Density

Once upon a time, there was a little girl named Nikki who loved to play with different kinds of toys. She had a big box full of balls, blocks, dolls, cars, and other things. One day, she decided to sort her toys by their size and shape. She took out all the balls and put them in a pile. Then she took out all the blocks and put them in another pile. She did the same for the dolls, the cars, and the other toys.

She noticed that some of the balls were bigger than others, but they all looked round and smooth. She wondered if they were all the same inside. She picked up a big golden coloured ball that was very light and easy to squeeze. She said, “This ball is big, but it is not heavy. It must have a lot of air inside.” She picked up a small white coloured ball that was very hard and heavy. She said, “This ball is small, but it is very heavy. It must have something solid inside.”

She wanted to know more about what was inside the balls. She asked her father for a pair of scissors and cut open the golden coloured ball and the white coloured ball. She saw that the golden coloured ball had a thin layer of rubber and a lot of air inside. She said, “This ball has a lot of space inside. The air does not weigh much.” She saw that the white coloured ball had a thick layer of metal and no air inside. She said, “This ball has no space inside. The metal weighs a lot.”

She learned that different things have different amounts of space and weight inside them. She learned that some things have more space and less weight, and some things have less space and more weight. She learned that this is called density. She understood, “Density is how much space and weight something has inside.”

She wanted to test her new knowledge. She filled a bucket with water and dropped different balls into it. She saw that some balls floated on the water and some balls sank to the bottom. She said, “The balls that float have more space and less weight than the water. The balls that sink have less space and more weight than the water.”

She was very happy with her discovery. She decided to try the same experiment with other toys. She found out that some blocks floated and some blocks sank, some dolls floated and some dolls sank, some cars floated and some cars sank, and so on.

She had a lot of fun playing with density. She said, “Density is very interesting. I can tell how much space and weight something has by how it behaves in water.” She thanked her father for the scissors and put her toys back in the box.