You can easily describe and/or calculate the density of substances if you understand that density is nothing more than a ratio comparing two quantities. The things being counted may vary but all densities are ratios that compare the quantity of a substance in a specific volume (or area).

Densities can be demonstrated using paperclips and index cards (or small equal size pieces of paper).

**Discover for Yourself:**

**1. **Place 16 paper clips on an index card. Spread the paperclips so that they are equally spaced from each other.

**2. **Repeat step one using a second card and 9 paperclips.

**Questions:
**

**1. **Which card has a greater density of paperclips?

2. How could you write the density of paperclips for each card?

**Answers: How to Find the Density of a Substance
**

**Think!**

**1. **Write the ratio comparing the number of paperclips to the area of the card. Ratio can be written as:

A: B or A/B

**2. **Let A = the number of paper clips; Let B = the area of the card

Note: Since the area of the cards are the same and you only want to compare the density instead of calculating a specific value for each, let area = 1 card.

**4. **Ratios for Red Card are: 16 paperclips: 1 card; 16 paperclips/1 card

**5. **Ratios for Blue Card are: 9 paper clips: 1 card; 9 paper clips/ 1 card

**6.** Which card has a larger ratio between paperclips and the card?

**Answer: Red card has a larger ratio, thus a greater density of paperclips.**

More Later, Janice

To understand the density formula as well as other science formulas, kids need an understanding math. For simple explanations about common math principles, see **Janice VanCleave’s Teaching the Fun of Math.**