Class 7 | Science | Chapter- 6 | Physical and Chemical Changes Notes

Class 7           Science

Chapter- 6

Physical and Chemical

Changes Notes

Changes can be of two types, physical and chemical change

Physical Changes- Physical changes are changes in the physical properties of substances. No new substances are formed in the changes. These changes may be reverible. Examples- Tearing of paper, mixing of sand and water, etc.

Physical properties- Properties such as shape, size, colour and state of a substance are called its Physical properties.

Chemical Changes- A change in which one or more new substances are formed is called a chemical change. Chemical changes are changes in which the composition and chemical properties of the substance get changed. It is permanent and irreversible. Example- Rusting of iron, burning of a candle and ripening of fruits, etc.

Chemical properties- One or more new products are formed. Heat, light or other radiation(UV, For example) may be given off or absorbed. Sound may be produced. May be change in smell. May be change in colour and a gas may be formed.

Rusting of Iron- It is a process in which iron turns into iron oxide. Iron rust due to the presence of both oxygen and water(or water vapour) . The process is a type of corrosion that occurs easily under natural conditions. 
Iron(Fe) + Oxygen(O2 from the air) + water(H20) ➡ rust(iron oxide Fe2O3)

Prevention of Rusting:- 

• By painting
• By oiling and greasing
• By Chromium plating
• By Galvanisation
• By Alloying

Rusting Iron

Galvanisation:- The process of depositing a layer of zinc on iron is called galvanisation.

Crystallisation:- Large crystals of pure substances can be formed from their solutions. The process is called crystallisation.

Class 7 | Science | Chapter- 5 | Acids, Bases and Salts Notes

Class 7           Science

Chapter- 5

Acids, Bases and Salts Notes

Acids- These are sour in taste.

The chemical nature of such substance is acidic. Like- Acetic acid, Formic acid, etc.

Bases- These are bitter in taste in taste and soapy to touch.

The basic nature of such substance is basic.

Neutral- Substances which are neither acidic nor basic are called neutral.

Indicators- Solution of substances that show different colour in acidic, basic and neutral solutions are called indicators.

Natural Indicators Around Us- 
Litmus- The most commonly used natural indicator is litmus. It is extracted from lichens. It has mauve(purple)  colour in distilled water. Acid turns blue litmus to red and Bases turns red litmus to blue. It is available in the form of a solution and strips of paper. Its is available as red and blue litmus paper.

Turmeric- It is yellow colour in neutral form and acidic solution but turns red in basic solution.

China Rose- It remains acidic solution to dark pink and basic solution to green.

Red Cabbage- it turns acidic solutions to red and basic solution to blue.

Phenolphthalein- It is an acid-base indicator. It is colourless in acidic solutions turns pink in alkali solutions.

 Neutralisation- The reaction between an acid and a base is known as Neutralisation. Salt and water produce in this reaction with the evolution of heat.
Acid+Base ➡ Salt+Water ( Heat is evolved)

Neutralisation in Everyday Life- 
Indigestion- Our stomach contains hydrochloric acid. It helps us to digest food. Too much of acid in the stomach causes indigestion. It is neutralized by taking an antacid Such as milk of magnesia.

Ant bite- When an ant bites, it injects the acidic liquid(Formic acid) into the skin. The effect of the acid can be neutralised by rubbing moist baking soda(sodium hydrogencarbonate) or calamine solution.

Soil treatment- When the soil is too acidic, it is treated with bases like quike lime( calcium oxide) or slaked lime(calcium hydroxide).

Factory waste- The wastes of many factories contain acids. 

Class 7 | Science | Chapter-4 | Heat Notes

Class 7           Science

Chapter-4

Heat Notes

Heat- It is a form of energy. Which makes any object hot and cold.

Temperature- Temperature is a measure of the degree of hotness of an object.

Our sense of touch is not always a reliable guide to the degree of hotness of an object.

The normal temperature of human body is 37℃ and slightly higher or slightly lower.

Thermometer- Thermometer is device used for measuring temperature.

Thermometer is classified in two categories

Clinical Thermometer- This thermometer is measure our body temperature is called clinical thermometer. Its range is 35℃ to 42℃. A clinical thermometer consist of a long, narrow, uniform glass tube. It has a bulb at one end. This bulb contain mercury, and near the bulb kink is present. Kink prevents mercury level from falling on its own.

Clinical Thermometer

Laboratory Thermometer- It is used in measuring water and chemicals temperature. its range is -10℃ to 110℃. In laboratory thermometer kink is absent.

                 Laboratory Thermometer

Transfer of Heat-

The heat flows from a body at a higher temperature to a body at a lower temperature.  There are three ways in which heat can flow from one object to another. These are  conduction, convection and radiation.

Conduction-  The process by which heat is transferred from the hotter end to the colder end of an object is known As conduction.

Convection- It is the flow of heat through a fluid from places of higher temperature to places of lower temperature by movement of the fluid itself.

Radiation- It is the mode of transfer of heat in which energy is directly transferred from one place to another.  It is not required any medium.

Conductors- The materials which allow heat to pass through them easily are called conductor.

Insulators- The materials which do not allow heat to pass through them easily are called insulators.

Sea Breeze- The warm air from the land moves towards the sea to complete the cycle. The air from the sea is called sea breeze. The Sea breeze form at During Day.

Land Breeze- The cool air from the land
moves towards the sea. This is called the land breeze. It is form at night.

Dark- coloured objects absorb more heat than the light coloured objects. That is the reason we feel more comfortable in light coloured clothes in the summer.

Wollen clothes keep us warm during winter. It is so because wool is a poor conductor of heat and it has air trapped in between the fibres.

Class 7 | Science | Chapter-3 | Fibre to Fabric Notes | By Dharmender

Class 7           Science

Chapter-3

Fibre to Fabric Notes

Fleece- The hair of sheep and yak.

Fibres- Fibres are long, Fine, Continuous thread or filament are obtained from plants and animals.

Fibres are divided into two categories-

(i)  Animal Fibres

(ii) Plant Fibres

Animal Fibres are silk and wool

Wool is obtained from sheep, goat, camel, etc.

Silk is obtained from silkworm.

Wool- Wool comes from sheep, goat, yak and some other animals. These wool yielding animals bear hair on the body and thick coat of hair.Hair trap a lot of air. Air is poor conductor of heat. So hair keeps these warm. Wool is derived from these hairy fibres.

The sheep has two types of fibres that from its fleece-

(i)   The coarse beard hair

(ii)  The fine soft under hair close to the skin

The process of selecting parents for obtaining special characters in their offspring, such as soft under hair in sheep, is termed 'selective breading'.

Animals that yield wool-

Yak- Yak wool is common in Tibet and Ladakh.

Angora Goat- Angora wool is obtained from angora goats. These found in hilly region(j&k).

The under fur of Kashmiri goat is soft. It is woven into fine shawls called Pashmina shawls.

The fur on the body of camel is also used as wool.

Llama and Alpaca are found south America, also yield wool.

From fibres to wool-

For obtaining wool, sheep are reared. Their hair is cut and processed into wool.

Processing fibres into wool-

Step I- The fleece of the sheep along with a thin layer of skin is removed from its body. This process is called shearing.

Step II- The sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt. This is called scouring.

Step III- After scouring, shorting is done, the hairy skin is sent to a factory where hair of different textures are separated or sorted.

Step IV- The small fluffy fibres, called burrs, are picked out from the hair. These are the same burrs which somtimes appears on your sweaters. The fibres are scoured again and dried. This is the wool ready to drawn into fibres.

Step V- The Fibres can be dyed in various colours, as the natural fleece of sheep and goats is black, brown or white.

Step VI- The fibres are straightened combed and rolled into yarn.

Silk- 

Silk is made when silkworm spin the silk fibres.

Sericulture- The rearing of silkworms for obtaining silk is called Sericulture.

Life history of silk moth-

The female silk moth lays egg on mulberry leave and they made silkworm and then they form developing moth and cocoon.

Rearing silkworms- A female silk moth lays hundreds of eggs at a time. The eggs are stored carefully on strips of cloth or paper and sold to silkworm farmers. The farmers keep eggs under hygienic conditions, the eggs are warmed to a suitable temperature fir the larvae to hatch from eggs. This is done when mulberry trees bear a fresh crop of leaves. The larvae called caterpillars or silkworm, eat day and night and increase enormously in size. The larvae are kept in clean bamboo trays along with freshly chopped mulberry leaves. After 25 to 30 days, the caterpillars stop eating and move to a tiny chamber of bamboo in small racks or twigs may be provided in the trays to cocoon get attached. The caterpillar or silkworm spin the cocoon inside which develops the silk moth

Class 7 | Science | Chapter-2 | Nutrition in Animals Notes | by Dharmender

Class 7           Science

Chapter-2

 Nutrition in Animals Notes

All the Animals are Classified on the basis of eating habits:-

Herbivorous- That animals eat plants and plant products are called Herbivorous. Example- Cow, sheep, goat, Giraffe, etc

Carnivorous- That animals eat only flesh of other animals are called carnivorous animals. Example- Lion, Tiger, etc.

Omnivores- Those animals which eat both, plants and animals are called omnivores. Examples are Man, Dog and Crow etc.

Scavengers:- Those animals which eat dead animals and clean environment are called scavengers.

Process of nutrition in animals

Holozoic nutrition: It is a process by which animals take in their food. It involves different steps namely, ingestion, digestion, absorption, assimilation and egestion. Human beings exhibit holozoic mode of nutrition involving five basic steps.

Ingestion: The process of taking food into the body is called ingestion.

Digestion: the process in which the food containing large, insoluble molecules is broken down into small, water soluble molecules is called digestion.

Absorption: The process in which the digested food passes through the intestinal wall into blood stream is called absorption.

Assimilation: The process in which the absorbed food is taken in by the body cells and used for energy, growth and repair is called assimilation.

Egestion: The process in which the undigested food is removed from the body is called egestion.

Nutrition in Amoeba
Amoeba is a microscopic organism which consists of only a single cell.
Amoeba is mostly found in pond water.
Figure given below shows the structure of amoeba.

Amoeba eats tiny plants and animals as food which floats in water in which it lives.

The mode of nutrition in Amoeba is holozoic.

The process of obtaining food by Amoeba is called phagocytosis.

Steps involved in the nutrition of Amoeba:

Ingestion: Amoeba ingests food by forming temporary finger-like projections called pseudopodia around it. The food is engulfed with a little surrounding water to form a food vacuole (‘temporary stomach’) inside the Amoeba.

Digestion: In Amoeba, food is digested in the food vacuole by digestive enzymes which break down the food into small and soluble molecules by chemical reactions.

Absorption: The digested simple and soluble substances pass out of food vacuole into the surrounding environment.

Assimilation: The absorbed food materials are used to obtain energy through respiration and make the parts of Amoeba cell which leads to the growth of Amoeba.

Egestion: The remaining undigested material is moved to the surface of the cell and thrown out of the body of Amoeba.

Nutrition in Paramecium:

Paramecium is also a tiny unicellular animal which lives in water.

Ingestion: Paramecium uses its hair like structures called cilia to sweep the food particles from water and put them into mouth.

Ingestion is followed by other steps such as digestion, absorption, assimilation and egestion which are same as those we studied in Amoeba

Nutrition in Hydra

Hydra is a simple multicellular animal.

It has a number of tentacles around its mouth, which are used for ingestion of food.

These tentacles entangle small aquatic animals and kill them with their stinging cells.

After this they push them into their mouth. Now inside their body cavity digestive juices are secreted by the surrounding cells.

These juices digest the food and the digested food is absorbed through the cavity walls and assimilated in the cells.

Human Digestive system

We take food through our mouth, digest and utilise it.

Figure given below shows the human digestive system 

Human digestive system consists of alimentary canal and its associated human-digestive-system.png glands.

Various organs of human digestive system in sequence are

Mouth (Buccal Cavity)

Oesophagus (food Pipe)

Stomach

Small intestine

Large intestine

Rectum

Anus.

The glands which are associated with human digestive system are

Salivary glands- Located in mouth or Buccal Cavity

Liver- It is the largest gland situated in the upper part of abdomen on the right side.

Pancreas- located just below the stomach

The ducts of various glands open into the alimentary canal and pour secretion of their juices into the alimentary canal.

Digestion in the mouth

We take food through our mouth and the process of taking food into the body is called ingestion.

The mouth or buccal cavity contains teeth, tongue and salivary glands.

Digestion begins in the mouth when we chew the food with the help of our teeth.

The teeth cut the food into smaller pieces, chew and grind it.

Chewing breaks down the food into smaller pieces and mixes them with saliva. This process is called mastication.

The salivary glands secrete watery liquid called saliva. Saliva is a digestive juice that helps to partially digest the starch present in the food.

The tongue helps in mixing saliva with the food.

Tongue is a muscular organ that helps you eat the food. It mixes saliva with the food during chewing and helps in swallowing it.

We also taste food with our tongue as it has taste buds that detect different tastes of food.

Teeth

Teeth are used for cutting, grinding and tearing the food before you swallow it.

You have different types of teeth to do the job.

Milk teeth:- A child has only 20 teeth, 10 in each jaw. These are known as milk teeth. They begin to fall at the age between 6 to 8 and then new set of teeth grows.

Permanent teeth:- This set contains 32 teeth, 16 in each jaw. There are 4 incisors, 2canines, 4 premolars and 6 molars in each jaw. As shown below in the figure: 

Your front teeth are incisors. They are used for biting and cutting.

Next to incisors are canines. These are pointed and are used for piercing and tearing pieces of food.

Teeth at the back of your mouth are broad with almost flat surface. These teeth crush and grind food and are called the premolars and molars. Molars are larger then premolars

White substance that covers your teeth is called enamel.

The food pipe/Oesophagus

The swallowed food passes into the food pipe or oesophagus as shown below in the figure

This figure shows the movement of food in food pipe which runs along the neck and chest.

So, the oesophagus leads from your mouth to the stomach. It is made up of the muscles.

Food is pushed down by movement of the wall of food pipe.

This movement called peristalsis, takes place throughout the alimentary canal and pushes the food downwards.

Stomach

Stomach is the thick walled bag present on the left side of the abdomen. (see human digestive system figure)

It is the widest part of the alimentary canal. Oesophagus brings slightly digested food from mouth into the stomach.

The stomach walls contain s three tubular glands in it walls which secrete gastric juice.

The gastric juice contains three substances: Hydrochloric acid, the enzyme pepsin and mucus.

The hydrochloric creates an acidic medium which facilitates the action of the enzyme pepsin that is the digestion of protein into simple substances.

The acid kills many bacteria that enter along with the food.

The mucus helps to protect the stomach wall from its own secretions of hydrochloric acid.

The partially digested food then goes from the stomach into the small intestine.

Small intestine

Small intestine is highly coiled and is about 7.5 m long.

After leaving stomach food enters small intestine and last steps of digestion takes place in small intestine.

It receives secretions from liver and pancreas and wall of small intestine also secrets juices.

Large intestine:-
The large intestine is wider and shorter than small intestine. It is about 1.5 metre in length. Its function is to absorb water and some salts from the undigested food material. The remaining waste passes into the rectum and remains there as semi-solid faeces. The Faeces matter is removed through the anus from time to time. This is  called egestion.

Liver:- Liver is the largest gland in the body and is situated in the upper part of the abdomen on the right side. It secrets bile juice that is stored in gall bladder

Pancreas:- It is the large cream coloured gland located just below the stomach. The pancreatic juice acts on carbohydrates, fats and proteins and converts them into simple form.

The partly digested food now reaches the lower part of the small

The walls of the small intestine contain glands which secretes intestinal juice.

The enzymes present in it finally convert the proteins into amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol.

Absorption:

The small intestine is the main region for the absorption of digested food.

The inner surface of the small intestine has numerous finger-like projections called villi which increase the surface area for rapid absorption of digested food.

The digested food which is absorbed through the walls of the small intestine goes into our blood.

Assimilation:

The blood carries digested and dissolved food to all the parts of the body where it becomes assimilated as part of the cells and is utilised for obtaining energy, building up new tissues and the repair of old tissues.

Egestion:

The unabsorbed food is sent into the large intestine where more villi absorb water from this material.

The rest of the material is removed from the body via the anus.

The exit of this waste material is regulated by the anal sphincter.

Digestion in grass eating animals

Buffaloes and other grass eating animals swallow grass and store it in a separate part of stomach called Rumen. These animals have complicated stomach.

In rumen food is partially digested and is called cud.

Later cud returns to the mouth in small lumps and the animals chews it. This process is called rumination and these animals are called ruminants.

Grass is rich in cellulose and we humans cannot digest it.

Class 7 | Science | Chapter-1| Nutrition in Plants Notes | by Dharmender

Class 7           Science

Chapter-1

 Nutrition in Plants Notes

Nutrients- Carbohydrate, Protein, fats, vitamins and minerals are components of food. These components of food are called nutrients.

Nutrition- Nutrition is the mode of taking food by an organism and its utilisation by the body.

All organisms take food for build there bodies, to grow, to repair damaged parts of their bodies.

Autotrophs- (auto= self; trophos= nourishment) That organism make own food themselves are called autotrophs. like- green plants.

Heterotrophs- (heteros= other; trophos= nourishment)They dependent on other organism for nutrition, They cannot make own food themselves are called heterotrophs. Like- Human, Animals and some plants.

Stomata- Tiny pores are present on the surface of leaves are called stomata.

Vessels- Vessels are like a pipes, They form a continuous path or passage for the nutrients to reach  the leaf. They are called Vessels.

Chlorophyll- The leaves have a green pigment called chlorophyll.

Photosynthesis- (Photo= Light; synthesis= to prepare) it is a process in which Green plants prepare own food with the help of carbon dioxide and water in presence of sunlight and chlorophyll are photosynthesis.

Sunlight and Chlorophyll are essential requirement for photosynthesis.

Oxygen is released during photosynthesis.

Algae- These are generally found in ponds or stagnant water bodies. These are generally formed by the growth of organisms are called algae. It is slimy and green patches.

Host- They cannot take food another plant are called host.

Parasites- That organism live on other body

All Parasitic plants feed on other plants

Parasites are two types-

(i) Partial parasites- obtain some of their nutrion on the host.Example- painted Cup

(ii) Total Parasites- These are totally dependent on host for nutrition. Example- mistletoe

Insectivorous Plants- Some Green Plants are obtain nourishment  partly from soil, atmosphere and partly from insects are Insectivorous plants.Examples - pitcher plant, venus fly trap etc.

Sapritrophic Nutrition- The mode of nutrition in which organisms take in nutrients from dead and decaying matter is called Saprotrophic nutrition.

Symbiosis- Some Organism live together and share both shelter and nutrients. This relationship is called Symbiosis. Examples- Certain fungi live inside the roots of plants.

In Lichens A chlorophyll Containing partner, which is an alga, and a fungus live together. The fungus provides shelter, water and minerals to the alga and in return, the alga prepare and provide food to the fungus.