Air Chapter Notes | Science Class 4 ICSE PDF Download

Air

• Matter is anything that has mass and takes up space.
• Matter exists in three states: solids, liquids, and gases.
• Substances are classified as solid, liquid, or gas based on their properties.
• Properties depend on the arrangement of tiny particles in matter.
• In solids, particles are tightly packed, giving them a fixed shape and size.
• Solids vary in nature; some, like stones and diamonds, are hard, while others, like cloth and paper, are soft.

Composition of Air

• Air is a mixture of gases in the Earth's atmosphere.
• Main gases in air are nitrogen and oxygen.
• Nitrogen is the most abundant gas, followed by oxygen.
• Air also contains small amounts of carbon dioxide, argon, and other gases.
• Oxygen is essential for humans and animals to breathe and survive.
• Oxygen is necessary for burning processes.
• Carbon dioxide is used by plants for photosynthesis.
• Water vapour, the gaseous form of water, is present in the atmosphere.
• Water vapour affects weather, leading to clouds, rain, and snow when it condenses.
• Nitrogen in air supports plant growth.
• Air also contains germs, smoke, and dust particles.

Properties of Air

• Air is colourless and odourless.
• Air occupies space, as seen when inflating a balloon, tyre, or football, which changes their shape.
• Air has weight, making an inflated balloon heavier than a deflated one.
• Air expands when heated, as its particles move faster and spread out, taking up more space.
• Air supports burning because of the oxygen it contains.

Process of Breathing

• Breathing is the process of taking in and releasing air, essential for survival.
• All living things require air to live.
• Plants breathe through stomata on the lower surface of their leaves.
• Aquatic animals mostly breathe through gills.
• Insects, like ants, breathe through spiracles.
• Humans breathe through their nose, with inhalation (taking in air) and exhalation (releasing air).

Air Pollution

• Air pollution occurs when smoke and harmful gases from vehicles, factories, and other sources mix with air.
• Pollutants are substances that make air dirty, such as smoke, dust, and harmful gases.
• Germs like bacteria and viruses are also pollutants, reducing air quality.

Causes of Air Pollution

• Air pollution can be caused by natural events or human activities.
• Natural causes include volcanic eruptions, dust storms, and forest fires.
• Human activities are the main cause of air pollution.
• Human causes include burning fuels (wood, coal, petroleum, natural gases), vehicle and factory emissions, bursting crackers, spraying insecticides and pesticides, and burning garbage.
• Pollutants like bacteria and viruses come from spitting, coughing, sneezing, improper garbage disposal, stagnant water, and unhygienic conditions.

Effects of Air Pollution

• Air pollution reduces air quality and harms human health.
• It causes health issues like flu, tuberculosis, asthma, chest pain, headaches, eye irritation, sneezing, and coughing.
• It disrupts nature, causing changes in climatic conditions.

Preventive Measures to Keep Air Clean

• Save electricity by turning off lights and fans when not in use.
• Plant more trees to keep air clean and fresh.
• Use renewable energy sources like wind and solar to reduce fuel burning.
• Use public transport or walk for short distances.
• Use CNG and LPG as vehicle fuels to reduce harmful gas emissions.
• Set up factories and industries away from residential areas.
• Install filters in factory chimneys to trap harmful pollutants.
• Recycle and reuse items like paper, plastic bags, and bottles to reduce pollution.
• Dispose of garbage in landfills instead of burning it.
• Maintain good personal and household hygiene, such as proper waste disposal, keeping surroundings clean, and covering the mouth and nose while sneezing or coughing.