Matter exists in three states (phases) ; Solid , Liquid and gaseous state . The three states of matter are interconvertible, as in same substance but in different state . E.g ice ( water in solid state) , liquid water and steam/ water vapour ( water in gaseous state ) .
In the solid state, particles are fixed in a uniform manner in definite position in a crystal lattice by strong force operating within them . Particles in a solid vibrate in their fixed position . The vibrations depends on the temperature, increase in temperature ( heat energy) increases the kinetic energy ( energy due to motion ) of the particles hence weakens the forces of attraction between the particles. At a given temperature of a solid , these forces of attraction becomes so weak that the solid structure breaks down in a process known as melting to form a solid .
In the liquid state, the particles can move freely i.e. posses translational motion, with only weak forces operating between the particles as compared to solids, and this is the reason as to why liquids have the ability to flow. Particles in a liquid can move but not in all directions though. The forces are however not weak enough to allow complete separation of the particles from one another. A liquid substance have definite volume but takes the shape of the container holding it , therefore, liquids have indefinite shape. The forces in liquids also depends on temperature. Increase in temperature of a liquid increases the movement of the liquid due to increase of kinetic energy of the particles in a liquid substance which weakens the forces holding them together. As in solids, at a certain temperature,the forces becomes so weak that the liquid state breaks down .i.e. evaporation/ vapourisation/ boiling takes place to form vapor/gas .
In gaseous state, there are weak forces of attraction between the particles, the distance between particles increases, particles moves in all directions, hence gases have no definite shape or volume ( since a gas can be compressed to fit a smaller container) .
The sensitivity to changes in volume in pressure and temperature is therefore:
Solid <Liquid<<Gas
- STRUCTURE OF AN ATOM AND THE PERIODIC TABLE . _Structure of an atom What is an atom ? An atom is the smallest particle of an element which can take part in a chemical reaction. – An atom has a diameter of 10–⁸ cm. ( 0.00000001) . – An atom is made up of three sub atomic particle; a) Protons b) Neutrons c) Electrons – The protons and neutrons are found inside the nucleus of an atom while electrons are found in the region around the nucleus ( in the shells or energy levels ) . – Protons are positively charged (+ve) while electrons are negatively charged (-ve) . The neutrons have no charge ( neutral particles ) . Why is an atom said to be electrically neutral ? In any given atom , the number of protons ( in the nucleus) equal to the number of electrons( in the shells ) p=e. Where p= protons e= electrons Why are protons and neutrons referred to as nucleons ? This is because both the protons and neutrons are found in the nucleus of an atom of an element.
- ATOMIC NUMBER AND ATOMIC MASS ( MASS NUMBER). – Atomic number: is the number of protons in the nucleus of an atom . Q. What is the atomic number of elements X with 5 electron in it’s energy levels ? Explain. -Element X has atomic number 5 , this is because it has 5e which equals the number of protons , therefore it has 5p which equals the atomic number. Atomic number= no. of protons= no. of electrons Mass Number ( Atomic mass ) : is the sum of the protons and neutrons in the nucleus of an atom. Mass number= protons (p) + neutrons (n) Q. An element Y has 8 protons , 8 electrons and 8 neutrons, find the mass number of the element Y. Mass number= p+ n = 8+8 = 16. Q. A Magnesium atom has atomic mass of 24 and atomic number 12 , how many neutrons are there in the magnesium atom ? Atomic number = p Atomic mass also known as mass number = p+n Therefore ; neutrons= atomic mass – no. of protons n = 24-12 n= 12. – Both mass number and atomic number can be written along with the symbol of an element. – Mass number is written as the superscript (above the symbol) while atomic number is written as a subscript ( below the symbol) to the left of the chemical symbol .
- Structure of an atom ⚛️
- The first 20 element in the periodic tableThe periodic table consists of elements arranged according to theirContinue reading “The first 20 element in the periodic table”
- IsotopesIsotopes are atoms of the same element, with the sameContinue reading “Isotopes”
Bonus
✓ Melting point of a pure substance is a constant temperature in which a pure solid substance changes into a liquid state when temperature is increased .
✓ Boiling point of a pure substance is a constant temperature in which a liquid substance changes in gaseous state when temperature is increased.
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