Notes, summaries, assignments, exams, and problems for Secondary education

Understanding Sound Types

Analogue Sound Explained

Analogue sound imitates the vibrations of real sound. Its electrical signal has an analogue curve similar to a real sound wave.

Digital Sound Explained

Digital sound recording does not imitate vibrations but converts them into a binary code, the language computers use.

Digital sound is obtained through a converter. It transforms real sound (analogue) into a computer-readable format.

The Digitization Process

Role of the Converter

A converter is a device that transforms real sound into digital sound. The process is called sampling.

Sound Reproduction

To reproduce sound, the converter follows the inverse process, transforming the digital information back into real sound.

The MIDI System: Digital Communication

Understanding Plastic Materials: Types and Applications

Thermoplastics: Properties and Common Uses

What are Thermoplastics?

Thermoplastics are composed of polymer chains that are weakly connected to each other. When thermoplastics are heated, they soften and can be molded into different shapes. Once they cool down, this process can be repeated as many times as needed, making them highly recyclable and versatile.

Key Types of Thermoplastics and Their Applications:

• Polyethylene Terephthalate (PET): Impermeable, transparent, and light.
  • Applications: Packaging for food, drinks, personal hygiene products, cosmetics, and cleaning products.
• High-Density Polyethylene (HDPE): Rigid and resistant.
  • Applications: Buckets, bottles, packaging for cleaning products,

Natural Cycles

In nature, chemical elements vital to life, such as oxygen, carbon, and nitrogen, are neither made nor destroyed. They are recycled, moving round and round in the natural world in the form of minerals and nutrients. On land, they move from the soil into the plants, then into animals that eat plants, and then sometimes into other animals that eat plant-eating animals. Minerals and nutrients return to the soil either through an animal’s droppings, or whenever any plant or animal dies and rots away. Microorganisms in the soil, such as bacteria, play an important part in releasing the nutrients and minerals from the decaying matter.

Polar Lands

The North Pole is surrounded by the permanently icy Arctic Ocean. At the opposite end of... Continue reading "Natural Cycles and Diverse Ecosystems" »

Understanding Plastics: Composition and Origin

Plastics consist of long chains of molecules, made of carbon, that are called polymers. Polymers are composed of smaller molecules called monomers.

Types of Plastics Based on Origin

There are two main types of plastics according to their origin:

• Natural Plastics: These are obtained directly from vegetable or animal sources. Examples include latex and cellulose (produced by plants), as well as casein (from milk).
• Synthetic Plastics: These are made with compounds derived from petroleum, natural gas, and coal (carbon). Most plastics used today are synthetic.

Industrial Production: Polymerization and Processing

The industrial process for producing plastic from raw materials is called polymerization.

Manufacturing

The Western Roman Empire followed a different evolution to the Byzantine Empire.

byzantine

The lands of Western Europe were occupied by peoples of Germanic origin.

germanic

The Germanic people came from Central Asia and settled for centuries near the borders of the Roman Empire.

nomadic

Germanic people mainly lived in villages and camps.

farming

Germanic people were organised into tribes, led by a tribal chief.

assembly

warriors

An increase in population and the need to seek pastures for cattle caused the Germanic people to move to Western Europe.

western

Some of the Germanic tribes that pushed the boundaries of the Roman Empire during the 3rd century took advantage of its weakness to settle there.

weaknessThese tribes settled in the territory of the Western... Continue reading "The Fall of the Western Roman Empire: Germanic Invasions" »

Germanic Invasions

The Western Roman Empire followed a different evolution to the Byzantine Empire, as the lands of Western Europe were occupied by peoples of Germanic origin.

1. Germanic Tribes

The Germanic people came from Central Asia and settled for centuries near the borders of the Roman Empire. They were nomadic people who did not build cities, as they mainly lived in villages and camps. They mainly worked in farming and were organised into tribes, led by a tribal chief who was elected by an assembly of free men. The leader was the military chief and ruled with the help of warriors, with whom he established pacts of loyalty.

An increase in population and the need to seek pastures for cattle caused the Germanic people to move to western Europe.... Continue reading "The Germanic Invasions and the Fall of Rome" »

Write the schedule of the main big bang events.

Dalton's Atomic Theory

John Dalton proposed that elements were made up of little solid spheres without internal structure. Atoms of the same element were equal. Atoms combine, forming compounds. Depending on the ratio, we can have different compounds.

J.J. Thomson

First model of the atom (1904). He discovered/proved the existence of tiny, negatively charged particles: electrons.

Rutherford's Model of the Atom

Gold foil experiment, Ernest Rutherford (1911). Alpha particles are tiny, positively charged particles much smaller than an atom. An atom is mostly empty space. Some particles will bounce back, and some others will pass but in a different way. The nucleus is something dense and positively charged.

Thomson's Atomic Model

In 1904, Thomson's atomic... Continue reading "Dalton's Atomic Theory and the Evolution of Atomic Models" »

File Management

File management is the system an operating system uses to organize and keep track of data. The operating system stores data in units called files, determines how files are stored, efficiently uses available storage space, creates a record of all file usage, and carries out every task related to files and folders.

File names typically have this structure:

filename.extension

Task and User Management

Task Management

Task management is the part of the operating system that controls the running of one or more programs on a computer simultaneously. Today's widely used operating systems support multitasking, allowing multiple tasks to run concurrently, taking turns using the computer's resources.

User Management

With user management, the operating... Continue reading "Understanding Operating Systems: File, Task, and User Management" »

Respiration: The Energy Source of Life

Every living cell needs energy. In humans, our cells need energy for:

• Contracting muscles
• Making proteins
• Making new cells
• Cell division
• Producing heat inside the body

All of this energy comes from the food that we eat. The food is digested (broken down) and absorbed from the intestine into the blood. Then, the blood goes to the body, and the cells take the nutrients.

Aerobic Respiration

Most of the time, our cells release energy from glucose by combining it with oxygen.

Aerobic respiration involves chemical reactions in cells that use oxygen to break down nutrient molecules to release energy.

glucose + oxygen → carbon dioxide + water

Anaerobic Respiration

Anaerobic respiration involves chemical reactions in cells... Continue reading "Cellular Respiration: Aerobic vs. Anaerobic Processes" »