Table of Contents
Have you ever wondered how things work and why certain substances behave differently? That’s where chemistry comes in! Chemistry is the study of matter and how it interacts with other substances. Learning chemistry helps us understand the world around us, from the air we breathe to the food we eat. We can explore the properties of different materials, conduct cool experiments, and even create new things. So, are you ready to discover the fascinating world of chemistry and learn its vocabulary?
Basic Concepts
1. Matter (noun) /ˈmætər/: Anything that has mass and takes up space, including solids, liquids, and gases.
Example: Rocks, water, and air are all examples of different types of matter.
2. Elements (noun) /ˈɛlɪmənts/: Pure substances made of only one type of atom, and cannot be broken down into simpler substances by chemical means.
Example: Oxygen, hydrogen, and gold are all examples of elements found on the periodic table.
3. Compounds (noun) /ˈkɒmpaʊndz/: Substances formed when two or more elements chemically combine in fixed proportions.
Example: Water (H₂O) is a compound made up of hydrogen and oxygen elements.
4. Atoms (noun) /ˈætəmz/: The smallest units of an element that retain the chemical properties of that element, consisting of protons, neutrons, and electrons.
Example: All elements are made up of tiny atoms that join together to form molecules in compounds.
5. Molecules (noun) /ˈmɒlɪkjuːlz/: Groups of two or more atoms bonded together, forming the smallest units of a compound that retain the compound’s properties.
Example: A water molecule consists of two hydrogen atoms and one oxygen atom bonded together.
6. Chemical reactions (noun) /ˈkɛmɪkəl riˈækʃənz/: Processes in which substances change into new substances by breaking and forming chemical bonds.
Example: When vinegar and baking soda are mixed together, they undergo a chemical reaction that produces carbon dioxide gas.
7. Chemical equations (noun) /ˈkɛmɪkəl ɪˈkweɪʒənz/: Representations of chemical reactions using symbols for elements and compounds, showing the reactants and products involved.
Example: The chemical equation for the reaction between hydrogen and oxygen to form water is 2H₂ + O₂ → 2H₂O.
8. States of matter (noun) /steɪts əv ˈmætər/: The physical forms in which matter exists, including solids, liquids, and gases.
Example: Water can exist in all three states of matter: ice (solid), liquid water, and water vapor (gas).
9. Properties of substances (noun) /ˈprɒpərtiz əv ˈsʌbstənsəz/: Characteristics that describe and identify substances, such as color, density, melting point, and boiling point.
Example: The properties of substances help chemists identify and classify elements and compounds.
10. Physical and chemical changes (noun) /ˈfɪzɪkəl ənd ˈkɛmɪkəl ˈʧeɪndʒɪz/: Physical changes are changes in the appearance or state of a substance without changing its composition, while chemical changes involve the formation of new substances with different properties.
Example: Melting ice is a physical change, while burning wood is a chemical change.
Periodic Table
1. Periodic Table (noun) /pəˈrɪədɪk ˈteɪbəl/: A chart that organizes elements based on their atomic number, electron configuration, and recurring chemical properties.
Example: The Periodic Table helps chemists understand the relationships between different elements and predict their behaviors.
2. Atomic number (noun) /əˈtɒmɪk ˈnʌmbər/: The number of protons in the nucleus of an atom, which determines the element’s identity and its position on the Periodic Table.
Example: The atomic number of oxygen is 8, meaning it has 8 protons in its nucleus.
3. Atomic mass (noun) /əˈtɒmɪk ˈmæs/: The average mass of an element’s atoms, usually expressed in atomic mass units (amu), and taking into account the relative abundance of its isotopes.
Example: The atomic mass of carbon is approximately 12.01 amu.
4. Periods (noun) /ˈpɪəriədz/: Horizontal rows on the Periodic Table, which represent the energy levels of an element’s electrons.
Example: Elements in the same period have the same number of electron energy levels.
5. Groups (noun) /ɡruːps/: Vertical columns on the Periodic Table, containing elements with similar chemical properties due to their electron configurations.
Example: Elements in the same group, like lithium and sodium, typically react in a similar way.
6. Metals (noun) /ˈmetəlz/: Elements characterized by their ability to conduct heat and electricity, malleability, and luster, usually found on the left side of the Periodic Table.
Example: Gold, silver, and copper are examples of metals.
7. Nonmetals (noun) /ˈnɒnˈmetəlz/: Elements that lack metallic properties, and often have low conductivity, brittleness, and dull appearance, found on the right side of the Periodic Table.
Example: Oxygen, nitrogen, and sulfur are examples of nonmetals.
8. Metalloids (noun) /ˈmetəlɔɪdz/: Elements with properties between those of metals and nonmetals, often used as semiconductors in electronics.
Example: Silicon and germanium are examples of metalloids.
9. Noble gases (noun) /ˈnoʊbəl ˈɡæsɪz/: A group of nonmetal elements found in Group 18 of the Periodic Table, known for their low reactivity due to their filled electron shells.
Example: Helium, neon, and argon are examples of noble gases.
10. Transition metals (noun) /trænˈzɪʃən ˈmetəlz/: Elements found in Groups 3-12 of the Periodic Table, characterized by their ability to form various oxidation states and colorful compounds.
Example: Iron, copper, and zinc are examples of transition metals.
11. Halogens (noun) /ˈhælədʒənz/: Elements found in Group 17 of the Periodic Table, known for their high reactivity and ability to form salts when combined with metals.
Example: Chlorine, fluorine, and iodine are examples of halogens.
Chemical Bonds
1. Covalent bonds (noun) /koʊˈveɪlənt ˈbɒndz/: Chemical bonds formed between atoms when they share one or more pairs of electrons, typically found in molecules containing nonmetals.
Example: In a water molecule, the oxygen atom forms covalent bonds with two hydrogen atoms.
2. Ionic bonds (noun) /aɪˈɒnɪk ˈbɒndz/: Chemical bonds formed between atoms when one or more electrons are transferred from one atom to another, typically found in compounds containing metals and nonmetals.
Example: In table salt (sodium chloride), the sodium and chlorine atoms are held together by ionic bonds.
3. Polar bonds (noun) /ˈpoʊlər ˈbɒndz/: Covalent bonds in which electrons are shared unequally between atoms, due to differences in electronegativity, resulting in a partial positive charge on one atom and a partial negative charge on the other.
Example: The bond between hydrogen and oxygen in a water molecule is a polar bond.
4. Nonpolar bonds (noun) /nɒnˈpoʊlər ˈbɒndz/: Covalent bonds in which electrons are shared equally between atoms, due to similar electronegativity values, resulting in no charge separation.
Example: The bond between two hydrogen atoms in a hydrogen molecule (H₂) is a nonpolar bond.
5. Lewis structures (noun) /ˈluːɪs ˈstrʌkʧərz/: Diagrams that show the arrangement of atoms and the distribution of electrons in molecules, using symbols for elements and dots for valence electrons.
Example: The Lewis structure for water (H₂O) shows the oxygen atom bonded to two hydrogen atoms, with two lone pairs of electrons on the oxygen.
6. Electronegativity (noun) /ɪˌlɛktrəʊnɛɡəˈtɪvɪti/: A measure of an atom’s ability to attract electrons in a chemical bond, with higher values indicating a stronger attraction.
Example: Fluorine has the highest electronegativity of all the elements, making it highly reactive.
7. Octet rule (noun) /ˈɒktɪt ˈruːl/: A guideline stating that atoms tend to form chemical bonds in order to achieve a stable electron configuration with eight valence electrons, similar to the noble gases.
Example: Sodium loses one electron to achieve a stable electron configuration, following the octet rule.
8. Valence electrons (noun) /ˈveɪləns ɪˈlɛktrɒnz/: Electrons located in the outermost energy level of an atom, which are involved in forming chemical bonds.
Example: Carbon has four valence electrons, allowing it to form four covalent bonds.
9. Bonding patterns (noun) /ˈbɒndɪŋ ˈpætərnz/: The specific ways in which atoms form bonds with other atoms, based on the number of valence electrons and the octet rule.
Example: Carbon often forms four single covalent bonds, following its typical bonding pattern.
10. Intermolecular forces (noun) /ˌɪntərˈmɒləkjuːlər ˈfɔːrsɪz/: Attractive forces between molecules that hold them together, such as hydrogen bonding, dipole-dipole interactions, and van der Waals forces.
Example: The boiling point of water is higher than that of methane due to the stronger intermolecular forces in water, specifically hydrogen bonding.
Chemical Reactions
1. Synthesis reactions (noun) /ˈsɪnθəsɪs rɪˈækʃənz/: Chemical reactions in which two or more reactants combine to form a single, more complex product.
Example: When hydrogen gas and oxygen gas combine, a synthesis reaction occurs, forming water.
2. Decomposition reactions (noun) /diːˌkɒmpəˈzɪʃən rɪˈækʃənz/: Chemical reactions in which a single compound breaks down into two or more simpler products.
Example: When heated, calcium carbonate undergoes a decomposition reaction to form calcium oxide and carbon dioxide.
3. Combustion reactions (noun) /kəmˈbʌsʧən rɪˈækʃənz/: Chemical reactions in which a substance reacts with oxygen gas, usually producing heat, light, and products such as water and carbon dioxide.
Example: When gasoline burns in a car engine, a combustion reaction occurs, releasing energy that powers the vehicle.
4. Acid-base reactions (noun) /ˈæsɪd-beɪs rɪˈækʃənz/: Chemical reactions in which an acid and a base react to form water and a salt, also called neutralization reactions.
Example: Mixing hydrochloric acid and sodium hydroxide results in an acid-base reaction that produces water and sodium chloride.
5. Redox reactions (noun) /ˈriːdɒks rɪˈækʃənz/: Chemical reactions involving the transfer of electrons between atoms, with one atom gaining electrons (reduction) and another atom losing electrons (oxidation).
Example: In the reaction between copper and silver nitrate, a redox reaction occurs, with copper losing electrons and silver gaining electrons.
6. Exothermic reactions (noun) /ˌɛksoʊˈθɜrmɪk rɪˈækʃənz/: Chemical reactions that release energy, usually in the form of heat or light.
Example: The reaction between baking soda and vinegar is an exothermic reaction, producing heat as well as carbon dioxide gas.
7. Endothermic reactions (noun) /ˌɛndoʊˈθɜrmɪk rɪˈækʃənz/: Chemical reactions that absorb energy, usually in the form of heat, resulting in a decrease in temperature.
Example: The reaction between barium hydroxide and ammonium chloride is an endothermic reaction, causing the temperature of the mixture to decrease.
8. Reaction rates (noun) /rɪˈækʃən reɪts/: The speed at which reactants are converted into products in a chemical reaction, often influenced by factors such as temperature, concentration, and the presence of catalysts.
Example: Increasing the temperature usually increases the reaction rate because the molecules move faster and collide more frequently.
9. Catalysts (noun) /ˈkætəlɪsts/: Substances that increase the reaction rate of a chemical reaction without being consumed or changed in the process.
Example: Enzymes are biological catalysts that speed up chemical reactions in living organisms.
10. Equilibrium (noun) /ɪˈkwɪlɪbriəm/: A state in which the rates of the forward and reverse reactions in a chemical system are equal, resulting in no net change in the concentrations of the reactants and products.
Example: When a saturated solution of sugar in water is in equilibrium, the rate at which sugar dissolves is equal to the rate at which it crystallizes.
Acids, Bases, and pH
1. pH scale (noun) /piːˈeɪʧ ˈskeɪl/: A numeric scale ranging from 0 to 14, used to measure the acidity or alkalinity of a solution, with 7 being neutral, values below 7 being acidic, and values above 7 being basic.
Example: Pure water has a pH of 7, making it a neutral substance on the pH scale.
2. Acidic solutions (noun) /əˈsɪdɪk səˈluːʃənz/: Solutions with a pH value below 7, containing a higher concentration of hydrogen ions (H⁺) than hydroxide ions (OH⁻).
Example: Lemon juice is an acidic solution with a pH value of around 2.
3. Basic solutions (noun) /ˈbeɪsɪk səˈluːʃənz/: Solutions with a pH value above 7, containing a higher concentration of hydroxide ions (OH⁻) than hydrogen ions (H⁺).
Example: Household ammonia is a basic solution with a pH value of around 11.
4. Neutralization reactions (noun) /ˌnuːtrəlɪˈzeɪʃən rɪˈækʃənz/: Chemical reactions in which an acid and a base react to form water and a salt, resulting in a solution with a pH close to 7.
Example: Mixing hydrochloric acid and sodium hydroxide results in a neutralization reaction that produces water and sodium chloride.
5. Strong acids (noun) /strɒŋ ˈæsɪdz/: Acids that completely dissociate (ionize) in water, releasing a high concentration of hydrogen ions (H⁺).
Example: Sulfuric acid is a strong acid used in car batteries and various industrial processes.
6. Strong bases (noun) /strɒŋ ˈbeɪsɪz/: Bases that completely dissociate (ionize) in water, releasing a high concentration of hydroxide ions (OH⁻).
Example: Sodium hydroxide is a strong base used in drain cleaners and soap-making.
7. Weak acids (noun) /wiːk ˈæsɪdz/: Acids that only partially dissociate (ionize) in water, releasing a low concentration of hydrogen ions (H⁺).
Example: Acetic acid, found in vinegar, is a weak acid with a pungent smell and sour taste.
8. Weak bases (noun) /wiːk ˈbeɪsɪz/: Bases that only partially dissociate (ionize) in water, releasing a low concentration of hydroxide ions (OH⁻).
Example: Ammonia is a weak base commonly used as a household cleaner and in fertilizers.
9. Acid-base indicators (noun) /ˈæsɪd-beɪs ˈɪndɪˌkeɪtərz/: Substances that change color depending on the acidity or alkalinity of a solution, used to determine the pH value of the solution.
Example: Litmus paper is an example of an acid-base indicator that turns red in acidic solutions and blue in basic solutions.
10. pH indicators (noun) /piːˈeɪʧ ˈɪndɪˌkeɪtərz/: Substances that change color depending on the pH value of a solution, used to determine the acidity or alkalinity of the solution.
Example: Phenolphthalein is a pH indicator that is colorless in acidic solutions and turns pink in basic solutions.
Organic Chemistry
1. Hydrocarbons (noun) /ˌhaɪdrəˈkɑrbənz/: Organic compounds consisting solely of hydrogen and carbon atoms, often used as fuels.
Example: Methane, the main component of natural gas, is a hydrocarbon commonly used for heating and cooking.
2. Alkanes (noun) /æˈlkeɪnz/: A class of hydrocarbons characterized by single bonds between carbon atoms, forming a saturated hydrocarbon chain.
Example: Propane is an alkane with the chemical formula C₃H₈, used as a fuel in portable stoves and gas grills.
3. Alkenes (noun) /æˈlkiːnz/: A class of hydrocarbons characterized by at least one double bond between carbon atoms, forming an unsaturated hydrocarbon chain.
Example: Ethene, also known as ethylene, is an alkene with the chemical formula C₂H₄, used in the production of plastics and other chemicals.
4. Alkynes (noun) /æˈlkaɪnz/: A class of hydrocarbons characterized by at least one triple bond between carbon atoms, forming an unsaturated hydrocarbon chain.
Example: Ethyne, also known as acetylene, is an alkyne with the chemical formula C₂H₂, used as a fuel in welding torches.
5. Functional groups (noun) /ˈfʌŋkʃənəl ˈɡruːps/: Specific groups of atoms within a molecule that determine the molecule’s chemical properties and reactivity.
Example: The hydroxyl group (-OH) is a functional group found in alcohols, giving them their characteristic properties.
6. Alcohols (noun) /ˈælkəhɒlz/: A class of organic compounds containing a hydroxyl (OH) functional group attached to a carbon atom.
Example: Ethanol, commonly known as alcohol, is an alcohol with the chemical formula C₂H₅OH, found in alcoholic beverages.
7. Carboxylic acids (noun) /kɑrˈbɒksɪlɪk ˈæsɪdz/: A class of organic compounds containing a carboxyl (-COOH) functional group, characterized by their acidic properties.
Example: Acetic acid is a carboxylic acid with the chemical formula CH₃COOH, responsible for the sour taste of vinegar.
8. Esters (noun) /ˈɛstərz/: A class of organic compounds derived from the reaction between an alcohol and a carboxylic acid, characterized by a carbonyl group (-C=O) and an ether linkage (-C-O-C-).
Example: Ethyl acetate is an ester with the chemical formula CH₃COOCH₂CH₃, used as a solvent in nail polish removers.
9. Amines (noun) /əˈmiːnz/: A class of organic compounds containing a nitrogen atom with a lone pair of electrons, derived from ammonia (NH₃) by replacing one or more hydrogen atoms with alkyl or aryl groups.
Example: Methylamine is an amine with the chemical formula CH₃NH₂, used in the synthesis of various chemicals and pharmaceuticals.
10. Polymers (noun) /ˈpɒlɪmərz/: Large molecules made up of repeating units called monomers, often used to create plastics, fibers, and other materials.
Example: Polyethylene is a polymer made from the monomer ethylene, commonly used to make plastic bags and containers.
Stoichiometry
1. Mole concept (noun): A method in chemistry for expressing the amount of a substance in terms of the number of particles (atoms, molecules, or ions) it contains.
Example: The mole concept allows chemists to relate the mass of a substance to the number of particles it contains, which is useful in balancing chemical equations.
2. Molar mass (noun): The mass of one mole of a substance, expressed in grams per mole (g/mol), equal to the sum of the atomic masses of the elements in the substance’s chemical formula.
Example: The molar mass of water (H₂O) is 18 g/mol, as the atomic mass of hydrogen is 1 g/mol and oxygen is 16 g/mol.
3. Avogadro’s number (noun): A constant, approximately 6.022 x 10²³ particles per mole, representing the number of atoms, molecules, or ions in one mole of a substance.
Example: Avogadro’s number helps chemists determine the number of particles in a given amount of a substance by relating it to the substance’s molar mass.
4. Percent composition (noun): The percentage by mass of each element in a compound, calculated by dividing the mass of an element in the compound by the total mass of the compound and multiplying by 100.
Example: The percent composition of water (H₂O) is about 11% hydrogen and 89% oxygen by mass.
5. Empirical formula (noun): The simplest whole-number ratio of elements in a compound, which indicates the relative number of atoms of each element but not the actual molecular structure.
Example: The empirical formula of glucose (C₆H₁₂O₆) is CH₂O, representing a 1:2:1 ratio of carbon, hydrogen, and oxygen atoms.
6. Molecular formula (noun): The actual number of atoms of each element in a molecule of a compound, which can be a multiple of the empirical formula.
Example: The molecular formula of glucose is C₆H₁₂O₆, indicating that each glucose molecule contains six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.
7. Stoichiometric calculations (noun): Mathematical calculations used to determine the quantities of reactants and products in a chemical reaction, based on the balanced chemical equation and the mole concept.
Example: Stoichiometric calculations enable chemists to predict the amounts of substances needed for a reaction and the amounts of products that will be formed.
8. Limiting reactant (noun): The reactant in a chemical reaction that is completely consumed and determines the maximum amount of product that can be formed, based on its stoichiometry.
Example: In the reaction between hydrogen gas and oxygen gas to form water, the limiting reactant controls the amount of water that can be produced.
9. Yield (noun): The amount of product obtained from a chemical reaction, usually expressed as a percentage of the maximum possible amount (theoretical yield) based on stoichiometry.
Example: A high yield in a chemical reaction indicates that the reaction is efficient and produces a large amount of the desired product.
10. Theoretical and actual yield (noun): The theoretical yield is the maximum amount of product that can be formed in a chemical reaction based on stoichiometry, while the actual yield is the amount of product actually obtained from the reaction.
Example: The difference between the theoretical and actual yield can be due to side reactions, incomplete reactions, or losses during the experimental process.
Chemical Equilibrium
1. Le Chatelier’s principle (noun): A principle in chemistry that states if a change is made to a system at equilibrium, the system will adjust in a way that counteracts the change and restores equilibrium.
Example: When pressure is increased on a gas mixture at equilibrium, Le Chatelier’s principle predicts that the system will shift to the side with fewer gas molecules.
2. Equilibrium constant (K) (noun): A value that describes the ratio of the concentrations of products to reactants in a chemical reaction at equilibrium, with each concentration raised to the power of its stoichiometric coefficient.
Example: A large equilibrium constant (K) indicates that the reaction favors the formation of products, while a small K value means the reactants are favored.
3. Reaction quotient (Q) (noun): A value that is calculated in the same way as the equilibrium constant, but using the initial or non-equilibrium concentrations of reactants and products in a chemical reaction.
Example: Comparing the reaction quotient (Q) to the equilibrium constant (K) helps predict the direction in which a reaction will proceed to reach equilibrium.
4. Shifts in equilibrium (noun): Changes in the relative concentrations of reactants and products in a chemical reaction at equilibrium, in response to changes in pressure, temperature, or concentration.
Example: If more reactants are added to a system at equilibrium, shifts in equilibrium will occur to restore the balance, often resulting in increased product formation.
5. Equilibrium expressions (noun): Mathematical formulas that represent the relationship between the concentrations of reactants and products at equilibrium, based on the equilibrium constant (K).
Example: Chemists use equilibrium expressions to calculate unknown concentrations in a reaction at equilibrium, given the K value and other known concentrations.
6. Acid-base equilibrium (noun): A state of balance in a chemical reaction between an acid and a base, where the forward reaction (donating or accepting a proton) occurs at the same rate as the reverse reaction.
Example: In the reaction between acetic acid and water, acid-base equilibrium is reached when the rate of proton transfer between the acid and water molecules is equal to the rate of proton transfer back to the acid.
7. Solubility equilibrium (noun): A state of balance in a solution between the dissolved solute and any undissolved solid particles, where the rate of dissolution is equal to the rate of precipitation.
Example: In a saturated solution of table salt, solubility equilibrium is maintained as sodium and chloride ions dissolve into the water at the same rate that they precipitate out as solid salt crystals.
8. Gas equilibrium (noun): A state of balance in a gaseous reaction, where the forward and reverse reactions occur at equal rates, maintaining constant concentrations of the reactants and products.
Example: In the reaction between nitrogen gas and hydrogen gas to form ammonia, gas equilibrium is reached when the rate of ammonia formation is equal to the rate of ammonia decomposition.
9. Factors affecting equilibrium (noun): External conditions, such as temperature, pressure, and concentration, that can influence the position of equilibrium in a chemical reaction.
Example: An increase in temperature often causes factors affecting equilibrium to shift the balance toward the endothermic reaction, which absorbs heat and counteracts the temperature increase.
10. Equilibrium in chemical systems (noun): A state of balance in a chemical reaction where the forward and reverse reactions occur at the same rate, resulting in constant concentrations of reactants and products over time.
Example: In a closed system, equilibrium in chemical systems is important for maintaining stable conditions and minimizing the potential for unexpected changes in concentration.
Congratulations on exploring the world of chemistry vocabulary! Now you have the tools to understand and communicate about elements, compounds, reactions, and more. Chemistry helps us make sense of the world by explaining the properties and behavior of matter. Whether you’re mixing ingredients in the kitchen or observing changes in nature, understanding chemistry will open up a whole new level of understanding. So keep exploring, experimenting, and unraveling the mysteries of the chemical world!