Science 2

Smallest Unit of an Element

The atom is the smallest unit of an element that maintains the properties of that element.

Atomic Composition

Each atom consists of:

• Protons

• Neutrons

• Electrons

Defining a Pure Element

An element is considered pure because it contains only one type of atom and cannot be broken down into a simpler form.

Periodic Table Fundamentals

1. Total Elements: There are 118 known elements.
2. Element Symbol: Represented by 1 or 2 letters.
3. Element Block contents: Includes the atomic number, symbol, name, and atomic mass.

Molecules vs. Compounds vs. Mixtures

1. Molecule: A substance of 2 or more atoms combined together.
2. Compound: A substance formed when two or more different elements combine together.
3. Mixture: A substance created when two or more substances combine, but each retains its physical properties.

Chemical Formulas: Subscripts vs. Coefficients

• Subscripts: Small lowered numbers identifying how many atoms of a particular element are in a chemical formula.
• Coefficients: The numbers in front of a chemical formula indicating the total number of molecules of a compound.

Analyzing the Formula 4K{2}CrO{4}

• Number of Molecules: 4
• Number of Elements: 3 (Potassium, Chromium, Oxygen)
• Number of Atoms: 28

Physical vs. Chemical Changes

• Physical Change: Alters the form or appearance of matter but does not turn it into a different substance.
• Chemical Change: A change in matter that produces one or more new substances.

Evidence of Chemical Change

• Color change
• Formation of precipitates
• Formation of gas
• Change in energy

Aqueous Solution Components

1. Aqueous Solution: A liquid homogeneous mixture where the solvent is water.
2. Solute: The substance being dissolved (found in smaller amounts).
3. Solvent: The substance doing the dissolving (found in larger amounts).

The Universal Solvent

Water is the universal solvent because it is able to dissolve a large variety of different substances.

Factors Affecting Rate of Dissolution

1. Temperature: Increasing temperature increases the rate.
2. Surface Area: Increasing surface area (smaller pieces) increases the rate.
3. Agitation: Stirring or shaking increases the rate.

Solubility and Saturation

• Solubility: The maximum amount of solute that can dissolve in a solvent at a specific temperature.
• Saturated Solution: When a solution contains the maximum amount of solute; any additional solute will settle at the bottom.

Motion Formulas

• Speed (S): S = D / T
• Time (T): T = D / S
• Distance (D): D = S imes T
• Velocity (V): V = \text{Displacement} / \text{Time}

Distance vs. Displacement

• Distance: The total path traveled.
• Displacement: The straight-line difference between the starting and ending points including direction.

Newton's Three Laws of Motion

1. 1st Law (Law of Inertia): An object at rest stays at rest, and an object in motion stays in motion unless acted upon by an unbalanced force.
2. 2nd Law (Law of Acceleration): Force equals mass multiplied by acceleration (F = m \times a).
3. 3rd Law (Action-Reaction): For every action, there is an equal and opposite reaction.

Balanced vs. Unbalanced Forces

• Balanced Force: Net force is 0 and there is no change in motion.
• Unbalanced Force: Causes a change in motion (acceleration).

Types of Heat Transfer

1. Conduction: Transfer through direct contact.
2. Convection: Transfer through liquids or gases (cannot occur in solids).
3. Radiation: Transfer through electromagnetic waves.

Thermal Energy vs. Temperature

• Thermal Energy: The total kinetic energy of all particles in a substance.
• Temperature: The measure of the average kinetic energy of the particles.

Thermal Equilibrium

The point where two interacting substances reach the same temperature. Heat always travels from hotter substances to colder substances.

Astronomical Measurement Units

• Astronomical Unit (AU): 150 million kilometers (distance from Earth to Sun).
• Light-year: 9.5 trillion kilometers (distance light travels in a year).

Inner vs. Outer Planets

• Inner Planets: Mercury, Venus, Earth, Mars. Made of rock and metal with solid outer layers.
• Outer Planets: Jupiter, Saturn, Uranus, Neptune. Made of gases with greater mass and stronger gravitational forces.

Meteors, Meteoroids, and Meteorites

• Meteoroid: A small rocky or metallic body in outer space.
• Meteor: A meteoroid that has entered Earth's atmosphere (shooting star).
• Meteorite: A meteor that makes contact with Earth's surface.

Planetary Survival Factors (Earth)

1. Energy Source: The Sun.
2. Water: Specifically liquid water.
3. Nutrients: Essential for life.
4. Atmosphere: Greenhouse gases maintain heat, and the Ozone layer protects from UV radiation.