chem flash cards for unit 1

Mass

Definition

• A measure of the amount of matter in an object.

Important Information

• It is a fundamental property of matter.

• Mass is not the same as weight; weight is a measure of the gravitational force on an object, which can change depending on gravity, while mass remains constant.

• Mass is an extensive property (depends on the amount of matter).

Examples

• The mass of a science textbook might be 2 \text{ kg}.

• A proton has a mass of approximately 1.67 \times 10^{-27} \text{ kg}.

Volume

Definition

• The amount of three-dimensional space an object occupies.

Important Information

• Can be calculated for regular shapes (e.g., length \times width \times height for a cube).

• Can be measured for irregular shapes by water displacement.

• Volume is an extensive property.

Examples

• The volume of a liquid is often measured in liters (L) or milliliters (mL).

• The volume of a solid is often measured in cubic meters (m^3) or cubic centimeters (cm^3).

• One liter is equivalent to 1000 \text{ mL} or 1000 \text{ cm}^3.

Extensive Property

Definition

• A property that depends on the amount of matter present in a sample.

Important Information

• The value of an extensive property changes if the amount of the substance changes.

• Extensive properties relate to the quantity of the substance.

Examples

• Mass: More substance means more mass.

• Volume: More substance means more volume.

• Energy: The total energy of a system increases with the amount of substance.

• Moles: The number of particles in a substance.

Intensive Property

Definition

• A property that does not depend on the amount of matter present in a sample.

Important Information

• The value of an intensive property remains the same regardless of the sample size.

• Intensive properties are often used to identify a substance because they are characteristic.

Examples

• Density: The ratio of mass to volume (\text{Density} = \frac{\text{Mass}}{\text{Volume}}). It's constant for a given substance at a specific temperature and pressure.

• Temperature: The measure of the average kinetic energy of particles.

• Melting Point: The temperature at which a solid turns into a liquid.

• Boiling Point: The temperature at which a liquid turns into a gas.

• Color, Odor, Hardness, Luster.

Substance

Definition

• Matter that has a uniform and definite composition; also known as a pure substance.

Important Information

• Cannot be separated into simpler components by physical means.

• Can be either an element (composed of only one type of atom, e.g., gold, oxygen) or a compound (composed of two or more elements chemically combined in fixed proportions, e.g., water, salt).

• Always has the same characteristic physical and chemical properties.

Examples

• Elements: Gold (Au), Oxygen (O_2), Iron (Fe).

• Compounds: Water (H_2O), Sodium Chloride (NaCl), Carbon Dioxide (CO_2).

• Unlike mixtures, substances have a consistent composition throughout.

Physical Property

Definition

• A characteristic of a substance that can be observed or measured without changing the substance's chemical identity.

Important Information

• Used to describe a substance purely by its physical characteristics.

• Observations of physical properties often involve senses (e.g., seeing color, smelling odor) or measurements (e.g., temperature, density).

Examples

• Observable: Color, odor, taste, texture, shape, state of matter (solid, liquid, gas).

• Measurable: Density, melting point, boiling point, hardness, viscosity, electrical conductivity, solubility.

Solid

Definition

• A state of matter characterized by a definite shape and a definite volume.

Important Information

• Particles are tightly packed together and arranged in fixed positions, vibrating in place.

• Strong intermolecular forces hold particles together.

• Solids are generally incompressible.

• Usually have the highest density among the three common states of matter for a given substance (water is an exception, where ice is less dense than liquid water).

Examples

• Ice

• Rock

• Wood

• Metals like iron or copper

Liquid

Definition

• A state of matter characterized by an indefinite shape (takes the shape of its container) and a definite volume.

Important Information

• Particles are close together but can move and slide past one another (fluidity).

• Intermolecular forces are significant but weaker than in solids.

• Liquids are only slightly compressible.

• Exhibit properties like surface tension and viscosity.

Examples

• Water

• Oil

• Mercury

• Alcohol

Gas

Definition

• A state of matter characterized by an indefinite shape (expands to fill its container) and an indefinite volume.

Important Information

• Particles are far apart and move rapidly and randomly; they have high kinetic energy.

• Intermolecular forces are very weak or negligible.

• Gases are highly compressible and expandable.

• Have very low densities compared to solids and liquids.

Examples

• Oxygen (O_2)

• Nitrogen (N_2)

• Helium (He)

• Steam (water vapor) (H_2O)

Vapor

Definition

• A substance in the gaseous state below its critical temperature, meaning it can be condensed into a liquid by increasing pressure alone, without lowering the temperature.

Important Information

• Often refers to a gas that is normally a liquid or solid at room temperature (e.g., water vapor, gasoline vapor).

• The terms "gas" and "vapor" are sometimes used interchangeably, but "vapor" specifically implies proximity to the liquid or solid phase.

• At its boiling point, a liquid changes into a vapor.

Examples

• Water vapor: Gaseous water, particularly H

,O in the air below its critical temperature.

• Iodine vapor: Formed when solid iodine sublimes.

• Alcohol vapor: Evaporating from an open bottle of rubbing alcohol.

Physical Change

Definition

• A type of change in which the form of matter is altered but one substance is not transformed into another. The chemical composition remains the same.

Important Information

• Does not result in the formation of new chemical substances.

• Often reversible through other physical changes.

• Involves changes in physical properties like state, shape, size, or appearance.

Examples

• Melting ice: Water changes from solid to liquid (H_2O(s) \rightarrow H_2O(l)).

• Boiling water: Water changes from liquid to gas (H_2O(l) \rightarrow H_2O(g)).

• Cutting paper: Changes the shape and size of paper, but it's still paper.

• Dissolving sugar in water: Sugar molecules are dispersed in water but remain sugar and water.

Mixture

Definition

• A physical blend of two or more substances that are not chemically combined.

Important Information

• The components of a mixture retain their own identities and properties.

• Can be separated by physical means (e.g., filtration, distillation).

• The proportions of components in a mixture can vary.

• Mixtures are classified based on the uniformity of their composition.

Examples

• Air: A mixture of nitrogen, oxygen, argon, etc.

• Saltwater: A mixture of salt and water.

• Salad: A mixture of vegetables.

Heterogeneous Mixture

Definition

• A mixture in which the components are not uniformly distributed and can be easily distinguished from one another.

Important Information

• The composition varies throughout the mixture.

• Typically contains visible distinct phases (parts).

• Its components can often be separated by simple physical means.

Examples

• Sand and water: Sand particles settle at the bottom and are visible.

• Oil and vinegar salad dressing: The oil and vinegar layers are distinct.

• Chocolate chip cookie: The visible chips and cookie dough.

• Granite: Contains visible crystals of different minerals.

Homogeneous Mixture

Definition

• A mixture in which the components are uniformly distributed and cannot be easily distinguished from one another.

Important Information

• Has a uniform composition and properties throughout.

• Appears as a single phase.

• Also known as a solution.

• Components are mixed at a molecular or ionic level.

Examples

• Saltwater: Salt is dissolved evenly in water.

• Air: A uniform mixture of various gases.

• Brass: An alloy (solid solution) of copper and zinc.

• Rubbing alcohol: A uniform mixture of isopropyl alcohol and water.

Solution

Definition

• A homogeneous mixture of two or more substances in a single phase.

Important Information

• Consists of a solute (the substance being dissolved) and a solvent (the substance doing the dissolving).

• The particles in a solution are very small (ions or molecules) and do not settle out.

• Solutions can be gaseous (e.g., air), liquid (e.g., saltwater), or solid (e.g., alloys like brass).

• The ability of a solute to dissolve in a solvent is called solubility.

Examples

• Sugar dissolved in tea: Sugar is the solute, tea (mostly water) is the solvent.

• Air: Oxygen and other gases are solutes in nitrogen.

• Vinegar: Acetic acid dissolved in water.

• Dental amalgram: Mercury dissolved in silver (a solid solution).

Phase

Definition

• Any part of a sample that has uniform composition and properties.

Important Information

• A substance can exist in different phases (e.g., solid, liquid, gas).

• In a homogeneous mixture, there is only one phase.

• In a heterogeneous mixture, there are two or more phases.

• Each phase is separated from other phases by a distinct boundary.

Examples

• Ice water: Consists of two phases: solid ice (H_2O(s)) and liquid water (H_2O(l)).

• Oil and water: Two immiscible liquid phases.

• Air: A single gaseous phase.

• Carbonated soda: Liquid phase (water with dissolved CO₂) and gaseous phase (CO₂ bubbles).

Element

Definition

• The simplest form of matter that has a unique set of properties and cannot be broken down into simpler substances by chemical means.

Important Information

• Composed of only one type of atom.

• Each element is identified by its atomic number, which represents the number of protons in its nucleus.

• Organized on the Periodic Table of Elements.

• Elements are the building blocks of all other substances.

Examples

• Oxygen (O): A key component of air and water.

• Gold (Au): A precious metal.

• Carbon (C): Found in all organic compounds.

• Hydrogen (H): The most abundant element in the universe.

Compound

Definition

• A substance that contains two or more different elements chemically combined in fixed proportions.

Important Information

• Can be broken down into simpler substances (elements) only by chemical means.

• The properties of a compound are typically different from the properties of its constituent elements.

• Formed through chemical bonds (ionic or covalent) between atoms.

• Represented by chemical formulas (e.g., H_2O, NaCl).

Examples

• Water (H_2O): Composed of hydrogen and oxygen.

• Sodium Chloride (NaCl): Table salt, composed of sodium and chlorine.

• Carbon Dioxide (CO_2): Composed of carbon and oxygen.

• Glucose (C_6H_{12}O_6): A sugar composed of carbon, hydrogen, and oxygen.

Chemical Change

Definition

• A type of change that results in the formation of one or more new substances with different chemical properties and composition.

Important Information

• Also known as a chemical reaction.

• Involves the breaking and forming of chemical bonds.

• Often irreversible, or difficult to reverse, by physical means.

• Evidence of a chemical change might include: production of a gas (bubbles), formation of a precipitate, change in color, change in temperature (release or absorption of heat), production of light or sound.

Examples

• Burning wood: Wood combines with oxygen to form ash, carbon dioxide, and water vapor.

• Rusting of iron: Iron reacts with oxygen and water to form iron oxide (rust).

• Baking a cake: Ingredients combine and undergo chemical reactions to form a new substance.

• Digestion of food: Food molecules are broken down into simpler molecules in the body.

Chemical Symbol

Definition

• A one or two-letter abbreviation used to represent an element.

Important Information

• The first letter is always capitalized, and the second letter (if any) is always lowercase.

• Used universally in chemistry to denote elements.

• Derived from the element's English name, Latin name, or another source.

• Helps in writing chemical formulas and equations concisely.

Examples

• H: Hydrogen

• O: Oxygen

• Fe: Iron (from Latin ferrum)

• Na: Sodium (from Latin natrium)

• Cl: Chlorine

Chemical Reaction

Definition

• A process that involves the rearrangement of the structure of molecules or ions, resulting in the formation of new chemical substances.

Important Information

• Another term for a chemical change.

• Represented by a chemical equation, showing reactants turning into products.

• Involves the breaking of existing chemical bonds and the formation of new ones.

• Does not involve changes to the nucleus of atoms (unlike nuclear reactions).

Examples

• Combustion: CH_4 (g) + 2O_2 (g) \rightarrow CO_2 (g) + 2H_2O (g)

• Acid-base neutralization: HCl (aq) + NaOH (aq) \rightarrow NaCl (aq) + H_2O (l)

• Photosynthesis: 6CO_2 (g) + 6H_2O (l) \rightarrow C_6H_{12}O_6 (aq) + 6O_2 (g)

Reactant

Definition

• A substance that is present at the start of a chemical reaction and is consumed during the reaction to form products.

Important Information

• Written on the left side of a chemical equation.

• The arrow (\rightarrow) in a chemical equation points from the reactants to the products.

• Undergo changes in their chemical identity during the reaction.

Examples

• In the combustion of methane: CH_4 (g) + 2O_2 (g) \rightarrow CO_2 (g) + 2H_2O (g)

  • Reactants: Methane (CH_4) and Oxygen (O_2).

• In the formation of water: 2H_2 (g) + O_2 (g) \rightarrow 2H_2O (l)

  • Reactants: Hydrogen (H_2) and Oxygen (O_2).

Product

Definition

• A substance that is formed as a result of a chemical reaction.

Important Information

• Written on the right side of a chemical equation.

• Represents the new substances created with different chemical properties from the reactants.

Examples

• In the combustion of methane: CH_4 (g) + 2O_2 (g) \rightarrow CO_2 (g) + 2H_2O (g)

  • Products: Carbon Dioxide (CO_2) and Water (H_2O).

• In the formation of water: 2H_2 (g) + O_2 (g) \rightarrow 2H_2O (l)

  • Product: Water (H_2O).

Precipitation

Definition

• In chemistry, the formation of an insoluble solid from a solution during a chemical reaction.

Important Information

• The insoluble solid formed is called a precipitate.

• Often occurs when two soluble ionic compounds in solution react to form an insoluble ionic compound.

• Can be observed as cloudiness, suspended particles, or solid settling at the bottom of the container.

Examples

• When silver nitrate solution (AgNO_3) is mixed with sodium chloride solution (NaCl), a white precipitate of silver chloride (AgCl) forms.

  • AgNO_3 (aq) + NaCl (aq) \rightarrow AgCl (s) + NaNO_3 (aq)

• When lead(II) nitrate is added to potassium iodide, lead(II) iodide (a yellow precipitate) forms.

Conservation

Definition

• A fundamental principle in science stating that a particular measurable property of an isolated physical system remains constant over time.

Important Information

• Two key laws of conservation in chemistry are the Law of Conservation of Mass and the Law of Conservation of Energy.

• Law of Conservation of Mass: States that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations. The mass of the products in a chemical reaction must equal the mass of the reactants.

• Law of Conservation of Energy: States that energy can be neither created nor destroyed; rather, it can only be transformed or transferred from one form to another.

Examples

• Conservation of Mass: If you burn a candle, the total mass of the wax and oxygen consumed will equal the total mass of carbon dioxide, water vapor, and any ash produced.

• Conservation of Energy: A roller coaster at the top of a hill has high potential energy, which is converted to kinetic energy as it moves down, but the total mechanical energy (potential + kinetic) remains constant (ignoring friction for simplicity).

Chemical Property

Definition

• A characteristic of a substance that describes its ability to undergo a specific chemical change, describing how matter reacts with other matter.

Important Information

• Can only be observed by changing the chemical identity of the substance (involves a chemical reaction).

• Distinguishes one substance from another based on its reactivity.

Examples

• Flammability: The ability of a substance to burn or ignite, causing fire or combustion (e.g., wood burning).

• Reactivity with acid: How readily a substance reacts with an acid (e.g., baking soda reacting with vinegar).

• Ability to rust: The tendency of iron to react with oxygen and water to form iron oxide.

• Toxicity: The degree to which a substance can harm an organism.