Class 10 | Science | Chapter- 1 | Chemical Reactions and Equations Notes

Class 10           Science

Chapter- 1

Chemical Reactions and Equations Notes

Some Chemical reactions in Every Day life:-

• Milk is left at room temperature during summers.
• An iron tawa/pan/nail/ is left exposed to humid atmosphere.
• Grapes get fermented.
• Food is cooked.
• Food gests digested in our body.
• We respire.

Following observations help us to determine chemical reaction:-

• Change in state
• Change in colour
• Evolution of a gas
• Change in temperature

CHEMICAL EQUATIONS:-

The simplest way to do this is to write it in the form of a word-equation.

The word-equation for the above reaction would be –

Magnesium + Oxygen → Magnesiumoxide

            (Reactants)                     (Product)

A word-equation shows change of reactants to products through an arrow placed between them. The reactants are written on the left-hand side (LHS) with a plus sign (+) between them. Similarly, products are written on the right-hand side (RHS) with a plus sign (+) between them.

The arrowhead points towards the products, and shows the direction of

the reaction.

Writing a Chemical Equation:-

we use chemical formulae instead of words. A chemical equation represents a chemical reaction. e.g. 

      

Count and compare the number of atoms of each element on the LHS and RHS of the arrow.  The number of atoms of each element the same on both the sides.

Balanced Chemical Equation:-

A chemical equation is balanced so that the numbers of atoms of each type involved
in a chemical reaction are the same on the reactant and product sides of the equation. Equations must always be balanced.

In Symbols:-

This is balanced Equation because both side all elements are same each type. So it Called Balanced equation.

Unbalanced Chemical Equation:-

In Unbalanced Chemical Equation the numbers of atoms are the different(not same) on the reactant and product sides of the equation. For Example:-

Balancing Equations 

Step-I

first draw boxes around each 

formula.

Step-II

List the number of atoms of different elements present in the unbalanced equation.

Step-III

Select the element which has the maximum 

number of atoms.

and Then,

Step-IV

Oxygen atoms balanced but another atoms not balanced. So, Balance another atoms. Like-

Step-V
Pick up the next element which is not balanced.

Step-VI

Finally, to check the correctness of the balanced equation, we count atoms of each element on both sides of the equation.

Step-VII
Writing Symbols of Physical States.

Types of chemical Reactions:-

Combination Reaction-
In this reaction a single product is formed from two or more reactants is known as a combination reaction.

Decomposition Reaction
 In a decomposition reaction, a single substance decomposes to give two or more substances.

Displacement Reaction-
When an element displaces another element from its compound, a displacement
reaction occurs.

Double Displacement Reaction-
Two different atoms or groups of atoms (ions) are exchanged in double displacement reactions.

Redox Reaction-
The processes of oxidation and reduction occur simultaneously and cannot happen independently of one another.

Corrosion-

When a metal is exposed to moisture, air, acid etc. for some time,  a layer of hydrated oxide is formed which weakens the metal and hence metal is said to be corroded.

Examples- Rusting of iron, black coating on silver and green coating on copper.

Corrosion can be prevented by galvanization, electroplating or by putting paints.

Rancidity-

The oxidation of fats and oils when exposed to air is known as rancidity. It leads to bad smell and bad taste of food.

Methods to Prevent Rancidity-
(i) By adding antioxidants
(ii) Keeping food in air tight containers
(iii) Replacing air by nitrogen
(iv) Refrigeration

Class 7 | Science | Chapter- 12 | Reproduction in Plants Notes

Class 7           Science

Chapter- 12

Reproduction in Plants Notes

Reproduction- The production of new individuals from their parents is known as reproduction.

All organisms multiply or reproduce their own kind.

MODES OF REPRODUCTION

Most plants have roots, stems and leaves. These are called the vegetative parts of a plants.

The flowers perform the function

of reproduction in plants. Flowers are
the reproductive parts of reproductive parts a plant. A flower may have either the male part or the female part or both male and female parts.

In plants there are two modes of reproduction, asexual and sexual.
Asexual reproduction-  In asexual reproduction reproduction plants can give rise to new plants without seeds.

There are several methods of asexual reproduction such as fragmentation, budding, spore formation and vegetative propagation.

Sexual reproduction- In sexual reproduction new reproduction plants are obtained from seeds.
Sexual reproduction involves the fusion of male and female gametes.

Vegetative propagation- In vegetative propagation new plants are produced from different vegetative parts such as leaves, stems and roots.

Cutting-  Cut a branch of rose or champa with a node. This piece of branch is termed a cutting.

Buds- Apart from flower buds, there are buds in the axil (point of attachment of the leaf at the node) of leaves which develop into shoots. These buds are called vegetative buds.

Eyes- Observe the scars on Fresh Potato.
You may find bud(s) in them. These scars
are also called “eyes”.

Budding is a type of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one particular site. The small bulb like projection coming out from the yeast cell is called a bud. The new organism remains attached as it grows, separating from the parent organism only when it is mature, leaving behind scar tissue. Since the reproduction is asexual, the newly created organism is a clone and is genetically identical to the parent organism.

Fragmentation -the process or state of breaking or being broken into fragments.

Spore Formation- Spore formation is a method of asexual reproduction which is found in non flowering plants such as fungi (Rhizopus) and bacteria. In this method of reproduction, the parent plant produces hundreds of tiny spores which can grow into new plants.

SEXUAL REPRODUCTION
The stamens are the male reproductive part stamens and the pistil is the female reproductive pistil part.

The flowers which contain either only the pistil or only the stamens are called unisexual flowers. The flowers which contain both stamens and pistil are called bisexual flowers.

A pistil consists male gametes of stigma, style and ovary. The ovary contains one or more ovules.
The female gamete female gamete or the female gamete egg is formed in egg an ovule.
In sexual reproduction a male and a female gamete fuse to form a zygote.

Pollination
The transfer of pollen from the anther to the stigma of a flower is called pollination.

If pollination the pollen lands
on the stigma of the same flower it is
called self-pollination.
 When the pollen of a flower lands on the stigma of another flower of the same plant, or that of a different plant of the same kind, it is called cross-pollination.

Fertilisation-
The zygote process of fusion of male and female gametes (to form a zygote) is called
fertilisation.

The cell which results after fusion of fusion
the gametes is called a zygote.
The zygote develops into an embryo.

FRUITS AND SEED FORMATION

After fertilisation, the ovary grows into

a fruit and other parts of the flower fall

off. The fruit is the ripened ovary. The

seeds develop from the ovules. The seed

contains an embryo enclosed in a

protective seed coat.

SEED DISPERSAL

Seed dispersal is aided by wind, water and animals.

 Seed dispersal helps the plants to

 (i) prevent overcrowding,

 (ii) avoid competition for sunlight, water and minerals and 

(iii) invade new habitats

Class 7 | Science | Chapter- 11 | Transportation in Animals and Plants Notes

Class 7           Science

Chapter- 11

Transportation in Animals  and Plants Notes

CIRCULATORY SYSTEM-

Circulatory system consists of the heart and blood vessels.

Blood-

Blood is the fluid which flows in blood vessels. It transports substances like digested food from the small intestine to the other parts of the body. It carries oxygen from the lungs to the cells of the body. It also transports waste for removal from the body.

The fluid part of the blood is called plasma. One type of cells are the red blood cells(RBC) which contain a red pigment called haemoglobin.

The blood also has white blood cells(WBC) which fight against germs that may enter our body.

After cut on the body blood is flow and the clot is formed because of the presence of another type of cells in the blood, called platelets.

Blood vessels-
Two types of blood vessels are present in the arteries and veins of the body.

Arteries- Arteries oxygen-rich blood from the heart to all parts of the body. Since the blood flow is rapid and at a high pressure, the arteries have thick elastic walls.

Veins- Veins the vessels which carry carbon dioxide-rich blood from all parts of the body back to the heart. The vein have thin walls. There are valves present in veins which allow blood to flow only towards the heart.

The arteries divide into smaller vessels. On

reaching the tissues, they divide further

into extremely thin tubes called capillaries. The capillaries join up to form veins which empty into the heart.


Heart-
The heart is an organ which beats continuously to act as a pump for the transport of blood, which carries other substances with it.

The heart is located in the chest cavity with its lower tip slightly tilted towards the left.
the heart has four chambers. The two upper chambers are called the atria (singular:atrium) and the two lower chambers are called the ventricles.
The partition between the chambers helps to avoid mixing up of blood rich in oxygen with the blood rich in carbon dioxide.

Heartbeat-
The walls of the chambers of the heart
are made up of muscles. These muscles
contract and relax rhythmically. This
rhythmic contraction followed by its relaxation constitute a heartbeat.

• The human heart beats about 70–80 times per minute in an adult person. This is called heart rate.

EXCRETION IN ANIMALS-

• Removal of waste products from the body is called excretion.
• Excretory system of humans consists of two kidneys, two ureters, a urinary bladder, and urethra.
• Salts and urea are removed along with water as sweat.
• Fish excrete waste substances which directly dissolve in water.
• Birds, insects and lizard excrete uric acid in semi-solid form.

Excretory system in humans-

• The waste which is present in the blood has to be removed from the body.
• When the blood reaches the two kidneys it contains both useful and harmful substances. The useful substances are absorbed back into the blood. The wastes dissolved in water are removed as urine. 
• From the kidneys, the urine urine goes into the urinary bladder through tube-like ureters. It is ureters stored in the bladder and is passed out through the urinary opening at the end of a muscular tube called urethra.

TRANSPORT OF SUBSTANCES IN PLANTS-

• Water and mineral nutrients are absorbed by roots from the soil.
• Nutrients are transported along with water to the entire plant via the vascular tissue called xylem.
• The vascular tissue for the transport of food to the various parts of the plant is phloem.
• A lot of water is lost by plants in the form of vapour through stomata during transpiration.
• Transpiration generates a force which pulls up water absorbed by the
• roots from the soil, to reach the stem and leaves.

Class 7 | Science | Chapter- 10 | Respiration in Organisms Notes

Class 7           Science

Chapter- 10

Respiration in Organisms Notes

• Respiration is essential for survival of living organisms. It releases energy from the food.

• The oxygen we inhale is used to breakdown glucose into carbon dioxide and water. Energy is released in the process.

cellular respiration- The process of breakdown of food in the cell with the release of energy is called cellular respiration.

Aerobic respiration-When breakdown of glucose occurs with the use of oxygen it is called aerobic respiration.

Anaerobic respiration- Food respiration can also be broken down, without using oxygen. This is called anaerobic respiration.

• During heavy exercise when the supply of oxygen to our muscle cells is insufficient, food breakdown is by anaerobic respiration.

Anaerobes- some organisms such as yeast that can survive in the absence of air. They are called anaerobes.

Breathing:- Breathing is a part of the process of respiration during which an organism takes in the oxygen-rich air and gives out air rich in carbon dioxide. The respiratory organs for the exchange of gases vary in different
organisms.

•  The taking in of air rich in oxygen into the body is called inhalation and inhalation giving out of air rich in carbon dioxide is known as exhalation.
• During inhalation, our lungs expand and then come back to the original state as the air moves out during exhalation.

The number of times a person breathes  in a minute is termed as the breathing      rate. breathing rate Both inhalation and      exhalation take place.

• On an average, an adult human being at rest breathes in and out 15–18 times in minute. During heavy exercise, the breathing rate can increase upto 25 times per minute.

HOW DO WE BREATHE? -

Normally we take in air through our nostrils. When we inhale air, it passes through our nostrils into the nasal cavity. From the nasal cavity, nasal cavity the air reaches our lungsthrough the windpipe. Lungs are present in the chest cavity chest cavity. This cavity is chest cavity surrounded by ribs on the sides. A large,
muscular sheet called diaphragm forms diaphragm the floor of the chest cavity.
Breathing involves the movement of the
diaphragm and the rib cage. During inhalation, ribs move up and outwards and diaphragm moves down. This movement increases space in our chest cavity and air rushes into the lungs. The lungs get filled with air. During exhalation, ribs move down and inwards, while diaphragm moves up to its former position. This reduces the size of the chest cavity and air is pushed out
of the lungs. These movements in our body can be felt easily.

BREATHING IN OTHER ORGANISMS-
Respiration in animals- 
In Some Animals- In animals like cow, buffalo, dog and cat the respiratory organs and the process of breathing are similar to those in humans.
Earthworm- Through their moist skin
Insects- Through entire body surface.
Fish- Through the gills.
Frogs- Through its, moist and thin skin when in water and lungs when on land.

Respiration in Plants- In a plant the roots take in air present in the soil. Leaves have tiny pores called stomata through which they exchange gases. The breakdown of glucose in the plant cells is similar to that in other living beings.

Class 7 | Science | Chapter- 9 | Soil Notes

Class 7           Science

Chapter- 9

Soil Notes

Soil- The mixture of rock particles and humus is called the soil. The top layer of the earth's surface in which plants can grow, consisting of rock and mineral particles mixed with decayed organic matter and having the capability of retaining water.

Formation of soil-

1. Soil is formed by weathering or disintegration of parent rocks.
2. Physical Weathering is degradation of rocks by physical agents like water, ice, wind, sun, etc. 
3. Chemical weathering is chemical decomposition of rocks.
4. Biological weathering is decomposition of parent rocks by bacteria and microorganisms.

Soil Profile- Soil profile is a section through different layers of the soil, Various layers

are called horizons. A vertical section through different layers of the soil is called the soil profile. Each layer differs in feel (texture),colour, depth and chemical composition.

                       Soil Profile

Humus- dead matter in the soil is called humus.

Weathering- the soil is formed by the breaking down of rocks by the action of wind, water and climate. This process is called weathering.

This layer is generally soft, porous and can retain more water. It is called the topsoil or A-horizon.

This layer is generally harder and more
compact and is called the B-horizon or B-horizon the middle layer.

The third layer is the C-horizon, C-horizon
which is made up of small lumps of
rocks with cracks and crevices.

bedrock is hard and difficult to dig with a spade.

SOIL TYPES-

Three types of soil: clayey, loamy and sandy.

(i)   Clayey Soil- The proportion of fine particles is relatively higher, then it is called clayey soil. It has an excellent water retention capacity and air circulation is sufficient. Clayey soil is used to make pots, toys and statues.

(ii)  Loamy Soil- The amount of large and fine particles in the soil is called loamy. It has a good water retention capacity and air circulation is sufficient. It contains good mixture of sand, clay and humus.

(iii) Sandy Soil- Soil contains greater proportion of big particles it is called sandy soil. It has a very low water retention capacity. It is not rich in humus.

Percolation rate of water in soil-Percolation rate of water is different in different types of soil. It is highest in the sandy soil and least in the clayey soil.

Calculate the rate of percolation by using the following formula:

SOIL MOISTURE - Soil holds water in it, which is called soil moisture.

SOIL AND CROPS- Different types of soils are found in different parts of India. In some parts there is clayey soil, loamy soil while in some other parts there is sandy soil. Soil is affected by wind, rainfall, temperature, light and humidity. These
are some important climatic factors
which affect the soil profile and bring
changes in the soil structure.Different types of soils are used to cultivate different types of crops. Clayey and loamy are suitable for growing wheat, gram and paddy. Cotton is
grown in sandy loam soil.

Class 7 | Science | Chapter- 8 | Winds, Storms and Cyclones Notes

Class 7           Science

Chapter- 8

Winds, Storms and Cyclones Notes

Air- The Invisible gaseous substance surrounding the earth.

Wind- The moving air is called the wind. Air moves from the region where the air pressure is high to the region where the pressure is low.

Air Properties:-

• Air around us exerts pressure.
• Air expands on heating and contracts on cooling.
• Warm air rises up, whereas comparatively cooler air tends to sink toward the earth’s surface.
• As warm air rises, air pressure at that place is reduced and the cooler air moves to that place.

Types of Air- 

• Wind Currents- Wind currents are generate due to uneven heating on earth.

• Thunderstorm- Storm with thunder and lighting along with the rain.

In Thunderstorm winds carry water droplets upwards, where they freeze, and fall down again. The swift movement of the falling water droplets along with the rising air create lightning and sound. It is this event that we call a thunderstorm.

Cyclone- A cyclone is a large scale air mass that rotates around a strong center of low atmospheric pressure. Cyclones are characterized by inward spiraling winds that rotate about a zone of low pressure.

 EFFECTIVE SAFETY MEASURES-

• A cyclone forecast and warning service.
• Rapid communication of warnings to the Government agencies, the ports, fishermen, ships and to the general public

Action on the part of the people

●  We should not ignore the warnings issued by the meteorological department through TV, radio, or newspapers.
●   We should — make necessary              arrangements to shift the essential household goods, domestic animals and    vehicles, etc. to safer places; avoid driving on roads through standing water, as floods may have damaged the roads; and keep ready the phone numbers of all emergency services like police, fire brigade, and medical centres.

Some other precautions, if you are

staying in a cyclone hit area —

●  Do not drink water that could be     contaminated. Always store drinking
water for emergencies.
●  Do not touch wet switches and fallen
power lines.

● Do not go out just for the sake of fun.

● Do not pressurise the rescue force

by making undue demands.

●  Cooperate and help your neighbours

and friends.

• Winds carrying water vapour bring rain.
• High-speed winds and air pressure difference can cause cyclones.
• It has become easier to monitor cyclones with the help of advance technology like satellites and radars.
• Self-help is the best help. Therefore it is better to plan in advance and be ready with defence against any approaching cyclone.
• The following flow chart will help you to understand the phenomena that lead to the formation of clouds and falling of rain and creation of storms and cyclones:

Class 7 | Science | Chapter- 7 | Weather, Climate and Adaptation of Animals to Climate Notes

Class 7           Science

Chapter- 7

Weather, Climate and Adaptation of Animals to Climate Notes

Weather- The day to day condition of the atmosphere at place with respect to the temperature, humidity, rainfall, wind-speed, etc., is called the weather.

Humidity- Humidity is the amount of water vapour present in the atmosphere and is measured by hygrometer.

Rain gauge- Rainfall is measured by an instrument called the rain gauge.

Elements of the weather- The temperature, humidity, and other factors are called elements of the weather.

Climate- The average weather pattern taken over a long  time, say 25 years, is called the climate of the place.

Factor affecting Climate:

• Topography
• Sea level
• Ocean currents
• Prevailing winds
• Human influence

CLIMATE AND ADAPTATION:

Adaptation- The featuresand habits that help animals to live in a habitat are called adaptation.

Classified according to adaptation in three regions:- 

(i) The polar regions-
The polar regions present an extreme climate. These regions are covered with snow and it is very cold for most part of the year. For six months the sun does not set at the poles while for the other six months the sun does not rise. In winters, the temperature can be as low as –37°C.


(ii) The tropical rainforests-
The tropical region has generally a hot climate because of its location around the equator. Even in the coldest month the temperature is generally higher than about 15°C. During hot summers, the
temperature may cross 40°C.  Tropical region having hot summers and plenty of rainfall.


(iii) Desert-
Have extreme climate receive less rainfall and large amount of sunlight.

Migration- The regular mass movement of animals from certain regions is known as migration. Migration is another means to escape the harsh, cold conditions.