Chemistry basics
65 flashcards covering Chemistry basics for the ACT Science section.
Chemistry basics involve the study of matter and its interactions, focusing on what substances are made of and how they change. At its core, it's about atoms—the building blocks of everything from water to metals—and how they combine to form elements, compounds, and mixtures. You'll explore concepts like chemical reactions, the periodic table, and properties of substances, which help explain everyday things like why iron rusts or how baking soda makes cakes rise. This foundation is crucial for understanding more complex scientific ideas.
On the ACT Science section, chemistry questions typically appear in data analysis, research summaries, or conflicting viewpoints passages, often requiring you to interpret graphs, tables, or experimental results. Common traps include misreading trends in data or confusing similar terms like "element" and "compound," so pay close attention to details. Focus on key areas like atomic structure, bonding, and basic reactions, as these test your ability to apply scientific reasoning quickly under time pressure.
Practice identifying variables in experiments to boost your accuracy.
Terms (65)
- 01
Atom
An atom is the basic unit of matter, consisting of a nucleus with protons and neutrons, surrounded by electrons, and it is the smallest part of an element that retains its chemical properties.
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Element
An element is a substance made of only one type of atom, defined by its atomic number, and it cannot be broken down into simpler substances by chemical means.
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Compound
A compound is a substance formed when two or more different elements chemically bond in a fixed ratio, resulting in new properties different from its components.
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Mixture
A mixture is a combination of two or more substances that are not chemically bonded, allowing the components to be separated by physical means and retaining their individual properties.
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Proton
A proton is a positively charged subatomic particle found in the nucleus of an atom, contributing to the atomic number and determining the element's identity.
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Neutron
A neutron is a neutral subatomic particle in the nucleus of an atom, with a mass similar to a proton, and it helps stabilize the nucleus without affecting the charge.
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Electron
An electron is a negatively charged subatomic particle that orbits the nucleus of an atom, and its arrangement determines the atom's chemical behavior and bonding.
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Atomic number
The atomic number is the number of protons in an atom's nucleus, which defines the element and its position in the periodic table.
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Mass number
The mass number is the total number of protons and neutrons in an atom's nucleus, used to identify isotopes of an element.
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Isotope
An isotope is a variant of an element with the same number of protons but a different number of neutrons, leading to different atomic masses but similar chemical properties.
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Periodic table
The periodic table is a chart organizing elements by increasing atomic number into periods and groups, reflecting trends in properties like reactivity and atomic size.
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Group in periodic table
A group in the periodic table is a vertical column of elements with similar valence electron configurations, resulting in comparable chemical behaviors.
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Period in periodic table
A period in the periodic table is a horizontal row of elements, indicating the number of electron shells and showing a gradual change in properties across the row.
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Metal
A metal is an element typically found on the left side of the periodic table, characterized by high electrical conductivity, malleability, and a tendency to lose electrons in reactions.
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Nonmetal
A nonmetal is an element usually on the right side of the periodic table, lacking metallic properties like poor conductivity and a tendency to gain electrons in reactions.
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Metalloid
A metalloid is an element along the periodic table's staircase line, exhibiting properties intermediate between metals and nonmetals, such as varying conductivity.
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Ionic bond
An ionic bond is the electrostatic attraction between oppositely charged ions, formed when one atom transfers electrons to another, typically between a metal and a nonmetal.
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Covalent bond
A covalent bond is a chemical bond where atoms share electrons to achieve stability, commonly occurring between nonmetal atoms to form molecules.
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Molecule
A molecule is a group of atoms bonded together, representing the smallest unit of a chemical compound that can exist independently and retain its properties.
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Ion
An ion is an atom or group of atoms that has gained or lost electrons, resulting in a net electrical charge, and it plays a key role in chemical reactions and solutions.
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Cation
A cation is a positively charged ion formed when an atom loses one or more electrons, typically metals in ionic compounds.
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Anion
An anion is a negatively charged ion formed when an atom gains one or more electrons, often nonmetals in ionic bonds.
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Chemical equation
A chemical equation is a symbolic representation of a chemical reaction, showing reactants on the left and products on the right, with arrows indicating the direction of the reaction.
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Balancing chemical equations
Balancing chemical equations involves adjusting coefficients to ensure the number of atoms of each element is the same on both sides, adhering to the law of conservation of mass.
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Reactant
A reactant is a substance that undergoes change during a chemical reaction, present on the left side of a chemical equation.
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Product
A product is a substance formed as a result of a chemical reaction, appearing on the right side of a chemical equation.
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Conservation of mass
The conservation of mass states that matter cannot be created or destroyed in a chemical reaction, so the total mass of reactants equals the total mass of products.
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Mole
A mole is the unit used in chemistry to count particles, equal to 6.022 × 10^23 entities, and it relates the amount of substance to atomic or molecular mass.
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Avogadro's number
Avogadro's number is 6.022 × 10^23, representing the number of atoms in exactly 12 grams of carbon-12, and it is used to convert between moles and particles.
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Molar mass
Molar mass is the mass of one mole of a substance, expressed in grams per mole, and it equals the atomic or molecular weight from the periodic table.
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Stoichiometry
Stoichiometry is the calculation of quantities in chemical reactions based on the balanced equation, involving moles, masses, and volumes to predict yields.
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Limiting reactant
The limiting reactant is the substance that is completely consumed first in a chemical reaction, determining the maximum amount of product that can form.
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Percent yield
Percent yield is the ratio of the actual amount of product obtained from a reaction to the theoretical amount, multiplied by 100, indicating reaction efficiency.
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States of matter
States of matter are the distinct forms in which matter can exist, including solid, liquid, gas, and plasma, each with different particle arrangements and energies.
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Solid
A solid is a state of matter with a fixed shape and volume, where particles are closely packed and vibrate in place, resisting deformation.
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Liquid
A liquid is a state of matter with a fixed volume but no fixed shape, allowing particles to move past each other while maintaining density.
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Gas
A gas is a state of matter with no fixed shape or volume, where particles are far apart and move freely, expanding to fill their container.
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Plasma
Plasma is a state of matter consisting of ionized gas with free electrons and ions, commonly found in stars and fluorescent lights, and it conducts electricity.
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Melting
Melting is the phase change from solid to liquid when a substance absorbs heat, increasing particle kinetic energy to overcome intermolecular forces.
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Freezing
Freezing is the phase change from liquid to solid as a substance loses heat, slowing particle movement and allowing them to form a structured lattice.
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Boiling
Boiling is the rapid phase change from liquid to gas throughout the substance, occurring at a specific temperature where vapor pressure equals atmospheric pressure.
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Condensation
Condensation is the phase change from gas to liquid when a substance loses heat, causing particles to slow and come together into a liquid state.
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Sublimation
Sublimation is the phase change directly from solid to gas without passing through the liquid state, as seen in dry ice turning into carbon dioxide gas.
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Acid
An acid is a substance that donates hydrogen ions in water, producing a solution with a pH less than 7 and reacting with bases to form salts.
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Base
A base is a substance that accepts hydrogen ions or donates hydroxide ions in water, resulting in a pH greater than 7 and often feeling slippery.
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pH scale
The pH scale measures the acidity or basicity of a solution on a scale from 0 to 14, where 7 is neutral, below 7 is acidic, and above 7 is basic, based on hydrogen ion concentration.
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Neutralization reaction
A neutralization reaction occurs when an acid and a base react to form water and a salt, resulting in a neutral pH if the reactants are in equivalent amounts.
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Solution
A solution is a homogeneous mixture where one substance (solute) dissolves in another (solvent), allowing the particles to be evenly distributed at the molecular level.
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Solute
The solute is the substance that is dissolved in a solution, typically present in a smaller amount, and it determines the solution's properties.
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Solvent
The solvent is the substance that dissolves the solute in a solution, usually present in the larger amount, such as water in aqueous solutions.
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Concentration
Concentration is a measure of how much solute is dissolved in a given amount of solvent or solution, often expressed in units like molarity.
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Molarity
Molarity is the concentration of a solution defined as the number of moles of solute per liter of solution, used for calculating reaction quantities.
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Solubility
Solubility is the maximum amount of solute that can dissolve in a specific amount of solvent at a given temperature, affected by factors like pressure and polarity.
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Exothermic reaction
An exothermic reaction releases heat to the surroundings, resulting in a net decrease in the system's energy and often increasing the temperature.
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Endothermic reaction
An endothermic reaction absorbs heat from the surroundings, requiring energy input and typically causing a decrease in temperature.
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Activation energy
Activation energy is the minimum energy required to start a chemical reaction by breaking bonds in reactants, determining the reaction rate.
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Catalyst
A catalyst is a substance that speeds up a chemical reaction without being consumed, by lowering the activation energy, and it can be recovered unchanged.
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Boyle's law
Boyle's law states that for a given amount of gas at constant temperature, the pressure and volume are inversely proportional, meaning pressure increases as volume decreases.
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Charles's law
Charles's law states that for a fixed amount of gas at constant pressure, the volume is directly proportional to its temperature in Kelvin, so volume increases with temperature.
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Ideal gas law
The ideal gas law, PV = nRT, relates pressure, volume, amount of gas, and temperature, assuming ideal behavior where gas molecules have no volume and no interactions.
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Common trap in balancing equations
A common trap in balancing equations is changing subscripts instead of coefficients, which alters the compound's identity and leads to incorrect chemical representations.
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Strategy for identifying limiting reactant
To identify the limiting reactant, compare the mole ratios from the balanced equation to the actual moles available, selecting the one that produces the least product.
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Worked example: Calculating molarity
For a solution with 2 moles of solute in 0.5 liters of solution, molarity is calculated as 2 moles divided by 0.5 liters, resulting in 4 moles per liter.
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pH calculation for strong acid
For a 0.01 M solution of HCl, a strong acid, the pH is calculated as the negative logarithm of the hydrogen ion concentration, so pH = -log(0.01) = 2.
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Gas law application: Boyle's example
If a gas at 2 atm pressure in a 1-liter container is compressed to 0.5 liters at constant temperature, Boyle's law predicts the new pressure as 4 atm.