How to Measure Mass in Chemistry Lab

Summary

In this instructional video, the presenter explains the fundamental steps for accurately measuring solid materials using a spatula and a scale. They demonstrate how to prepare a clean weigh boat, zero the scale, and carefully add a specified mass of solid (2.50 grams) while minimizing contamination. The technique involves using both the fat and fine ends of the spatula for coarse and precise measurements. The presenter emphasizes the importance of maintaining cleanliness and proper technique throughout the process to ensure accurate results, concluding with a reminder to recap the material bottle and prepare for the next steps.

Takeaways

• 😀 The spatula has two ends: a fat end for coarse measurements and a fine end for precise measurements.
• 📏 Always start by placing a clean, dry weigh boat on the scale.
• ⚖️ Zero out the scale to ignore the mass of the weigh boat before adding any solid.
• 🔒 Keep the bottles sealed when not in use to prevent contamination.
• 🔍 Measure the solid using the coarse end of the spatula to get an initial estimate.
• 🧪 Be cautious when transferring solids; anything that falls off the spatula is considered contaminated.
• 📊 For precise measurements, switch to the fine end of the spatula to add small amounts gradually.
• 🌀 If the scale fluctuates, it's usually due to draughts; that's normal during measurement.
• 💧 After obtaining the desired measurement, ensure the spatula is clean before setting it aside.
• 👋 Recap the bottle after use and prepare for the next steps in your procedure.

Q & A

What is the purpose of using a weigh boat in this procedure?

The weigh boat is used to hold the solid material being measured, ensuring that the scale only records the mass of the solid and not the mass of the container.

How do you prepare the scale before measuring a solid?

Before measuring, you need to place a clean and dry weigh boat on the scale and then zero out the scale to ignore the mass of the weigh boat.

What should you do to prevent contamination of the solid while measuring?

You should handle the spatula carefully and ensure that the mouth of the bottle is positioned over the weigh boat while transferring the solid to avoid spills.

Why is it important to use the coarse end of the spatula first?

Using the coarse end allows for faster collection of the solid material, giving a better feel for the amount being transferred before making fine adjustments with the narrow end.

What is the significance of the measurement being at exactly 2.50 grams?

Achieving an exact measurement is crucial because any excess will be considered waste, and precision is necessary for the accuracy of the procedure.

What should you do if the scale readings fluctuate?

If the scale fluctuates due to drafts or other disturbances, it’s generally acceptable as long as the measurement is stabilized at the desired value.

What does the speaker mean by saying 'anything I overshoot is going to be waste'?

This means that any amount of the solid that exceeds the target weight of 2.50 grams cannot be used and will be discarded.

How can you ensure that nothing is left on the spatula after transferring the solid?

You can check the spatula by tapping it against the side of the weigh boat to dislodge any remaining particles before disposing of it.

What is the final step after measuring the solid?

After measuring, recap the bottle containing the solid to keep it sealed and safe for future use.

What should you do with the weigh boat after you are finished measuring?

After completing the measurement, the weigh boat should be set aside, preferably near the sink, for cleaning later.