Writing a Descriptive Lab Report 1. Title page: (this is a page all of itself) You need to write the title of the lab in all capital letters. Also include your name, class, period, teacher, and date. 2. Label the following and put in paragraph form: Abstract: This is a very brief summary of what you did in the lab (highlights). Materials: (this is the only section that is in a list form with either numbers or bullets) What did you use? -Ex, slides, microscope, etc. Procedure: What did you do? What were the steps? (MUST BE IN PARAGRAPH) -Ex. The first step to successfully completing this lab was to properly sterilize the equipment used. This was done by lighting a Bunsen burner and running the inoculating wand through the heat three or four times to insure that any unwanted bacteria was killed. Results and Conclusion: What did you see? Was there any human error (mistakes, faulty equiptment, etc.) 1. Note: Human error is used ONLY when the experiment did not have the desired outcome (for example, when you begin to fill a semi-permeable tied bag to observe osmosis, you spill green dye into the sample water). It is not a copout for being lazy and not completing the lab as assigned. 2. If there is a major error, explain what went wrong and how the lab was supposed to come out.
3. Questions: (last page, separate) If the teacher gives you any questions to answer about the lab, you are to write the question AND answer it here.
SAMPLE REPORT MAY NOT TURN IN FOR CREDIT
OSMOSIS John Doe Biology I, 2nd Period Mrs. Langford Aug. 5, 2007
Abstract Osmosis is a specialized case of diffusion that involves the passive transport of water. In osmosis, water moves through a selectively permeable membrane from a region of its higher concentration to a region of its lower concentration. The membrane selectively allows passage of certain types of molecules while restricting the movement of others. The solute concentration in the beaker is higher than that placed in the dialysis bag, and thus the water concentration is lower in the beaker than in the bag. This causes water to move from the bag into the beaker. This can be observed by adding a dye to the solution within the dialysis bag. Materials gram scale beaker dialysis bag green food coloring yarn 0.2M solution 0.8M solution
Procedure The first step of this experiment is to fill an empty beaker with a 0.8M solution given by the instructor, followed by preparing a dialysis semi-permeable bag in which to measure osmosis. To prepare the bag, one must first gently loosen the two semipermeable walls from one another to open what now looks like a flimsy tube. Gently, tie off one end of the tube tightly with the yarn. Next, fill the bag with a 0.2M solution given by the instructor and add one drop of green food coloring. Finally, tie off the open end of the bag as tightly as possible. Once the beaker and bag has been prepared, the next step is to weigh and record the initial weight of the semi-permeable bag. After completing this step, one is to place the prepared bag into the prepared beaker and wait for about eight minutes. After allowing the bag to sit inside the solution within the beaker, the bag is removed from the beaker and weighed again. Finally, this new weight is subtracted from the initial weight to show how much water the dialysis bag lost due to osmosis. Finally, to further prove osmosis occurred, one is to look at the remaining solution in the beaker. If there is a hint of green, then one can conclude that osmosis took place. Results and Conclusion The results of this lab mirrored what was to be expected. There are often several different types of molecules in a solution. The motion of each type of molecule is random and independent of other molecules in the solution. Each molecule moves down its own concentration gradient, from a region of its high concentration to a region of its low concentration. Though the net movement of molecules is down their concentration gradient, at any time molecules can move in both directions as long as the membrane is permeable to
the molecule. Keep this in mind while you take a closer look at the beaker below. Some human errors that could have occurred would be mostly focused around opening and properly closing the dialysis bag. Some participants had issues in gently opening the bag which resulted in a tear in the bag leading to a leaking of the 0.2M solution. Others did not tie of the bag securely enough which caused a greater outflow of the solution and therefore a greater loss of water. Questions 1. Will there be a net movement of water between two isotonic solutions? No, there will be no net change in the concentration of water on either side of the membrane. 2. Why don't red blood cells pop in the bloodstream? Red blood cells don't pop because the blood provides an isotonic environment for the cells.