MgO(s) in powder weighs 17.9g.
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
- Magnesium (ribbons)
- Magnesium (powder)