## Reflection: Rigor Mixtures: Characteristic Properties - Solid Identification - Section 5: Discovery Activity

When I started teaching science in 1999, I went to a wonderful two week camp for physical science teachers that used the book Introduction to Physical Science.

One of the first things the students do in this curriculum is learn to find mass using a four beam balance.  The instructors of the course were very set on students using the 4 beam balances for a variety of reasons.  First, it provides the students the opportunity to use a delicate science tool.  It also helps teach the concepts of accuracy and reliability as well as error.  Finally, it is more accurate than the electronic scales.  For all these reasons I happily used the balances for 10 years.  The only drawback to the tool that I found was that it took about 2 weeks of measuring items for students to be able to be accurate and reliable and it was very difficult to get students to understand that there was a certain measurement of error.  One lab I did back then was have the students compare the accuracy of the balances to the electronic scale.  The students were always surprised to find out how much more accurate the balances are.  Students are so used to electronic gadgets they tend to think they are better for everything.

In the last few years though, I've gone back to only using the electronic scales.  This is mainly because our curriculum changed and what we used to teach in a semester we now have 3 weeks to cover.  This doesn't allow for the deep learning about balances and scales and makes it impossible for students to use the balances correctly.  Using the scales allows me to make sure that students understand the concepts of Conservation of Mass and Density even if we don't get to have rich discussion about accuracy, reliability, and error.

If you have the freedom of getting to go deep into these measuring concepts and have access to the balances you might think about using them with students for a really authentic learning experience.

4- Beam balances vs Scales
Rigor: 4- Beam balances vs Scales

# Mixtures: Characteristic Properties - Solid Identification

Unit 8: Mixtures: Characteristic Properties
Lesson 5 of 11

## Big Idea: Density is a characteristic property.

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Standards:
Subject(s):
Science, density, solids, liquid, gas, mixture, property
52 minutes

### Andrea Pless

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