Science Final 8th grade

Non-contact Forces

Forces that act without physical contact; examples include gravitational, electric, and magnetic forces.

Contact Forces

Forces that require physical contact; examples include friction, tension, and applied forces.

Newton’s Laws of Motion

1. Law of Inertia: An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by a force.
2. Law of Acceleration: The acceleration of an object is directly proportional to the net force acting on the object, is in the same direction as the net force, and is inversely proportional to the mass of the object. F = ma
3. Law of Action-Reaction: For every action, there is an equal and opposite reaction.

Equation for Newton’s Second Law of Motion

F = ma, where:
- F is the net force acting on the object (in Newtons, N)
- m is the mass of the object (in kilograms, kg)
- a is the acceleration of the object (in meters per second squared, m/s²)

Types of Waves

• Transverse Waves: Particles oscillate perpendicular to the direction of wave motion (e.g., light waves).
• Longitudinal Waves: Particles oscillate parallel to the direction of wave motion (e.g., sound waves).

Properties of Waves

• Wavelength (\lambda): The distance between two consecutive crests or troughs.
• Frequency (f): The number of waves that pass a point per unit time.
• Amplitude: The maximum displacement of a point on a wave from its equilibrium position.
• Speed (v): The speed at which the wave travels through the medium; v = \lambda f

Types of Waves in the Electromagnetic Spectrum

• Radio Waves: Used for communication, broadcasting.
• Microwaves: Used in microwave ovens and communication.
• Infrared: Used in thermal imaging and remote controls.
• Visible Light: The portion of the EM spectrum that is visible to the human eye.
• Ultraviolet: Can cause skin damage and is used in sterilization.
• X-rays: Used in medical imaging.
• Gamma Rays: Used in cancer treatment and sterilization.

Electromagnetic Spectrum

The electromagnetic spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. Wavelength decreases and frequency increases as you move from radio waves to gamma rays.

Solar Nebula Hypothesis

The theory that the solar system formed from a large cloud of gas and dust (solar nebula) that collapsed under its own gravity.

Types of Galaxies

• Spiral Galaxies: Disk-shaped with spiral arms.
• Elliptical Galaxies: Smooth, oval-shaped.
• Irregular Galaxies: No defined shape.

DNA Structure

DNA is a double helix composed of nucleotides, each containing a sugar, phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or thymine).

Mutation

A change in the DNA sequence. Types include:
- Point Mutation: Single base change.
- Frameshift Mutation: Insertion or deletion of bases.
- Chromosomal Mutation: Changes in chromosome structure or number.

Adaptation

An inherited trait that enhances survival and reproduction of an organism in a particular environment.

Variation

Any difference between cells, individual organisms, or groups of organisms of any species caused either by genetic differences or by the effect of environmental factors.

Natural Selection

The process where organisms better adapted to their environment tend to survive and reproduce more successfully.

Cell Organelles

• Plant Cells: Cell wall, chloroplasts, large central vacuole.
• Animal Cells: Lysosomes, centrioles.

Transcription and Translation

• Transcription: DNA is transcribed into RNA.
• Translation: RNA is translated into protein.

Diffusion

The movement of molecules from an area of higher concentration to an area of lower concentration.

Osmosis

The movement of water across a semipermeable membrane from an area of higher water concentration to an area of lower water concentration.

Mitosis

Cell division that results in two identical daughter cells.

Photosynthesis

The process by which plants convert light energy into chemical energy in the form of glucose, using carbon dioxide and water.

Cellular Respiration

The process by which cells break down glucose to produce energy in the form of ATP.

Complete Dominance

One allele completely masks the effect of another allele.

Incomplete Dominance

Neither allele is completely dominant, resulting in a blended phenotype.

Codominance

Both alleles are expressed equally in the phenotype.

Pedigrees

A diagram that shows the inheritance of a trait over several generations.

Punnett Squares

A diagram that shows the possible genotypes of offspring from two parents.

Probability

The likelihood that a specific event will occur.

H-R Diagram

A graph that plots stars based on their luminosity and temperature. The x-axis represents temperature (or spectral class), and the y-axis represents luminosity (or absolute magnitude).

Variables on the H-R Diagram

Luminosity and Temperature

Location of the Main Sequence on the H-R Diagram

Most stars are located on the main sequence, which runs from the upper left (hot, luminous stars) to the lower right (cool, dim stars).

Acids, Bases, and the pH Scale

Acids have a pH less than 7, bases have a pH greater than 7, and neutral substances have a pH of 7. The pH scale measures the concentration of hydrogen ions (H^+) in a solution.

Properties of Water

• Adhesion: Water molecules stick to other substances.
• Cohesion: Water molecules stick to each other.
• High Specific Heat: Water requires a lot of energy to change temperature.

Importance of High Specific Heat Capacity of Water

Helps maintain stable environmental and internal temperatures for organisms.

Stages of Mitosis

Mitosis includes prophase, metaphase, anaphase, and telophase.

Purpose of Mitosis

Growth, repair, and asexual reproduction in cells.

Prophase

Chromosomes condense and become visible; the nuclear envelope breaks down; spindle fibers form.

Metaphase

Chromosomes line up along the metaphase plate (center) of the cell.

Anaphase

Sister chromatids separate and move