pure substances

Substances with a definite chemical composition and physical and chemical properties. They are homogenous.

mixtures [ impure substances]

They are made of 2 or more elements, compounds, or both in any proportion. They do not have any definite properties and instead retain the properties of their components. They can be either homogeneous or heterogeneous.

element

It is a pure substance that cannot be converted to anything simpler than itself by any physical or chemical process. They are made of the same types of atoms.

characteristics of elements

1. Simplest type of pure homogeneous substance. 2. Cannot be broken down into simpler substances that exhibit all the properties of that element. 3. They have fixed melting and boiling points. 4. Elements can react chemically with other elements and compounds to form new substances.

metals states

All are solid except for mercury [ liquid ].

non metals states

All are gas or solid except bromine [ liquid ].

metalloids states

all are hard solids

atomicity

the no. of atoms in a molecule of an element.

monoatomic molecules

metals, metalloids, inert gases

polyatomic/ diatomic/ triatomic molecules

non- metals

metal properties

1. lustrous 2. hard solids 3. malleable 4. ductile 5. good conductors of heat and electricity 6. sonorous

exceptions to metal properties

1. sodium and potassium are soft materials. 2. mercury is liquid 3. zinc is brittle 4. tungsten is a poor conductor of electricity

non metal properties

1. no lustre 2. can be soft solids, liquids, or gases 3. neither malleable nor ductile 4. bad conductors of heat and electricity 5. not sonorous

exceptions to non metal properties

1. iodine and graphite are lustrous 2. carbon fiber is ductile 3. graphite is good conductor of electricity 4. diamond is hardest naturally occurring substance

metalloids

have properties of metals and non-metals

noble gases properties

1. not reactive in nature 2. all gases 3. found in traces in air

water

H₂O

ammonia

NH₄

carbon dioxide

CO₂

sodium chloride

NaCl

glucose

C₆H₁₂O₆

sodium bicarbonate/ baking soda

NaHCO₃

sodium carbonate

Na₂CO₃

calcium carbonate/ marble/ chalk

CaCO₃

silicon dioxide/ sand

SiO₂

acetic acid/ vinegar

CH₃COOH

copper sulphate

CuSO₄

magnesium oxide

MgO

potassium hydroxide

KOH

calcium hydroxide

Ca(OH)₂

hydrochloric acid

HCl

nitric acid

HNO₃

sulphuric acid

H₂SO₄

silver nitrate

AgNO₃

barium chloride

BaCl₂

calcium oxide

CaO

characteristics of compounds

1. they have definite melting and boiling points 2. they are pure and homogenous substances 3. all molecules of a compound have identical physical and chemical properties 4. they have fixed formulae to represent their molecules. 5. during its formation, energy is either liberated or absorbed. 6. its components can only be separated by chemical processes.

how are properties of water different from hydrogen and oxygen

1. unlike its gaseous components, water is in liquid state. 2. hydrogen supports combustion and oxygen is combustible, but water cannot support combustion and is used to extinguish fire.

how are properties of iron sulphide different from iron and sulphur

1. iron is magnetic, and sulphur can dissolve in carbon disulphide, but iron sulphide is neither. 2. iron sulphide is a black solid while iron is a grey metal and sulphur is a yellow non-metal.

mixtures

A kind of matter formed by mixing 2 or more pure substances in a non- defined proportion, such that they keep their components' chemical properties.

characteristics of mixtures

1. they can be homogenous or heterogenous substances. 2. it is made of 2 or more substances mixed together in any proportion. 3. it retains the properties of its components 4. cannot be represented by chemical formulae 5. does not have fixed melting or boiling points 6. can be separated by simple physical methods 7. no exchange of energy takes place

homogenous solid-solid mixtures

alloys such as brass, bronze, and steel

brass

copper+zinc

bronze

copper+tin

steel

iron+carbon

solid-solid heterogenous mixtures

salt+sand, salt+chalk, sand+stone

solid-liquid homogenous mixtures

sugar+water, salt+water, sulphur+carbon disulphide, iodine+alcohol

solid-liquid heterogenous mixtures

sand+water, mud+water, sugar+oil

liquid-liquid homogenous mixtures

alcohol+water, acetone+water

liquid-liquid heterogenous mixtures

oil+water

liquid-gas homogenous mixtures

tap water, carbonated drinks

liquid-gas heterogenous mixtures

water+soap lather

gas-gas homogenous mixtures

air

gas-gas heterogenous mixtures

all gases are miscible

why do we need to separate mixtures

1. to remove harmful and unwanted substances 2. to separate pure substances to make other useful products 3. to obtain useful substances

handpicking

used if the quantity is small and the components are large and visible. Also, the substance to be separated should be less than the mixture's amount. It should also be a different size, shape, and colour.

magnetic separation

used if one of the components is magnetic.

gravity separation

works on the principle of relative density, with one component lighter than water and the other heavier, both insoluble. To perform this method, pour water into the mixture; the lighter component will float on the water's surface. Then, we decant the water containing the lighter component. Then, we filter it to obtain the lighter component as the residue.

sublimation

works if one of the components can sublime. To do this, you need to heat the mixture with a lid on it, and the vapours of the sublimable substance will deposit on the lid as a solid [deposition] while the other is left behind.

solvent extraction

It works on the basis of one of the components being soluble in a solvent and the other being insoluble. The solvent is mixed into the mixture, then it is filtered. The insoluble solid is left behind. The soluble solvent can be recovered by evaporation.

solvent of sulphur

carbon disulphide

solvent of paint

turpentine oil

solvent of rubber

benzene

solvent of nail polish

acetone

solvent of rust

oxalic acid

solvent of grease

petrol

solvent of potassium nitrate [nitre]

water

solvent of chlorophyll

methylated spirits

solvent of iodine

ethyl alcohol

fractional crystallization

It is used when the solubility of 2 solids in a liquid is different. ex: salt and potassium nitrate - On heating, potassium nitrate is more soluble in water than salt. The solution of salt and potassium nitrate is heated, then left to cool. Potassium nitrate crystallises first, leaving behind the salt. The solution left behind is boiled to remove more potassium nitrate.

sedimentation & decantation

used when the solid is insoluble and heavier than the liquid.

sediment

the insoluble solid left after decantation

supernatant liquid

the liquid recovered after sedimentation and decantation

filtration

the process of separating insoluble soluble particles by allowing it to pass through a filter.

filtrate

the liquid obtained after filtration

residue

the insoluble solid particles left on the filter

how can you increase the process of sedimentation

Through the process of loading, which means adding a substance called alum to a solid-liquid mixture with very fine solid particles.

evaporation

the process of heating a solid-liquid mixture so that the liquid is evaporated out and the solid is left behind

crystallisation

the process of cooling down a hot supersaturated solid-liquid mixture until the solid form crystals while the liquid evaporates.

how do we obtain pure sugar from water

by the process of crystallisation

what is a crystal

A crystal is a lustrous solid particle with a definite shape and size.

distillation

a process of separation in which both the soluble solid component and the liquid component are retrieved.

centrifugation/churning

it is the process of separating suspended solid particles in a homogeneous mixture. it is used to separate cream from milk and is also used in labs to test blood and urine.

centrifuge

It is an apparatus used to conduct centrifugation. The mixture is poured into it, and it is rotated at a high speed so that the denser particles settle at the bottom and the lighter particles settle at the top.

separating funnel

It is a device used to separate components of liquid-liquid heterogeneous mixtures based on differences in density. The mixture is poured into the funnel and left to settle till the components form 2 clear layers. The heavier component slowly trickles out, leaving the lighter liquid in the funnel. The funnel is closed when the lighter component reaches close to the opening

fractional distillation

It works completely only if the difference in the boiling points of the miscible components is 30* C or more. The mixture is heated in a distilling flask, and the liquid with a lower boiling point vapourises, then is condensed and sent to a receiver. If the difference is less than 30*C, then a fractionating column is fitted over the flask.

how do we obtain petrol, diesel, and kerosene from petrol

through the process of fractional distillation

chromatography

it is based on the difference in the rates of absorption of different components on the surface of a suitable adsorbent.

meaning of chromatography

colour writing. it was named so because earlier, it was only used to separate coloured components.

what is the principle

It separates the components of a mixture on the basis of 2 phases - stationary phase and mobile phase.

what is the simplest type of chromatography

paper chromatography. A special kind of filter paper is taken, and a line is drawn on it in pencil near the bottom edge. A drop of the mixture is placed on the paper. The paper is then dipped into a solvent in such a way that the line drawn on the paper touches the surface, and not the drop of mixture. As the solvent rises through the fibres of the paper, the component of the mixture which is more soluble moves faster. As it dries, we can see multiple spots on the paper, each indicating a component of the mixture.

what paper is used in chromatography

Whatman filter paper

advantages of chromtography

1. a small quantity of mixture can be separated 2. components with similar physical properties can be separated. 3. it helps quantify the exact amounts of the components used in the mixture 4.it helps identify the components.

uses of chromatography

1. it is used to separate drugs from blood 2. separates colours from a dye 3. purifies industrial products 4. separates pigments from natural colours

separating liquid-gas mixtures

The mixtures must be heated so that dissolved gas escapes from the liquid. It works on the principle that a gas's solubility in a liquid decreases as the temperature increases.

diffusion

it works on the difference of densities of gases in the mixture. the lighter gases diffuses faster than the denser one.

solvent extraction

it works if a gas is soluble in a liquid and the other is not, or is less soluble.

how can we separate carbon dioxide from carbon monoxide

we dissolve the mixture in water. carbon dioxide will dissolve but carbon monoxide will not.

liquefaction

this method is based on the fact that some gases [like ammonia and carbon dioxide] liquify very easily at high pressure and low temperature, while others do not.

separating components of mixtures with 2 or more components

1. iron, sulphur, and salt - magnetic separation, solvent extraction, boiling 2. sand, salt, ammonium chloride - sublimation, solvent extraction, boiling