Lifestyle Chemistry Part 1: The Substances You Use

What are some substances that you use on a daily basis?

Properties of Substances The properties of a chemical depend on: the particles that make up the chemical how the particles are arranged the forces (interactions) between the particles.

Properties of Substances Physical Properties A physical property is a property of the substance by itself. For example: state of matter (solid, liquid, gas) colour density how it feels to touch odour taste

Properties of Substances Chemical Properties A chemical property is a property of the substance reacting with another chemical. Chemical properties are what we observe when a substance reacts with another chemical.

Properties of Substances Chemical Properties Elements Made up of only one type of atom Compounds Contain more then one type of atom joined together Mixtures Contain different substances not chemically combined

Mixtures Vocab A homogeneous mixture is a mixture where the components that make up the mixture are uniformly distributed throughout the mixture. A heterogeneous mixture is a mixture where the components of the mixture are not uniform or have localized regions with different properties.

Types of Mixtures Solutions Contain dissolved substances that are uniformly spread throughout the solvent. A true solution is transparent and may be coloured. The solute is dissolved entirely in the solvent.

Types of Mixtures Solutions Characteristics that define a solution are: particles smaller than 10-6 mm ( mm) no settling of particles an electric field has no effect on the solution no residue is left after passing through filter paper a light beam shone through a solution cannot be seen in the solution.

Suspensions Insoluble solids suspended in liquids are called suspensions. The solids eventually settle upon standing. Types of Mixtures

Suspensions Characteristics that define a suspension are: particles larger than 10-3 mm (0.001 mm) particles settle out on standing an electric field has no effect on the mixture residue is left after passing through filter paper a light beam can be seen when shone through the mixture. Types of Mixtures

Colloids Mixtures where large molecules or small clusters of molecules are dispersed through the liquid and do not settle out are colloids. Types of Mixtures

Colloids Characteristics that define a colloid are: particles are between 10-3 mm and 10-6 mm (0.001 mm and mm) particles do not settle out on standing an electric field will cause some particles to move to one electrode no residue is left after passing through filter paper the path of a light beam can be seen when shone through the mixture. Types of Mixtures

Solution Colloid

Solution Suspension Colloid

Solution Colloid

Types of Mixtures Solutions Solid dissolved in a liquid (saltwater) Gas dissolved in a liquid (oxygen in water)

Types of Mixtures Suspension Solid particles suspended in a liquid (soluble aspirin) Liquid particles suspended in a liquid (Fresh milk)

Types of Mixtures Colloids Emulsions: Liquid particles suspended in a liquid (mayonnaise) Oil in water Water in oil Foams: Gas particles suspended in a liquid (shaving cream, whipped cream, froth) Solid particles suspended in a liquid (paint) Solid or liquid particles suspended in a gas (smoke)

Types of Mixtures Questions 1.A solid or gas dissolved in a liquid is called a _____________________________. 2.The difference between a suspension and a colloid is that 3.How can a suspension be separated? 4.Do suspensions involve gases? 5.How can a solution be separated? 6.What is a gas suspended in a liquid?

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

Surface Tension Vocab Cohesive forces between water molecules cause them to ‘stick’ together. The water molecules are attracted to the glass through adhesive forces. Meniscus is the curved upper or lower surface of a liquid in a tube.

Water’s Surface Tension Water molecules are strongly attracted to each other. Water molecules on the surface of water are strongly attracted to the surrounding surface molecules and the molecules beneath the surface. This strong attraction causes the surface of the water to resist attempts to increase its surface area, thus allowing objects denser than water to sit on the surface.

Water’s Surface Tension Water molecules are strongly attracted to each other. Water molecules on the surface of water are strongly attracted to the surrounding surface molecules and the molecules beneath the surface. This strong attraction causes the surface of the water to resist attempts to increase its surface area, thus allowing objects denser than water to sit on the surface.

Water’s Surface Tension At the surface of a liquid, the forces do not act equally on the molecules. Molecules have a strong attraction to the molecules below but not the air above. Forces Balanced Forces Unbalanced

Water’s Surface Tension Explain in your own words why falling water drops appear tear shaped.

Water’s Surface Tension Falling water drops appear tear shaped because gravity causes most of the water molecules to condense towards the bottom of the drop, leaving fewer molecules at the top.

Water’s Surface Tension The water surface curves up at the edges. This curved surface is the meniscus (plural: menisci). The water molecules are attracted to the glass through adhesive forces.

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

Surfactants Surfactants are molecules that act at the surface of a liquid, lowering the liquid's surface tension.

Surfactants Surfactants added to water allow the water to make oil and dirt more easily removed. Surfactants help dissolve oil in water. Surfactants are therefore a great cleaning agent.

Surfactants Surfactants make the oils “dissolve” in water. This makes the oil/dirt and water mixture into a liquid- in-liquid colloid (emulsion) and so the process in called emulsification.

Surfactants Surfactants are shaped like tadpoles. The head is water soluble and the tail is oil soluble. Hydrophobic Hydrophilic

Surfactants There are four different types of surfactants: anionic (negatively charged head) cationic (positively charged head) non-ionic (no charge) amphoteric (positive and negative charges depending on the pH of the liquid).

Surfactants Anionic Cationic Non-Ionic Amphoteric

Surfactants