20 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. A shampoo measures pH 9. Compared with pure water at pH 7, how many times more alkaline is it?
- A.10 times more alkaline
- B.100 times more alkaline✓ Answer
- C.1,000 times more alkaline
- D.2 times more alkaline
The pH scale is logarithmic, so each whole number represents a tenfold change in hydrogen-ion concentration. Two whole numbers therefore equal 10 x 10 = 100 times, not simply double.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Basics of Chemistry, pH scale is logarithmic (NIC Domain I.C, 'Recognize the values of the pH scale')Report a problem with this question
2. What effect does a strongly alkaline product have on the hair?
- A.It raises the cuticle and swells the hair shaft✓ Answer
- B.It lowers the porosity of the hair
- C.It has no effect until heat is applied
- D.It contracts and hardens the cuticle
Healthy hair sits at pH 4.5 to 5.5, so a product above that range softens and swells the keratin and lifts the cuticle scales, which is how perms, relaxers and permanent color reach the cortex. Acidic products do the opposite: they contract and close the cuticle.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Basics of Chemistry: pH of hair and skin (4.5-5.5) and the effect of alkalinity on the cuticleReport a problem with this question
3. Organic chemistry is the study of substances that:
- A.Dissolve completely in water
- B.Carry an electrical charge
- C.Contain carbon✓ Answer
- D.Are safe and natural for the skin
Organic chemistry deals with substances that contain carbon, while inorganic chemistry deals with those that do not. The word organic says nothing about safety, and most salon products are organic even though many are hazardous if misused.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Basics of Chemistry, organic vs. inorganic chemistryReport a problem with this question
4. Why is the surfactant in shampoo able to lift oil from the hair and let it rinse away in water?
- A.It converts the oil into a gas that evaporates
- B.It raises the pH of the rinse water above 10
- C.It carries a strong positive charge that repels all oils
- D.Its molecule has a water-loving (hydrophilic) head and an oil-loving (lipophilic) tail✓ Answer
A surfactant molecule has two ends with opposite affinities: the lipophilic tail attaches to oil and debris while the hydrophilic head is pulled by the water, so rinsing carries the oil away. This dual nature is also what allows an emulsifier to hold oil and water together in a product.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Basics of Chemistry: surfactants, hydrophilic head and lipophilic tailReport a problem with this question
5. Which statement best describes an oil-in-water (O/W) emulsion?
- A.A solid evenly suspended inside another solid
- B.Oil droplets dispersed in a water base, which feels lighter✓ Answer
- C.A mixture of two gases held together by pressure
- D.Water droplets dispersed in an oil base, which feels greasier
In an oil-in-water emulsion the oil is the dispersed phase and water is the continuous base, held together by an emulsifier, which makes the product lighter and less greasy. Water-in-oil emulsions reverse the phases and feel heavier, which is why O/W is the most common form in salon lotions and conditioners.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Basics of Chemistry: solutions, suspensions and emulsions (O/W vs. W/O)Report a problem with this question
6. Which of the following is a chemical change rather than a physical change?
- A.Oxidative haircolor developing inside the cortex✓ Answer
- B.Dissolving a conditioner in warm water
- C.Shaking a suspension before use
- D.Blow-drying wet hair straight
A chemical change produces a new substance with new chemical properties, and oxidation of an aniline-derivative tint creates larger color molecules trapped in the cortex that shampooing cannot remove. The other choices change only form or state, so they are physical changes.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Basics of Chemistry: physical change vs. chemical change; oxidative haircolorReport a problem with this question
7. A thioglycolate permanent waving lotion changes the hair by:
- A.Dissolving the peptide bonds of the polypeptide chain
- B.Adding oxygen to rebuild disulfide bonds
- C.Removing a sulfur atom to create a lanthionine bond
- D.Adding hydrogen to break disulfide bonds✓ Answer
Ammonium thioglycolate is a reducing agent, and reduction is the addition of hydrogen (or the removal of oxygen), which splits the strong disulfide side bonds so the hair can take the shape of the rod. Rebuilding those bonds with oxygen happens later, at the neutralizing step.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Chemical Texture Services: reduction reactions and ammonium thioglycolateReport a problem with this question
8. What is the chemical function of the neutralizer used after a permanent wave?
- A.It oxidizes the hair, rebuilding the disulfide bonds in their new shape✓ Answer
- B.It adds protein in order to lower the hair's porosity
- C.It removes metallic salts left by home color
- D.It reduces the hair further so the curl relaxes
Permanent wave neutralizers are usually hydrogen peroxide, an oxidizing agent, and oxidation reconnects the disulfide bonds that the waving lotion broke, locking the hair into the curl formed on the rod. Without this oxidation step the bonds stay broken and the curl will not hold.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Chemical Texture Services: neutralization is an oxidation reaction (hydrogen peroxide)Report a problem with this question
9. A sodium hydroxide relaxer permanently straightens hair through a process called:
- A.Emulsification
- B.Polymerization
- C.Saponification
- D.Lanthionization✓ Answer
Hydroxide relaxers permanently remove one sulfur atom from a disulfide bond, converting it into a single-sulfur lanthionine bond, a change that oxidation cannot reverse. That is why hydroxide relaxers are neutralized with an acid-balanced normalizing shampoo instead of peroxide, and why hydroxide and thio products must never be used over one another.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Chemical Texture Services: hydroxide relaxers and lanthionizationReport a problem with this question
10. A 20-volume hydrogen peroxide developer contains what percentage of hydrogen peroxide?
- A.9%
- B.12%
- C.6%✓ Answer
- D.3%
Volume is simply another way of stating concentration: 10 volume equals 3%, 20 volume equals 6%, 30 volume equals 9% and 40 volume equals 12%. Twenty volume gives one to two levels of lift and is the standard choice for gray coverage and deposit, and the rule is to use the lowest volume that achieves the goal.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Haircoloring: developer volume-to-percentage conversion and levels of liftReport a problem with this question
11. A client has received the same aniline-derivative permanent tint for ten years with no reaction. Before the next application, the cosmetologist should:
- A.Dilute the developer to half strength as a precaution
- B.Perform only a strand test on the day of the service
- C.Skip the predisposition test, because tolerance is already established
- D.Perform a predisposition (patch) test 24 to 48 hours in advance✓ Answer
Sensitivity to a chemical develops from repeated or prolonged overexposure over time, so a client who has tolerated a tint for years can still become allergic to it. For that reason a predisposition test is required 24 to 48 hours before every aniline-derivative application; a strand test only predicts color result and timing, not an allergic reaction.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Haircoloring: predisposition (patch) test 24-48 hours before aniline-derivative tints; overexposure and sensitizationReport a problem with this question
12. Under the OSHA Hazard Communication Standard, a Safety Data Sheet (SDS) must contain how many standardized sections in a set order?
- A.20 sections
- B.16 sections✓ Answer
- C.8 sections
- D.12 sections
The Hazard Communication Standard adopts the GHS format, which fixes the SDS at 16 numbered sections in a mandated order, beginning with identification and hazard identification and ending with other information. The employer must keep an SDS for every hazardous product accessible to employees, and the older term MSDS is obsolete.
Source: OSHA Hazard Communication Standard, 29 CFR 1910.1200(g) and Appendix D - 16-section Safety Data SheetReport a problem with this question
13. Which agency registers the disinfectants used in salons and approves the efficacy claims printed on their labels?
- A.FDA
- B.OSHA
- C.The state cosmetology board
- D.EPA✓ Answer
The Environmental Protection Agency registers antimicrobial products as pesticides and approves the bactericidal, virucidal and fungicidal claims on the label, which is why salon disinfectants must carry an EPA registration number. OSHA governs Safety Data Sheets, labeling, employee training and workplace safety, while the state board governs licensing and salon sanitation rules.
Source: EPA antimicrobial pesticide registration (FIFRA); contrasted with OSHA 29 CFR 1910.1200 (NIC Domain I.A, 'Identify requirements of government agencies: OSHA, EPA')Report a problem with this question
14. The three routes by which salon chemicals can enter the body are:
- A.Inhalation, skin absorption and ingestion✓ Answer
- B.Absorption, saponification and inhalation
- C.Ingestion, oxidation and reduction
- D.Inhalation, evaporation and combustion
Chemicals reach the body only by being breathed in, passing through the skin, or being swallowed, so control measures target those three routes. Volatile organic compounds evaporate readily, which makes inhalation the leading concern and is why ventilation, closed and clearly labeled containers, gloves and storage away from heat and light are required.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Infection Control and Chemical Safety: routes of entry (inhalation, absorption, ingestion); OSHA 29 CFR 1910.1200 container labelingReport a problem with this question
15. Which unit measures the pressure or force that pushes electrons forward through a conductor?
- A.Ohm
- B.Volt✓ Answer
- C.Ampere
- D.Watt
The volt measures electrical pressure, the force that moves electrons along the circuit. The ampere measures the strength or amount of current (a milliampere is one one-thousandth of an ampere, the scale used for facial machines), the ohm measures resistance, and the watt measures how much electrical energy is used in one second.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Basics of Electricity: volt, ampere, milliampere, ohm and wattReport a problem with this question
16. Which type of current is a constant flow travelling in one direction, such as the current used in galvanic treatments?
- A.Direct current (DC)✓ Answer
- B.Sinusoidal current
- C.Alternating current (AC)
- D.Tesla high-frequency current
Direct current is constant and even and flows in one direction only, which is what batteries supply and what galvanic treatments require. Alternating current is rapid and interrupted and reverses direction, which is what a wall outlet supplies, so a rectifier is used to change AC into the DC a galvanic device needs.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Basics of Electricity: direct current vs. alternating current; rectifierReport a problem with this question
17. What is the correct way to disconnect an electrical appliance in the salon?
- A.Unplug it only when the cord begins to feel warm
- B.Pull on the cord until the plug comes out of the outlet
- C.Leave it plugged in and simply switch off the circuit breaker
- D.Grasp the plug itself and pull it straight out of the outlet✓ Answer
Pulling on the cord stresses and frays the wiring where it enters the plug, and exposed conductors create a shock and fire hazard, so the plug must always be grasped directly. The same reasoning supports the other standing rules: one appliance per outlet, never use equipment with a damaged cord, keep appliances away from water, and unplug them when not in use.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Basics of Electricity: electrical safety guidelinesReport a problem with this question
18. Desincrustation of oily, congested skin uses which pole of galvanic current, and why?
- A.The positive pole, because it creates an acidic reaction that tightens tissue
- B.The negative pole, because it creates an alkaline reaction that softens and emulsifies sebum✓ Answer
- C.The positive pole, because it forces alkaline solutions into the follicle
- D.The negative pole, because ozone gives it a germicidal, drying effect
At the negative pole (cathode) galvanic current reacts with the salts in the skin to form sodium hydroxide, a soapy alkaline substance; this reaction is called saponification, and it emulsifies sebum and softens follicular debris. The positive pole (anode) produces the opposite, acidic effect used in cataphoresis to tighten, calm and soothe, while ozone is produced by high-frequency current, not galvanic.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Facial Treatments/Electrotherapy: galvanic current, desincrustation and saponification; anaphoresis vs. cataphoresisReport a problem with this question
19. How does Tesla high-frequency current differ from the other electrotherapy modalities?
- A.It delivers a constant direct current
- B.It requires two electrodes in order to complete the circuit
- C.It uses a single glass electrode and has no polarity✓ Answer
- D.It must be applied directly over broken skin
High-frequency current is a thermal, rapidly oscillating current applied through one glass electrode, and because it has no positive or negative pole it is the only modality that does not need a second electrode to complete the circuit. It produces ozone, giving it a germicidal and drying effect, and it must never be used over broken skin; all metal jewelry is removed first.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Electrotherapy: Tesla high-frequency current, single electrode, no polarity, ozoneReport a problem with this question
20. Which type of ray has the longest wavelength and produces the deepest heat?
- A.Blue LED light
- B.Infrared rays✓ Answer
- C.Ultraviolet rays
- D.Visible light
Infrared rays have the longest wavelength of the three bands used in the salon, so they penetrate most deeply and are felt as heat that relaxes tissue and increases circulation. Ultraviolet rays have the shortest wavelength, are germicidal and are called cold or actinic rays, and visible light falls between the two.
Source: Milady Standard Cosmetology & Foundations, 14th ed. - Light Therapy: ultraviolet, visible and infrared rays, relative wavelength and penetrationReport 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 →