8 standard science question paper 2019 answers

Science is an important subject that helps students understand the world around them. This set of questions and answers is based on the 2019 science paper for 8th standard students. It covers topics in Physics, Chemistry, and Biology, offering educational content to improve knowledge and exam preparation.

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Physics Questions and Answers

Question: What is force?

Answer: Force is a push or pull on an object that can change its state of motion or shape.

Question: Define Newton’s first law of motion.

Answer: Newton’s first law states that an object remains at rest or in uniform motion unless acted upon by an external force.

Question: What is the unit of force?

Answer: The unit of force is Newton (N).

Question: What is friction?

Answer: Friction is the force that opposes the motion of an object when it is in contact with a surface.

Question: Why does a moving ball stop eventually on the ground?

Answer: A moving ball stops eventually due to the force of friction acting against its motion.

Question: What is the speed of light in a vacuum?

Answer: The speed of light in a vacuum is approximately 3 × 10⁸ meters per second.

Question: Define potential energy.

Answer: Potential energy is the energy possessed by an object due to its position or configuration.

Question: What is the law of reflection?

Answer: The law of reflection states that the angle of incidence is equal to the angle of reflection.

Question: What is meant by uniform motion?

Answer: Uniform motion occurs when an object covers equal distances in equal intervals of time.

Question: What is work?

Answer: Work is done when a force is applied to an object, and the object moves in the direction of the force.

Question: State the formula for work.

Answer: The formula for work is Work = Force × Displacement × cos(θ).

Question: What is gravitational force?

Answer: Gravitational force is the force of attraction between two objects due to their masses.

Question: Define kinetic energy.

Answer: Kinetic energy is the energy an object possesses due to its motion.

Question: What is power?

Answer: Power is the rate at which work is done or energy is transferred.

Question: What is the SI unit of power?

Answer: The SI unit of power is Watt (W).

Question: Why does a car skid on a wet road?

Answer: A car skids on a wet road due to reduced friction between the tires and the road surface.

Question: What is momentum?

Answer: Momentum is the product of the mass and velocity of an object.

Question: What is an electric circuit?

Answer: An electric circuit is a closed path through which electric current flows.

Question: Define Ohm’s law.

Answer: Ohm’s law states that the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance.

Question: What is the function of a fuse in a circuit?

Answer: A fuse protects electrical circuits by breaking the circuit when excessive current flows through it.

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Chemistry Questions and Answers

Question: What is an atom?

Answer: An atom is the smallest unit of matter that retains the properties of an element.

Question: What are molecules?

Answer: Molecules are two or more atoms chemically bonded together.

Question: Define the periodic table.

Answer: The periodic table is a tabular arrangement of elements based on their atomic number and properties.

Question: What is an acid?

Answer: An acid is a substance that releases hydrogen ions (H⁺) in an aqueous solution.

Question: What is a base?

Answer: A base is a substance that releases hydroxide ions (OH⁻) in an aqueous solution.

Question: What is pH?

Answer: pH is a measure of the acidity or alkalinity of a solution.

Question: What are noble gases?

Answer: Noble gases are inert elements found in Group 18 of the periodic table, such as helium and neon.

Question: What is the chemical formula for water?

Answer: The chemical formula for water is H₂O.

Question: Define chemical reaction.

Answer: A chemical reaction is a process in which substances react to form new substances with different properties.

Question: What is a catalyst?

Answer: A catalyst is a substance that speeds up a chemical reaction without being consumed in the process.

Question: What is the difference between physical and chemical changes?

Answer: Physical changes affect only the state or appearance of a substance, while chemical changes form new substances.

Question: What is rusting?

Answer: Rusting is the chemical reaction of iron with oxygen and moisture, forming iron oxide.

Question: What are hydrocarbons?

Answer: Hydrocarbons are organic compounds composed only of carbon and hydrogen atoms.

Question: What is electrolysis?

Answer: Electrolysis is the process of using electricity to decompose a substance.

Question: What is the atomic number?

Answer: The atomic number is the number of protons in the nucleus of an atom.

Question: What is an isotope?

Answer: Isotopes are atoms of the same element with the same atomic number but different mass numbers.

Question: What is a chemical bond?

Answer: A chemical bond is a force of attraction between atoms that holds them together in a molecule.

Question: What is the law of conservation of mass?

Answer: The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction.

Question: Define alloy.

Answer: An alloy is a mixture of two or more metals or a metal and a non-metal.

Question: What is the formula for carbon dioxide?

Answer: The formula for carbon dioxide is CO₂.

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Biology Questions and Answers

Question: What is photosynthesis?

Answer: Photosynthesis is the process by which green plants use sunlight to make food from carbon dioxide and water.

Question: Define cell.

Answer: A cell is the basic structural and functional unit of life.

Question: What are organelles?

Answer: Organelles are specialized structures within a cell that perform specific functions.

Question: What is the function of chloroplasts?

Answer: Chloroplasts are organelles that carry out photosynthesis in plant cells.

Question: What is the role of the nucleus?

Answer: The nucleus controls cell activities and contains genetic material.

Question: What is an ecosystem?

Answer: An ecosystem is a community of living organisms interacting with their environment.

Question: Define biodiversity.

Answer: Biodiversity is the variety of living organisms in an area.

Question: What are the three types of blood cells?

Answer: The three types of blood cells are red blood cells, white blood cells, and platelets.

Question: What is the function of the heart?

Answer: The heart pumps blood throughout the body.

Question: Define digestion.

Answer: Digestion is the process of breaking down food into simpler substances for absorption.

Question: What are the main parts of the human digestive system?

Answer: The main parts of the human digestive system are the mouth, esophagus, stomach, small intestine, and large intestine.

Question: What is a food chain?

Answer: A food chain shows the transfer of energy through different organisms in an ecosystem.

Question: What are decomposers?

Answer: Decomposers are organisms that break down dead matter and recycle nutrients.

Question: Define habitat.

Answer: A habitat is the natural environment where an organism lives.

Question: What is respiration?

Answer: Respiration is the process of releasing energy from food.

Question: What is the role of mitochondria?

Answer: Mitochondria are organelles that produce energy for the cell.

Question: Define adaptation.

Answer: Adaptation is a characteristic that helps an organism survive in its environment.

Question: What is a gene?

Answer: A gene is a unit of heredity that determines a trait in an organism.

Question: What is the difference between a herbivore and a carnivore?

Answer: A herbivore eats plants, while a carnivore eats other animals.

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Science improves critical thinking and problem-solving skills. Understanding basic scientific concepts equips students to better grasp the natural world and its phenomena. By revisiting these questions and answers, students can strengthen their knowledge and excel academically.