Ready to try out the scientific method yourself? Then let’s get started on our first experiment!

Have you ever wondered how raindrops form? Water molecules are attracted to each other and stick together through a property called “surface tension.” Surface tension forms a kind of “skin” on the surface of a liquid. In this experiment, you will hypothesize the number of drops of water that can fit on a coin.

Materials

(1) 100 mL Beaker
(1) Piece of Graph Paper
(1) Pipette
*(1) Ruler
*Paper Towel or Cloth
* (1) Coin
*Tap Water

*You must provide.

Procedure

Observe your coin. What type of coin are you using? What does the coin look like? What is the diameter of the coin? Record your observations on a piece of paper so that you can share it in the discussion later.

Hypothesize how many drops of water will fit on the coin and record it in Table 1. Be sure to include why you think that many drops of water will fit!

Rinse your coin in tap water and thoroughly dry it with a paper towel or cloth.

Put the coin on the table. Be sure to record what side of the coin you are using – you will want to use the same side of the coin for each trial you perform!

Fill your 100 mL beaker with tap water – you want it to be about half full.

Use the pipette to draw up 2 mL of water.

Carefully drop individual drops of water onto the coin. Be sure to count each drop!

When the water spills over the edge of the coin, stop adding drops.

Record the number of drops of water that fit on the coin in Table 1.

Repeat Steps 3 – 9 four more times, making sure to completely dry the coin with the paper towel or rag each time.

Calculate the average number of drops that fit on the coin across the five trials (Hint: The average is equal to the sum of all five trials, divided by five). Record the average in Table 1.

Create a bar graph comparing how many drops you hypothesized would fit on the coin and the average number of drops that fit on the coin. You can use Microsoft^® Excel or the free graph maker provided by the National Center for Education Statistics (https://nces.ed.gov/nceskids/createagraph/ (Links to an external site.)).

Compare your hypothesis and actual results – was your hypothesis correct?

Share your hypothesis and the results of your experiment on the discussion board. Be sure to include what kind of coin you used!

Download your Data Collection Sheet

Table 1: Number of Drops of Water that Fit on a Coin