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NATE_CORE NEC 2023

NATE Core Practice Test 5

This practice test covers states of matter, pressure, and temperature scales from the NATE Core exam blueprint. You will see questions on solid, liquid, and gas states, how pressure affects boiling point, and Fahrenheit-Celsius conversions.

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NATE Core

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Frequently Asked Questions

Yes — completely free with no signup required. Every question includes a full explanation of the correct answer.

Two: the NATE Core exam plus at least one specialty exam (for example AC Service, Heat Pump Service, or Air Distribution Service). You can take them on the same day or separately.

The Core exam has 50 questions and each installation or service specialty exam has 100 questions. You need 70% on each to pass — 35 of 50 on Core and 70 of 100 on a specialty. Check natex.org for the current format before you book.

NATE certification lasts two years. To renew, you submit 16 hours of continuing education or retake the specialty exam before your certification expires.

No. These are independent practice tests written to match the published NATE exam topics. They are not official NATE exam questions.

Exam Tip: Remember: raising pressure raises boiling point, and lowering pressure lowers boiling point. This one idea explains how the whole refrigeration cycle works.

30

Questions

30 min

Time

70%

Pass

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NATE Core Practice Test 5 — Question List

Question 1: Which three states of matter are most relevant to how a refrigeration system works?

Solid, liquid, and gas (vapor)
Plasma, liquid, and gas
Solid, plasma, and vapor
Liquid and gas only, solid is never relevant

Question 2: At standard atmospheric pressure, at what Fahrenheit temperature does water freeze?

0°F
32°F
100°F
212°F

Question 3: At standard atmospheric pressure, at what Fahrenheit temperature does water boil?

32°F
100°F
212°F
180°F

Question 4: At standard atmospheric pressure, what are the freezing and boiling points of water on the Celsius scale?

32°C and 212°C
0°C and 32°C
10°C and 90°C
0°C and 100°C

Question 5: Convert 68°F to Celsius using the formula C = (F − 32) × 5/9. What is the result?

20°C
36°C
15°C
25°C

Question 6: Convert 25°C to Fahrenheit using the formula F = (C × 9/5) + 32. What is the result?

45°F
77°F
68°F
90°F

Question 7: How does increasing the pressure on a liquid generally affect its boiling point?

It has no effect on boiling point
It lowers the boiling point
It raises the boiling point
It changes the liquid into a solid immediately

Question 8: How does decreasing the pressure on a liquid generally affect its boiling point?

It has no effect on boiling point
It raises the boiling point
It always freezes the liquid
It lowers the boiling point

Question 9: What is the basic definition of "matter"?

Anything that has mass and takes up space
Only solid objects
Only substances that conduct electricity
Energy with no physical form

Question 10: What is the name of the process when a solid changes into a liquid?

Condensation
Melting
Evaporation
Sublimation

Question 11: What is the name of the process when a liquid changes into a gas or vapor?

Condensation
Freezing
Evaporation
Melting

Question 12: What is the name of the process when a gas or vapor changes into a liquid?

Evaporation
Sublimation
Melting
Condensation

Question 13: What is "pressure", in basic physical terms?

The amount of force applied over a given area
The total weight of an object
The temperature of a gas
The speed at which air moves

Question 14: What does "psi" stand for, a common unit used to measure refrigerant pressure?

Pounds per square foot
Pounds per square inch
Pressure per square inch
Pints per square inch

Question 15: In general, how do the molecules in a gas compare to the molecules in a solid?

Gas molecules are fixed tightly in place, like a solid
Gas molecules do not move at all
Gas molecules move freely and are spread far apart compared to a solid
There is no real difference between gas and solid molecules

Question 16: Inside the evaporator coil of an air conditioning system, the refrigerant is kept at a low pressure. Why does this help the refrigerant absorb heat from the air?

Low pressure makes the refrigerant turn solid
Low pressure has no effect on the refrigerant's boiling point
Low pressure raises the boiling point so refrigerant stays liquid longer
Low pressure lowers the refrigerant's boiling point, so it can boil (evaporate) at a cool temperature and absorb heat from the warmer air

Question 17: Inside the condenser coil, the refrigerant is kept at a high pressure. Why does this help the refrigerant release heat outdoors?

High pressure raises the refrigerant's condensing temperature above the outdoor air temperature, allowing heat to flow out of the refrigerant
High pressure has no effect on condensing temperature
High pressure lowers the condensing temperature below freezing
High pressure turns the refrigerant into a solid

Question 18: Which temperature scale is most commonly used in everyday life in the United States?

Celsius
Fahrenheit
Kelvin
Rankine

Question 19: Which basic property is true of a gas but NOT true of a solid?

It has a fixed shape
It has a fixed volume and fixed shape
It expands to fill the shape and volume of its container
It cannot be compressed at all

Question 20: Which basic property is true of a liquid?

It has a fixed shape but no fixed volume
It expands to fill any container completely, like a gas
It cannot flow or move
It has a fixed volume but takes the shape of its container

Question 21: Which formula correctly converts a Fahrenheit temperature to Celsius?

C = (F − 32) × 5/9
C = F × 9/5 + 32
C = F + 32
C = F × 2

Question 22: Convert 50°F to Celsius. What is the result, rounded to the nearest whole number?

18°C
10°C
15°C
22°C

Question 23: A pressure gauge reads 0 psi when it is open to the outside air. What does this actually mean?

There is no pressure anywhere in the atmosphere
The gauge is broken
The gauge is reading pressure relative to normal atmospheric pressure, not true zero pressure
The reading means there is a vacuum inside the gauge

Question 24: Which of these is NOT one of the three basic states of matter discussed in HVACR training?

Solid
Liquid
Gas
Voltage

Question 25: Which process describes water vapor in the air turning directly into frost on a cold surface, without becoming liquid first?

Deposition (a direct gas-to-solid change)
Evaporation
Boiling
Melting

Question 26: Which temperature scale is commonly used in scientific work and in most countries outside the United States?

Fahrenheit
Celsius
Rankine
PSI

Question 27: Water boils at a lower temperature on top of a high mountain than at sea level. What basic principle explains this?

Mountains are always colder, which changes the chemical makeup of water
Water cannot boil above a certain altitude
Atmospheric pressure is lower at high altitude, and lower pressure lowers the boiling point
Altitude has no effect on boiling point

Question 28: What is the basic difference between temperature and heat?

They are exactly the same thing
Temperature always measures pressure, not heat
Heat only exists in solids
Temperature measures how hot or cold something is; heat is the energy that moves between objects at different temperatures

Question 29: As refrigerant travels through a basic vapor-compression system, in which order does it typically pass through, low-pressure to high-pressure and back?

Low-pressure vapor is compressed into high-pressure vapor, condenses to high-pressure liquid, expands to low-pressure liquid, then evaporates back to low-pressure vapor
The refrigerant only exists as a solid throughout the whole cycle
The refrigerant stays a gas the entire time and never becomes a liquid
The refrigerant stays a liquid the entire time and never becomes a gas

Question 30: True or False: Raising the pressure on a refrigerant raises the temperature at which it will condense back into a liquid.

False, pressure has no effect on condensing temperature
True
False, raising pressure always lowers condensing temperature
False, refrigerant cannot condense under high pressure

EXAM CARD NATE_CORE

Questions30

Time limit30 min

Pass score70%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

Timer starts immediately. Progress is auto-saved.

Source: NEC 2026 (NFPA 70)