CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE

CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE

CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE. Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that ranges from the elements that make up matter to the compounds made up of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances.CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE.

CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE

CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE
CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE.

CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE

CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE. In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called central science because it provides a basis for understanding both basic and applied scientific disciplines at a fundamental level. [7] For example, chemistry explains aspects of plant chemistry (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the properties of the soil in the moon, how drugs work (pharmacology), and how to collect DNA evidence at a crime scene. CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE.

CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE

CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE
CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE

CLASS 9th SCIENCE NOTES CHAPTER 2 CHEMISTRY AND LIFE

UNIT-2

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Q.1: Write the physical and chemical properties of table salt.

Ans: Chemical Composition:

Table salt is a mineral composed of sodium chloride (NaCl).

Properties of Salt:

It is in crystal form. Salt is odorless. Its colour is white, pale, pink or light gray. It is mainly taken from sea water or rocks. It has one of the basic human tastes. Refined, unrefined and iodized are different forms of salt. It is soluble in water. Salty water is a good conductor of electricity

Q.2: Write the physical and chemical properties of sugar?

Ans: Chemical Composition:

Sugar molecule is derived from glucose and fructose. Its molecular formula is C6H12O11

Properties of Sugar:

Sugar is generic name for sweet-tasting carbohydrates. Sucrose is organic form of table sugar. It is used to sweeten foods. It is soluble in water. It is white and odorless. It is in crystalline form. It is found in the tissues of most plants.

It can enhance taste and aroma. It can affect the weight and volume of food. It is used in the fermentation process also

Q.3: Write a short note on elements and compounds?

Ans: Elements:

Elements are the basic building blocks of life. They cannot be broken down into simpler substances. About 92 elements are found in nature.

compounds :

Two or more elements combine and form a compound. We find compounds all around us e.g. the Water that we drink, the food that we eat. Compounds can be decomposed into simpler substances.

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Q.1: Write the chemical composition and physical and chemical properties of plastic.

Ans: PLASTIC CHEMICAL COMPOSITION:

Plastics are based on carbon and organic materials. Chemically plastics are synthetic high molecular weight chain molecule.

PHYSICAL PROPERTIES:

Plastic is a light weight material. Plastic is flexible, durable and strong material.

Plastic is moisture resistant. Plastic is inexpensive material. It can be clear or opaque.

CHEMICAL PROPERTIES:

Plastic is heated on moderate temperature. Polymer chain flows past each other after heating. It cannot withstand high temperature. It begins to decompose around 392 F.

Q.2: Write some Physical and Chemical properties of Hydrogen

Ans: Physical Properties:

Hydrogen is a colorless, tasteless and odorless gas. It changes from gas to liquid at -252oC. It changes from solid to liquid at -259oC. It has the lowest density. It is slightly soluble in water,

Alcohol and some other liquids.

Chemical properties

Hydrogen has one electron and one proton. Its atomic number is 1

It exists in diatomic gaseous molecule.

It is highly flammable and reactive.

It has three major isotopes.

Q.3: Write the physical and chemical properties of Copper.

Ans: Physical Properties:

Copper is reddish brown in color. Copper can be bent and shaped without cracking. It can be stretched into a thin wire. It has a shine or glow. It is a heavy metal

It is a good conductor of heat and electricity. These wires keep their tightness

Chemical Properties:

Its chemical formula is Cu. Its large amount can be poisonous. It does not react with water so it will not rust. It corrodes when respond to air. It has high conductivity. It dissolves in alkalis. It combines with carbon dioxide and water in moist air producing hydrated copper carbonate.

Q.4: Write the physical and chemical properties of water.

Ans: Physical Properties:

Water is colorless, tasteless and has no smell. It is found in all three states- liquid, solid and gas. It has a high melting or boiling point. It is an excellent solvent.

Chemical properties:

Pure water has a pH of 7 which makes it neutral. It means water is neither acidic nor basic. Water is highly reactive. It reacts with a lot of substances to form different compounds. During photosynthesis water is oxidized to O2

Q.5: Write three examples of chemical changes which we encounter in our daily life?

Ans: The three chemical changes in our daily life are the following.

(1). Burning:

Burning is an example of chemical change. It takes place in the presence of oxygen. This reaction is called exothermic as it produces heat. When wood or some other organic compound burns in the presence of Oxygen, they produce carbon dioxide and water.

(2). Rusting: Rusting of iron is an example of chemical change. During this change iron reacts with the atmospheric oxygen and makes iron oxide. In this reaction oxygen makes a bond with iron and creates an oxide of iron.

(4). Fermentation: Fermentation is an example of chemical change. It is a natural process in some foods. In this chemical reaction, yeast or bacteria convert sugar or carbohydrates into acid or alcohol. It takes place in oxygen free conditions.

Q.7: Recycling is the need of the day. Different types of waste materials like rubber plastic and copper etc if not recycled can pose serious threats to the environment. Elaborate the statement?

ANS: According to a common saying, “Take care of your planet and it will take care of you.” If waste materials are not recycled, they will cause the following problems of life.

Consumption of resources: Recycling helps to save/conserve our natural resources-the raw material. If used materials are not recycled, raw material will be consumed more quickly. It will exhaust the available resources on Earth.

Energy consumption:

It needs less energy to make new products from recycled materials. While it needs more energy to make new products from raw material. It takes a lot of energy to extract, transport, refine and process raw material.

Pollution: To extract, transport, refine and process raw material, makes air, water and land pollution. If things are not recycled then piles of rubbish and garbage will pollute the world. Recycling saves all this pollution.

Destruction of natural habitat: Cutting trees to make paper and other things destroys the natural habitat and natural beauty. Recycling of paper and other things saves this loss.

Unemployment: Lots of manpower is involved in recycling plants. If recycling process is stopped, it will lead to unemployment.

Burden on economy: It needs more money to make new products from raw material. While it needs less money to make new products from recycling.

Q. State the Advantages of Recycling of copper.

Ans. Copper is 100% recyclable and its quality would not degrade after recycling. Recycled copper is cheaper than the mined copper. Recycled copper is worth up to 90%. It reduces landfill costs. Recycling protects the environment. It helps to prevent pollution. It saves a lot of energy. Mining, transporting and refining copper requires lots of resources which creates a burden on the economy of a country. Recycled copper helps to conserve copper ore.

Q. State the Advantages of Recycling of plastic.

Ans. Plastic recycling is the process of recovering of scrap or waste plastic and reprocessing the material into useful products. Some plastic can be up cycled to make plastic of higher quality. Some plastic is down cycled to make plastic of lesser quality. Plastic recycling helps to protect environment specially the marine life. Its recycling reduces the economic burden on a country. Its recycling saves energy. A large amount of petroleum is used in the production of new plastic products. Its recycling reduces 40% of oil consumption. It reduces landfill costs.

Q. State the Advantages of Recycling of rubber.

Ans. Recycling of rubber is difficult than recycling of other materials. Recycled rubber can cost half that of natural or synthetic rubber. Recovered rubber has better properties than natural rubber. Recovered rubber requires less energy. It helps to protect environment. It saves lots of space in the landfills. Its recycling is environment friendly. Its recycling reduces the consumption of oil which is used in the production of synthetic rubbers.

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