Lab Help

• Data Notebook Guidelines How should I organize my lab book?
• What to include for Lab Write-ups
• More Lab Write-up Advice (includes list of constants you should consider)
• Lab Write-up Checklist
• Lab Layout: Download and fill in relevant sections for your lab report
• I need help with
• Writing a hypothesis
• Writing Procedures
• Recording raw data
• Showing example calculations
• Calculating percent error
• Writing a conclusion
• Lab Safety Links
• Lab Techniques Links
• Distillation
• Gas Collection Methods
• Spectroscopy (Spec 20)
• Titration
• Vacuum Filtration

  Suction Filtration from Frances Fullerton on Vimeo.

I will break down each lab into skills so that each lab will get 1 to 7 grades depending on what you are required to do. Not all skills will be assessed in a quarter, although I make an attempt to do so. Each skill will be given a score on the 4 to 0 scale. Each skill is about 5% of your grade (some are less, please see syllabus). The point of this is that you recognize the skills that are being assessed in a particular lab rather than just seeing a lab as independent from all other labs. My hope is that you will start to view each lab as an opportunity to improve your skills in collecting data, designing experiments, drawing conclusions, etc and internalize the knowledge of what makes a good lab. The lab skills you will be assessed on are:

• Formatting/Data Notebook
• Design (defining a question, identification and definition of variables, procedures, controls
• Data Collection and Organization
• Data Processing (showing logical argument with math, graphs, presentation of data, answering questions)
• Analysis and Conclusion
• Error Analysis and Improvements
• Error Propagation (IB ONLY)
• Safety

Data notebooks will be graded up to two times per quarter as a whole. This grade is to ensure that you are maintaining a lab notebook as expected. This grade is in addition to the formatting grade you get with each specific lab. Lab notebook checks will be assessed based on the following:

• All labs accounted for and completed
• Pages numbered, dated, and signed
• Table of contents filled in
• Clean-up stickers received (part of safety grade)

Lab write-ups will generally be collected the class after a lab write-up is assigned. They will be graded according to the Lab Report Guidelines document. You will be told before turning it in what sections will be graded. Generally, every lab will have a data notebook grade, a data collection grade and a data processing grade. When I collect lab write-ups, you can tear out your hand written data to staple with the rest of your typed lab report.

See above for links to lab guidelines documents and checklist.

When writing a hypothesis you must make a prediction and justify your prediction using scientific terms

Example:

• Hypothesis: The heat given off by the solvation of calcium chloride in a fixed amount of water, is directly proportional to the amount of calcium chloride added to the water. Since calcium chloride is an ionic compound and ionic compounds are known to separate in water in a process called solvation, and since solvation produces heat, than the more particles that dissolve, the more heat will be produced causing an increase in temperature in the water. The heat of solvation is produced via the breaking of the ionic bonds into Calcium and Chloride ions followed by the attraction of water molecules to the charged ions. The heat of solution for calcium chloride is X kJ/mol (give reference)…using various heat equations, a theoretical temperature can be calculated.
• Note that your hypothesis doesn't have to be correct (i.e. your investigation might prove it incorrect), just reasonable.

Raw data is any value that is directly measured. Here is an example of the difference between raw data and calculated data

Let's say you want to calculate the volume of a peanut by displacement...

• Fill a graduated cylinder with water
• (RAW DATA) Record the initial level of the water
• Put the peanut in the graduated cylinder
• (RAW DATA) Record the new level of the water
• (ANALYZED DATA) Subtract the initial level from the final level to get the volume of the peanut.

What should the data table look like?

Why is it important to write down raw data? Because if you make a mistake in your calculations and all you wrote down was the analyzed data - it is impoossible to go back later and correct your mistake.

The purpose of showing your calculations is to make it clear how a particular value was calculated. This is most important when the calculation you do is unique or when there are other methods possible.

It is not necessary to write out every single calcuation you do for an experiment. It is only necessary to show examples of the type of calculations you did.

Let's say you are calculating the density of a type of plastic and you have measured three different size pieces and have the following data:

Trial	Mass	Volume	Density
1	5.0 g	1.0 L	5.0 g/L
2	10.0 g	2.0 L	5.0 g/L
3	15.0 g	3.0	5.0 g/L
Average			5.0 g/L

Under the calculations heading you should show a sample density calculation and a sample average calculation. Even though you did three density calculations, just show one. Your example should include data from your experiment - not just random numbers.

Calculations
Density = mass/volume = 5.0g/1.0L = 5 g/L
Average = (5.0 g/L + 5.0 g/L + 5.0 g/L)/3 = 5.0 g/L

• Calculated density (measured by you in lab): 5.0 g/L
• Actual density (according to a book): 5.2 g/L

1. Find difference = 5.0 - 5.2 = 0.2
2. Calculate % error = 0.2/5.2 = 4%

**It is not acceptable for Honors or IB students to use this template word for word and is generally not thorough enough by itself.

• Conclusion Template
  • In this lab we attempted to (answer the question / figure out why / measure / verify)      (question you tried to answer)      by      (describe method you chose)     . Our results (were /showed / gave)      (state conclusion)      which (ageed / somewhat agreed / did not agree) with our hypothesis. This means that      (what you learned about chemistry concepts from this lab)     . The problems we encounterd in this lab were      (sources of error)     . We (do / do not) believe these errors significantly affected our results (and / but) we could improve our results by      (list ways you could have designed/performed the lab so that these problems did not occur)     . Further questions we could investigate here are      (other possible answers to the lab question)     .
• For quantitative results (actual numbers) include your percent error when discussiong whether or not your hypothesis was right.