Class 7 Science

Here you can find Class 7 Science Notes. These notes include important revision points, simple explanations of “Curiosity”

Chapter 1. The Ever-Evolving World of Science 

This chapter introduces science as a dynamic and continuously growing way of understanding the world, not just a set of fixed facts. Science develops when humans observe nature, ask questions, and test ideas through experiments. From studying tiny cells to observing the movement of the Earth, Moon, and Sun, science helps us explore both the nearby and distant universe. The chapter emphasizes that curiosity, imagination, and logical thinking are at the heart of scientific learning. It also highlights how different branches of science are interconnected and how science plays an important role in human life, society, and environmental responsibility.

Key Points

• Science is a process of learning based on curiosity, observation, and experimentation.

• Science is ever-evolving, meaning ideas change and improve with new evidence.

• Asking “how”, “why”, and “what if” is central to scientific thinking.

• Learning science goes beyond textbooks and involves real-life experiences and activities.

• Different branches of science are interconnected and support each other.

• Simple observations have led to major developments like flight, time measurement, and understanding natural patterns.

• Science explains changes in materials, growth in living beings, heat, light, and motion.

• Human growth, plant life processes, the water cycle, and celestial movements are all studied in science.

• Science is closely linked to society and helps solve real-world problems.

• Responsible use of science is necessary to protect nature and ensure a sustainable future.

👉 👉Science begins with curiosity and grows through questioning. When used wisely and responsibly, science helps us understand the world better and build a safe, balanced, and sustainable future.

Chapter 2. Exploring Substances: Acidic, Basic, and Neutral 

This chapter explains that substances around us have different chemical natures, which can be identified as acidic, basic, or neutral. It shows how simple observations and experiments help us understand these properties. By using indicators like litmus, flower extracts, turmeric, and even odours, we can test and classify substances. The chapter also explains how acids and bases react with each other in a process called neutralisation, which is useful in many day-to-day situations such as treating ant bites, improving soil quality, and managing industrial waste.

Key Points

• Substances can be classified as acidic, basic, or neutral.

• Acidic substances turn blue litmus red and usually taste sour.

• Basic substances turn red litmus blue and feel slippery to touch.

• Neutral substances do not change the colour of red or blue litmus paper.

• Litmus is a natural indicator obtained from lichens.

• Natural indicators like red rose extract, hibiscus, turmeric, and purple cabbage can also be used.

• Red rose extract turns red in acids and green in bases.

• Turmeric turns red in basic substances but remains yellow in acidic and neutral substances.

• Some substances change their smell in acidic or basic conditions and are called olfactory indicators.

• When an acid reacts with a base, neutralisation occurs, forming salt, water, and heat.

• Neutralisation helps solve real-life problems like ant bites, acidic soil, and polluted water.

👉 👉By carefully observing, testing, and thinking scientifically, we can understand the nature of substances around us. Using this knowledge responsibly helps solve everyday problems and protects both human health and the environment.

Chapter 3. Electricity: Circuits and Their Components 

This chapter introduces electricity as a useful form of energy that helps us operate many devices used in daily life. It explains how electricity flows through a closed circuit and how different components work together to make electrical devices function. By learning about cells, bulbs, switches, and connecting wires, students understand how simple circuits are made. The chapter also highlights the importance of safety while using electricity and encourages careful handling of electrical appliances at home and school.

Key Points

• Electricity is a form of energy that flows through a circuit.

• An electric circuit is a complete path through which electric current flows.

• A cell is the source of electricity in a simple circuit.

• The positive terminal (+) and negative terminal (–) of a cell help current flow.

• A bulb glows when electric current passes through its filament.

• Connecting wires are used to join different components of a circuit.

• A switch controls the flow of current by opening or closing the circuit.

• A closed circuit allows current to flow, while an open circuit stops it.

• Electric symbols are used to draw circuit diagrams clearly and neatly.

• Proper handling of electricity is important to avoid electric shocks and accidents.

👉 👉Electricity makes life easier, but it must be used with care and responsibility. Understanding circuits helps us use electrical devices safely and wisely.

Chapter 4. The World of Metals and Non-metals  

This chapter explains how materials around us can be grouped as metals and non-metals based on their properties and behaviour. It shows how metals like iron, copper, and aluminium are commonly used because they are strong, lustrous, and useful in daily life. The chapter also discusses special properties such as malleability, ductility, sonority, and conductivity. It explains how metals react with air and water, leading to rusting and corrosion, and how this damage can be prevented. The chapter further highlights that non-metals are equally important, as they play a vital role in life processes, agriculture, and health.

Key Points

• Materials are classified into metals and non-metals based on their properties.

• Metals are usually lustrous, hard, and strong.

• Malleability is the property by which metals can be beaten into thin sheets.

• Ductility allows metals to be drawn into wires.

• Sonority is the property that makes metals produce a ringing sound.

• Metals are good conductors of heat and electricity.

• Non-metals are generally dull, brittle, and poor conductors.

• Rusting occurs when iron reacts with moist air (air + water).

• Corrosion is the gradual damage of metals due to air and water.

• Rusting can be prevented by painting, oiling, greasing, and galvanisation.

• Metals form basic oxides, while non-metals form acidic oxides.

• Non-metals like oxygen, nitrogen, carbon, chlorine, and iodine are essential for life.

👉 👉Both metals and non-metals are essential for life and development. By understanding their properties and using them wisely and responsibly, we can reduce waste, protect resources, and support sustainable living.

Chapter 5. Changes Around Us – Physical and Chemical  

This chapter explains that changes are constantly happening around us in our daily life and in nature. Some changes affect only the shape, size, or state of a substance, while others lead to the formation of new substances. Based on this, changes are classified as physical changes and chemical changes. The chapter helps us understand how to identify different types of changes using simple examples like melting, burning, rusting, and cooking. It also explains concepts such as reversible and irreversible changes, combustion, and ignition temperature, showing how changes can be useful or harmful depending on the situation.

Key Points

• Changes are classified into physical and chemical changes.

• A physical change involves a change in shape, size, or state without forming a new substance.

• Physical changes are usually reversible.

• A chemical change results in the formation of one or more new substances.

• Chemical changes are generally irreversible.

• Rusting, burning, curdling of milk, and cooking food are chemical changes.

• Combustion is a chemical change in which a substance reacts with oxygen to produce heat and light.

• Substances that burn easily are called combustible substances.

• Ignition temperature is the minimum temperature required for a substance to catch fire.

• Some processes, like burning of a candle, involve both physical and chemical changes.

• Changes can be desirable (useful) or undesirable (harmful).

• Natural processes such as weathering and erosion bring slow changes on the Earth’s surface.

👉 👉Changes are a natural part of life. By understanding different types of changes and their effects, we can make better choices, use resources wisely, and reduce harmful impacts on the environment.

Chapter 6. Adolescence – A Stage of Growth and Change  

This chapter explains adolescence as a special stage of life between childhood and adulthood, usually occurring between the ages of 10 and 19 years. During this period, the body undergoes many physical, emotional, and behavioural changes as it prepares for adulthood. The chapter describes visible changes such as increase in height, change in voice, development of body hair, and skin changes, along with internal changes related to reproductive maturity. It also highlights the importance of understanding emotions, maintaining good health habits, following personal hygiene, eating a balanced diet, staying physically active, and making responsible choices to make adolescence a healthy and positive experience.

Key Points

• Adolescence is the stage of development between childhood and adulthood.

• It usually begins around 10 years of age and continues up to 19 years.

• Rapid increase in height is one of the most noticeable changes during adolescence.

• Boys and girls experience changes in body structure, weight, and strength.

• Change in voice occurs due to growth of the voice box; it is more noticeable in boys.

• Pimples (acne) may appear due to increased activity of oil glands in the skin.

• Growth of hair in armpits and pubic region occurs in both boys and girls.

• Features like facial hair in boys and development of breasts in girls are called secondary sexual characteristics.

• Puberty marks the beginning of changes that make the body capable of reproduction.

• In girls, the start of the menstrual cycle indicates reproductive maturity.

• Adolescence is also marked by emotional and behavioural changes, such as mood swings and increased sensitivity.

• Proper nutrition, personal hygiene, physical activity, and balanced social behaviour are important during adolescence.

• Harmful substances like tobacco, alcohol, and drugs should be strictly avoided.

• Changes during adolescence are controlled by hormones produced in the body.

👉 👉Adolescence is a natural and important stage of life. By understanding the changes that occur, maintaining healthy habits, and making responsible decisions, adolescents can grow into confident, healthy, and responsible adults.

Chapter 7. Heat Transfer in Nature   

This chapter explains how heat moves from one place to another and how it affects our surroundings. It introduces the three main modes of heat transfer—conduction, convection, and radiation—and explains them using simple daily-life examples. The chapter shows why metals are used for cooking, why warm air rises, and how wind patterns like land breeze and sea breeze are formed. It also explains how the Sun’s heat drives natural processes such as the water cycle, evaporation, condensation, and rainfall. The chapter helps us understand the role of heat in weather, climate, house design, clothing choices, and water conservation.

Key Points

• Heat is a form of energy that flows from a hotter object to a colder one.

• Conduction is the transfer of heat through solids without movement of particles.

• Metals are good conductors of heat, while wood, plastic, air, and clay are poor conductors (insulators).

• Convection is heat transfer through the actual movement of particles in liquids and gases.

• Hot air and hot liquids become lighter and rise, while cooler ones sink.

• Smoke rising, boiling water, and wind movement are examples of convection.

• Land breeze blows from land to sea at night due to faster cooling of land.

• Sea breeze blows from sea to land during the day due to faster heating of land.

• Radiation is the transfer of heat without any medium.

• Heat from the Sun reaches the Earth through radiation.

• Light-coloured clothes reflect heat, while dark-coloured clothes absorb heat.

• Heat transfer processes work together in many situations, like heating water in a pan.

• Heat from the Sun causes evaporation, which plays a major role in the water cycle.

• The water cycle involves evaporation, condensation, precipitation, and infiltration.

• Infiltration allows water to seep underground and form groundwater stored in aquifers.

• Heat transfer knowledge helps in designing houses, clothing, and water conservation systems.

👉 👉Heat plays a vital role in nature and daily life. By understanding how heat is transferred, we can make better choices in clothing, housing, and resource use, and learn to live more comfortably and sustainably with nature.

Chapter 8. Measurement of Time and Motion  

This chapter explains how time and motion are measured to understand events and movement around us. It describes how early humans observed natural events like sunrise, sunset, and phases of the Moon to measure time. The chapter introduces modern devices such as clocks and watches for accurate time measurement. It also explains motion as the change in position of an object with time and describes different types of motion using simple examples from daily life. The importance of uniform and non-uniform motion and the need for standard units of measurement are also highlighted.

Key Points

• Time helps us measure the duration of events.

• Early methods of measuring time were based on natural events.

• Clocks and watches are used today for accurate measurement of time.

• Second is the standard unit of time.

• Motion occurs when an object changes its position with time.

• Objects at rest do not change their position.

• Uniform motion means an object covers equal distances in equal intervals of time.

• Non-uniform motion means unequal distances are covered in equal time intervals.

• Motion can be observed along a straight path, circular path, or back-and-forth path.

• Examples of motion include a moving car, swinging pendulum, and rotating fan.

• Measurement allows comparison of speed and movement of different objects.

• Accurate measurement helps in planning activities and understanding natural processes.

👉 👉Measurement of time and motion helps us understand and organise our daily activities. Accurate observation and measurement make science reliable and useful in real life.

Chapter 9. Life Processes in Animals   

This chapter explains the life processes that help animals survive and function properly. It mainly focuses on nutrition and respiration in animals, especially humans. Animals obtain energy from food, which must be broken down into simpler substances through digestion. The chapter describes the structure and working of the human digestive system, including the role of organs like the mouth, stomach, small intestine, liver, and pancreas. It also explains how different animals digest food in different ways based on their eating habits. The chapter further discusses breathing and respiration, showing how oxygen is used to release energy from food and how animals have adapted different breathing organs to suit their habitats.

Key Points

• Life processes are activities essential for survival, such as nutrition and respiration.

• Nutrition provides energy needed for growth, repair, and daily activities.

• Digestion breaks down complex food into simpler substances that the body can use.

• The alimentary canal is a long tube from mouth to anus where digestion takes place.

• Saliva begins digestion by breaking down starch into sugar.

• The oesophagus pushes food to the stomach by wave-like movements.

• The stomach churns food and uses acid and digestive juices to digest proteins.

• The small intestine completes digestion and absorbs nutrients into the blood.

• Liver secretes bile to help digest fats and neutralise acids.

• Pancreas releases juices that digest carbohydrates, proteins, and fats.

• The large intestine absorbs water and forms waste called stool.

• Ruminants like cows chew food twice through a process called rumination.

• Breathing involves inhalation and exhalation of air.

• Respiration is the process of releasing energy from food using oxygen.

• Alveoli in lungs help in exchange of oxygen and carbon dioxide.

• Different animals breathe using lungs, gills, skin, or a combination of these.

• Breathing is a physical process, while respiration is a chemical process.

👉 👉Life processes work together to keep animals alive and healthy. By understanding how our body functions and respecting healthy habits, we can protect our health and appreciate the diversity of life around us.

Chapter 10. Life Processes in Plants  

This chapter explains how plants perform essential life processes to grow, survive, and reproduce. It focuses on nutrition, photosynthesis, respiration, and transport of substances in plants. The chapter describes how green plants prepare their own food using sunlight, carbon dioxide, water, and chlorophyll. It also explains how plants respire day and night to release energy and how water, minerals, and food are transported within the plant body. The role of different plant parts such as roots, stems, and leaves is highlighted to show how plants function as living organisms.

Key Points

• Plants are autotrophs, meaning they make their own food.

• Photosynthesis is the process by which plants prepare food using sunlight.

• Chlorophyll is the green pigment that traps sunlight for photosynthesis.

• Carbon dioxide enters leaves through tiny pores called stomata.

• Water and minerals are absorbed from the soil by roots.

• The food prepared by plants is mainly glucose, which is stored as starch.

• Oxygen is released as a by-product during photosynthesis.

• Respiration in plants releases energy from food.

• Plants respire all the time, both day and night.

• Gaseous exchange in plants occurs through stomata and lenticels.

• Xylem transports water and minerals from roots to other parts of the plant.

• Phloem transports prepared food to all parts of the plant.

• Transpiration is the loss of water as water vapour from leaves.

• Transpiration helps in cooling the plant and upward movement of water.

• Each life process is essential for the growth and survival of plants.

👉 👉Plants are living organisms that quietly support all life on Earth. By understanding their life processes, we learn to value plants and protect them, ensuring a healthy and balanced environment.

Chapter 11. Light – Shadows and Reflections 

This chapter explains light as an important form of energy that helps us see objects around us. It introduces sources of light and distinguishes between luminous and non-luminous objects. The chapter explains that light travels in a straight line, which leads to the formation of shadows when objects block its path. It also discusses how light behaves when it falls on transparent, translucent, and opaque materials. Further, the chapter explains reflection of light by mirrors, characteristics of images formed by a plane mirror, and the concept of lateral inversion. It also introduces simple devices like the pinhole camera, periscope, and kaleidoscope, showing practical applications of light in daily life.

Key Points

• Objects that give out their own light are called luminous objects.

• Objects that do not emit light but reflect it are non-luminous objects.

• The Sun is the main natural source of light on Earth.

• Light always travels in a straight line.

• Transparent materials allow light to pass completely through them.

• Translucent materials allow light to pass partially.

• Opaque materials do not allow light to pass through.

• A shadow is formed when an opaque object blocks the path of light.

• Shadows require a light source, an opaque object, and a screen.

• The size and shape of a shadow depend on the position of the object, light source, and screen.

• Reflection is the change in direction of light when it strikes a shiny surface or mirror.

• A plane mirror forms an image that is erect, same size, and laterally inverted.

• Images formed by plane mirrors cannot be obtained on a screen.

• Lateral inversion means left appears right and right appears left in a mirror image.

• A pinhole camera forms an inverted image on a screen.

• A periscope helps us see objects not directly visible using reflection.

• A kaleidoscope creates beautiful patterns due to multiple reflections.

👉 👉Light helps us understand and explore the world around us. By learning how light behaves and applying this knowledge wisely, we can create useful tools, appreciate natural phenomena, and use technology responsibly.

Chapter 12. Earth, Moon, and the Sun  

This chapter explains the movements of the Earth, Moon, and Sun and how these motions affect life on Earth. It describes the rotation of the Earth, which causes day and night, and the revolution of the Earth around the Sun, which leads to changes in seasons and variation in the night sky during the year. The chapter also explains solar and lunar eclipses, showing how shadows are formed when the Sun, Earth, and Moon come in a straight line. Overall, the chapter helps us understand how celestial motions influence time, seasons, and natural events on Earth. 

Key Points

• The Earth rotates on its axis in about 24 hours.

• Rotation of the Earth from West to East causes day and night.

• The Sun appears to rise in the East and set in the West due to Earth’s rotation.

• The Earth revolves around the Sun in about 365 days and 6 hours.

• The path of revolution is called an orbit.

• The tilt of the Earth’s axis and its spherical shape cause seasons.

• Summer occurs when a hemisphere is tilted towards the Sun and receives longer sunlight.

• Winter occurs when a hemisphere is tilted away from the Sun.

• Equinox is when day and night are nearly equal.

• Solstice marks the longest and shortest days of the year.

• A solar eclipse occurs when the Moon comes between the Sun and Earth.

• A lunar eclipse occurs when the Earth comes between the Sun and Moon.

• Solar eclipses must never be viewed directly with naked eyes. 

👉 👉The movements of the Earth, Moon, and Sun follow a perfect natural balance that controls time, seasons, and life on Earth. Understanding these motions helps us appreciate the order of nature, encourages scientific thinking, and removes fear and myths related to natural events like eclipses.