Chemistry Exam - Mixtures, Properties, Gravimetric Analysis

is hydrogen a metal, non metal or a metalloid

non metal

mnemonic to remember where the non-metals start

cats purr softly, enjoying, itchy, restful naps

do reactive elements exist as uncombined elements in nature?

no. for example reactive sodium is seen as NaCl but not by itself as Na

what is reactivity?

• describes how readily an element reacts with another to form compounds

• elements are reactive if they gain, donate or share electrons with other elements (so not noble gases)

what are the physical properties of a semi-metal/metalloid

they have some metallic properties and some non metal properties

what are the physical properties of a non-metal?

• non malleable

• non-ductile

• dull in appearance

• less dense than metals

• poor conductor of heat and electricity

what are the physical properties of a metal?

• hard

• solid at room temp (except mercury)

• high melting point

• shiny

• great conductor of electricity and heat (copper)

• dense

• ductile

• malleable

what is the purpose of gravimetric analysis

determines the percentage of each element that makes up a specific compound

define ductile

ability for a material to stretch and bend into long, thin wires without breaking

define solubility

the ability of a solute to dissolve in a solvent to form a solution.

define viscosity

a substance resistance to flow

eg. water - low viscosity (flows very easily)

eg. honey - high viscosity (takes longer to come out of its bottle)

define malleable

ability to be changed into different shapes

what is melting point

the temperature at which the solid melts to become a liquid.

what is boiling point

the temperature at which a liquid boils and becomes vapour

define explosive

the ability to produce an explosion

define pyrophoric

has the ability to ignite when exposed to air

define combustibility

material that can catch on fire easily

define oxidiser

ability to strip an electron off another substance, gaining one for itself

define corrosive

the ability to destroy other substances in a chemical reaction

what is radioactivity (chemical property)

how the nucleus of an atom will change over time

what is flammability

how a substance will react in an open flame

list different chemical properties

• flammability

• reactivity

• corrosive

• oxidiser

• combustible

• toxicity

• explosive

• pyrophoric

• chemical stability

what is a chemical property?

a change which can not be seen unless a reaction occurs. It is the breaking and forming of bonds

list different physical properties

• melting point

• boiling point

• malleable

• colour

• smell

• texture

• density

• solubility

• ductile

• viscosity

what is a physical property?

a property that can be observed, measured or a change of matter occurs (solid-liquid-gas)

Homogeneous mixture

A mixture with uniformly distributed properties, where components are evenly combined. can mix together

Heterogeneous mixture

A mixture composed of non-uniformly distributed components which are unevenly combined. can not mix together

Solutions

Homogeneous mixtures in which the dissolved particles are invisible to the naked eye, consisting of one solvent and at least one solute.

Solvent

a substance present in higher concentrations that dissolves a solute to form a solution.

Solute

The substance present in lower concentrations that dissolves in a solvent to form a solution.

Filtration

A separation technique where solids are separated from fluids using a filter that allows fluid to pass but solid particles to hold

• separates insoluble substances from soluble substances

Distillation

A separation technique where two miscible liquids are separated by their boiling points, often used to turn saltwater into fresh water.
- one component turns into gas and is cooled back into a liquid using a condenser

What method would be utilised to separate gold and sand?

A heterogeneous mixture of gold and sand, physically separable using a sieve due to uneven combination of components.

What method would be utilised to separate seawater?

The process of using distillation to separate salt and water in a homogeneous mixture.

what is a mixture?

two or more elements or compounds that are physically bonded but not chemically combined, thus can be separated

what are the similarities between a homogenous mixture and a heterogenous mixture

- both are types of mixtures
- both are physically bonded
- can be separated using physical separation techniques

define physical change

a change of matter from one form to another without a change in chemical properties

what are examples of a physical change?

- changing between a solid, liquid or gas
- physically separating components
- dissolving
- precipitating

Sieving

A separation technique where particles are separated by size. a sieve is used to separate the smaller particles

Density

mass/volume

Name one example of objects having the same mass but different densities

a 1kg textbook has the same mass as 1kg of feathers. When they are both thrown into the ocean, the book will sink and the feathers will float as they both have different densities.

Sedimentation

process of heavier solid particles settling to the bottom of the container.
- separates solids from liquids
- less dense at the top, more dense at the bottom

Decantation

A method of separating solid insoluble particles from a liquid by leaving the particles to settle and pouring off the liquid.

define miscibility

the ability of a liquid solute to dissolve in a liquid solvent. forms a homogeneous mixture

define immiscible

the inability of two liquids in each other regardless of the proportions they are mixed in. forms a heterogenous mixture

provide an example of a miscible mixture

salt and water

provide an example of a immiscible mixture

oil and water

Centrifugation

process of separating out particles of different sizes and densities by spinning them at high speed in a centrifuge.
- like sedimentation but faster

Separation Funnel

lab glassware that separates two immiscible liquids of different densities

what steps are taken to use a separation funnel

1. pour mixture
2. shake mixture
3. leave to settle (dense liquid will settle to the bottom, less dense liquid will float to the top)
4. the denser liquid is then dripped out by a tap, leaving the less dense liquid in the funnel

Melting Point

the temperature at which a substance changes from a solid to a liquid, or a liquid to solid (freezes)

Boiling Point

the temperature at which a substance changes from a liquid to a gas

Freeze Concentration

Separation technique that depends on a difference in melting point. The temp of the mixture is put below melting point for only ONE component. one substance freezes, the other remains a liquid

Evaporation

separation technique where a mixture is heated so that one component is turned to a gas
(commonly used when there is a large difference between boiling points of a soluble solid and a liquid in a mixture)

Name one difference between evaporation and distillation

- evaporation is used to collect the substance that does not evaporate (stable)
- distillation is used to collect the substance that evaporates easily (volatile)