Class 10 Science: Chemical Reactions and Equations

• These notes cover various topics in Class 10 Science, presented in a format suitable for MCQ preparation.

Chemical Reactions and Equations

• A balanced chemical equation has an equal number of atoms of each element on both sides of the equation.
• Combination reactions involve two or more reactants combining to form a single product.
• Decomposition reactions involve a single reactant breaking down into two or more products.
• Displacement reactions involve one element replacing another in a compound.
• Double displacement reactions involve the exchange of ions between two compounds.
• Redox reactions involve both oxidation (loss of electrons) and reduction (gain of electrons).
• Oxidation is the addition of oxygen or removal of hydrogen.
• Reduction is the addition of hydrogen or removal of oxygen.
• Corrosion is the process where metals are eaten up gradually by the action of air, moisture, or a chemical.
• Rancidity is the oxidation of fats and oils in foods, resulting in an unpleasant smell and taste.

Acids, Bases, and Salts

• Acids have a sour taste and turn blue litmus red.
• Bases have a bitter taste and turn red litmus blue.
• Acids release H+ ions in aqueous solutions.
• Bases release OH- ions in aqueous solutions.
• pH scale measures the acidity or alkalinity of a solution (0-14).
• pH values less than 7 indicate acidic solutions.
• pH values greater than 7 indicate basic solutions.
• pH value of 7 indicates a neutral solution.
• Strong acids and bases completely dissociate in water.
• Weak acids and bases partially dissociate in water.
• Salts are formed by the reaction of an acid and a base (neutralization).
• Common salt (NaCl) is used in food and as a raw material for many chemicals.
• Baking soda (NaHCO3) is used in baking and as an antacid.
• Washing soda (Na2CO3.10H2O) is used in cleaning and softening water.
• Bleaching powder (CaOCl2) is used for disinfecting water and bleaching.
• Plaster of Paris (CaSO4.1/2H2O) is used for setting fractures and making casts.

Metals and Non-metals

• Metals are generally hard, lustrous, malleable, and ductile.
• Non-metals are generally brittle and non-lustrous.
• Metals are good conductors of heat and electricity.
• Non-metals are poor conductors of heat and electricity (except graphite).
• Metals react with oxygen to form basic oxides.
• Non-metals react with oxygen to form acidic or neutral oxides.
• Metals react with acids to liberate hydrogen gas.
• Reactivity series arranges metals in order of their decreasing reactivity.
• Ionic compounds are formed by the transfer of electrons between metals and non-metals.
• Covalent compounds are formed by the sharing of electrons between non-metals.
• Minerals are naturally occurring inorganic substances in the Earth's crust.
• Ores are minerals from which metals can be extracted profitably.
• Metallurgy involves the extraction of metals from their ores.
• Corrosion of iron is called rusting.
• Alloys are homogeneous mixtures of two or more metals, or a metal and a non-metal.

Carbon and Its Compounds

• Carbon is a versatile element that forms a large number of compounds.
• Catenation is the ability of carbon to form long chains and rings.
• Tetravalency is the ability of carbon to form four covalent bonds.
• Hydrocarbons are compounds containing only carbon and hydrogen.
• Saturated hydrocarbons (alkanes) have single bonds between carbon atoms.
• Unsaturated hydrocarbons (alkenes and alkynes) have double or triple bonds between carbon atoms.
• Isomers are compounds with the same molecular formula but different structures.
• Homologous series is a series of compounds with the same general formula and similar chemical properties.
• Functional groups are atoms or groups of atoms that determine the properties of organic compounds.
• Important functional groups include alcohols, aldehydes, ketones, carboxylic acids, and esters.
• Ethanol (C2H5OH) is an important alcohol used in beverages and industry.
• Ethanoic acid (CH3COOH) is a carboxylic acid commonly known as acetic acid.
• Soaps are sodium or potassium salts of long-chain carboxylic acids.
• Detergents are synthetic cleaning agents.

Life Processes

• Nutrition is the process of obtaining and utilizing food.
• Autotrophic nutrition is the mode of nutrition in which organisms make their own food (e.g., plants).
• Heterotrophic nutrition is the mode of nutrition in which organisms obtain food from other organisms (e.g., animals).
• Respiration is the process of breaking down food to release energy.
• Aerobic respiration uses oxygen to break down glucose completely.
• Anaerobic respiration occurs in the absence of oxygen and produces less energy.
• Transportation is the process of carrying substances to different parts of the body.
• In humans, blood transports oxygen, nutrients, and waste products.
• Excretion is the process of removing waste products from the body.
• In humans, the kidneys filter blood and remove waste in the form of urine.
• Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to produce glucose and oxygen.
• Transpiration is the loss of water vapor from plants.

Control and Coordination

• Nervous system controls and coordinates body activities through electrical and chemical signals.
• Neurons are the basic units of the nervous system.
• Brain is the central processing unit of the nervous system.
• Spinal cord connects the brain to the rest of the body.
• Reflex actions are automatic responses to stimuli.
• Endocrine system controls and coordinates body activities through hormones.
• Hormones are chemical messengers produced by endocrine glands.
• Important endocrine glands include pituitary, thyroid, adrenal, and pancreas.
• Plant hormones (phytohormones) regulate plant growth and development.
• Examples of plant hormones include auxins, gibberellins, cytokinins, abscisic acid, and ethylene.

How do Organisms Reproduce?

• Reproduction is the process by which organisms produce new individuals.
• Asexual reproduction involves a single parent and produces genetically identical offspring.
• Sexual reproduction involves two parents and produces genetically diverse offspring.
• Fission is a type of asexual reproduction in which an organism splits into two or more individuals.
• Fragmentation is a type of asexual reproduction in which an organism breaks into fragments, each of which can develop into a new individual.
• Regeneration is the ability of an organism to regrow lost or damaged body parts.
• Budding is a type of asexual reproduction in which a new organism develops from an outgrowth or bud on the parent organism.
• Vegetative propagation is a type of asexual reproduction in plants in which new plants are produced from stems, roots, or leaves.
• Spore formation is a type of asexual reproduction in which spores develop into new individuals.
• Pollination is the transfer of pollen from the stamen to the pistil of a flower.
• Fertilization is the fusion of male and female gametes to form a zygote.

Heredity and Evolution

• Heredity is the transmission of traits from parents to offspring.
• Genetics is the study of heredity and variation.
• Genes are the units of heredity that determine traits.
• Chromosomes are structures in the nucleus that carry genes.
• DNA (deoxyribonucleic acid) is the genetic material that carries the instructions for building and maintaining an organism.
• Mendel's laws of inheritance describe the patterns of inheritance of traits.
• Evolution is the gradual change in the characteristics of a species over time.
• Natural selection is the process by which organisms with advantageous traits are more likely to survive and reproduce.
• Speciation is the process by which new species arise.
• Fossils are the preserved remains or traces of ancient organisms.

Light – Reflection and Refraction

• Reflection of light is the bouncing back of light when it strikes a surface.
• Laws of reflection state that the angle of incidence is equal to the angle of reflection.
• Refraction of light is the bending of light as it passes from one medium to another.
• Snell's law relates the angles of incidence and refraction to the refractive indices of the two media.
• Lenses are transparent materials that refract light to form images.
• Convex lenses converge light rays.
• Concave lenses diverge light rays.
• Human eye uses a lens to focus light onto the retina.
• Myopia (nearsightedness) is corrected using concave lenses.
• Hyperopia (farsightedness) is corrected using convex lenses.

The Human Eye and the Colourful World

• Human eye is a natural optical instrument that forms an image on the retina.
• Cornea is the transparent front part of the eye that refracts light.
• Iris controls the amount of light entering the eye.
• Pupil is the opening in the iris through which light enters.
• Lens focuses light onto the retina.
• Retina contains photoreceptor cells (rods and cones) that detect light.
• Persistence of vision is the phenomenon that the image formed on the retina remains for a short time even after the removal of the object.
• Dispersion of light is the splitting of white light into its constituent colors.
• Atmospheric refraction is the bending of light by the Earth's atmosphere.
• Scattering of light is the phenomenon by which light is redirected in different directions by particles in the atmosphere.
• Tyndall effect is the scattering scatters light by particles in a colloid or fine suspension.

Electricity

• Electric charge is a fundamental property of matter.
• Electric current is the rate of flow of electric charge.
• Electric potential difference is the work done to move a unit charge from one point to another.
• Ohm's law states that the current through a conductor is directly proportional to the potential difference across it.
• Resistance is the opposition to the flow of electric current.
• Factors affecting resistance include length, area of cross-section, and material of the conductor.
• Series combination of resistors increases the total resistance.
• Parallel combination of resistors decreases the total resistance.
• Electric power is the rate at which electrical energy is consumed or dissipated.
• Heating effect of electric current is the production of heat due to the flow of electric current.

Magnetic Effects of Electric Current

• Magnetic field is the region around a magnet or a current-carrying conductor where magnetic force is experienced.
• Magnetic field lines represent the direction and strength of the magnetic field.
• Right-hand thumb rule gives the direction of the magnetic field around a current-carrying conductor.
• Force on a current-carrying conductor in a magnetic field is given by Fleming's left-hand rule.
• Electric motor converts electrical energy into mechanical energy.
• Electromagnetic induction is the phenomenon of inducing an electric current in a conductor due to a changing magnetic field.
• Electric generator converts mechanical energy into electrical energy.
• Fleming's right-hand rule gives the direction of the induced current.
• Domestic electric circuits use alternating current (AC).

Sources of Energy

• Conventional sources of energy include fossil fuels (coal, petroleum, natural gas).
• Non-conventional sources of energy include solar energy, wind energy, hydro energy, and geothermal energy.
• Fossil fuels are non-renewable resources.
• Solar energy is the energy from the sun.
• Wind energy is the energy from moving air.
• Hydro energy is the energy from flowing water.
• Geothermal energy is the energy from the Earth's interior.
• Nuclear energy is the energy released from nuclear reactions.
• Biomass is organic matter used as a fuel.
• Renewable resources can be replenished naturally.

Our Environment

• Ecosystem is a community of living organisms and their physical environment interacting as a unit.
• Producers are organisms that make their own food (e.g., plants).
• Consumers are organisms that obtain food from other organisms (e.g., animals).
• Decomposers are organisms that break down dead organic matter.
• Food chain is a sequence of organisms through which energy and nutrients pass.
• Food web is a network of interconnected food chains.
• Trophic level is the position of an organism in a food chain or food web.
• Environmental pollution is the contamination of the environment with harmful substances.
• Ozone layer protects the Earth from harmful ultraviolet radiation.
• Greenhouse effect is the warming of the Earth's atmosphere due to the trapping of heat by greenhouse gases.
• Waste management involves reducing, reusing, and recycling waste materials.

Management of Natural Resources

• Natural resources are materials or substances that occur in nature and can be used for economic gain.
• Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.
• Forest and wildlife conservation involves protecting forests and wildlife.
• Water conservation involves using water wisely and preventing water pollution.
• Coal and petroleum conservation involves using these resources efficiently and finding alternative sources of energy.
• Integrated watershed management involves managing land and water resources in a holistic manner.
• People's participation is essential for the successful management of natural resources.