Section 1.3—Designing Your Own Labs

Designing Labs This is not giving a “scientific method”…rather it’s giving hints at how to stay focused on the goal when designing a lab to allow you to write them more efficiently It gives you a plan of attack, but you can adjust it as you need for various labs

Identify the purpose, problem, question If variables are appropriate (relationship or effect lab), identify them in the problem  Example of a purpose: To determine the effect of temperature on pressure If variables are not appropriate, be as descriptive as possible  Example of a question: What is the concentration of a saturated NaCl solution at room temperature? You can phrase it as a purpose or question You should also identify any important constants

Gather Background Information The background information section is where you put together all the different concepts you know together to solve your problem or answer your question It might contain:  Definitions  Known relationships  Equations

Write a hypothesis Only when appropriate—only in relationship or effect labs After looking at all your background information, make a hypothesis (prediction with explanation for why you think so)

Set-up the Results/Calculations section Write any equations that you will need to solve your problem or answer your questions. You won’t have numbers to plug in, but you can set up the equations/calculations now.

Set-up the Data Table Go through the calculations you set up and make a data table that asks for each quantity you’ll need Remember that some measurements must be taken indirectly & you will need to take that into account:  For example, you can’t put a chemical directly on the balance, so you’ll need the mass of the container (beaker or weighing dish) and then the mass of the container & chemical in your data table Your data table should not contain any calculated values (even just subtracting out the mass of the beaker)…only those you will actually measure with an instrument!

Write your Procedure Procedures should be:  Clear, Concise, Numbered list of steps  Repeatable by someone of your same level of experience/education Go through your data table and write a procedure step to measure each thing asked for in your data table. If the data table includes masses or volumes of chemicals, give an approximate amount in the procedure  Example: Add approximately 2 g of NaCl to the beaker. Find exact mass & record.

Write your Materials List Go through your procedure and make a list of each piece of equipment and chemical that you’ll need Be sure to include how many of each type of equipment and what approximate quantity of chemical  You don’t need to specify the amount of water needed!

Write your Safety Concerns Go through your procedure & materials list and specify any safety concerns. Possibilities include:  Wear goggles (anytime you use glass or chemicals)  Use caution with glassware  Use caution with hot glassware or hot chemicals  Any cautions specific to a chemical you’re using (your teacher will tell you these)  Report any spills, breaks or incidents to your teacher immediately  Wear aprons or gloves, if necessary

Now you’re ready to do your lab! Begin performing your lab (after your teacher checks it for safety, if necessary) If you need to make changes to your procedure at any time (you realize it’s not quite right)…that’s OK  Just make sure you change the written procedure as well so that when you’re done, the written report reflects what you actually did Record your data in the data table Complete the calculations you’ve set up

Write your Conclusion Restate the purpose Completely answer the purpose with your results Address any earlier hypothesis…does your evidence support or not support it?  If it does not support the hypothesis, propose a new hypothesis Suggest possible sources of error  “human error” is not specific enough & “Calculations” doesn’t count