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GRADE 10 , SCIENCE/ CHEMISTRY/ FOURTH QUARTER

Typology: Study notes

2023/2024

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Download SCIENCE (CHEMISTRY) REVIEWER Q4 and more Study notes Earth science in PDF only on Docsity! SCIENCE (CHEMISTRY) REVIEWER Q4 GAS One of the three states of matter. Made of tiny particles called atoms and are spaced far apart. PROPERTIES OF GASES: 1. HIGHLY COMPRESSIBLE. Applying pressure on gases decreases its volume because the volume that a gas occupies is mostly empty space since its molecules are far apart from each other 2. EXPLAND WHEN HEATED. When heated, its particles move faster and farther from each other, increasing the total volume. 3. FLOW EASILY AND ARE MISCEABLE. Can flow more freely, can escape easily through tiny openings. 4. LOWER DENSITIES THAN SOLIDS AND LIQUIDS. Particles are far apart from each other its volume is mostly empty. THE KINETIC MOLECULAR THEORY (KMT) OF GASES is a model that explains the physical behavior of gases. It assumes that gases are made up of tiny particles that are constantly moving in random directions, and are too small to see with a microscope. The KMT has five main postulates: The particles in a gas are in constant, random motion The combined volume of the particles is negligible The particles exert no forces on one another Any collisions between the particles are completely elastic The average kinetic energy of a collection of gas particles is directly proportional to absolute temperature WHAT ARE THE GAS LAWS? The gas laws are a group of laws that govern the behavior of gases by providing relationships between the following: The volume occupied by the gas. The pressure exerted by a gas on the walls of its container. The absolute temperature of the gas. The amount of gaseous substance (or) the number of moles of gas. The gas laws were developed towards the end of the 18th century by numerous scientists (after whom the individual laws are named). The five gas laws are listed below: Boyle’s Law: It provides a relationship between the pressure and the volume of a gas. Charles’s Law: It provides a relationship between the volume occupied by a gas and the absolute temperature. Gay-Lussac’s Law: It provides a relationship between the pressure exerted by a gas on the walls of its container and the absolute temperature associated with the gas. Avogadro’s Law: It provides a relationship between the volume occupied by a gas and the amount of gaseous substance. The Combined Gas Law (or the Ideal Gas Law): It can be obtained by combining the four laws listed above. Under standard conditions, all gasses exhibit similar behavior. The variations in their behaviors arise when the physical parameters associated with the gas, such as temperature, pressure, and volume, are altered. The gas laws basically describe the behavior of gases and have been named after the scientists who discovered them. We will look at all the gas laws below and also understand a few underlying topics. Boyle’s Law Boyle’s law gives the relationship between the pressure of a gas and the volume of the gas at a constant temperature. Basically, the volume of a gas is inversely proportional to the pressure of a gas at a constant temperature. Boyle’s law equation is written as: V ∝ 1/P Or P ∝ 1/V Or PV = k1 Where V is the volume of the gas, P is the pressure of the gas, and K1 is the constant. Boyle’s Law can be used to determine the current pressure or volume of gas and can also be represented as, P1V1 = P2V2 Problems Related to Boyle’s Law An 18.10mL sample of gas is at 3.500 atm. What will be the volume if the pressure becomes 2.500 atm, with a fixed amount of gas and temperature? Solution: By solving with the help of Boyle’s law equation P1V1 = P2V2 V2 = P1V1 / P2 V2 = (18.10 * 3.500 atm)/2.500 atm V2 = 25.34 mL Charles’s Law Charles’s law states that at constant pressure, the volume of a gas is directly proportional to the temperature (in Kelvin) in a closed system. Basically, this law describes the relationship between the temperature and volume of the gas.Mathematically, Charles’s law can be expressed as, V ∝ T Where, V = volume of gas, T = temperature of the gas in Kelvin. Another form of this equation can be written as, V1 / T1 = V2 / T2 Problems Related to Charles’s Law A sample of carbon dioxide in a pump has a volume of 21.5 mL, and it is at 50.0 °C. When the amount of gas and pressure remain constant, find the new volume of carbon dioxide in the pump if the temperature is increased to 75.0 °C. Solution: V2 = V1T2/T1 V2 = 7,485.225/ 323.15 V2 = 23.16 mL Gay-Lussac Law Gay-Lussac law gives the relationship between temperature and pressure at constant volume. The law states that at a constant volume, the pressure of the gas is directly proportional to the temperature of a given gas. If you heat up a gas, the molecules will be given more energy; they move faster. If you cool down the molecu les, they slow down, and the pressure decreases. The change in temperature and pressure can be calculated using the Gay-Lussac law, and it is mathematically represented as, P ∝ T Or P / T = k1 or P1 / T1 = P2 / T2 Where, P is the pressure of the gas, and T is the temperature of the gas in Kelvin. Problems Related to Gay-Lussac Law Determine the pressure change when a constant volume of gas at 2.00 atm is heated from 30.0 °C to 40.0 °C. Solution: P1 = 2.00 atm P2 =? T1 = (30 + 273) = 303 K T2 = (40 + 273) = 313 K According to the Gay-Lussac law, P ∝ T P/T = constant P1/T1 = P2/T2 P2 =( P1 T2 ) / T1 = (2 x 313) / 303 =2.06 atm Avogadro’s Law Avogadro’s law states that if the gas is an ideal gas, the same number of molecules exists in the system. The law also states that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. This statement can be mathematically expressed as, V / n = constant Or V1 / n1 = V2 / n2