Let Us Weigh Lettuce

An easy lesson in measuring mass, collecting data, graphing (if you wish), percentages and plants. And a great experiment to start at the beginning of the school year.

You'll need a leaf of lettuce and a balance.  The precision of an electronic balance is nice for this particular activity, if you have one available.

If you have a balance that can remain dedicated to this activity, you can place the lettuce leaf right on it.  Record the mass.  Each day when the students come to class, they should record the mass of the lettuce.  Continue recording the mass every day for a month.

[If you cannot dedicate a balance to the activity, you'll need to first find the mass of a weighing paper.  Record that, then place the lettuce on the weighing paper and record that mass.  Lift the paper with the lettuce on top and keep in a safe place while the balance is being used elsewhere.  Return the paper and lettuce to the balance each day to find the mass.  You'll have to subtract the mass of the weighing paper from each measurement to get the mass of the lettuce.]

Once you've collected all the data, you can graph it if you wish.  Is the water lost at the same rate throughout the month or does it change?

You can also determine how much of lettuce (by mass) is water.

Mass of lettuce at start - Mass of lettuce at end = Mass of water

(Mass of water / Mass of lettuce at start) * 100 = % of lettuce mass that was water

If you've caught your students' attention with this one, you can proceed to follow the same procedure to find the water content in other items.  Maybe your students will want to compare the water content in different types of lettuces or different types of leaves or different types of fruits or vegetables.  Lots of possibilities - you could have something going every month of the school year!

Zack's Alligator: Measurement and Graphing Exercises

Zack's Alligator is the story of a boy who is given a tiny alligator on a key chain, with the instructions to water her every day.  When given water, Zack's alligator grows and grows and they're off on all sorts of adventures. 

You can have your own adventures in science with a growing alligator.  (Of course you can use another other "Growing" animal, the alligator just complements the book nicely).

Before you place the alligator in any water, take some measurements.  The number and type of measurements you take will depend upon the age of your students.  Some possibilities:

• Length (nose to tail)
• Width - across the head
• Width - from toe to toe
• Thickness
• Mass
• Volume
• Density (not a measurement, but could be calculated if you have mass and volume data)

I did this with a very young student, for whom measurements are meaningless, so we traced around the alligator.   (FYI, I used the back side of a sheet of freezer paper - I could get a nice long sheet of paper, and it's plasticated, which was important since future tracings would be made when the alligator was wet).

After measuring, the alligator can be placed in a large tub of water (you want to make sure it has room to grow). 

Each day, for about a week, take each of the measurements.

At the end of the week, you'll have a collection of data.

Our data was a picture, showing the alligator's growth:

If you have numerical data, you can create graphs that illustrate the rate of growth.  You can then analyze whether the alligator grew faster in one dimension than another or if they all grow at the same pace. 

Graphing: Class Data

A day or two before you want to have the students create the graphs, have the students complete a questionnaire.  Here are the questions I've asked (it provided me with enough data for groups of students in 3 classes):

• In which month were you born?
• How many siblings do you have?
• What's your favorite color?
• Whats your favorite food?
• What's your favorite TV show?
• What's your favorite movie?
• What's your favorite book?
• What's your favorite subject/class?
• What's your favorite sport?
• What's your favorite outdoor winter activity?
• What's your favorite outdoor summer activity?
• What's your favorite season?
• What's your favorite restaurant?
• Who's your favorite musician/band?
• What's your least favorite vegetable?
• What color are your eyes?
• In which state were you born?
• How do you get to school?
• What's your zodiac sign?
• What pets do you have?
• What do you want to be when you grow up?

 

 

Cut the responses apart and put them in groups.

 

Divide students into groups and provide each group with one set of data. 

 

Students sort data and decide on an appropriate way to graph it.

 

Some of the data sets will require more work than others.  Some of it will need to be put into groups before it can be graphed.  For example, you will probably get a large variety of responses for "What is your favorite restaurant?", so the students may need to graph types of restaurants (i.e. Italian, Chinese, fast food, etc.) rather than specific restaurant names.  On the other hand, "What's your favorite season?" is pretty straight forward and easy to graph. 

Graphing: Candy Data

This is a pretty classic activity for students learning to graph (but older students who are reviewing graphing enjoy it too)...

Each student needs a snack-size pack of candy that comes in multiple colors: M&Ms, Skittles, Smarties, etc.

Sort the candy by color, then graph - bar graph, pictograph, pie chart or all of the above.

Graphing & Extrapolating: How Many Licks Does it Take?

Last week, we started to find out How Many Licks Does it Take to Get to the Center of a Tootsie Roll Pop.  Last time largely focused on data collection, which is a great skill, but doesn't answer the question at hand. 

Since we weren't able to complete enough licks to get our answer, we need to graph the data and then extrapolate to find the answer.  You can do this by hand or using Excel. 

Here are the instructions for creating the graph on Excel*
Open a new excel worksheet

Label column A "Number of Licks"

Label column B "Mass"

Fill in number of licks, continuing by 10s until you reach 200 (yes, go to 200 even if you didn't get anywhere near that many licks done).

Fill in corresponding masses

Highlight the numerical data (don't include the column titles in your highlighting)

Go to Insert, then Chart

Click on XY Scatter, then click Next

Click Next

Enter a chart title (name of lab), the x-axis label (Number of Licks), and the y-axis label (Mass (g))

Click Next

Select the option to place the chart as a new sheet

Click Finish

Click on one of the points on the graph - all the points should be highlighted

Go to Chart, then Add trendline

Click Okay

Click on the legend and delete it

Double click on the numbers on the y-axis.

Click on Scale

Change Minimum to 0

Double click on the background of the graph

Set area to none

Print the graph

Draw a horizontal line at the value you had for the stick and wrapper

At the point where the line you drew hits the line on the graph, draw a vertical line to the x-axis.

Estimate the value for where the line hits the axis - that is the number of licks it would take to get to the center of a Tootsie Roll Pop



*I wrote these instructions using an older version of Excel, which is still what I have access to. If you use a newer version and find that some of the terminology needs to be changed, please let me know.  Also, please let me know if something is unclear or you just aren't sure about something and I'll do my best to help.

Graphing: Growing Monkey

Look around your favorite retailer for these Growing "Things". I've seen turtles, crocodiles, princesses, pirates, etc.

We happened to have a monkey (thanks Aunt Amy - I told you it would show up on here!).

Take some measurements of your "thing" before you do anything with it.

Then place it in water.

Most of these say they'll take up to 72 hours (that's 3 days) to reach full size. I recommend you start on Monday, so you'll have all week to watch it.

Each day, at the same time (or as close as you can come), retake the same measurements you took initially.

At the end of the week, you should have several data points that can be graphed. Older students could determine the rate of growth.

You may even want to have them look at the data after 24 and 48 hours and ask them to predict how large it will grow by 72 hours.

*****
My apologies, my "after" pictures of your monkey didn't turn out, so I don't have much for you. Our monkey about doubled in size. Some of the "things" out there are a lot smaller to start with and claim to increase by 600%, which should give you some great measurements.