18 Chemistry & Electricity Practice Questions & Answers

1. 1. On the pH scale, which range describes an acidic solution?

   • A.0 up to but not including 7✓ Answer
   • B.Only 14
   • C.Above 7 up to 14
   • D.Exactly 7

   The pH scale runs from 0 to 14; a value of 7 is neutral, values below 7 are acidic, and values above 7 are alkaline, because acidity reflects a higher concentration of hydrogen ions.

   Source: NIC Cosmetology Theory: Basic Chemistry — pH scale (0-14, 7 neutral)Report a problem with this question

2. 2. What is the approximate natural pH of healthy hair and skin?

   • A.Around 1.0 to 2.0 (strongly acidic)
   • B.Around 8.5 to 9.5 (alkaline)
   • C.Exactly 7.0 (neutral)
   • D.Around 4.5 to 5.5 (slightly acidic)✓ Answer

   Healthy hair and skin are slightly acidic, with a pH of about 4.5 to 5.5, which is why this range is called the acid mantle that helps protect against microorganisms and moisture loss.

   Source: NIC Cosmetology Theory: hair/skin natural pH 4.5-5.5 (acid mantle)Report a problem with this question

3. 3. What does an alkaline product do to the hair cuticle?

   • A.Has no effect on the cuticle
   • B.Tightens and contracts it closed
   • C.Causes it to swell, soften, and lift open✓ Answer
   • D.Permanently dissolves it

   Alkaline substances raise the hair's pH, which swells and softens the hair and lifts the cuticle scales open, allowing products such as color or perm solution to penetrate the cortex.

   Source: NIC Cosmetology Theory: alkalinity swells hair and opens cuticleReport a problem with this question

4. 4. A physical mixture in which a solid is evenly and permanently distributed in a liquid so it does not separate is called a:

   • A.Suspension
   • B.Solution✓ Answer
   • C.Water-in-oil emulsion
   • D.Ointment

   A solution is a stable, uniform mixture of a solute completely dissolved in a solvent, so unlike a suspension its particles do not settle out or separate over time.

   Source: NIC Cosmetology Theory: Chemistry — solutions vs suspensionsReport a problem with this question

5. 5. How does a suspension differ from a solution?

   • A.Its particles are fully dissolved and never separate
   • B.It contains no liquid at all
   • C.Its particles are larger and tend to separate/settle over time✓ Answer
   • D.It is always a gas

   In a suspension the particles are larger and only temporarily dispersed, so they settle out and must be shaken before use, unlike a solution whose dissolved particles stay uniformly mixed.

   Source: NIC Cosmetology Theory: Chemistry — suspensions separate over timeReport a problem with this question

6. 6. An emulsion in which oil droplets are dispersed in a water base (oil-in-water) is best described as:

   • A.A pure solution with no oil present
   • B.A dry powder with no water present
   • C.A heavy product that always feels very greasy
   • D.A lighter product that feels less greasy on the skin✓ Answer

   In an oil-in-water (O/W) emulsion the continuous outer phase is water, so the product feels lighter and less greasy, whereas water-in-oil emulsions have oil as the outer phase and feel heavier.

   Source: NIC Cosmetology Theory: Chemistry — oil-in-water vs water-in-oil emulsionsReport a problem with this question

7. 7. What ingredient allows oil and water to stay mixed together in an emulsion?

   • A.An oxidizer
   • B.A pure solvent alone
   • C.A reducing agent
   • D.An emulsifier (surfactant)✓ Answer

   An emulsifier, or surfactant, has one end that attracts water and one that attracts oil, so it surrounds the droplets and keeps the two normally immiscible liquids from separating.

   Source: NIC Cosmetology Theory: Chemistry — emulsifiers/surfactants stabilize emulsionsReport a problem with this question

8. 8. In chemistry, what is oxidation?

   • A.A change in which no electrons move at all
   • B.A reaction in which a substance only gains water
   • C.The freezing of a liquid into a solid
   • D.A reaction in which a substance combines with oxygen or loses hydrogen (loses electrons)✓ Answer

   Oxidation is the chemical addition of oxygen or loss of hydrogen (a loss of electrons); it is central to salon services because hair color and lighteners rely on oxidation reactions.

   Source: NIC Cosmetology Theory: Chemistry — oxidation (gain of oxygen/loss of electrons)Report a problem with this question

9. 9. In permanent hair color and lighteners, what role does hydrogen peroxide developer play?

   • A.It only adjusts the fragrance of the product
   • B.It neutralizes the color so it cannot develop
   • C.It acts as a reducing agent that softens keratin bonds
   • D.It acts as the oxidizing agent that develops color and lifts pigment✓ Answer

   Hydrogen peroxide is an oxidizing agent: it releases oxygen that develops the color molecules and lightens existing melanin, which is why it is called the developer or oxidizer.

   Source: NIC Cosmetology Theory: Hair Color — hydrogen peroxide as oxidizing developerReport a problem with this question

10. 10. During permanent waving, the waving lotion breaks disulfide bonds. This step is chemically a:

    • A.Physical change only
    • B.Neutralization by evaporation
    • C.Oxidation reaction (adding oxygen)
    • D.Reduction reaction (adding hydrogen)✓ Answer

    The thio waving lotion is a reducing agent that adds hydrogen to break the disulfide bonds, allowing the hair to take a new shape; the later neutralizer then re-forms the bonds by oxidation.

    Source: NIC Cosmetology Theory: Chemical Texture — reduction breaks disulfide bondsReport a problem with this question

11. 11. In permanent waving, what does the neutralizer do after the rods are set?

    • A.Permanently dissolves the hair bonds
    • B.Oxidizes the hair to rebuild the disulfide bonds in the new shape✓ Answer
    • C.Only rinses away leftover lotion with plain water
    • D.Reduces the hair further to soften it more

    The neutralizer is an oxidizing agent that rebonds the broken disulfide bonds in their new curled position, which is why perming is a redox process: reduction to break, oxidation to reform.

    Source: NIC Cosmetology Theory: Chemical Texture — neutralizer oxidizes/rebondsReport a problem with this question

12. 12. Which of the following is a chemical change rather than a physical change?

    • A.Wrapping hair on rollers to set a curl
    • B.Dissolving salt in water
    • C.Oxidizing hair color to a new permanent shade✓ Answer
    • D.Melting ice into water

    A chemical change forms a new substance with different properties, as when oxidation permanently changes the color molecules; the other options only change form or state, not chemical identity.

    Source: NIC Cosmetology Theory: Chemistry — chemical vs physical changeReport a problem with this question

13. 13. What is the main difference between direct current (DC) and alternating current (AC)?

    • A.They are identical in every way
    • B.DC reverses direction; AC flows in one direction
    • C.DC flows in one constant direction; AC rapidly reverses direction✓ Answer
    • D.DC has no voltage while AC has no current

    Direct current is a constant, even-flowing current moving in one direction, while alternating current is a rapid, interrupted current that reverses direction, which is why wall outlets supply AC.

    Source: NIC Cosmetology Theory: Electricity — direct vs alternating currentReport a problem with this question

14. 14. What is the function of a rheostat in salon equipment?

    • A.To ground the appliance to the earth
    • B.To measure the pH of a product
    • C.To convert AC into DC
    • D.To regulate the strength of the current (for example, adjust speed or heat)✓ Answer

    A rheostat is an adjustable resistor used to increase or decrease the flow of current, which is how devices like dryers or facial units vary speed or heat.

    Source: NIC Cosmetology Theory: Electricity — rheostat regulates currentReport a problem with this question

15. 15. A converter (rectifier) in an electrotherapy device is used to:

    • A.Change direct current into alternating current only
    • B.Change alternating current into direct current✓ Answer
    • C.Increase the pH of the current
    • D.Ground the client to the floor

    A converter, or rectifier, changes alternating current into direct current, which is necessary because galvanic electrotherapy treatments require a constant direct current.

    Source: NIC Cosmetology Theory: Electricity — converter/rectifier AC to DCReport a problem with this question

16. 16. Which safety device shuts off current to prevent electric shock in wet areas such as near a shampoo bowl?

    • A.A rheostat
    • B.A step-up transformer
    • C.A ground-fault circuit interrupter (GFCI)✓ Answer
    • D.An emulsifier

    A GFCI monitors current flow and quickly cuts power if it detects a leak to ground, protecting against shock, which is why codes require them near water sources like shampoo bowls.

    Source: NIC Cosmetology Theory / NEC: GFCI required near water for shock protectionReport a problem with this question

17. 17. Why should you avoid plugging too many appliances into one circuit?

    • A.It grounds the circuit automatically
    • B.It raises the pH of the wiring
    • C.It converts the current from AC to DC
    • D.It can overload the circuit and cause overheating or fire✓ Answer

    Drawing more current than a circuit is rated for is an overload; the excess current generates heat in the wiring, which can trip a breaker or start a fire, so appliances should be spread across circuits.

    Source: NIC Cosmetology Theory: Electrical safety — circuit overload hazardReport a problem with this question

18. 18. How do galvanic and faradic currents differ in electrotherapy?

    • A.Galvanic is alternating and faradic is direct current
    • B.Galvanic is a form of light and faradic is a form of heat
    • C.Both are the same continuous current with no difference
    • D.Galvanic is a constant direct current producing chemical effects; faradic is an alternating current producing muscle contractions✓ Answer

    Galvanic current is a constant direct current that produces chemical (ionic) reactions used in treatments like desincrustation, while faradic is an alternating current that causes muscular contractions for facial toning.

    Source: NIC Cosmetology Theory: Electrotherapy — galvanic (DC/chemical) vs faradic (AC/muscle)Report a problem with this question

Practice questions based on the NIC national cosmetology theory content outline and standard salon science. Not affiliated with NIC, PSI, or any state board. Your state may add state-law and practical content — check your board's requirements before testing. About NIC exams →