Quiz 1:   Fullscreen Mode Exothermic and Endothermic Reactions Exothermic and Endothermic Reactions Chemical reactions can be classified into two main categories based on energy changes: exothermic reactions and endothermic reactions . Exothermic Reactions An exothermic reaction is one that releases energy in the form of heat to the surroundings. During this reaction, the temperature of the surroundings increases due to the energy released. A common example of an exothermic reaction is the combustion of fuels, such as methane (CH₄). The combustion reaction of methane can be written as follows: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) + ΔH Here, ΔH has a negative value, indicating that energy is released during this process. The combustion of methane in oxygen produces carbon dioxide and water, releasing about 728 kJ/mol of energy. Characteristics of Exothermic Reactions: Energy Released: Energy in the form of heat is released to the surround...

Audio Podcast Quiz 1:   Fullscreen Mode Quiz 2:   Fullscreen Mode  5.2.1 Detection of radioactivity ## Radioactivity Detection Radioactivity is the process of releasing radiation from an unstable atomic nucleus. We are all exposed to radiation from various sources every day. Let's discuss some important things about radioactivity: ## Background Radiation Sources Background radiation comes from a variety of sources, both natural and artificial: - Cosmic rays from the sun - Radon gas in the air - Radon-containing granite rocks - Potassium-40 in food - Medical procedures that use radioisotopes - Nuclear power plants and the rest of the nuclear bomb tests ## Ionization Effect Radiation can cause ionization, which is the process of releasing electrons from atoms or molecules. This can be evidenced by: Electroscope Experiments: - When a fire or radium source is brought close to a charged electroscope, the charge is lost - Fire or radiation causes air molecules...

Quiz 1:   Fullscreen Mode Quiz 2:   Fullscreen Mode Fundamentals of Magnets Magnets are objects that have two poles - a north (N) pole and a south (S) pole. Every magnet always has these two poles, and cannot have only one pole (Ruoho & Arkkio, 2008). Properties of Magnets: Like poles repel each other Opposite poles attract each other The strength of the magnetic force decreases as the distance increases Magnetic Field The magnetic field is the region around a magnet where the magnetic force can still be felt. The strength of the magnetic field is shown by the magnetic field lines: The closer the field lines, the stronger the magnetic field The direction of the magnetic field is always from the north pole to the south pole Types of Magnetic Materials Magnetic Materials: Examples are iron, steel, nickel, and cobalt Can be attracted by magnets Can be magnetized Non-magnetic Materials: Examples are aluminum and wood Cannot be attr...

Quiz 1:   Fullscreen Mode Quiz 2:   Fullscreen Mode The Speed or Rate of the Reaction The Speed or Rate of the Reaction The rate of a chemical reaction is a measure of how quickly reactants are converted into products. In everyday life, reactions can vary significantly in speed; for instance, the formation of silver chloride precipitate when silver nitrate is mixed with sodium chloride occurs almost instantaneously, while the rusting of iron is a slow process that can take years. The rate of reaction can be quantified by measuring the change in concentration of reactants or products over time. For example, when zinc (Zn) reacts with sulfuric acid (H 2 SO 4 ), the rate can be assessed by the volume of hydrogen gas (H 2 ) produced per unit time. One of the simplest methods to determine the rate of reaction is to measure the volume of gas produced using a gas syringe. Various factors influence the rate of reaction, includin...

Quiz 1:   Fullscreen Mode Quiz 3:   Fullscreen Mode Electricity And Chemical Change: Electrochemistry Electricity And Chemical Change: Electrochemistry 1 Conductors and Insulators Testing Conductivity We can test whether a substance conducts electricity by inserting it into a simple electrical circuit consisting of a battery, wires, and a light bulb. If the bulb lights up, the substance is a conductor. If the bulb does not light up, the substance is an insulator. Testing Results Metals and graphite are solid conductors: Example: Tin conducts electricity when tested. Reason: The presence of free electrons that can move. Molecular substances do not conduct electricity: Example: Ethanol does not conduct electricity when tested. Reason: There are no charged particles that can move freely. Ionic substances have special proper...

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Quiz 1:   Fullscreen Mode Teori dan Rumus Ikatan Kimia Teori dan Rumus Ikatan Kimia A. Kestabilan Unsur-Unsur Konfigurasi elektron beberapa unsur gas mulia: Nama Unsur Nomor Atom Konfigurasi Elektron Gambar Susunan Elektron Elektron Valensi Helium 2 2 2 Neon 10 2.8 8 Argon 18 2.8.8 8 Aturan Duplet: konfigurasi elektron stabil dengan dua elektron pada kulit terluar. Aturan Oktet: konfigurasi elektron stabil dengan delapan elektron pada kulit terluar. Pada saat atom-atom membentuk ikatan, hanya elektron-elektron pada kulit terluar yang berperan yaitu elektron valensi. Elektron valensi dapat digambarkan dengan struktur Lewis atau gambar titik elektron. B. Ikatan Ion Pembentukan Senyawa NaCl: Pembentukan Senyawa C...

Quiz 1:   Fullscreen Mode Struktur Atom dan Konfigurasi Elektron Struktur Atom dan Konfigurasi Elektron 1. Teori Dasar Struktur Atom Atom adalah unit terkecil dari materi yang memiliki sifat kimia suatu unsur. Struktur atom terdiri dari beberapa komponen utama: Inti Atom (Nukleus) Berisi proton (bermuatan positif) dan neutron (netral) Memiliki muatan positif dan massa hampir seluruh atom Elektron Partikel bermuatan negatif yang mengelilingi inti Bergerak dalam orbital-orbital di sekitar inti 2. Partikel Dasar Atom Partikel Muatan ...