Lifestyle Chemistry Notes

LIFESTYLE CHEMISTRY

1. The use of a substance depends on its physical properties

* Identify that a wide range of substances are used daily as part of our food, our hygiene and maintenance of our health.

- Food: simple and complex carbohydrates, protein, fats and oils, vitamins, minerals, water, acids, bases, alcohols, etc.

- Hygiene: soap, shampoo, deodorant, toothpaste, cleansing creams and lotions are mixtures of chemicals like glycerol, fats and oils, salts and water

- Health: body hygiene, household cleaners and pesticides mixtures or compounds, often containing methylated spirits, sodium hydroxide and salt.

- Surfactant chemicals - help water wet a dirty surface and lift dirt off

- Degreasers - Dissolve oil fats and greases

- Used to reduce friction between two moving surfaces

* Identify that solutions, colloids and suspensions occur in wide range of consumer products

Solutions, colloids and suspensions are types of mixtures, which occur, in a wide range of consumer products.

Solutions - tea, soft drink

Colloids - sun cream, mayonnaise

Suspension - flavored milk, paint and medicines

* Explain that mixtures can be:

➢ Solutions that contain dissolved substances and are uniform throughout

➢ Suspensions containing particles that settle out or form layers quickly

➢ Colloids with particles for long periods

- Solutions: mixtures that contain dissolved substances and are uniform throughout

- solid in liquid - saltwater

- gas dissolved in liquid - oxygen in water

- Colloids: Mixtures where particles remain suspended, particles spread out evenly throughout substances

- Oil-in-water (milk)

- Water-in-oil

- Gas-in-liquid (whipped cream, shaving cream)

- Liquid-in-gas (hairspray)

- Liquid-in-liquid

- Liquid-in-solid

- Suspensions: mixtures constraining particles that settle into layers quickly

- Can be separated easily

- E.g. mayonnaise

* Explain surface tension in terms of the forces experienced by particles at the surface of a liquid

At the surface of a liquid, forces do not act equally on the molecule. Molecules are strongly attracted by the molecules below in the liquid. Molecules are weakly attracted by the molecules in the air above the liquid. This imbalance in forces is called surface tension.

- At the surface of the liquid, strong inward forces are stronger between water-water particles then in water-air particles. This causes a surface effect, called surface tension, which appears like a thin transparent skin. The same forces cause droplets of liquid to be spherical

- Forms a 'skin' at the surface. This is why insects such as pond skaters have the ability to walk on water

* Describe surfactants as substances that affect the surface tension of a liquid

Surfactants are substances that reduce the surface tension of a liquid.

normally water and oil for an immiscible mixture. The surfactant lowers the surface tension of the water and allows it to make more contact with the surface being cleaned. Resulting in a liquid-in-liquid colloid, an emulsion forms

2. A wide range of cleaning products are made from colloids and surfactants

* State the relationship between the properties of an emulsion and the types of molecules present

Emulsion →

- Mixture of two substances that do not normally mix well (oil and water).

Emulsifying agent→

- Reduce the surface tension between two substances which make it possible to make a colloid or emulsion

→ Emulsifiers are put on a scale 1-20 HLB - Hydropholic-lipophilic balance

- The name of the emulsions tells you the phase the emulsifier had the greater affinity (relationship) for - oil-in-water - affinity water

- 7-14 oil-in-water

- 3-6 water-in-oil

Oil-in-water emulsions:

Water-in-oil emulsions:

* Outline the purpose of emulsifying agents in a range of consumer cleaning products

The molecules in emulsifying agents such as detergents, have a negative end when dissolved. Allowing them to keep any oily substances away from any article with negative charges - glass and crockery

Molecules in personal cleaning products are amphoteric (positive and negative ends).

Allows them to keep oily substances away both positive and negatively charged surfaces

- Positive ends - alkaline

- Negative ends - acidic solutions

* Identify that soaps and detergents are emulsifying agents and surfactants

- Soaps and detergents are emulsifying agents because they assist two immiscible (not joining) substances to mix - oil and water

- Work by lowering the surface tension of water and emulsifying the particles of dirt and great with the water - Soaps and detergents allow oil to disperse in water.

- Soaps and detergents are surfactants because they act at the surfaces between two immiscible substances - oil and water.

* Explain why cleaning products must be surfactants and emulsifiers

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