| What is a state of matter? | The physical condition a substance is in (solid, liquid, gas, or plasma), describing how particles are arranged and how freely they can move. | State affects storage, handling, and system behavior on aircraft. | Hydraulic fluid (liquid) and oxygen (gas) behave differently in servicing. | State = how particles “behave”. | Expect simple definition questions at Level 1. | Easy | #states-of-matter #easy #module-2.1 |
| What is the key property of a solid? | A solid has a definite shape and volume because its particles are tightly bound. It resists changes in shape and volume. | Aircraft structures depend on stable solid behavior under loads. | Aluminum skin panels keep their shape during normal operations. | Solid = fixed shape + fixed volume. | EASA often tests basic solid/liquid/gas properties. | Easy | #solid #easy #module-2.1 |
| What is the key property of a liquid? | A liquid keeps a nearly constant volume but flows to take the shape of its container. It is nearly incompressible compared with a gas. | This is why hydraulics can transmit force efficiently. | A320 hydraulics use liquid pressure to move actuators. | Liquid = volume stays, shape changes. | If you see “incompressible”, think liquid. | Easy | #liquid #easy #module-2.1 |
| What is the key property of a gas? | A gas expands to fill its container and is easily compressible. Its particles are far apart compared with liquids and solids. | Gas behavior is central to pressurization and pneumatics. | Cabin air changes density/pressure with altitude and system control. | Gas = fills space and compresses. | EASA loves: “Which state is compressible?” | Easy | #gas #easy #module-2.1 |
| What is plasma? | Plasma is an ionized gas containing free electrons and ions, which makes it electrically conductive. It needs high energy compared with normal gases. | It helps explain why arcs can conduct strongly and cause damage. | An electrical arc can form a brief plasma path across a gap. | Plasma = gas with charge carriers. | Know plasma = ionized + conductive. | Easy | #plasma #easy #module-2.1 |
| Why can the same substance exist as solid, liquid, or gas? | Because changing energy changes particle motion and spacing. The chemical identity stays the same, but the physical arrangement and movement change. | This helps you predict behavior during heating/cooling in aircraft systems. | H2O can be ice, liquid water, or vapor without changing its chemistry. | Energy changes motion, not identity. | State change is not automatically a chemical change. | Medium | #phase-change #medium #module-2.1 |
| Why are liquids nearly incompressible? | Liquid particles are packed close together, so pressure cannot easily reduce their spacing. That makes volume changes small compared with gases. | This is why hydraulics transmit force smoothly. | Hydraulic fluid delivers steady actuator movement without springiness. | Packed close = hard to squeeze. | Force transmission questions usually point to incompressible liquids. | Medium | #hydraulics #medium #module-2.1 |
| What is latent heat? | Latent heat is energy absorbed or released during a phase change without changing temperature. It is used to rearrange particles rather than raise kinetic energy. | It explains constant-temperature boiling/condensing behavior. | Evaporation absorbs latent heat; condensation releases it onto surfaces. | Latent = hidden for change. | Classic trap: temperature stays constant during state change. | Medium | #latent-heat #medium #module-2.1 |
| Why can temperature stay constant while boiling? | Because the added heat becomes latent heat to convert liquid into vapor. Temperature rises again after the liquid has fully changed state. | This prevents incorrect assumptions during testing or troubleshooting. | Boiling in a controlled setup holds temperature until phase change completes. | Boiling = change first, rise later. | If it says “boiling steadily”, pick “constant temperature”. | Medium | #boiling #medium #module-2.1 |
| How does pressure affect boiling point? | Higher pressure raises boiling point, while lower pressure lowers boiling point. Reduced pressure makes it easier for a liquid to become vapor. | This matters at altitude and in low-pressure system areas. | Warm fuel plus low pressure increases vapor formation risk. | Pressure down → boiling down. | EASA often links pressure change to boiling point. | Medium | #pressure #medium #module-2.1 |
| What is vapor pressure? | Vapor pressure is the pressure of vapor above a liquid in a closed container at a given temperature. It rises with temperature and is unique for each substance. | High vapor pressure means easier vapor formation and more volatility issues. | Fuel vapor pressure affects venting and vapor lock risk in warm conditions. | Warm up → vapor pressure up. | Don’t confuse vapor pressure (property) with ambient/system pressure. | Medium | #vapor-pressure #medium #module-2.1 |
| What does “volatile” mean for a liquid? | A volatile liquid forms vapor easily, meaning it can develop relatively high vapor pressure at normal temperatures. It often has a lower boiling point under the same pressure. | Volatility affects safety, storage, and system performance. | Fuel volatility influences hot start behavior and vapor lock susceptibility. | Volatile = evaporates easily. | EASA may test volatility via vapor pressure wording. | Medium | #volatility #medium #module-2.1 |
| Scenario: A liquid is boiling but the temperature reading does not rise. Is that necessarily a fault? | No. During boiling, added heat can be used as latent heat to change state, so temperature can stay constant until the phase change is complete. | This prevents misdiagnosing instruments and misunderstanding test results. | In bench tests, steady temperature during phase change can be normal. | Boiling = latent heat time. | EASA scenarios often test “constant temperature during change of state”. | Hard | #latent-heat #hard #module-2.1 |
| Scenario: After a hot turnaround, an A320 shows signs of vapor formation in fuel lines. What concept explains it? | Higher temperature increases vapor pressure, and low local pressure reduces boiling point. Together they make vapor bubbles more likely, which can affect pump performance. | This links phase behavior to real fuel system reliability issues. | Warm lines + low inlet pressure areas increase vapor lock/cavitation risk. | Hot up + pressure down = vapor risk. | Watch for “hot” + “low pressure” + “bubbles” hints in EASA questions. | Hard | #fuel #hard #module-2.1 |
| Scenario: A tech says cabin air is “incompressible like hydraulic fluid.” What’s the correction? | Cabin air is a gas and is compressible, so pressure changes can change its volume and density. Hydraulic fluid is a liquid and is nearly incompressible, which is why it transmits force well. | Mixing these up causes bad troubleshooting assumptions. | Pressurization manages gas compression; hydraulics rely on liquid incompressibility. | Gas = compressible; liquid = nearly not. | EASA often compares compressibility directly. | Hard | #compressibility #hard #module-2.1 |