Unit2: Measuring & Calculating
Reading
BJU Chemistry book: Ch. 3 "Measuring and Calculating"
Zumdahl Chemistry book: Ch. 1 "Chemical Foundations"
Topics
Lab
Glassware Fabrication and Lab Safety
BJU Chemistry book: Ch. 3 "Measuring and Calculating"
Zumdahl Chemistry book: Ch. 1 "Chemical Foundations"
Topics
- Metric system
- Conversion factors
- Significant digits
- Calculations involving the above
- The concept of 'density'
Lab
Glassware Fabrication and Lab Safety
| chemistry_measurement_class_notes_2021.docx |
Below: A rather dramatic demonstration of the energy which is contained in hydrogen gas (H2). Matter can exist as a gas, liquid, or solid... and a fourth category called 'plasma'. We will make small quantities of hydrogen gas - and safely study its properties - in a later lab.
Lecture outline
By around 1960, most nations had officially adopted the metric system or System International (SI) as their official measurement system. The metric system is based on "tens", and uses the meter, gram, liter, and second as basic units.
In the United States, we still use the Imperial System (inches, feet, pounds, gallons) in many fields, but in Chemistry we use the metric system because it's easier and because it is the recognized standard. Since Americans need to know both systems, we use conversion factors to convert back and forth between them. Historically, the Imperial System was used throughout the British Empire up through the mid-1900's, and since the British Empire included most of North America, we still have it.
Metric base units and prefixes shown below:
By around 1960, most nations had officially adopted the metric system or System International (SI) as their official measurement system. The metric system is based on "tens", and uses the meter, gram, liter, and second as basic units.
In the United States, we still use the Imperial System (inches, feet, pounds, gallons) in many fields, but in Chemistry we use the metric system because it's easier and because it is the recognized standard. Since Americans need to know both systems, we use conversion factors to convert back and forth between them. Historically, the Imperial System was used throughout the British Empire up through the mid-1900's, and since the British Empire included most of North America, we still have it.
Metric base units and prefixes shown below:
In the metric system, we also have derived units, such as area, volume, density, and pressure.
Density
- The density of something is its mass divided by its volume. Density = mass/volume.
- The density of water is 1,000 g/L (one thousand grams per liter).
- The density of rock is around 2,000 g/L. Therefore, a rock will sink in a beaker of water.
Accuracy vs. Precision
Significant Figures
- Accuracy is how close you are to the "true" value. Shooting an arrow directly in the bullseye is being 'accurate'.
- Precision has to do with 'repeatability', or how tightly grouped your measurements are. Shooting 10 arrows near the bullseye is 'precision'.
- Precision is also an indication of how small the scale 'gradations' are on your measuring instrument. A measurement like 5.125 L is "more precise" than 5.1 L, for example (even though neither one is perhaps very "accurate").
Significant Figures
- We have to be careful how many digits we show in our answer.
- For addition & subtraction, you can keep as many place values in your answer as the least precise measurement contains
- For multiplication & division, you can keep as many significant figures in your answer as the measurement with the least significant figures has
Scientific Notation
- Chemistry uses very small - and also very large - numbers. We use scientific notation to write these numbers.
- For example, 6 x 10^3 means a 6 with 3 zeroes, or 6,000 Or.... 6 x 10^23 means a 6 with 23 zeroes.
Lab: Glassware Fabrication & Lab Safety
Objectives: We will go over the safety rules pertaining to chemicals, glassware, and heat sources. Learn how to safely cut, bend, and draw glass. Make a functioning laboratory wash bottle. Read and sign the lab safety rules agreement.
Objectives: We will go over the safety rules pertaining to chemicals, glassware, and heat sources. Learn how to safely cut, bend, and draw glass. Make a functioning laboratory wash bottle. Read and sign the lab safety rules agreement.
| _glassware_lab_student handout - print and bring to class |
| lab_report instructions_-_glassware_fabrication_lab.docx |
| lab_safety_rules_agreement_2021 - sign and return original.docx |
AP take-home lab: Measurement, Significant Digits, and Graphing
| 1._Lab Handout: Measurement_significant_digits_and_graphing_lab.doc |
| 1._Sig Figs_background_lecture.docm |
Homework
| 1._measurement_homework__problems.docx |
