Titan is the largest moon of Saturn. Its surface has lakes and rivers, and its atmosphere contains clouds that produce rain. The average surface temperature of Titan is −179 °C.
The table shows the melting points and boiling points of four substances found on Titan.
| Substance | Melting point / °C | Boiling point / °C |
|---|---|---|
| methane | −182 | −162 |
| ethane | −183 | −89 |
| nitrogen | −210 | −196 |
| water | 0 | 100 |
Deduce the state of each substance at −179 °C.
methane
nitrogen
water
Methane gas rises into the colder upper atmosphere of Titan and forms rain. Explain, in terms of particles, why methane gas forms liquid droplets when it cools.
In winter the temperature at Titan's poles can fall to −185 °C. A scientist claims that at this temperature the methane lakes would freeze but the ethane lakes would stay liquid. Evaluate this claim using the data in the table.
A space probe collects liquid from one of Titan's lakes. The liquid starts to freeze at −186 °C and is not completely solid until −195 °C. Explain what this shows about the liquid in the lake, and use this to evaluate the scientist's claim in (c).
53 exam-style questions on Edexcel GCSE Chemistry 3.1 States of matter, covering 3.1.1 The three states of matter and changes of state. Each one has a worked solution and a mark scheme showing where the marks go.