1. Chemical Reactions and Equations

A chemical reaction is a process in which one or more substances are converted into new substances with new properties. In a chemical equation, the substances that react are called reactants and the substances formed are called products. The equation must be balanced because atoms are conserved during a reaction. Common signs of a chemical reaction are change in colour, change in temperature, evolution of gas, and formation of precipitate.

Students must understand the main types of reactions: combination, decomposition, displacement, and double displacement. Oxidation and reduction are especially important because they are connected with corrosion, respiration, burning, and food spoilage. Daily-life examples such as rusting of iron and rancidity of food make this chapter highly practical and board-relevant.

Quick Revision Points

• Balanced equation follows the law of conservation of mass.
• Combination reaction forms one product from two or more reactants.
• Decomposition reaction breaks one compound into simpler substances.
• Oxidation means addition of oxygen or removal of hydrogen.
• Reduction means removal of oxygen or addition of hydrogen.
• Corrosion slowly damages metals like iron.
• Rancidity affects oils and fats due to oxidation.

PYQ-style Questions

1. Why do we balance a chemical equation? Explain with one example.
2. Differentiate between oxidation and reduction.
3. What is corrosion? How can it be prevented?
4. What is rancidity? State one method to reduce it.

Practice Questions

1. Classify reaction types with suitable examples.
2. Balance: Fe + H₂O → Fe₃O₄ + H₂
3. Why is respiration an exothermic reaction?

2. Acids, Bases and Salts

Acids produce hydrogen ions in aqueous solution and bases produce hydroxide ions in aqueous solution. Indicators such as litmus, phenolphthalein, and methyl orange help identify acidic and basic substances. The pH scale measures how acidic or basic a solution is. A pH below 7 is acidic, 7 is neutral, and above 7 is basic.

This chapter also explains neutralisation and the role of pH in everyday life. Students should remember the uses of baking soda, washing soda, and bleaching powder. This chapter is highly scoring because it combines concept clarity with daily-life examples such as antacids, tooth decay, soil treatment, and self-defence by stinging insects.

Quick Revision Points

• Acids turn blue litmus red.
• Bases turn red litmus blue.
• Acid + base gives salt + water.
• Acid + metal carbonate gives salt + water + carbon dioxide.
• pH is important in agriculture, digestion, and medicine.

PYQ-style Questions

1. What is pH? Why is it important in everyday life?
2. Why do acids show acidic behaviour only in aqueous solution?
3. Name two products obtained from common salt and write one use of each.

Practice Questions

1. Differentiate between strong acid and concentrated acid.
2. Why is baking soda used in antacids?
3. Why are sour substances not stored in metallic vessels like copper?

3. Life Processes

Life processes are the basic functions necessary to keep an organism alive. In Class 10, the major life processes are nutrition, respiration, transportation, and excretion. Plants prepare food by photosynthesis, while animals depend on external food sources. Humans perform holozoic nutrition involving ingestion, digestion, absorption, assimilation, and egestion.

Respiration releases energy from food. Transportation in humans is carried out by blood and heart, while plants use xylem and phloem. Excretion removes waste products from the body, and kidneys play a central role in this process. This chapter is one of the most important biology chapters for boards because it contains many diagram-based and explanation-based questions.

Quick Revision Points

• Photosynthesis occurs in the presence of chlorophyll and sunlight.
• Alveoli provide large surface area for gas exchange.
• Heart ensures circulation of blood to all body parts.
• Xylem transports water; phloem transports food.
• Kidney filters blood and forms urine.

PYQ-style Questions

1. What is photosynthesis? Write its equation.
2. Explain the role of alveoli in respiration.
3. Differentiate between xylem and phloem.
4. What is a nephron? State its function.

Practice Questions

1. Why is transport necessary in multicellular organisms?
2. Explain double circulation briefly.
3. How do plants remove waste products?

4. Light – Reflection and Refraction

Reflection is the bouncing back of light from a surface and refraction is the bending of light when it passes from one medium to another. This chapter includes spherical mirrors, lenses, image formation, mirror formula, lens formula, and magnification. It is one of the highest-scoring physics chapters if students practise ray diagrams properly.

Concave mirrors can form real and virtual images depending on object position. Convex mirrors always form virtual and diminished images. Convex mirrors are used as rear-view mirrors because they provide a wider field of view.

Quick Revision Points

• Mirror formula: 1/f = 1/v + 1/u
• Magnification for mirror: m = -v/u
• Power of lens: P = 1/f
• Convex mirror forms virtual, erect, diminished image.
• Refraction occurs due to change in speed of light.

PYQ-style Questions

1. Why is convex mirror used as rear-view mirror?
2. State the laws of reflection.
3. Define principal focus of a concave mirror.

Practice Questions

1. Draw ray diagrams for image formation by convex lens.
2. Why does a pencil appear bent in water?
3. Differentiate between real and virtual image.

5. Electricity

Electricity deals with electric current, potential difference, resistance, Ohm’s law, resistors in series and parallel, heating effect of current, and electric power. Students must focus on formula application and circuit understanding.

Series circuits increase resistance and parallel circuits reduce effective resistance. Domestic circuits are connected in parallel so that each appliance gets proper voltage and works independently.

Quick Revision Points

• Current: I = Q/t
• Ohm’s law: V = IR
• Power: P = VI
• Series resistance: R = R₁ + R₂ + R₃
• Parallel combination lowers effective resistance.

PYQ-style Questions

1. State Ohm’s law with graph.
2. Why are household circuits connected in parallel?
3. Define electric power and write its SI unit.

Practice Questions

1. Find equivalent resistance of resistors in series and parallel.
2. Why is fuse wire made of low melting point material?
3. Calculate power for 220 V and 2 A.

6. Metals and Non-Metals

Metals are generally lustrous, malleable, ductile, sonorous, and good conductors of heat and electricity. Non-metals usually do not show these properties. However, there are some exceptions. For example, graphite is a non-metal but conducts electricity. Sodium and potassium are soft metals and can be cut with a knife.

Metals react with oxygen, water, and acids in different ways depending on their reactivity. The reactivity series helps compare the reactivity of metals. More reactive metals displace less reactive metals from their compounds. Ionic compounds formed by metals and non-metals have high melting and boiling points and conduct electricity in molten or aqueous state.

PYQ-style Questions

1. Differentiate between metals and non-metals.
2. What is the reactivity series? Why is it useful?
3. Why do ionic compounds have high melting points?

Practice Questions

1. Why is sodium stored in kerosene?
2. What happens when zinc reacts with dilute hydrochloric acid?
3. Why is aluminium used for making utensils despite being reactive?

7. Carbon and Its Compounds

Carbon is unique because it forms a very large number of compounds. This is due to catenation and tetravalency. Carbon compounds are mainly covalent, so they generally have lower melting and boiling points compared to ionic compounds. Important categories include saturated hydrocarbons, unsaturated hydrocarbons, alcohols, and carboxylic acids.

Ethanol and ethanoic acid are important compounds in this chapter. The chapter also covers soaps and detergents, and students should understand how soap cleans by forming micelles. This chapter is frequently asked in board exams through structure-based, reasoning-based, and use-based questions.

Quick Revision Points

• Carbon is tetravalent and shows catenation.
• Saturated hydrocarbons have single bonds.
• Unsaturated hydrocarbons have double or triple bonds.
• Ethanol is an alcohol; ethanoic acid is an acid.
• Soap molecules form micelles to trap oily dirt.

PYQ-style Questions

1. Why does carbon form a large number of compounds?
2. Differentiate between saturated and unsaturated hydrocarbons.
3. What is a micelle? How does soap clean clothes?

Practice Questions

1. Write two properties of covalent compounds.
2. Why does ethanol have a lower boiling point than ionic compounds?
3. What happens when ethanoic acid reacts with baking soda?

8. Control and Coordination

Living organisms respond to changes in their surroundings. In animals, control and coordination are carried out by the nervous system and endocrine system. The brain, spinal cord, and nerves form the nervous system. Hormones are chemical messengers secreted by endocrine glands.

Plants also show coordination, but through chemical means and movement responses like phototropism, geotropism, and hydrotropism. Reflex actions are rapid automatic responses that do not involve conscious thinking. This chapter is very important because it combines biology concepts, diagrams, and daily-life applications.

Quick Revision Points

• Neuron is the structural and functional unit of nervous system.
• Reflex action is quick and automatic.
• Hormones regulate body growth, development, and metabolism.
• Plants show tropic movements in response to stimuli.

PYQ-style Questions

1. What is reflex action? Give one example.
2. Differentiate between nervous control and hormonal control.
3. What is phototropism? Explain with one example.

Practice Questions

1. Draw a labelled diagram of a neuron.
2. Name the main endocrine glands in humans.
3. How do plants coordinate without a nervous system?