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 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.
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 carrying out a weighing, it is necessary to ensure that the scale’s sliders are at zero and that the tray is clean.
2. Check that the black arrow located to the right of the scale indicates zero point (small horizontal black line). If the arrow is not aligned with the zero point, calibrate the scale with the small adjustment screw located to the left of the scale under the tray.
3. Place the object to be weighed on the scale’s tray.
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. Calculate the mass of the substance in the following way: (mass of the container and substance) – (mass of the empty container).
Measure the mass of a whole solid
1. Adjust the balance level using the adjustment screw.
2. Weigh the weighing basket using the scale.
3. Put all the magnesium ribbons in the basket on the scale tray using the clamp.
4. Weigh the basket and the ribbons.
5. Calculate the mass of the substance in the following way: mass of the container and substance – mass of the empty container.
6. Throw the magnesium ribbons in the black trash can and put the empty basket back on the counter.
Measure the mass of a powdered solid
1. Take 5 mL of magnesium oxide powder using the large spatula and place it in the basket.
2. Weigh the basket and the magnesium oxide powder.
3. Calculate the mass of the substance in the following way: (mass of the container and substance) – (mass of the empty container).
4. Throw the magnesium oxide powder into the black trash can and put the empty basket back on the counter.
5. Reset the balance sliders 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)