CHEM 1061 Mastery Checkpoint #1

What is matter made of?

atoms

What is the smallest distinguishable part of an element?

atom

Why do atoms/molecules attract each other?

because of the attractive electrical forces between them

Do attractions or repulsions lower the potential energy?

Attractions

Do attractions or repulsions lower the kinetic energy?

Attractions

Where do stable systems form?

where the attractive forces and the repulsive forces are equal

What did Dalton's model show?

Atoms as solid, indivisible spheres

What did Thomson's Plum Pudding Model show?

A positively charged "soup" with electrons embedded.

What did Rutherford's Nuclear Model show?

A dense nucleus surrounded by orbiting electrons.

What are the key differences between gravitational force and electromagnetic force?

Strength, Type of Charge, Scope of Influence

Is electromagnetic or gravitational force stronger?

Electromagnetic forces are vastly stronger than gravitational forces.

Are electromagnetic/gravitational force attractive or repulsive?

Electromagnetic forces can be attractive or repulsive; gravitational forces are always attractive.

What happens to the potential energy as two helium atoms approach?

Decreases as they are attracted, reaching a minimum when they are at an optimal distance.

What happens to the kinetic energy as two helium atoms approach?

Initially may decrease as they move closer, but if repulsion occurs at very close range, kinetic energy increases.

What happens to the total energy as two helium atoms approach?

A balance where total energy is lowest at the optimal distance, indicating stability.

How does the strength of London dispersion forces relate to the melting and boiling points of atoms and molecules?

Larger atoms or molecules have stronger London dispersion forces, resulting in higher melting and boiling points.

Why does iodine (I₂) have a higher boiling point than neon (Ne)?

Iodine has a higher boiling point than neon due to stronger London dispersion forces.

What is a law?

Describes a phenomenon

What is a theory?

Explains a phenomenon

Scientific Theory

Best available explanation, explains how and/or why, makes testable predictions, can be proven falce, susceptible to change with new evidence

Fact

A statement that can be verified

Hypothesis

Prediction that can be tested

Question

Something that is asked

What is an atom?

Smallest unit of measurement

Element

Contain one type of atom

Compound

Contains more than two types of elements

All compounds are molecules:

But not all molecules are compounds

Molecule

Contains more than 2 atoms

What is Daltons Atomic Theory?

Elements are composed of small, indivisible, indestructible particles called atoms; All etoms of an element are identical and have the same mass and properties; atoms of a given element are different from atoms of other elements; compounds are formed by combinations of atoms of two or more elements; chemical reactions are due to the rearrangements of atoms; atom matter are created nor destroyed during a chemical reaction

Plum Pudding Model

Modeled after Cathode Ray Tube Experiment

Important findings of Cathode Ray Tube Experiment

Particles emerged from the cathode and mooved to the other anode; these particles were deflected by electrical and magnetic fields in a direction that would indicate the were negatively charged

Planetary Model

Modeled after Rutherford Experiment (Gold Foil)

Planetary Model states

Nucleus of a atom is filled with tightly conjoined protons and neutrons

What did the Gold Foil experiment reveal?

Most particles went through, but some were deflected; the plum pudding model would have had all particles go through; Atoms are mostly empty space and the existence of a positive nucleus

Isotope

Same # of protons and electrons but different number of neutrons

Neutrons

Discovered 1932, hard to detect, and cannot be manipulated

An atom of an element

A molecule of an element

A molecule of a compound

Atom of a compound

Not possible

Coulombos Law

Opposite charges attract

What is a force

A push or a pull/ an interaction

Gravity

Responsible for attraction between objects that have mass

Electromagnetic forces

Responsible for attraction AND repulsion between objects that have electric charge

Strong forces

short range force thats between protons and neutrons

Weak forces

short range force between elementary particles

Gravity’s Law (Newtons Law of Universal Gravitation)

Inverse Square Law

As R increases, F decreases by a factor of 1/r²

Between electromagnetism and gravity, which force is stronger?

electromagnetism, it is both attractive and repulsive

What is energy?

Definition is circular: any change in matter is accompanied by a change in energy, which is caused by changes in forces

System

The part of the universe youre looking at

Surroundings

Everything else in the universe

Kinetic Energy

Energy associated with motion

Potential

STORED IN THE FIELD BETWEEN OBJECTS, position of a system of objects in a field (gravity, electromagnetic, etc), requires 2 or more objects,

London Dispersion Forces

Attractive forces that exist between partcles

Thermal energy

A measure of the average kinetic energy of the atoms

Temperature

Directly related to average kinetic energy

What causes London Dispersion Forces?

Fluctuations of electron density in the molecule, inducing a temporary dipole in the other atom

What parts of Daltons Theory is still true?

Atoms of a given element are different from atoms of other elements; Compounds are formed by combinations of atoms of two ore more elements

Where are London Dispersion Forces present?

Between all molecules in neutral spaces

How do atoms know the temperature is increasing?

Energy is being transferred from other atoms that have collided with the walls of the container

How does size affect LDF?

The bigger the surface area of the particles (the electron cloud), the easier LDF happen

Covalent Bond

CHEMICAL link formed between two atoms that share pairs of valance electrons

Pic of Covalent Bonds

Pic of LDF

What happens with like charges repel?

What happens when opposite charges interact?