Classifying & Separating Substances Flashcards
What is a mixture? Identify some characteristics:
When two or more substances mix without a chemical change occurring. A mixture’s material properties are dependent on the identity and relative amounts of the substances it contains.
Characteristics Include:
- The components of a mixture each keep their original properties
- Components of a mixture can be fairly easily seperated through conventional methods.
What is a solution? Identify some characteristics:
A solution is a homogeneous combination of two or more substances.
Characteristics Include:
- The substances within the solution exist on the same state (solid, liquid, gas)
- Particles in a solution are not visible to the naked eye
- Light can pass through a solution (it appears transparent)
Describe Homogeneous materials:
These are materials of uniform composition that cannot be mechanically separated into different materials. Homogeneous materials include elements (all one type of atom), components and mixtures (where the contents of the mixture are uniformly distributed).
Describe Heterogeneous materials:
These are materials of non-uniform composition that can typically be mechanically separated into different materials. Heterogeneous materials are always non-uniform mixtures.
Describe the difference between homogeneous and heterogeneous mixtures:
Homogeneous mixtures include all solutions, and contain a uniform distribution of all their components (not necessarily an equal distribution). Homogeneous mixtures MUST be made up of components of the same state (solid/liquid/gas).
Heterogeneous mixtures contain a non-uniform distribution of all their components, and can be made up of
Identify 5 Physical Properties:
- Melting Point
- Boiling Point
- Electrical and Thermal Conductivity
- Density
- Solubility
Identify 2 Chemical Properties:
- Reactivity in different states
- Reactivity with water, acids, bases and oxygen
- Decomposition by heat
What is the difference between physical and chemical changes?
Physical changes are changes to a substance’s physical properties.
Chemical changes are any changes in which at least one new substance is formed. These are also known as chemical reactions, indicated by common signs such as bubbles (a gas is formed), a solid (called a precipitate) is formed, there is a significant change in temperature, a change of colour occurs, an insoluble solid disappears.
Describe the process of sieving:
Sieving is a process of separating multiple solid particles of different sizes or large solid particles from a liquid. This process relies on separation by difference in particle size, and works by pouring a mixture through a fine mesh, trapping the larger type of particles from passing through it.
Describe the process of Filtration:
Filtration is a process that relies on separation by difference in particle size, and separates liquids and solids, where the solid’s particles are very small. This works by passing a mixture through fine filter paper, which allows the liquid to drip through as filtrate into a collection flask, and traps the solid (now known as residue).
Describe the process of Vaporisation:
Vaporisation is a process that relies on separation by difference in boiling point, and typically works to seperate a solid that has been dissolved in a liquid (a solution). This is done by heating a liquid mixture and allowing the liquid to evaporate, leaving behind the solid particles.
Describe the process of Simple Distillation:
Simple Distillation is a process that relies on separation by difference in boiling point, and typically works to seperate multiple liquids or a liquid from a solid (solution). This technique relies on a difference of at least 50*C in boiling point between components, and works by evaporating a substance in the mixture, but trapping it and redirecting it to a collection beaker in the form of liquid distillate.
Describe the process of Fractional Distillation:
Fractional Distillation is a process that relies on separation by difference in boiling point, and typically works to seperate multiple liquids or a liquid from a solid (solution). This technique is designed for liquid mixtures with small changes in boiling point between components. This works by evaporating most substances in the mixture, where they rise up a column. Substances with a higher boiling point will change back to a liquid towards the base of the column, and be collected as they do so, while substances with a lower boiling point will reach the top before liquifying.
Describe one method of separating liquids by density and solubility:
Separating funnels can be used to seperate two immiscible liquids (liquids that don’t mix). By opening a valve at the bottom of the funnel, the more dense liquid (on the bottom) will flow into the beaker below the funnel, leaving the less dense liquid in the funnel.
