How to write a Lab Report

A guide to writing effective reports in the classroom.

Purpose of the report

A Lab Report should be a document that tells the reader what was done in an experiment or activity, and what was discovered.

It should be written so that the reader can duplicate the activity and results if they so desire.  Some labs will be performed from handouts or lab manuals, while in others you will devise your own procedure.

This is supposed to be a general guide so you can write a clear lab report from any class activity in any science class.  Some of the details will be different from teacher to teacher, so make sure you ask and take notes!

Title

This should be the first thing the reader sees when they look at your report.  It should include your name, the name of anyone you actually worked with (write "no partner" if you worked alone), the date the lab is due, the class and period, and of course the title of the lab.

Some teachers may want you to include their name too, so make sure you ask.  If there is a handout for the lab, it may include most of this information already, so you may not need to make a separate section or page.

If the teacher does not limit the number of pages to turn in, a separate title page is always good.

Purpose/Hypothesis This section should be short, and should tell the reader why the

experiment was performed.  Do not describe the procedure or repeat the introduction section of any handouts - this section should be short!  This section may actually be unnecessary if it is included on the lab handout, and you are allowed to include the handout.

        Activities that are designed to prove a point, determine a value, or identify an unknown will have a stated purpose.  It should be short: one or two sentences stating the goal of the activity.

        Activities designed to answer a question should have a hypothesis.  This is an "If...Then..." statement that can be proven or disproven.  For example:  "If the balloons are filled with oxygen, then they will cause a glowing match to reignite."

        Did I mention this section should be short?

Procedure

A concise numbered list of instructions describing what you actually did - not what you meant to do.  If this is on your lab handout you may not need to re-write it, but you should note any changes you made.  Also, if you performed a procedure from a lab manual, don't re-write the steps, just tell the reader exactly where they can find the procedure.

Data and Observations

Data is any information you read directly off a tool or instrument (like temperature, but not like change in temperature).  This should always be in table form.

Make sure every single number has a description, a value, and a label (this can be condensed if you have many similar pieces of data by labeling a column heading such as "Length (m)").

Make sure you read your instruments correctly.  There should not be any information that isn't data, and there shouldn't be anything missing.

Data should be presented in the order it was obtained.  Spend time making sure this section is clear and easy to read.

Recording data 1. Data means any number that you read from a tool. This

includes temperature, mass, volume, etc. 2. Remember to record the units of measure (deg C, grams, etc). 3. Every tool has a smallest marked division. Most of our

thermometers have a mark every 1 degree. When recording data, make sure to record all of the numbers marked, and one more digit that you estimate. On our thermometers, this means record to the 0.1 deg C. It's up to you to estimate this last number; if you think it's "on the line" then you are estimating a "0".

4. Record the numbers when you read them. Don't put the zeroes in later, and don't memorize the number to write it down somewhere else. Bring your notebook with you!

5. Record the numbers exactly as you read them. If you are looking at the age of a penny, write the year it says (1998), not the age (2 years). Any number that you have to calculate is a result, not data.

Presenting data

Data should always be presented in columns in a data table. The table must have a title or heading.

2. Every piece of data should be named (ex. "mass of cold water")

3. Every piece of data should have a number (ex. "23.718") 4. Every piece of data should have a label (ex. "grams") 5. If there are many measurements of the same type, you can

name them in the column heading, rather than individually. The same is true for the labels.

6. Always line up the decimal points in the column of numbers. This can be done using decimal-aligned tabs, or presenting data tables in a font such as Courier (where each letter gets the same width).

7. Spread it out! Make your data table as wide as the page. You can align the decimals on the red margin line you can see through the page.

8. Relevant observations should be included with data.

Graph(s)

Sometimes it is easier to show information or perform calculations on a graph than a list of numbers.  In some cases, a graph will be shown but not the data it came from (keep the data in your notebook!).

A graph should always fill the available space.  The axes should be named and labeled ("Mass in grams").  The scales should be consistent but they don't have to be the same (you can count by 5's on the y-axis as long as you count by 5's on the whole y-axis, and you can count by 2's on the x-axis as long as you count by 2's on the whole x-axis).

You only need to use a range to include your data - if the temperature stays between 20 and 70 Centigrade, your graph doesn't need to go from 0 to 100.

How to make a good graph

Remember that the x-axis goes across and the y-axis goes up and down.

1. Every graph should have a title ("Mass and Age of Pennies"). 2. Every graph should have a heading (your name, partner's name,

class, date). 3. Some graphs may need a key (to explain colors or symbols). 4. The graph should fill the available space. If you make a graph

with a computer, you can copy & paste it into your final report, and size it to fit your layout.

5. If you make a graph by hand it should always be on graph paper. 6. The axes should each be titled AND labeled to match the data

table ("mass of pennies, grams").

How to make a good graph-cont.

7. The range of each axis may be different. They should each be large enough to cover the needed range without lots of extra space. They do not need to start at zero.

8. The scale of each axis may be different, but each one must be consistent. If one box represents one year at the beginning of the graph, one box always represents one year.

9. The axes should be numbered to the same number of decimal places as the data was recorded. You don't need to number every box - usually every ten boxes will be adequate.

10. The independent variable always goes on the x-axis. If time is one of the measurements being graphed, it always goes on the x-axis.

11. Error bars may be used to indicate uncertainty in a measurement. The proper use depends on the graph and will be discussed as necessary.

How to make a good graph-cont.

12. Sometimes a line connecting points is OK. When this is true, it is usually best to draw the best smooth curve that goes near the data points. Look for general patterns rather than details.

13. If any calculations are done using points from a graph, the points used should be indicated (a small arrow labeled "calculation 1" should be adequate).

14. The less ink you use, the easier it is to read. Try it!

Analysis or Questions

this part depends on the lab.  You may have specific questions to answer or calculations to perform.

Most handouts or lab manuals include a few questions or instructions after the procedure.  Show these clearly and fully answered in the order they turn up. 

Show all your work for calculations (including names and labels; see below) and answer every question with full sentences and clear explanations.

Analysis

Here are two sample calculations (one addition, one multiplication):       mass of beaker with water 271.445g-  mass of beaker 166.202g = mass of water 105.243g

 heat transferredq = mtCpq = (42.101 g)(5.5 C)(1cal/gC)q = 230 cal

Grading

Your lab should be Neat - The sections must be in the correct order, one side of each sheet, stapled in the top left corner, typed (or neatly written in dark ink), few or no cross outs, no notebook "snow," and good general presentation.

Honors and AP must be typed to receive a score point 5.

Promptness

Your lab should also be Prompt.  There will be a penalty for each day the lab report is late

Rewrites

And finally, every lab has several dates attached to it: the day we did it in class, the day it is due, the day the re-writes are due (usually the Friday after I pass it back to you), and the day I officially "lose interest" and will not accept the lab (usually the Friday after the re-writes are due).

It is up to you to pay attention in class to know when these dates are coming.

Rubrics

For the first several labs of the year you will be given a specific point-by-point scoring guide describing what should be passed in, but after that you will be expected to extract this information from the lab handouts or your experience in the classroom.

I will still use them to correct every lab, but you will only see them for the re-writes.  If you ever have any questions, first check with your partner, then refer to your lab handout, then finally ask me.