HSC
SENIOR SCIENCE
STUDY NOTESLifestyle Chemistry
1. The use of a substance depends on its Physical and chemical properties.
i. Chemicals can be categorised into the following groups a. Detergent
b. Lubricant c. Pesticide d. Solvent e. Metal cleaner
f. Body hygiene chemicals g. Cosmetic
ii. Solution contains dissolved substances that are uniform throughout e.g. salt water, vinegar.
Suspensions contain particles that settle out of form layers quickly e.g. calamine lotion, oil and water.
Colloids contain particles that remain suspended in another for a long period of time. They can be placed into different categories:
o Gas-in-liquid, (foam) shaving cream o Solid-in-liquid, (solid foam) Styrofoam o Liquid-in-gas, (aerosol) hairspray
o Liquid-in-liquid, (emulsion) homogenised milk o Liquid-in-solid, (gel) jellies
o Solid-in-gas, (solid aerosol) dust or smoke in air o Solid-in-liquid, (sol) ink
o Oil-in-water, cream o Water-in-oil, butter
iii. Surface tension is the result of strong forces between molecules in a liquid, pulling them inward. You can demonstrate surface tension by
o Attach a balloon to the top of a jar. Pour water into the balloon and observe its shape as it stretches.
o Water in a beaker. You can observe the shape of the meniscus
iv. A surfactant is a group of chemicals that contain surface-active-agents (molecule with one end attracted to water, the other attracted to oil). Lowers surface tension of liquid giving water the greater ability to wet the dirty/oily surface and the dirt or oil can be removed more easily.
2. A wide range of cleaning products are made from Colloids and surfactants.
i. Oily substances and water do not mix well, when put together they form a colloid or suspension. For a cleaning product to be effective, it must change the surface tension of water and dissolve dirt, grease and oil. Emulsifiers are in cleaning products. They are partially water-soluble and partially oil-soluble bringing the oil and water together.
ii. The purpose of the emulsifying agent in a cleaning product is to reduce the surface tension of the water are lift the unwanted substances of the item e.g. stain in clothes, grease on plate.
iii. Soap is made from renewable resources and is readily broken down by bacteria after being released into the environment. Soap cannot lift all types of soils. Can also form scum that blocks drains.
iv. Detergents are preferred over soaps as they are much more versatile and have better cleaning powers. They can perform other tasks while cleaning e.g. brightens clothes by bleaching and stain removal. Detergents do not create scum like soap.
v. Initially soap was biodegraded easier than detergents however recently biodegradable, phosphate-free detergents have been developed. The first
detergents were branched-chain alkyl benzene sulphonates which do not biodegrade in sewage treatment plants. They also contained phosphates which caused problems in water systems.
3. Cleaning products used on the human body must be compatible with the physical and chemical properties of the skin.
i. The four main functions of the skin include:
a. An organ to separate the body from the external environment.
b. Body temperature control through the use of warm and cold receptors and sweat glands.
ii. Microflora on the skin refers to the populations of naturally occurring micro-organisms such as fungi and bacteria. Good microflora can help combat disease causing organisms. However an imbalance of microflora can cause conditions such as tinea and thrush.
iii. Factors which cause the skin to have a naturally acidic pH (4.5 – 6.0) are:
a. Sebum – natural oil produced by glands in the skin. Sebum is slightly acidic. b. Perspiration – sweat produced by heat is more acidic than sweat from exercise. c. The action of microflora can change the pH of the skin.
iv. Skin soaps consist of a hydrocarbon chain which is repelled by water but attracted to oil, grease and dirt, and a carboxylic (fatty) acid which is attracted to water. They can contain perfumes and coloring.
v. Cleansers contain mineral oil, water and stearate. Sometimes moisture absorber. They dissolve sebum and loosen particles of grime and dirt.
vi. Shampoos contain coconut oil, olive oil, alcohol, glycerol, water, detergent or soap and perfume. They lather in the hair to remove dirt and grease.
4. The nature of a solvent plays an important Role in the application of a mixture.
i. Water is used as a solvent for hair shampoos, moisturizing creams, conditioners and hair gels. Some substances do not dissolve in water so alcohol is used as the solvent.
ii. Alcohol is used as a solvent in aftershave, deodorants, sun tan oil, and menthol rubs (deep heat), nail polish. Alcohol evaporates quickly from the mixture to leave the solute on the surface.
5. The solubility of materials used in drugs has an effect on the way in which The body responds to them.
i. The digestive system:
a. Mouth – food broken down, mixed with saliva b. Oesophagus – transfers food from mouth to stomach c. Stomach – stores food, protein digestion,
d. Small intestine – breakdown of food completed here, carbohydrates converted to
glucose, protein digestion, most fats are dissolved.
ii. The pH in the stomach is acidic, small intestine is alkaline this neutralizes the contents from the stomach.
iii. Drugs are substances that can alter the physical and chemical structure of the body. Drugs move around the body via the bloodstream and diffusion across membranes, the skin and the walls of the stomach and small intestine.
iv. The rate of drug diffusion depends on the size of the molecule and solubility of the drug.
v. Water-soluble, fat-soluble and alcohol soluble drugs are absorbed by the walls of the stomach and transported by the blood.
vi. Fat-soluble vitamins are vitamins A, D, E, K. because they are fat-soluble they can be stored in the body tissue.
vii. Drugs may be administered through the mouth, inhalation, skin, creams, injections and drops. Depending on the rate of solubility of the drug, different forms of administration may be more appropriate.
viii. Water-soluble drugs e.g. B1, B2, B6, B12, vitamin C. These must be consumed daily because the body excretes them through urine.
GLOSSARY
Adhesive forces – forces acting between molecules of a substance and molecules of another
substance.
Acid – pH below 7 Alkali – pH above 7
Biodegradable – a substance capable of being broken down by the action of living
organisms. E.g. fungi
Colloid – are cloudy mixtures with particles that remain suspended in for a long period of
time. Particles will not settle out.
Dermal patch – patch applied to the skin, delivers medication to the body via the dermis
into the bloodstream.
Dermis – innermost layer of the skin. Contains sweat glands, blood vessels. Emulsifier – is an emulsifying agent such as soap, detergents.
Emulsifying agent – reduce the surface tension between two substances which makes it
possible to make a colloid or emulsion.
Emulsion – mixture of two substances that do not normally mix well (oil and water). To form
an emulsion emulsifying agent is added.
Epidermis – outermost layer of the skin protects the underlying tissue, forma a barrier from
heat loss, water loss and micro-organisms.
Hair – traps heat on the surface of the skin. Hair bulb – site of growth
Hydrophobic – water repelling, attracted to oil. Hydrophilic – attracted to water, oil repelling.
Meniscus – the surface shape of a liquid. Dependant on cohesive forces between molecules
and the adhesive forces between molecules and the container.
Microflora – populations of naturally occurring micro-organisms (fungi, bacteria) that are
common in and on the human body. An imbalance of microflora on the skin can cause conditions such as tinea and thrush.
Non-polar – molecule with no electric charge. Non-ionic. Oesophagus – tube connecting mouth to stomach.
Pancreas – produces enzymes that aid digestion of proteins, lipids (fats) and carbohydrates. pH – measure of acidity or alkalinity. Ranges from 0 (acid) – 14 (alkaline).
Polar – molecule containing an electric charge.
Sebum- oil produced by the sebaceous gland in the dermis. Small intestine –site of digestion and absorption.
Soluble – capable of dissolving.
Solution – contains dissolved substances that are uniform throughout. Transparent. Solvent –the substance in which a solute dissolves.
Stomach – site of protein digestion. Strong acid.
Sub-dermal implant – inserted under the skin to release medication over a period of time
through the blood stream.
Surface tension – result of strong forces between molecules in a liquid.
Surfactant – group of chemicals that contain surface-active-agents (molecule with one end
attracted to water, the other attracted to oil). Lowers surface tension of liquid giving water the greater ability to wet the dirty/oily surface and the dirt or oil can be removed more easily.
