| A | B |
|---|
| launched | something started in motion or set off |
| particles | small bits or pieces of an element |
| dense | things that are thick or packed closely together |
| inflate | to cause to swell by filling with air or gas |
| anchor | held firmly in place |
| hydrogen | light gas that burns easily |
| scientific | having to do with or used in science |
| companion | a person or animal who keeps somebody company |
| altitude | the measurement of the distance above Earth’s surface |
| chemist | an expert in chemistry, the science that deals with the characteristics of elements |
| helium | a very light, colorless, odorless gas that does not burn |
| generalization | a broad statement made by combining the facts presented in the text with reader's own prior knowledge |
| Similes | uses "like" or "as" in a comparison of two unlikely things |
| Metaphors | does not use "like" or "as" in a comparison of two unlikely things |
| Number Prefixes | prefixes that refer to an amount |
