What Is Mass?

When Emma was just 4 years old and had just started at Mayo Demonstration School for Science and Technology, she was having her after school snack and asked me, "Mom, what's mass?"

I freaked out.  I was so ecstatic.  My 4 year old daughter who had just started school was learning about mass and asking me to explain it to her????  I said as calmly as I could "Well Emma Jane, I am so glad you asked.  Mass is the amount of matter in a substance irregardless of gravity.  Your mass here is the same as your mass on the moon, but your weight would be different. For example, my weight here on earth is 135 but my weight on the moon would be 23 pounds.  Weight is related to gravity but mass is independent of gravity."

Then I went to get a pan balance that I just happen to have in the craft room and set up a quick experiment in the kitchen in which we were going to determine the mass of the Oreos she was eating.  I was explaining that we were going to compare the mass of the Oreos to something with a known mass.  She hesitated for a moment, knowing that she was derailing the science train barreling down the track and said, "Mom, I think it's church.  Sophie invited me to go on Saturday."

"Oh,"  I said.