Chemistry Most important Definitions for the short questions and mcqs science chemistry for test and exams preparations for student exams. Chemistry is the study of Chemicals here i have designed for students, chemistry textbook short definitions for tests and mcqs preparations. Here all of most important MCQs of Chemistry with online Quiz Test for students Test preparations for chemistry book. Organic and Inorganic Chemistry Quiz Tests for subject of chemistry help to students.
Acid:-compound that gives off H+ ions in solution.
Acidic:-describes a solution with a high concentration of H+ ions.
Anion:-ions with a negative charge.
Anode:-the electrode where electrons are lost (oxidized) in redox reactions.
Atmospheres:-common units for measuring pressure.
Atom:-the smallest object that retains properties of an element. Composed of electrons and a nucleus (containing protons and neutrons).
Atomic number:-number of protons in an element.
Avogadro's number:-number representing the number of molecules in (1) mole: 6.022 * 10 to the 23 power.
Base:-substance which gives off hydroxide ions (OH-) in solution
Basic:-having the characteristics of a base
Bohr's atom:-He made significant contributions to the atom. He understood the line spectra--the reason why only certain wavelengths are emitted when atoms jump down levels.
Buffer solutions:-solutions that resist change in their ph, even when small amounts of acid or base are added
Catalyst:-substances that speed up a chemical process without actually changing the products of reactions
Cathode:-electrode where electrons have gained (reduction) in redox reactions
Cations:-ion with positive charge
Central atom:-in a Lewis structure, usually the atom that is the least electronegative
Charge:-describes an object's ability to repel or attract other objects. Protons have a positive ...while electrons have a negative... Like ...repel each other, while opposites attract.
Chemical changes:-processes or events that have altered the fundamental structure of something.
Chemical equation:-an expression of a fundamental change in the chemical substance
Colligative properties:-properties of a solution that depend only on the number of particles dissolved in it, not the properties of the particles themselves. The main ones are boiling point elevation and freezing point depression.
Combustion:-when substances combine with oxygen and release energy
Compound:-two or more atoms joined together chemically, with covalent or ionic bonds
Concentration:-the amount of a substance in a specified space
Conjugate acid:-a substance which can lose H+ ion to form a base
Conjugate base:-a substance which can gain H+ ion to form an acid
Covalent bonds:-when two atoms share at least one pair of electrons
Decay:-change of an element into a different element, usually with some other particle(s) of energy emitted
Density:-mass per unit volume of a substance
Dipole-dipole forces:-intermolecular forces that exist between polar molecules. Active only when the molecules are close together. The strengths of intermolecular attractions increase when polarity increases
Dispersion forces (London dispersion forces):-dispersion is an intermolecular attraction force that exists between all molecules. These forces are the result of the movement of electrons which cause slight polar moments. Generally very weak, when their molecular mass increases, so does their strength
Dissociation:-breaking down of a compound into its components to form ions from an ionic substance
Double bond:-when an atom is bonded to another atom by two sets of electron pairs
Effusion:-movement of gas molecules through a small opening
Electrochemical cell:-gives an electric current with a steady voltage as a result of an electron transfer reaction
Electrodes:-device that moves electrons into or out of a solution by conduction
Electrolysis:-changing the chemical structure of a compound using electrical energy
Electromagnetic spectrum:-complete range of wavelengths which light can have. These include infrared, ultraviolet and all other types of radiation as well as visible light
Electrong:-one of the parts of an atom having a negative charge. Indivisible particle with a charge of -1
Electronegativity:-measure of a substance's ability to attract electrons
Electrostatic forces:-forces between charged objects
Element:-substance consisting of only one type of atom
Empirical formula:-formula showing the simplest ratio of elements in a compound
Endothermic:-process that absorbs heat from its surroundings as the reaction proceeds
Energy:-ability to do work
Enthalpy:-change in heat at constant pressure
Entropy:-measure of the disorder of a system
Equilibrium:-when the reactants and products are in a constant ratio. The forward reaction and the reverse reactions occur at the same rate when a system is in this state
Equilibrium constant:-value that expresses how far the reaction proceeds before reaching equilibrium. A small number means that equilibrium is towards the reactants side while a large number means that the equilibrium is towards the product side
Equilibrium expression:-the expression giving the ratio between the products and reactants. It is equal to the concentration of each product raised to its coefficient in a balanced chemical equation and multiplied together, divided by the concentration of the product of reactants to the power of their coefficients
Equivalence point:-occurs when the moles of acid equal the moles of base in a solution
Exothermic:-process that gives off heat to the environment
Frequency:-number of events in a given unit of time. When describing a moving wave, means the number of peaks which would pass a stationary point in a given amount of time
Geiger counter:-instrument that measures radiation output
Gibb's free energy:-the energy of a system that is available to do work at a constant temperature and pressure
Graham's law:-the rate of diffusion of a gas is inversely proportional to the square root of its molar mass
Half life:-the amount of time it takes for half an initial amount to disintegrate
Heisenberg uncertainty principle:-the principle states that it is not possible to know a particle's location and momentum precisely at any time
Hydrogen bonding:-strong type of intermolecular dipole-dipole attraction. Occurs between hydrogen and F, O or N
Hydrolysis:-the reactions of cations with water to produce a weak base or of anions to produce a weak acid
Ideal gas law: = n
Intermolecular forces:-forces between molecules
Intramolecular forces:-forces within molecules. Forces caused by the attraction and repulsion of charged particles
Ion:-removing or adding electrons to an atom creates an ... (a charged object very similar to an attom)
Ionic bond:-when two oppositely charged atoms share at least one pair of electrons but the electrons spend more time near one of the atoms than the other
Ionization energy:-energy required to remove an electron from a specific atom
Isotopes:-elements with the same number of protons but have different numbers of neutrons, and thus different masses
Kelvin:-The SI unit of temperature. It is temperature in degrees Celsius plus 273.15
Kinetic energy:-energy an object has because of its mass and velocity. Objects that are not moving do not have this.
Le Chatlier's Principle:-states that a system at equilibrium will oppose any change in the equilibrium conditions
Lewis structures:-a way of representing molecular structures based on valence electrons
Limiting reagent:-the reactant that will be exhausted first
Mass number:-the number of protons and neutrons in an atom
Mixture:-composed of two or more substances, but each keeps its original properties
Molality:-the number of moles of solute (the material dissolved) per kilogram of solvent (what the solute is dissolved in)
Molar:-a term expressing molarity, the number of moles of solute per liters of solution
Molarity:-the number of moles of solute (the material dissolved) per liter of solution. Used to express the concentration of a solution
Mole:-a collection of 6.022 * 10 to the 23 power number of objects. Usually used to mean molecules
Molecular formula:-shows the number of atoms of each element present in a molecule
Molecular geometry (VSEPR):-shape of a molecule, based on the relative position of the atoms
Molecular mass:-the combined mass (as given on the periodic table) of all the elements in a compound
Molecule:-two or more atoms chemically combined
Mole fraction:-the number of moles of a particular substance expressed as a fraction of the total number of moles
Neutral:-an object that does not have a positive or negative charge
Neutron:-a particle found in the nucleus of an atom. It is almost identical in mass to a proton, but carries no electrical charge
Nm:-abbreviation for nanometers. A nanometer is equal to 10 to the -9 power meters
Nucleus:-the central part of an atom that contains the protons and neutrons. Plural=nuclei
Octet:-In Lewis structures, the goal is to make almost all atoms have this structure. This means they will have access to (8) electrons regularly, even if they do have to share some of them
Orbitals:-an energy state in the atomic model which describes where an element will likely be
Oxidation number:-a number assigned to each atom to help keep track of the electrons during a redox-reaction
Oxidation-reduction-reaction:-a reactions involving the transfer of electrons
Parent isotopes:-an element that undergoes nuclear decay
Partial pressure:-the pressure exerted by a certain gas in a mixture
Particle:-small portion of matter
Percent composition:-expresses the mass ratio between different elements in a compound
Periodic table:-grouping of the known elements by their number of protons. There are many other trends such as size of elements and electronegativity that are easily expressed in terms of the periodic table
Ph:-measures the acidity of a solution. It is the negative log of the concentration of the hydrogen ions in a substance
Photon:-massless packet of energy, which behaves like both a wave and a particle
Physical property:-a property that can be measured without changing the chemical composition of a substance
Planck:-What is h ?
Planck:-He contributed to the understanding of the
Poh:-Measures the basicity of a solution. It is the negative log of the concentration of the hydroxide ions
Polar molecules:-Molecule with a partial charge
Potential energy:-The energy an object has because of its composition or position
Pressure:-Force per unit area
Principal quantum number (n):-The number related to the amount of energy an electron has and therefore describing which shell the electron is in
Products:-The compounds that are formed when a reaction goes to completion
Proportion:-An equality between two ratios
Proton:-Particle found in a nucleus with a positive charge. Number of these gives the atomic number
Quantum:-Something that comes in discrete units
Quantum numbers:-Set of numbers used to completely describe an electron
Radiant energy:-Energy which is transmitted away from its source, for example, energy that is emitted when electrons transition down one level to another
Radiation:-Energy in the form of photons
Radioactive:-Substance containing an element which decays
Ratio:-The relative size of two quantities expressed as the quotient of one divided by the other; a:b or a/b
Reactants:-Substances initially present in a chemical reaction
Reduction reaction:-A reaction in which a substance gains at least one electron
Salts:-Ionic compounds that can be formed by replacing one or more of the hydrogen ions of an acid with another positive ion
Shells (orbitals):-Where the electrons generally are; they are composed of four types of sub...; s, p, d and f
Single bond:-When an electron pair is shared by two atoms
SI Unit:-Standards for Systeme International d'Unites, an international system which establishes a uniform set of measurement units
Solute:-The substance (solid, liquid or gas) dissolved in a solution, for example, the salt in saltwater
Solution:-Mixture of a solid and a liquid where the solid never settles out, for example, saltwater
Solvent:-Liquid in which something is dissolved, for example the water in saltwater
Specific heat:-The amount of heat it takes for a substance to be raised by one degree Celsius
Spontaneous reaction:-A reaction that will proceed without any outside energy
States of matter:-Solid, liquid, gas and plasma. Plasma is a "soup" of disassociated nuclei and electrons, normally found only in stellar objects
Stoichiometry:-The study of the relationships between amounts of products and reactants
STP:-Standard Temperature and Pressure. 0 degrees Celsius and 1 atm
Subshell (suborbital):-One part of a level, each of which can hold different numbers of electrons
Thermodynamics:-The study of temperature, pressure, volume and energy flow in chemical reactions
Titration:-The process used to take a solution of unknown concentration with a solution of a known concentration for the purpose of finding out more about the unknown solution
Valence electrons:-The electrons in the outermost shell of an atom
Van der Waals equations:-An equation for non-ideal gases that accounts for intermolecular attraction and the volumes occupied by gas molecules
Velocity:-Speed of an object; the change in position over time
Volume:-Measures the size of an object using length measurements in three dimensions
Wave:-A signal which propagates through space
Wavelength:-On a periodic curve, the length between two consecutive troughs (low points) or peaks (high points)
Weak acid:-Substances capable of donating hydrogen but do not completely ionize in solution
Weak bases:-Substances capable of accepting hydrogen but do not completely ionize in solution
Work:- Expression of the movement of an object against some force
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Short Definitions Of Chemistry Chapter Wise
Acid:-compound that gives off H+ ions in solution.
Acidic:-describes a solution with a high concentration of H+ ions.
Anion:-ions with a negative charge.
Anode:-the electrode where electrons are lost (oxidized) in redox reactions.
Atmospheres:-common units for measuring pressure.
Atom:-the smallest object that retains properties of an element. Composed of electrons and a nucleus (containing protons and neutrons).
Atomic number:-number of protons in an element.
Avogadro's number:-number representing the number of molecules in (1) mole: 6.022 * 10 to the 23 power.
Base:-substance which gives off hydroxide ions (OH-) in solution
Basic:-having the characteristics of a base
Bohr's atom:-He made significant contributions to the atom. He understood the line spectra--the reason why only certain wavelengths are emitted when atoms jump down levels.
Buffer solutions:-solutions that resist change in their ph, even when small amounts of acid or base are added
Catalyst:-substances that speed up a chemical process without actually changing the products of reactions
Cathode:-electrode where electrons have gained (reduction) in redox reactions
Cations:-ion with positive charge
Central atom:-in a Lewis structure, usually the atom that is the least electronegative
Charge:-describes an object's ability to repel or attract other objects. Protons have a positive ...while electrons have a negative... Like ...repel each other, while opposites attract.
Chemical changes:-processes or events that have altered the fundamental structure of something.
Chemical equation:-an expression of a fundamental change in the chemical substance
Colligative properties:-properties of a solution that depend only on the number of particles dissolved in it, not the properties of the particles themselves. The main ones are boiling point elevation and freezing point depression.
Combustion:-when substances combine with oxygen and release energy
Compound:-two or more atoms joined together chemically, with covalent or ionic bonds
Concentration:-the amount of a substance in a specified space
Conjugate acid:-a substance which can lose H+ ion to form a base
Conjugate base:-a substance which can gain H+ ion to form an acid
Covalent bonds:-when two atoms share at least one pair of electrons
Decay:-change of an element into a different element, usually with some other particle(s) of energy emitted
Density:-mass per unit volume of a substance
Dipole-dipole forces:-intermolecular forces that exist between polar molecules. Active only when the molecules are close together. The strengths of intermolecular attractions increase when polarity increases
Dispersion forces (London dispersion forces):-dispersion is an intermolecular attraction force that exists between all molecules. These forces are the result of the movement of electrons which cause slight polar moments. Generally very weak, when their molecular mass increases, so does their strength
Dissociation:-breaking down of a compound into its components to form ions from an ionic substance
Double bond:-when an atom is bonded to another atom by two sets of electron pairs
Effusion:-movement of gas molecules through a small opening
Electrochemical cell:-gives an electric current with a steady voltage as a result of an electron transfer reaction
Electrodes:-device that moves electrons into or out of a solution by conduction
Electrolysis:-changing the chemical structure of a compound using electrical energy
Electromagnetic spectrum:-complete range of wavelengths which light can have. These include infrared, ultraviolet and all other types of radiation as well as visible light
Electrong:-one of the parts of an atom having a negative charge. Indivisible particle with a charge of -1
Electronegativity:-measure of a substance's ability to attract electrons
Electrostatic forces:-forces between charged objects
Element:-substance consisting of only one type of atom
Empirical formula:-formula showing the simplest ratio of elements in a compound
Endothermic:-process that absorbs heat from its surroundings as the reaction proceeds
Energy:-ability to do work
Enthalpy:-change in heat at constant pressure
Entropy:-measure of the disorder of a system
Equilibrium:-when the reactants and products are in a constant ratio. The forward reaction and the reverse reactions occur at the same rate when a system is in this state
Equilibrium constant:-value that expresses how far the reaction proceeds before reaching equilibrium. A small number means that equilibrium is towards the reactants side while a large number means that the equilibrium is towards the product side
Equilibrium expression:-the expression giving the ratio between the products and reactants. It is equal to the concentration of each product raised to its coefficient in a balanced chemical equation and multiplied together, divided by the concentration of the product of reactants to the power of their coefficients
Equivalence point:-occurs when the moles of acid equal the moles of base in a solution
Exothermic:-process that gives off heat to the environment
Frequency:-number of events in a given unit of time. When describing a moving wave, means the number of peaks which would pass a stationary point in a given amount of time
Geiger counter:-instrument that measures radiation output
Gibb's free energy:-the energy of a system that is available to do work at a constant temperature and pressure
Graham's law:-the rate of diffusion of a gas is inversely proportional to the square root of its molar mass
Half life:-the amount of time it takes for half an initial amount to disintegrate
Heisenberg uncertainty principle:-the principle states that it is not possible to know a particle's location and momentum precisely at any time
Hydrogen bonding:-strong type of intermolecular dipole-dipole attraction. Occurs between hydrogen and F, O or N
Hydrolysis:-the reactions of cations with water to produce a weak base or of anions to produce a weak acid
Ideal gas law: = n
Intermolecular forces:-forces between molecules
Intramolecular forces:-forces within molecules. Forces caused by the attraction and repulsion of charged particles
Ion:-removing or adding electrons to an atom creates an ... (a charged object very similar to an attom)
Ionic bond:-when two oppositely charged atoms share at least one pair of electrons but the electrons spend more time near one of the atoms than the other
Ionization energy:-energy required to remove an electron from a specific atom
Isotopes:-elements with the same number of protons but have different numbers of neutrons, and thus different masses
Kelvin:-The SI unit of temperature. It is temperature in degrees Celsius plus 273.15
Kinetic energy:-energy an object has because of its mass and velocity. Objects that are not moving do not have this.
Le Chatlier's Principle:-states that a system at equilibrium will oppose any change in the equilibrium conditions
Lewis structures:-a way of representing molecular structures based on valence electrons
Limiting reagent:-the reactant that will be exhausted first
Mass number:-the number of protons and neutrons in an atom
Mixture:-composed of two or more substances, but each keeps its original properties
Molality:-the number of moles of solute (the material dissolved) per kilogram of solvent (what the solute is dissolved in)
Molar:-a term expressing molarity, the number of moles of solute per liters of solution
Molarity:-the number of moles of solute (the material dissolved) per liter of solution. Used to express the concentration of a solution
Mole:-a collection of 6.022 * 10 to the 23 power number of objects. Usually used to mean molecules
Molecular formula:-shows the number of atoms of each element present in a molecule
Molecular geometry (VSEPR):-shape of a molecule, based on the relative position of the atoms
Molecular mass:-the combined mass (as given on the periodic table) of all the elements in a compound
Molecule:-two or more atoms chemically combined
Mole fraction:-the number of moles of a particular substance expressed as a fraction of the total number of moles
Neutral:-an object that does not have a positive or negative charge
Neutron:-a particle found in the nucleus of an atom. It is almost identical in mass to a proton, but carries no electrical charge
Nm:-abbreviation for nanometers. A nanometer is equal to 10 to the -9 power meters
Nucleus:-the central part of an atom that contains the protons and neutrons. Plural=nuclei
Octet:-In Lewis structures, the goal is to make almost all atoms have this structure. This means they will have access to (8) electrons regularly, even if they do have to share some of them
Orbitals:-an energy state in the atomic model which describes where an element will likely be
Oxidation number:-a number assigned to each atom to help keep track of the electrons during a redox-reaction
Oxidation-reduction-reaction:-a reactions involving the transfer of electrons
Parent isotopes:-an element that undergoes nuclear decay
Partial pressure:-the pressure exerted by a certain gas in a mixture
Particle:-small portion of matter
Percent composition:-expresses the mass ratio between different elements in a compound
Periodic table:-grouping of the known elements by their number of protons. There are many other trends such as size of elements and electronegativity that are easily expressed in terms of the periodic table
Ph:-measures the acidity of a solution. It is the negative log of the concentration of the hydrogen ions in a substance
Photon:-massless packet of energy, which behaves like both a wave and a particle
Physical property:-a property that can be measured without changing the chemical composition of a substance
Planck:-What is h ?
Planck:-He contributed to the understanding of the
Poh:-Measures the basicity of a solution. It is the negative log of the concentration of the hydroxide ions
Polar molecules:-Molecule with a partial charge
Potential energy:-The energy an object has because of its composition or position
Pressure:-Force per unit area
Principal quantum number (n):-The number related to the amount of energy an electron has and therefore describing which shell the electron is in
Products:-The compounds that are formed when a reaction goes to completion
Proportion:-An equality between two ratios
Proton:-Particle found in a nucleus with a positive charge. Number of these gives the atomic number
Quantum:-Something that comes in discrete units
Quantum numbers:-Set of numbers used to completely describe an electron
Radiant energy:-Energy which is transmitted away from its source, for example, energy that is emitted when electrons transition down one level to another
Radiation:-Energy in the form of photons
Radioactive:-Substance containing an element which decays
Ratio:-The relative size of two quantities expressed as the quotient of one divided by the other; a:b or a/b
Reactants:-Substances initially present in a chemical reaction
Reduction reaction:-A reaction in which a substance gains at least one electron
Salts:-Ionic compounds that can be formed by replacing one or more of the hydrogen ions of an acid with another positive ion
Shells (orbitals):-Where the electrons generally are; they are composed of four types of sub...; s, p, d and f
Single bond:-When an electron pair is shared by two atoms
SI Unit:-Standards for Systeme International d'Unites, an international system which establishes a uniform set of measurement units
Solute:-The substance (solid, liquid or gas) dissolved in a solution, for example, the salt in saltwater
Solution:-Mixture of a solid and a liquid where the solid never settles out, for example, saltwater
Solvent:-Liquid in which something is dissolved, for example the water in saltwater
Specific heat:-The amount of heat it takes for a substance to be raised by one degree Celsius
Spontaneous reaction:-A reaction that will proceed without any outside energy
States of matter:-Solid, liquid, gas and plasma. Plasma is a "soup" of disassociated nuclei and electrons, normally found only in stellar objects
Stoichiometry:-The study of the relationships between amounts of products and reactants
STP:-Standard Temperature and Pressure. 0 degrees Celsius and 1 atm
Subshell (suborbital):-One part of a level, each of which can hold different numbers of electrons
Thermodynamics:-The study of temperature, pressure, volume and energy flow in chemical reactions
Titration:-The process used to take a solution of unknown concentration with a solution of a known concentration for the purpose of finding out more about the unknown solution
Valence electrons:-The electrons in the outermost shell of an atom
Van der Waals equations:-An equation for non-ideal gases that accounts for intermolecular attraction and the volumes occupied by gas molecules
Velocity:-Speed of an object; the change in position over time
Volume:-Measures the size of an object using length measurements in three dimensions
Wave:-A signal which propagates through space
Wavelength:-On a periodic curve, the length between two consecutive troughs (low points) or peaks (high points)
Weak acid:-Substances capable of donating hydrogen but do not completely ionize in solution
Weak bases:-Substances capable of accepting hydrogen but do not completely ionize in solution
Work:- Expression of the movement of an object against some force
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