• 19 blanks
  • Checked October 2026

Phase Diagram of Carbon Dioxide Worksheet

Two real phase diagrams with numbered blanks: carbon dioxide, where dry ice sublimes, and water, whose melting curve leans left.

Phase Diagram of Carbon Dioxide Worksheet

Name Date

Numbered phase diagram

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
More options

Write the name of each numbered blank.Answer key

  1. Solid
  2. Liquid
  3. Gas
  4. Sublimation
  5. −56.6 °C
  6. 5.1 atm
  7. 31 °C
  8. 72.8 atm
  9. Positive slope
  10. Solid
  11. Liquid
  12. Gas
  13. Melting
  14. Boiling
  15. 0.01 °C
  16. 0.006 atm
  17. 374 °C
  18. 218 atm
  19. Negative slope

Drawn for this site on 2026-10-03 by script from the table of two substances it holds. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a blank is answered.

Next step Next: name the curves of a blank phase diagram

All 19 blanks on the diagram

Show the list

Carbon dioxide 9

  1. Solid Solid carbon dioxide is called dry ice. Low temperature and high pressure favor a solid.
  2. Liquid Liquid carbon dioxide exists only above 5.1 atm. That is the pressure of its triple point.
  3. Gas The gas fills the warm, low-pressure side of the chart. High temperatures and low pressures favor a gas.
  4. Sublimation At 1 atm dry ice turns straight into gas. It does so at about −78.5 °C, with no liquid between.
  5. −56.6 °C Carbon dioxide's triple point is at −56.6 °C. That is 216.58 K.
  6. 5.1 atm Carbon dioxide's triple point is at 5.1 atm. Below that pressure it has no liquid state.
  7. 31 °C The critical point of carbon dioxide is at 31 °C. That is 304.18 K.
  8. 72.8 atm The critical point of carbon dioxide is at 72.8 atm. That is 73.80 bar.
  9. Positive slope The melting curve of carbon dioxide leans to the right. Its melting point rises as the pressure rises, as for most substances.

Water 10

  1. Solid Solid water is ice. Low temperatures favor a solid.
  2. Liquid Liquid water lies between the two upper curves. It exists only at or above the pressure of the triple point.
  3. Gas Water as a gas is called water vapor. High temperatures and low pressures favor a gas.
  4. Melting At 1 atm ice melts at 0 °C. The arrow crosses the curve between solid and liquid there.
  5. Boiling At 1 atm water boils at 100 °C. The arrow crosses the curve between liquid and gas there.
  6. 0.01 °C Water's triple point is at 0.01 °C. That is 273.16 K.
  7. 0.006 atm Water's triple point is at 0.006 atm. Below that pressure ice does not melt: it sublimes.
  8. 374 °C The critical point of water is at 374 °C. That is 647 K.
  9. 218 atm The critical point of water is at 218 atm. That is 220.64 bar.
  10. Negative slope The melting curve of water leans to the left. Ice melts at a lower temperature when the pressure rises.

How this list was compiled: Checked on 2026-10-03. The triple point and the critical point of carbon dioxide and of water: NIST Chemistry WebBook, phase change data (carbon dioxide: triple point 216.58 K and 5.185 bar, critical point 304.18 K and 73.80 bar; water: triple-point pressure 0.0061 bar, critical point 647 K and 220.64 bar, boiling point 373.17 K), turned into degrees Celsius and atmospheres by the drawing script and rounded; against Wikipedia, text only (Triple point; Critical point (thermodynamics); Carbon dioxide (data page); Water (data page); Phase diagram; Dry ice) and Averill and Eldredge, Principles of General Chemistry, section 11.7 Phase Diagrams (carbon dioxide: triple point -56.6 °C and 5.11 atm, sublimes at 1 atm at -78.5 °C, critical point 30.98 °C and 72.79 atm, melting curve leaning right as it rises; water: triple point 0.01 °C and 0.00604 atm, melting curve that leans slightly left as it rises). What the regions, curves and the line at 1 atm mean: Purdue University, General Chemistry topic review, Phase Diagrams, and the University of Texas at Austin, CH302 Phase Diagrams. Every printed value is NIST's figure after rounding and is matched by the other two at that rounding, except the 0.01 °C of water's triple point, which the NIST page does not list: it is the 273.16 K of the other two. Licence: own work

The drawing: Drawn for this site on 2026-10-03 by script from the table of two substances it holds. Own work, nothing traced. Not to scale. Licence: own work

How it works

This phase diagram of carbon dioxide worksheet has a phase diagram for water worksheet on the same sheet. Each chart has numbered blanks for the phases, the values of the triple and critical points, and the changes at 1 atm.

Read the full guide

Carbon dioxide at 1 atm

The three curves meet at the triple point. The dashed line at 1 atm passes below it, so the arrow crosses only the curve between solid and gas: dry ice sublimes and never melts. The curve between liquid and gas stops at the critical point.

Water at 1 atm

Here the line passes above the triple point. The arrow crosses two curves: ice melts, then water boils. The melting curve leans left. The blanks on the axes ask for the temperature and pressure of each special point.

  • The charts are sketches. The numbers that belong in the blanks are real; the distances between them are not.

Questions and answers

What is the triple point of carbon dioxide?

About −56.6 °C and 5.1 atm. Solid, liquid and gas exist together there. Below that pressure carbon dioxide has no liquid state.

Why does dry ice sublime instead of melting?

Ordinary air pressure, 1 atm, is below the 5.1 atm of the triple point of carbon dioxide, where no liquid can exist. So solid carbon dioxide turns straight into gas, at about −78.5 °C.

How is the phase diagram of water different?

On a phase diagram of water worksheet the melting curve leans left: ice melts at a lower temperature as the pressure rises. For carbon dioxide, as for most substances, it leans right.

What is the critical point of water?

About 374 °C and 218 atm. The curve between liquid and gas ends there, and beyond it liquid water and water vapor cannot be told apart.

More quizzes

Show 6 more

Browse Science Quizzes