CEM 141 – Introduction to Chemistry

This set of flashcards covers key concepts in CEM 141 on chemistry principles, atomic structure, reactions, and the behavior of matter.

What is chemistry?

The study of matter and its interactions.

What are the two main components of matter?

Atoms and molecules.

What is one property of matter?

Matter is composed of atoms that are mostly empty space.

What property connects energy and matter?

Energy and matter are versions of the same thing.

What determines observable properties of substances?

The molecular level structure determines observable properties.

What is emergent property in chemistry?

Properties that are different from the sum of the reactants.

What is a scientific question?

A question that can be answered by experiments, observations, or measurements.

What must scientific claims be supported by?

Evidence from experiments.

What are the three parts of a scientific explanation?

Claim, evidence, and reasoning.

What is a scientific theory?

A comprehensive explanation of existing evidence that can make predictions.

How does a scientific law differ from a theory?

A law describes what happens, while a theory explains why it happens.

What is Dalton's Atomic Theory?

A theory that states elements are made of indivisible particles called atoms.

What did the Greeks believe about atoms?

That the shape of atoms determines their properties.

What fraction of the matter in the universe is atomic?

Approximately 5%.

What are atomic models used for in chemistry?

They help us make sense of observations and predict outcomes.

What is an example of a subatomic particle?

Proton, neutron, or electron.

What evidence supports the existence of electrons?

The particles emitted from cathode rays deflected towards the positive electrode.

What is Rutherford's model of the atom?

Proposes that the atom has a small, dense nucleus surrounded by electrons.

What is the nucleus of an atom composed of?

Protons and neutrons.

What causes the strong force within an atomic nucleus?

The interaction between quarks in protons and neutrons.

What is necessary for elements to exist as collections of atoms?

They must bond through electromagnetic interaction.

What type of charge do protons carry?

Positive charge.

What type of charge do electrons carry?

Negative charge.

What is the difference between an atom and an element?

An atom is the smallest unit of an element; an element is a substance that cannot be broken down further.

What are intermolecular forces (IMFs)?

Forces that occur between individual atoms or molecules.

Which is stronger, a covalent bond or an intermolecular force?

A covalent bond is stronger.

What are London Dispersion Forces?

Weak intermolecular forces that arise from temporary dipoles.

What factors affect London Dispersion Forces?

Size of the atoms or molecules and their surface area.

What happens to potential energy as two atoms approach each other?

Potential energy decreases until the atoms reach a stable point.

How does temperature relate to kinetic energy?

Temperature is directly related to the average kinetic energy of particles.

What is the law of conservation of energy?

Energy cannot be created or destroyed; it can only be transformed.

What role do thermal energy and collisions play in phase changes?

They facilitate transitions between solid, liquid, and gaseous states.

What happens during a chemical reaction involving bond breaking?

Energy is absorbed to break bonds.

What happens when bonds form during a chemical reaction?

Energy is released.

What characterizes an ionic bond?

The electrostatic attraction between oppositely charged ions.

What occurs in a covalent bond?

Atoms share pairs of electrons.

What is the impact of increasing temperature on molecular motion?

It increases the kinetic energy and motion of the molecules.

What does the atomic mass of an element tell us?

It's the weighted average of the masses of an element’s isotopes.

What is meant by the term 'isotope'?

Atoms of the same element with different numbers of neutrons.

What is the significance of the periodic table in chemistry?

It organizes elements based on their properties and atomic structure.

What does conservation of mass imply in chemical reactions?

Matter is neither created nor destroyed in a chemical reaction.

What is an example of a phase change?

Melting, freezing, condensation, or evaporation.

What does a molecular model help chemists understand?

The structure, shape, and dynamics of molecules.

How does electronegativity influence bond formation?

It determines how strongly an atom can attract electrons in a bond.

What is the electron configuration of an atom?

It describes the distribution of electrons in atomic orbitals.

What factors can shift the position of equilibrium in a reaction?

Concentration, temperature, and pressure changes.

How does temperature affect the rate of reactions?

Increasing temperature typically increases reaction rates.

What is the ideal gas law?

PV=nRT; relates pressure, volume, temperature, and amount of gas.

What is an atomic orbital?

A mathematical function that describes the location of an electron.

What is electronegativity?

A measure of an atom's ability to attract electrons in a bond.

What happens to bonding in metals?

They share electrons freely, forming a metallic bond.

What is the result of a high electronegativity difference between atoms?

The formation of ionic bonds.

What is hydrogen bonding?

A special type of dipole-dipole interaction involving hydrogen and a highly electronegative atom.

What is a molecular ion?

An ion formed from a molecule by the loss or gain of electrons.

What do covalent compounds typically have in terms of physical properties?

Lower melting and boiling points compared to ionic compounds.

What are the signs of a chemical change?

Bubbles, color change, heat absorption or release, and precipitate formation.

What is the primary factor that influences the speed of gas particles?

Temperature.

What is the rate of a reaction?

The speed at which reactants are converted into products.

What happens during sublimation?

A solid transforms directly into a gas without passing through a liquid state.

What is the process of moving from a gas to a liquid called?

Condensation.

What is the definition of kinetics in chemistry?

The study of the rates of chemical reactions.

How can you find the molarity of a solution?

Molarity = moles of solute/liters of solution.

What is the significance of the mole in chemistry?

It is a unit that measures the amount of a substance.

What is the concept of limiting reactants?

The reactant that is fully consumed first and limits the amount of product formed.

What is an equilibrium constant?

A value that expresses the ratio of the concentrations of products to reactants at equilibrium.

What is a molecular formula?

The actual number of atoms of each element in a molecule.

What is a polar molecule?

A molecule that has a partial positive charge on one side and partial negative charge on the other.

What are isotopes?

Atoms of the same element with different numbers of neutrons.

What is molality?

The number of moles of solute per kilogram of solvent.

What is the definition of specific heat?

The amount of heat required to raise the temperature of one gram of a substance by one degree Celsius.

What is the difference between heat and temperature?

Heat is energy transferred due to temperature difference, while temperature is a measure of thermal energy.

What is kinetic-molecular theory?

A model that explains gas behavior in terms of particles in motion.

What are transition metals known for?

Their ability to form various oxidation states and colored compounds.

What is the role of ligands in coordination complexes?

They donate electron pairs to a central metal ion.

What is the significance of the octet rule?

Atoms tend to bond in a way that achieves a full outer shell of electrons.

What are the names for the different types of chemical bonds?

Ionic, covalent, and metallic bonds.

What are the two types of covalent bonds?

Polar and nonpolar covalent bonds.

What is the purpose of a chemical equation?

To represent a chemical reaction with symbols and formulas.

What is stoichiometry?

The calculation of reactants and products in chemical reactions.

What is an endothermic reaction?

A reaction that absorbs energy from its surroundings.

What is a balanced equation?

An equation with equal numbers of each type of atom on both sides.

What is the difference between a chemical and a physical change?

Chemical changes alter the identity of a substance, physical changes do not.

Diamond, Graphite, Quartz

Only some solids have covalent bonds and these are substances that are made up of covalent networks

electrostatic Forces

-Can be attractive or repulsive

-Depends on charge

-much stronger

-atomic scale

gravitational forces

-always attractive

-Depends on massand distance between objects.

-Weaker than electrostatic forces.

What happens to energy as two opposite charges move closer?

• They attract.

• As they get closer:

  • PE decreases (becomes more negative)

  • KE increases (they speed up)

  • Total energy stays constant

Reason: The attractive force pulls them in and converts PE → KE.

What happens to energy when two same charges move closer?

• They repel.

• As they get closer:

  • PE increases (becomes more positive)

  • KE decreases (they slow down)

  • Total energy stays constant

Reason: They have to “fight” against repulsion, so KE gets converted → PE.

Why do two isolated atoms attract when far apart?

Attraction at moderate distance

• Electrons in atoms are always moving.

• These movements create temporary dipoles.

• Temporary dipoles create London dispersion forces, which attract atoms.

So at longer distances → atoms pull toward each other.

Why do two isolated atoms repel when close together?

Repulsion at short distances

If atoms get too close:

• Their electron clouds begin to overlap.

• Electrons don’t want to be in the same space (Pauli exclusion).

• This creates a very strong repulsive force.

So at close range → atoms push away strongly.

Repulsion region- Two Helium Atoms Get closer

• Electron clouds overlap when too close.

• PE increases sharply

• KE decreases (they slow down)

• Total energy stays constant the whole time.

Attractive Region- Two Helium Atoms get closer

• Dispersion forces pull them together.

• PE decreases a little (becomes slightly negative)

• KE increases a little (they speed up)

London Dispersion Forces increase

as the number of electrons increases.

LDFs:

weak, temporary attractions between molecules, cause a small drop in potential energy.

Breaking an LDF is a phase change;

Covalent bonds

strong, stable attractions through electron sharing, cause a large drop in potential energy.

breaking a covalent bond is a chemical reaction.