22 Chemistry & Electricity Practice Questions & Answers
Every Chemistry & Electricity practice question from the Cosmetology Practice Test, with the correct answer and a short explanation.
Start practice test →1. On the pH scale, how much more alkaline is a product at pH 9 than pure water at pH 7?
- A.One hundred times as alkaline, because each number is a tenfold change✓ Answer
- B.Twice as alkaline, because the scale adds one unit of alkali per number
- C.Ten times as alkaline, because the scale counts two whole numbers here
- D.Nine times as alkaline, because alkalinity is counted upward from zero
The pH scale is logarithmic: every whole number is a tenfold change in hydrogen ion concentration, so two steps from 7 to 9 means 10 times 10, or one hundred times more alkaline.
Source: Milady Standard Cosmetology, basic chemistry chapter — the pH scale; NIC National Cosmetology Theory Examination content outline, Scientific Concepts (values of the pH scale)Report a problem with this question
2. What does a strongly alkaline product do to the hair shaft?
- A.It dissolves the medulla and seals the cuticle against any outside moisture
- B.It swells the shaft and raises the cuticle so that the product reaches the cortex✓ Answer
- C.It hardens the keratin and closes the cuticle so that the hair resists entry
- D.It contracts the shaft and tightens the cuticle so that light reflects better
Alkaline solutions soften and swell hair, lifting the cuticle scales so that color, waving lotion, or relaxer can pass into the cortex; acids do the reverse and contract the shaft.
Source: Milady Standard Cosmetology, basic chemistry chapter — effect of alkalis and acids on hairReport a problem with this question
3. Which statement correctly separates organic chemistry from inorganic chemistry?
- A.Organic substances occur in nature, while inorganic ones are made in a laboratory
- B.Organic substances contain oxygen, while inorganic ones contain no oxygen at all
- C.Organic substances dissolve in water, while inorganic ones remain undissolved
- D.Organic substances contain carbon, while inorganic ones contain no carbon at all✓ Answer
Organic chemistry studies substances that contain carbon, most of which will burn; inorganic substances contain no carbon and include water, metals, and minerals. Whether a substance is natural or laboratory made has nothing to do with the division.
Source: Milady Standard Cosmetology, basic chemistry chapter — organic and inorganic chemistryReport a problem with this question
4. How does the surfactant in shampoo lift oil off the hair so it rinses away?
- A.Its acid head dissolves the oil while its alkaline tail clings to the cuticle
- B.Its water-loving head binds the water while its oil-loving tail grips the oily sebum✓ Answer
- C.Its oil-loving head binds the water while its water-loving tail grips the sebum
- D.Its protein head coats the oil while its mineral tail binds the hard water
A surfactant molecule has a hydrophilic, water-loving head and a lipophilic, oil-loving tail. The tail attaches to sebum and dirt while the head is pulled away by the rinse water, carrying the oil off the hair.
Source: Milady Standard Cosmetology, shampoo chemistry — surfactant molecule structureReport a problem with this question
5. Which description fits an oil-in-water emulsion, the commonest salon form?
- A.Oil dissolves evenly into the water, so the blend needs no emulsifier at all
- B.Water droplets are spread through oil, giving a heavy, greasy cold-cream feel
- C.Oil and water settle into two layers and must be shaken well before each use
- D.Oil droplets are spread through water, giving a lighter and less greasy feel✓ Answer
In an oil-in-water emulsion the oil is the dispersed phase held in a water base by an emulsifier, so the product feels light and rinses easily; in a water-in-oil emulsion the phases are reversed and the product feels greasy.
Source: Milady Standard Cosmetology, basic chemistry chapter — physical mixtures and emulsionsReport a problem with this question
6. Which of these is a chemical change rather than a physical change?
- A.Stirring a powder into water, which spreads the powder all through the liquid
- B.Melting a styling wax in the palms, which alters its state but not its makeup
- C.Setting damp hair on rollers, which alters its shape only while it dries
- D.Lightening hair with peroxide, which turns the melanin into a new substance✓ Answer
A physical change alters only the form or state of a substance, while a chemical change produces a new substance with new properties. Oxidizing melanin during lightening permanently changes the pigment itself, so it is a chemical change.
Source: Milady Standard Cosmetology, basic chemistry chapter — physical and chemical changesReport a problem with this question
7. What chemical action does thioglycolate waving lotion carry out in the hair?
- A.It breaks the salt bonds by lowering the pH so the cuticle can swell wide open
- B.It softens the peptide bonds by adding water so the chains slide past one another
- C.It oxidizes the disulfide bonds by adding oxygen so they set in the new shape
- D.It reduces the disulfide bonds by adding hydrogen so those bonds come apart✓ Answer
Waving lotion is a reducing agent: it adds hydrogen to the disulfide bonds of the cortex, splitting each cystine bond into two cysteine groups so the hair can take the shape of the rod. Oxidation comes later, at the neutralizing step.
Source: Milady Standard Cosmetology, chemical texture services — chemistry of permanent wavingReport a problem with this question
8. What does the neutralizer accomplish at the end of a thio permanent wave?
- A.It raises the pH so the cuticle stays open and the curl keeps on developing
- B.It reduces the hair further so the bonds relax fully around the shape of the rod
- C.It oxidizes the hair so the broken disulfide bonds rebuild in the new shape✓ Answer
- D.It coats the hair in protein so the broken bonds are sealed beneath a film
The neutralizer is an oxidizing agent, usually hydrogen peroxide or sodium bromate. It removes the hydrogen added by the waving lotion so the disulfide bonds re-form in their new position around the rod, locking in the curl.
Source: Milady Standard Cosmetology, chemical texture services — neutralization and oxidationReport a problem with this question
9. By what reaction does a hydroxide relaxer straighten the hair permanently?
- A.Oxidation, which adds oxygen to the disulfide bonds and holds them straight
- B.Neutralization, which pairs an acid with an alkali to give water and a salt
- C.Lanthionization, which takes away a sulfur atom and leaves a lanthionine bond✓ Answer
- D.Polymerization, which joins the keratin chains into one longer straight chain
Hydroxide relaxers break a disulfide bond by lanthionization: one sulfur atom is removed from the cystine bond, converting it into a single lanthionine bond that can never be re-formed, which is why the straightening is permanent.
Source: Milady Standard Cosmetology, chemical texture services — hydroxide relaxers and lanthionizationReport a problem with this question
10. After a hydroxide relaxer is rinsed out, what returns the hair to a normal pH?
- A.An alkaline clarifying shampoo, which strips the residue the relaxer leaves
- B.A thio-based normalizing lotion, which reverses the action of the relaxer
- C.An acid-balanced neutralizing shampoo, which lowers the pH the relaxer left✓ Answer
- D.A peroxide neutralizer, which rebuilds the bonds the relaxer has taken apart
Lanthionine bonds cannot be re-formed, so there is nothing for an oxidizing neutralizer to rebuild. The hair is rinsed and then washed with an acid-balanced neutralizing shampoo, which brings the very high pH of the hydroxide back down.
Source: Milady Standard Cosmetology, chemical texture services — normalizing after hydroxide relaxersReport a problem with this question
11. A developer marked 20 volume contains hydrogen peroxide at what strength?
- A.Three percent, the deposit-only strength chosen when no lift is wanted
- B.Twelve percent, the strength kept for high-lift tints used off of the scalp
- C.Nine percent, the strength chosen when two to three levels of lift are needed
- D.Six percent, the standard strength that lifts one to two levels of color✓ Answer
Volume and percentage are two scales for the same measure of available oxygen: 10 volume is 3 percent, 20 volume is 6 percent, 30 volume is 9 percent, and 40 volume is 12 percent. Twenty volume is the standard developer for gray coverage.
Source: Milady Standard Cosmetology, haircoloring chapter — hydrogen peroxide developer volumesReport a problem with this question
12. Why is a predisposition test required before every aniline-derivative tint, even for a longtime client?
- A.Porosity shifts with the season, so the test sets the correct processing time
- B.Scalp oil changes with age, so the test shows whether a protective base is needed
- C.Sensitivity to the dye can appear at any time, so past use proves nothing✓ Answer
- D.The tint weakens on the shelf, so the test shows whether it will still lift
Allergic sensitization to para-phenylenediamine and related aniline derivatives can develop after years of uneventful use, so a patch test is applied 24 to 48 hours before each service; a history of safe applications does not rule out a reaction.
Source: Milady Standard Cosmetology, haircoloring chapter — predisposition (patch) test for aniline derivative tintsReport a problem with this question
13. Which list names the routes by which salon chemicals most often enter the body?
- A.Product absorbed through skin, exposure to sunlight, and residue taken in
- B.Vapor inhaled, product absorbed through skin, and residue taken in by mouth✓ Answer
- C.Vapor inhaled, product absorbed through the nail plate, and metal contact
- D.Vapor inhaled, product absorbed through the hair shaft, and dust taken in
Products enter the body by inhalation, by absorption through the skin, and by ingestion, which is why ventilation, gloves, and hand washing are the standard controls; hair and nail keratin are not pathways into the bloodstream.
Source: Milady Standard Cosmetology, infection control and chemical safety — routes of entry into the bodyReport a problem with this question
14. Which unit measures the strength or amount of an electric current?
- A.The watt, which measures how much energy the device uses each second
- B.The ampere, which measures how much current moves through the wire✓ Answer
- C.The ohm, which measures how much the conductor resists that current
- D.The volt, which measures the pressure that pushes the current forward
An ampere is the unit of the strength or quantity of an electric current, and facial machines are rated in milliamperes, one thousandth of an ampere. Pressure is measured in volts, resistance in ohms, and energy used in watts.
Source: Milady Standard Cosmetology, electricity chapter — units of electrical measurementReport a problem with this question
15. The force that pushes an electric current along a conductor is measured in what?
- A.Volts, the measure of the electrical pressure behind the flow of current✓ Answer
- B.Amperes, the measure of how many electrons pass a point each second
- C.Ohms, the measure of how strongly a material resists the flow of current
- D.Watts, the measure of the electrical energy a device consumes each second
A volt is the unit of electrical pressure, the force that pushes current through a conductor. Amperes measure the quantity of the flow, ohms measure the resistance a conductor offers, and watts measure the energy consumed.
Source: Milady Standard Cosmetology, electricity chapter — volt, ampere, ohm and wattReport a problem with this question
16. How does direct current differ from alternating current?
- A.It flows evenly in one direction and produces a mechanical action
- B.It reverses direction rapidly and produces a mechanical action
- C.It reverses direction rapidly and produces a chemical reaction
- D.It flows evenly in one direction and produces a chemical reaction✓ Answer
Direct current is a constant, even-flowing current travelling in one direction and it produces a chemical reaction, which is why galvanic devices use it. Alternating current is rapid and interrupted, reverses direction, and produces a mechanical action.
Source: Milady Standard Cosmetology, electricity chapter — direct and alternating currentReport a problem with this question
17. What is the safe way to disconnect an appliance from a wall outlet?
- A.Wind the cord around the hand and tug the plug free from the outlet
- B.Take hold of the plug itself and draw it straight out of the outlet✓ Answer
- C.Take hold of the cord close to the plug and draw the plug from the outlet
- D.Take hold of the cord at its middle and draw the plug out of the outlet
Pulling on the cord instead of the plug loosens the wires inside the plug and frays the insulation, which can cause a short circuit or a shock. Grasp the body of the plug and pull it straight out of the receptacle.
Source: Milady Standard Cosmetology, electricity chapter — electrical equipment safety rulesReport a problem with this question
18. During desincrustation, what does the negative pole of galvanic current do?
- A.It sets up an alkaline reaction that softens sebum and relaxes the pores✓ Answer
- B.It sets up an acidic reaction that firms the tissue and closes the pores
- C.It gives off germicidal ozone that dries the surface and calms the nerves
- D.It gives off a gentle heat that raises tissue warmth and opens the pores
Desincrustation uses the negative pole, the cathode, with an alkaline solution. The alkaline reaction saponifies and emulsifies sebum, softening the hardened debris in the follicles so that blackheads can be extracted.
Source: Milady Standard Cosmetology, facial machines chapter — galvanic current and desincrustationReport a problem with this question
19. What effect does the positive pole of galvanic current have on the skin?
- A.A drying, peeling effect that loosens dead cells and thins the horny layer
- B.An alkaline, softening effect that opens the pores and stimulates the nerves
- C.An acidic, firming effect that closes the pores and soothes the nerve endings✓ Answer
- D.A warming, relaxing effect that raises tissue heat and reddens the surface
The positive pole, or anode, produces an acidic reaction: it firms and hardens tissue, closes the pores, soothes nerve endings, and is germicidal. This is the basis of cataphoresis, which drives acidic solutions into the skin.
Source: Milady Standard Cosmetology, facial machines chapter — polarity of galvanic current (anode and cathode)Report a problem with this question
20. How does Tesla high-frequency current differ from galvanic current?
- A.It is a very low direct current that copies the body's own nerve impulses
- B.It is a rapid alternating current that gives off heat and germicidal ozone gas✓ Answer
- C.It is a long infrared wave that warms the tissue well below the surface
- D.It is a constant direct current that drives water-soluble solutions inward
Tesla high-frequency is a thermal, oscillating alternating current. It produces heat and ozone, which makes it germicidal and antiseptic, but it does not carry ions into the skin the way galvanic current does.
Source: Milady Standard Cosmetology, facial machines chapter — Tesla high-frequency currentReport a problem with this question
21. Which statement describes infrared light as it is used in skin care?
- A.It has a long wavelength, builds collagen, and does not warm the tissue
- B.It has the longest wavelength, penetrates deepest, and produces a warming heat✓ Answer
- C.It has a middle wavelength, kills acne bacteria, and dries out oily skin
- D.It has the shortest wavelength, penetrates least, and destroys surface germs
Infrared has the longest wavelength of the light used in the treatment room, so it penetrates most deeply and produces heat that relaxes tissue and increases circulation; the shorter the wavelength, the less deeply light penetrates.
Source: Milady Standard Cosmetology, light therapy — infrared rays and wavelength penetrationReport a problem with this question
22. What sets ultraviolet light apart from the rest of the light spectrum?
- A.Its wavelength is the shortest, so it reaches least deeply and kills germs✓ Answer
- B.Its wavelength is the longest, so it reaches deepest and warms the tissue
- C.Its wavelength is the shortest, so it reaches deepest and heats the tissue
- D.Its wavelength is mid-range, so it reaches the dermis and rebuilds collagen
Ultraviolet rays have the shortest wavelength in the spectrum, so they penetrate the least. They are germicidal and produce vitamin D in the skin, and in excess they cause sunburn and premature aging.
Source: Milady Standard Cosmetology, light therapy — ultraviolet rays and the visible spectrumReport 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 →