| It's a Gas! | | Across | | | 2. | | This gas can be used to fill party balloons. | | | 4. | | This gas is used to make yellow-green 'neon' signs. | | | 6. | | This gas is widely used in luminous signs. | | | 7. | | Nearly 1% of the earth's atmosphere is... | | | 9. | | About 21% of the earth's atmosphere is... | | | 10. | | Most of the visible universe is made of... | | | 11. | | This gas is used in strobe lights. | |
| | Down | | | 1. | | When combined with tin, this gas helps keep your teeth strong. | | | 3. | | This gas helps keep swimming pools clean. | | | 5. | | About 78% of the earth's atmosphere is... | | | 8. | | A radioactive gas. | |
|
| | |