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!

Erosion & Run-Off: What affect does vegetation have?

 This is a really simple demonstration, but it does require some planning ahead (not always my strong suit... )

You'll need two shallow pans or boxes.  Fill each pan with dirt.  Sprinkle grass seed on one of the pans of dirt.  Keep the soil moist as the grass seed germinates and grows.  (You don't need to do anything with the other pan of dirt right now).

Once you have a nice crop of grass in the one pan, take both pans outside.  Prop up one end of each pan using bricks (or something else that will raise it a few inches).

Begin to spray both pans with a hose or spray bottles of water.  You can spray in any manner you'd like, just try to get both pans equally.

While you're spraying, observe what happens to both the soil and the water in each situation. 

When you've finished, discuss the impact of vegetation on soil erosion and/or water run-off. 

Transporting Water and Finding Equilibrium

You may have seen images of this activity before... I know versions of it have been prevalent on Pinterest.  We'll go through the basics and then we'll talk a bit about stepping it up and stretching your kids' brains!

In its basic form, you begin with 3 cups, some water, food coloring and a paper towel.

Fill two of the cups with water and color the water in each cup a different color.

Arrange the cups in a line, with the empty cup between the cups with colored water.

Take a piece of paper towel (I used half a paper towel) and twist the middle a little.  Then bend the towel so that it creates a bridge from one cup to another.  Repeat with another paper towel to connect the other two cups.

Observe.


The water will move from each of the cups, through the paper towels into the empty cup.  You'll know water has moved because there is now water where before there was none and you'll know that it has come from both cups because the center cup will contain green water (the combination of yellow water and blue water).

The movement happens fairly quickly - the process will be complete within a couple of hours.  

It may not be terribly obvious, because we tend to start with about equal amounts of water in the two cups with which we start, but the water will keep moving until all three cups have equal amounts of water in them.  

At that point, water stops moving and system will basically just sit there.  The cups have reached equilibrium. You can let the cups sit there for days and you won't notice much changing. 

I took this photo before the system had reached equilibrium and forget to take another one after the process was complete.  But I can assure you that all three cups finished with an equal amount of water.

Now is when you can really challenge your students to figure out what's going on within the system.  What will happen if more water is added to the system?

You can add water by pouring more water into any one of the cups in the system.  Or you can add a fourth cup to the system and connect it with a paper towel.

I chose to add another cup of water (uncolored this time) and connect it to the middle (green) cup with a paper towel.

Make sure the cup you add to the system has a different water level than what's in the other cups or you won't get any movement.  I was trying to move water into the green cup, so I made sure my new cup was pretty full of water.  You could also connect an empty cup to the system via paper towel and watch the water flow in the other direction.

The system that had been sitting dormant for several days sprang into action. 

Colorless water flowed into the green cup (as evidenced by the lightening of the green color).  Green water then flowed into the blue and yellow cups (as evidenced by the color change in those cups). 

A really simple experiment with a lot of permeations - you can keep playing with it day after day, adding water or empty cups at different spots in the system.  Really great for inquiry learning and exploring!

Body Systems: Nervous System: Brain Model

The human brain, at full-size,  is about the size of a full sheet of newspaper (or a pillow case), that's folded up to fit in your skull.

Keep your eyes open for a sheet of newspaper that has a full page ad that has some writing, but a large white space.  When you're born, your brain already has a lot of information stored in it, represented by the writing on the page.  But there's also a lot of room to learn more.  That's the white space on the paper - the brain space that's left to "write" on.
 
It's difficult to put numbers on how "full" one's brain is at birth and how much "room" there is for future learning, as the more you learn the more connections your brain makes.  It appears that there's always room for more learning to take place and that the brain is never "full" (to our current knowledge). 

Compound Story

Have your students write some "science fiction".  

Each student chooses a compound (see below for some ideas) about which to write a story.  While not a report, the story should include scientific information about the compound and include the compound's empirical and structural formulas. 

Encourage your students to be creative in their writing and get into character - they could tell the story from the compound's point of view.  They could "be" one of the elements within the compound.  They could be reporting on a big news story involving the compound. 


If students are having a hard time getting started, they may want to look up their compound to find out what it's used for and where it's found - what they learn may be the start of a story. 

To make sure students don't get too carried away with the fiction aspect and forget the science part, you might wish to require them to use 12 (or whatever number you deem suitable) science terms.  Some possibilities:

• metal
• nonmetal
• solid
• liquid
• gas 
• chemical change
• physical change
• compound
• mixture
• periodic table
• family(ies)
• atomic number
• atomic mass
• stable
• unstable
• positive
• negative
• neutral
• valence electrons
• valence number
• empirical formula
• structural formula
• subscripts
• octet rule
• arms
• giver
• taker
• bonds
• share
• scientific name
• react
• reaction
• atom
• molecule

A list of compounds, to get you started:

• methane
• ethane
• propane
• butane
• octane
• acetylene
• benzene
• toluene
• carbon tetrachloride
• methanol
• ethanol
• propanol
• butanol
• carbon monoxide
• carbon dioxide
• calcium bicarbonate
• calcium oxide
• hydrochloric acid
• carbonic acid
• nitric acid
• water
• hydrogen peroxide
• hydrogen sulfide
• sulfuric acid
• ammonia
• nitric oxide
• nitrous oxide
• sodium chloride
• sodium nitrate
• sodium bicarbonate
• sodium hydroxide
• ozone
• silicon dioxide
• fructose
• sucrose
• potassium chloride
• citric acid
• vitamin C
• silver fluoride
• sodium fluoride
• silver chloride

The Expanding Universe: Balloon Model

 On a flat, not-yet-inflated balloon, mark a series of points using a permanent marker.  You may wish to make some of the points closer together and others farther apart. 

These marks represent parts components of the universe.  You may wish to have students measure the distance between points to make it more quantitative, of you may wish to just keep it a visual activity. 

 As you begin to inflate the balloon, the points mover farther and farther away from each other.  The universe is expanding and distance between points is growing. 

Rate of Reaction: How Does Surface Area Affect the Rate of Reaction?

 The combination of Alka-Seltzer and water produce a chemical reaction.

To see how surface area affects the rate at which this reaction takes place, you'll need two Alka-Seltzer tablets and two glasses of water. 

 Keep one of the tablets intact and crush the other tablet (crushing it into an actual powder would be even better than the pieces I've shown here - good chance to break out the mortar and pestle if you've got them).

Drop the whole tablet and the crushed tablet into the water (each tablet into its own glass of water) and observe the length of time it takes each reaction to finish.