Chemical vs. Physical Changes
What is the main difference between a physical and chemical change in skincare products?
A chemical change creates a new substance, while a physical change changes the appearance without altering its formulation
What is matter? Why Is it important in skincare chemistry?
Matter is anything that has mass and takes up space.
All skincare products are made of matter
What does pH stand for, and what does it measure in skincare products?
Potential Hydrogen. Measures how acidic or alkaline something is
What is an emulsion in skincare?
A mixture of oil and water that doesn’t natural blend, but is stabilized with emulsifiers.
What are free radicals and how do they damage the skin?
Unstable molecules that damage healthy cells by stealing electrons, thus speeding up aging.
Melting wax for hair removal is an example of what kind of change? Why?
Physical change. The wax melts but its chemical structure/formulation stays the same
True or False: All skincare products are made from matter. Explain
True. Water, creams, and serums are all made of matter
Why is maintaining an acidic pH important for the skin barrier?
The acid mantle protects against bacteria and moisture loss. A balanced pH helps keep it intact.
What‘s the difference between an oil-in-water and water-in-oil emulsion? Which one is lighter?
O/W has more water and feels lighter. W/O has more oil and feels heavier or greasy.
Why are antioxidants important in skincare products?
They donate electrons to neutralize free radicals and prevent skin cell damage.
What is happening on a chemical level when hydrogen peroxide lightens the hair?
It oxidizes the melanin pigment in the hair, changing its chemical structure and lightening the color
What are the two main types of mixtures in cosmetic chemistry, and how do they differ?
Solutions = Solvent + Solute. Stays mixed together (water + sugar)
Suspension = two immiscible ingredients that don’t mix and need shaking or an emulsifier to mix. (Ex: oil + water, oil + vinegar)
A product with a pH of 9 is classified as what? How might it affect the skin?
Alkaline/Base. May dry out or irritate the skin by stripping it of its natural oils.
Why are emulsifiers necessary in skincare products like lotions and creams?
They keep oil and water from separating in products like lotions and creams.
What does it mean when an ingredient is “lipid-soluble”? How does that affect product absorption?
Able to dissolve in fat or oil. This helps ingredients better penetrate our lipid bilayer
Which of the following is a chemical change:
Applying moisturizer
Using an enzyme peel
Freezing toner.
Explain
Using an enzyme peel
It breaks down the proteins in the skin
Identify which of the following are pure substances:
Oxygen
Vitamin C Serum
Steam
Gold
Oxygen and Gold
If the skin’s natural pH is between 4.5 and 5.5, what types of products might disrupt this balance?
Harsh soaps, baking soda, some bar cleansers may raisle skin’s pH and cause irritation.
How could you tell if a product is more oil-based or water-based just by looking at the label or dispense mechanism?
Look at the first few ingredients: if water/aqua listed first, it’s usually water based. If oils are listed first, it’s oil based.
What is the role of humectants in skincare, and give an example
They pull moisture into the skin. EX: HA, Honey, Glycerin
During a facial a client uses an exfoliating enzyme mask followed by a cool jade roller. Identify which is a physical change and which is a chemical change, and explain why
Chemical change = Enzyme mask. It breaks down the proteins in the skin
Physical change: Jade roller. Cools the skin and reduces puffiness by constricting blood vessels
How would you explain the difference between a solution and a suspension using skincare examples?
Solution = Ingredients are fully dissolved. (Toner)
Suspension = Has visible particles that may settle or need shaking. (Exfoliating scrub)
Compare the effects of acidic vs. alkaline products on acne-prone skin. Why does it matter?
Acidic products may help balance acne prone skin, while alkaline products may worsen breakouts by drying or disrupting the barrier.
A client with acne-prone skin wants a lightweight moisturizer. Should you recommend a W/O or an O/W emulsion and why?
Recommend O/W because it is water based and less likely to clog pores or feel greasy.
Compare emollients, humectants, and occlusives. Which would be best for someone with dry, flaky skin and why?
Emollients = Smooth and Soften
Humectant = Hydrate by attracting water
Occlusives = seal in moisture
All three