Chemical reaction and equation

Class 10th Science
Notes on Chemical Reactions and Equations

1.  Chemical reactions- The transformation of chemical substance into a new chemical substance by making and breaking of bonds between different atoms is known as Chemical Reaction.

2.  Signs of a chemical reaction- These factors denote that a chemical reaction has taken place- change of state of substance, change of color of substance, evolution of heat, absorption of heat, evolution of gas and evolution of light.

3.  Chemical Equation: The representation of chemical reaction by means of symbols of substances in the form of formulae is called chemical equation. E.g. - H2 + O2 ⇒ H2O

4.  Balanced Chemical Equation: A balanced chemical equation has number atoms of each element equal on both left and right sides of the reaction.

      *Note- According to Law of Conservation of Mass, mass can neither be created nor destroyed in a chemical reaction. To obey this law, the total mass of elements present in reactants must be equal to the total mass of elements present in products.

5.  Types of Chemical Reactions-

                      I.  Combination- When two elements or one element and one compound or two compounds combines to give one single product.

                     II.  Decomposition- Splitting of a compound into two or more simple products.

                    III.  Displacement- It takes place when a more reactive metal displaces a less reactive metal.

                    IV.  Double displacement- Reactions in which ions are exchanged between two reactants forming new compounds are called double displacement reactions.

                     V.  Precipitation- The insoluble compound called precipitate forms in this reaction.

                    VI.  Exothermic- Reactions which produce energy are called exothermic reaction. Most of the decomposition reactions are exothermic.

                   VII.  Endothermic- Reactions which absorb energy are called endothermic reaction. Most of the combination reactions are endothermic.

                  VIII.  Oxidation: Gain of oxygen or removal of hydrogen or metallic element from a compound is known as oxidation.

                     IX.  Reduction: Addition of hydrogen or removal of oxygen from a compound is called reduction.

                       X.  Redox- A chemical reactions where oxidation and reduction both take place simultaneously are also known as redox reaction.

                             Eg - NaOH + HCl ⇒ NaCl + H2O

6.  Rusting- When iron reacts with oxygen and moisture forms a red substance called rust.

7.  Rancidity- Oils and fats when get oxidized on exposure to air show a change in taste and smell.

8.  Corrosion- Metals when attacked by oxygen, water, acids, gases, present in air changes its surface which is called corrosion.

Carbon and it's compound

Class X Science
Notes for Carbon and its C ompounds

Acid, Bases and Salt

SYLLABUS

Their definitions in term of furnishing of H+ and OH- ions, General properties, examples and uses, Concept of pH scale (Definition relating to logarithm not required), Importance of pH in everyday life; Preparation and uses of Sodium hydroxide, Bleaching powder, Washing soda and Plaster of Paris.

Facts that Matter

Acids : Acids are sour in taste, turn blue litmus to red, dissolve in water to release H+ ions.

E.g., vinegar, hydrochloric acid and sulphuric acid.

            •   Reaction with Metal

Acid + Metal → Salt + Hydrogen gas

e.g., 2HCl + Zn → ZnCl2 + H2

            •   Reaction with Metal carbonate

Acid + Metal carbonate → Salt + CO2 + H2O

e.g., 2HCl + Na2CO3 → 2NaCl + CO2 + H2O

            •   Reaction with Metal hydrogen carbonate

Acid + Metal hydrogen carbonate Salt + CO2 + H2O

e.g. HCl + NaHCO3 → NaCl + H2O + CO2

            •   Reaction with Metallic oxide

Acid + Metal oxide → Salt + Water

e.g. 2HCl + CuO → CuCl2 + H2O

            •   Acids in water:

Acids produce H+ ions when dissolved in water. H+ ions cannot exist alone. They combine with water molecule (H2O) to form H3O+ (hydronium ions). It conducts electricity.

            •   Decrease in H30+ ions concentration per unit volume results in formation of dilute acids.

            •   It is a highly exothermic reaction.

Acids when dissolved in water release large amount of heat. If water is added to concentrated acid then the heat generated may cause the mixture to splash out and cause bums. Hence to avoid burns acid must be added drop wise into water with constant stirring. So that the heat generated spreads over in water.

strong acids → release more H+ ions → HCl

weak acids → releases less number of H+ ions → acetic acid

strong base → give more OH– ions → NaOH

weak base → gives less OH– ions → CH3COOH

Bases: Bases are bitter in taste, turns red litmus to blue and when dissolved in water releases OH– ions;

e.g., NaOH and KOH.

            •   Reaction with metal

            Base + Metal → Salt + H2 gas

e.g., 2NaOH + Zn → Na2ZnO2 + H2

This reaction is possible only with reactive metals like sodium and potassium.

            •   Reaction with non-metallic oxide

            Base + Non-metallic oxide → Salt + H2O

Bases in water → Bases produce OH– ions when dissolved in water. Bases soluble in water are called alkalis. It conducts electricity.

            •   Decrease in OH– ions single concentration per unit volume results in formation of dilute bases.

            •   It is a exothermic reaction.

To make basic solution, base must be added drop wise into water with constant stirring, so that the heat generated spreads over in water.

Indicators: Indicators are those substances which tell us whether a substance is acidic or basic by change in colour. For e.g., litmus solution.

            •   Olfactory indicators: Those substances whose odour changes in acidic or basic media are called lfactory indicators. For e.g., clove, vanilla, onion.

            •   Natural indicators: Turmeric, litmus (obtained from lichen)

            •   Synthetic indicators: Methyl orange, phenolphthalein.

Indicator	Acids	Bases
1. Red litmus	remains red	turns blue
2. Blue litmus	turns red	remains blue
3. Phenolphthalein	colourless	pink
4. Methyl orange	red	yellow

Life processes

Life processes

    •   Constantly exhibit the functions of maintenance and repair in living organisms

    •   Some Examples- Digestion, Respiration, Circulation etc.

Nutrition

    •   Process of obtaining nutrients from the environment i.e. intake of food and then its digestion in the body.

    •   Two types – Autotrophic (self-sufficient for food) and Heterotrophic (dependent on others for food).

Autotrophic nutrition

    •   Synthesis of food by photosynthesis- ‘photo’ means light and ‘synthesis’ means production. It is the production of food with the help of sunlight.

    •   Photosynthesis equation-

          6CO2+6H2O give C6H12O6+6O2

    •   Events of photosynthesis are as follows: Absorption of light energy chlorophyll which is the green pigment and gives energy for activation of reaction. Then the splitting of water into its constituent’s hydrogen and oxygen leading to the Synthesis of ATP and NADPH2 and finally reduction of CO2 to carbohydrates.

Heterotrophic nutrition

    •   Generally take up energy from plants and animals by using them as food.

    •   Mostly of three types—holozoic, parasitic, and saprophytic.

    •   Digestion- mechanical and chemical reduction of ingested nutrients which can be then converted to energy for use.

    •   Human digestive system- consists of the long alimentary canal that includes mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus.

    •   Organs for assistance- pancreas, liver

Nutrition in humans:

    •   Saliva is secreted by salivary glands located under the tongue which contains digestive enzymes like salivary amylase, which break down starch into sugar. So, digestion of carbohydrates starts in the mouth itself.

    •    Tongue helps in chewing, moistening, rolling and swallowing of food.

    •   The food from mouth then goes down the oesophagus, which is the food pipe to the stomach, through the movement of walls of oesophagus (peristalsis)

    •   Stomach mixes the food hence received with various digestive juices.

    •   Inner lining of stomach secretes:

                •   Mucus – protects the lining of stomach from being corroded by the acid.

                •   Hydrochloric acid – creates an acidic medium and dissolves bits of food.

                •   Digestive juices – break down protein into simpler substances.

The food from stomach eventually moves into the small intestine.

            •   Digestion in small intestine: It is the longest part (about 7.5 m long) of alimentary canal. It is the site where complete digestion of carbohydrates, proteins, and fats takes place. It gets intestinal juices from two different glands – liver and pancreas that help in the further digestion of food.

   Liver is the largest gland of the body and secretes bile juice. Bile juice is stored in the gall bladder and has a significant role in the digestion of fats.

   Pancreas has enzymes that help in total digestion of all food components.

    •   The digestive tract and associated glands together constitute the digestive system.

Respiration

    •   It is controlled by enzymes and energy is released from the breakdown of organic substances. It is of two types that are aerobic and anaerobic

Aerobic respiration

    •   Oxidation of food materials by oxygen

    •   Produces 36 ATP

    •   The steps followed in cellular respiration

First step is breakdown of glucose (6C) into pyruvates (3C) in the cytoplasm

Second step- Pyruvate is then broken down to CO2 and water and it takes place in the mitochondria where energy is produced in ATP form.

Anaerobic respiration

    •   It is the Oxidation of nutrients without using up the molecular oxygen

    •   It gives 2 ATPs.

    •   First step- glycolysis in cytoplasm, 2 pyruvate produced

    •   Second step is the break down of pyruvic acid into ethanol and water and energy (in yeast) and lactic acid and energy (in muscle cells)

Human respiration

    •   It consists of the nose, pharynx, trachea, bronchi, bronchioles and alveoli

    •   Bronchioles then divide into many alveoli which are sites of gaseous exchange.

    •   O2 present in alveolar blood vessels is then transported to various cells of the body.

Hemoglobin pigment present in blood is majorly responsible for transportation of carbon dioxide and oxygen.

Transportation

First and foremost things, a liquid medium is required always for transportation.

Transportation in humans

    •   Double circulation occurs in human beings i.e. the blood goes through the heart twice during each cardiac cycle.

    •    Blood and lymph are both involved in transportation

    •   Components of blood are RBCs, WBCs, platelets, and plasma.

    •   Three types of blood vessels are arteries, veins and capillaries.

    •   Arteries carry oxygenated blood in them, except one that is pulmonary artery

    •   Veins carry deoxygenated blood in them, except pulmonary vein

The Human heart is divided into four chambers – right auricle, right ventricle, left auricle, and left ventricle

    •   The Right side of the heart gets deoxygenated blood from different cells of the body

    •   The Left side of the heart receives oxygenated blood from lungs.

Transportation in plants

    •   Transportation of water is through xylem tissues

    •   Transport of water occurs due to transpiration pull, root pressure and difference in pressure gradient.

    •   Transport of food or translocation takes place through phloem and it requires energy.

Excretion

It involves the removal of harmful metabolic wastes from the body of organisms by various processes.

Excretion in humans

The excretory system consists of- a pair of kidneys, a pair of ureters, a urinary bladder, and a urethra.

    •    Nitrogenous wastes such as urea and uric acid are removed

    •   Nephron- basic filtration unit

    •    Main components of the nephron - glomerulus, Bowman’s capsule, renal tube

    •   The process of Removing of nitrogenous wastes through artificial kidney is called dialysis.

Our Environment

1.  Biodegradable substances can be further broken down by the action of bacteria e.g. � paper, vegetables, clothes etc. On the other hand the substances which can not be further broken down by the action of bacteria are non- biodegradable substances e.g. � plastics, glass etc.

2.  All biotic and abiotic components form the ecosystem. The biotic components are all living organisms. The non-biotic components are physical factors like air, water, soil, wind etc.

3.  The food chain consists of producers, consumers and decomposers. Green plants and algae that make food by photosynthesis are producers. Organisms that depend upon producers for their food, directly or indirectly are called consumers. And microorganisms like bacteria and fungi that break down the complex organic substances in dead plant and animal into simple inorganic substances are called decomposers.

4.  The series of organisms that take part in transferring food energy from producers to consumers to decomposers is called a food chain. Food chain link with each other to form food web.

5.  Every step of food chain is called a trophic level. There are four trophic levels

       I. I trophic level � producers/autotrophs

       II. II trophic level � primary consumers/herbivores

       III. III trophic level � secondary consumers/small carnivores

       IV. IV trophic level � tertiary consumers/large carnivores

6.  Green plants convert 1% of solar energy into food energy. The flow of energy is unidirectional.

7.  Ozone is present at a very high level in the atmosphere. It blocks the UV radiation of sun. Ozone is a product of UV radiation.

8.  At high level in the atmosphere the UV rays split the oxygen molecules to form oxygen atoms. These combine with oxygen molecules to form ozone. Ozone causes skin cancer, cataract and reduces crop production.

Management of Nature Resources

How do Organisms Reproduce

Asexual Reproduction in Plants

•   Spore formation → eg. Bacteria, fungi

•   Budding → eg. Fungi (yeast)

•   Fragmentation → eg. Algae, fungi

•   Vegetative propagation

(a)   Natural method

•   By roots → eg. Sweet potato

•   By stems → eg. Ginger, potato

•   By leaves → eg. Bryophyllum

(b)   Artificial method

•   Cutting → eg. Rose

•   Layering → eg. Strawberry, lemon

•   Grafting → eg. Mango, rose.

•   Micropropagation → eg. Orchids, dahlia

Sexual Reproduction in Plants

•   Flower is the reproductive organ.

•   It has four whorls – Calyx, Corolla, Androecium, Gynoecuim.

•   Calyx and corolla are accessory parts.

•   Androecium - Male reproductive organ producing pollen grains.

•   Gynoecium - Female reproductive organ having ovule (egg).

•   Pollination – Transfer of pollens from anther to stigma for fertilization.

•   Fertilization – Fusion of male and female gametes.

•   Double fertilization (Triple fusion and syngamy) – unique events in the embryo sac of ovules.

Asexual Reproduction in Animals

•   Fission

(a) Binary fission → eg. Amoeba

(b) Multiple fission → eg. Plasmodium

•   Budding → eg. Hydra

•   Regeneration → eg. Planaria, Hydra

Sexual Reproduction (Human)

•   Human being is heterosexual.

•   Reproductive system includes:

(a) Primary sex organs: Testes (males) and ovaries (females)

(b) Secondary sex organs: Genital ducts and glands (males) and fallopian tubes, uterus, vagina (females)

•   Male sex hormone is testosterone and female sex hormones are progesterone and estrogen.

•   Puberty is attained at the age of 13 – 14 years in males and 10 – 12 years in females.

•   The zygote formed after fertilization develops into embryo which gets implanted in uterus.

•   Placenta (a disc-like special tissue) develops between uterine wall and embryo for nourishment of the embryo.

•   Gestation period in humans is 280 days.

Reproductive Health

•   Birth control prevents unwanted pregnancies.

(a) Barrier methods

(b) Chemical methods

(c) Intrauterine contraceptive device

(d) Surgical method

•   Sexually transmitted diseases (STD) are caused by bacteria, protozoa and viruses.

•   AIDS is an incurable viral disease.

Heredity and Evolution

Notes for Chapter 2 Acids, Bases and Salt

SYLLABUS

Their definitions in term of furnishing of H+ and OH- ions, General properties, examples and uses, Concept of pH scale (Definition relating to logarithm not required), Importance of pH in everyday life; Preparation and uses of Sodium hydroxide, Bleaching powder, Washing soda and Plaster of Paris.

Facts that Matter

Acids : Acids are sour in taste, turn blue litmus to red, dissolve in water to release H+ ions.

E.g., vinegar, hydrochloric acid and sulphuric acid.

            •   Reaction with Metal

Acid + Metal → Salt + Hydrogen gas

e.g., 2HCl + Zn → ZnCl2 + H2

            •   Reaction with Metal carbonate

Acid + Metal carbonate → Salt + CO2 + H2O

e.g., 2HCl + Na2CO3 → 2NaCl + CO2 + H2O

            •   Reaction with Metal hydrogen carbonate

Acid + Metal hydrogen carbonate Salt + CO2 + H2O

e.g. HCl + NaHCO3 → NaCl + H2O + CO2

            •   Reaction with Metallic oxide

Acid + Metal oxide → Salt + Water

e.g. 2HCl + CuO → CuCl2 + H2O

            •   Acids in water:

Acids produce H+ ions when dissolved in water. H+ ions cannot exist alone. They combine with water molecule (H2O) to form H3O+ (hydronium ions). It conducts electricity.

            •   Decrease in H30+ ions concentration per unit volume results in formation of dilute acids.

            •   It is a highly exothermic reaction.

Acids when dissolved in water release large amount of heat. If water is added to concentrated acid then the heat generated may cause the mixture to splash out and cause bums. Hence to avoid burns acid must be added drop wise into water with constant stirring. So that the heat generated spreads over in water.

strong acids → release more H+ ions → HCl

weak acids → releases less number of H+ ions → acetic acid

strong base → give more OH– ions → NaOH

weak base → gives less OH– ions → CH3COOH

Bases: Bases are bitter in taste, turns red litmus to blue and when dissolved in water releases OH– ions;

e.g., NaOH and KOH.

            •   Reaction with metal

            Base + Metal → Salt + H2 gas

e.g., 2NaOH + Zn → Na2ZnO2 + H2

This reaction is possible only with reactive metals like sodium and potassium.

            •   Reaction with non-metallic oxide

            Base + Non-metallic oxide → Salt + H2O

Bases in water → Bases produce OH– ions when dissolved in water. Bases soluble in water are called alkalis. It conducts electricity.

            •   Decrease in OH– ions single concentration per unit volume results in formation of dilute bases.

            •   It is a exothermic reaction.

To make basic solution, base must be added drop wise into water with constant stirring, so that the heat generated spreads over in water.

Indicators: Indicators are those substances which tell us whether a substance is acidic or basic by change in colour. For e.g., litmus solution.

            •   Olfactory indicators: Those substances whose odour changes in acidic or basic media are called lfactory indicators. For e.g., clove, vanilla, onion.

            •   Natural indicators: Turmeric, litmus (obtained from lichen)

            •   Synthetic indicators: Methyl orange, phenolphthalein.

Indicator	Acids	Bases
1. Red litmus	remains red	turns blue
2. Blue litmus	turns red	remains blue
3. Phenolphthalein	colourless	pink
4. Methyl orange	red	yellow