Nutrition in Plants Class 7 Science - Chapter 1 7 Ch 1... · 2020. 4. 11. · E.g. Amoeba Organisms with more than one cell in their body are called multicellular organisms. All human

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Nutrition in Plants Class 7 Science - Chapter 1

Introduction to Nutrition in Plants

Living and Non-Living Organisms

Living organisms like human beings, plants and animals need food to survive and exist.

Living organisms reproduce, respond to the environment and also adapt.

Living organisms respire and excrete as well

Cells

Cells are tiny units that help make up a living organism. Hence they are also

called building blocks of an organism.

A cell is constituted of three major parts :

A thin outer layer called the cell membrane.

A spherical structure located at the centre of the cell called a nucleus.

A jelly-like substance that surrounds a nucleus called the cytoplasm.

Single and Multi-Cellular Organisms

Organisms that are made up of just one cell are called single-celled or Unicellular

organisms. E.g. Amoeba

Organisms with more than one cell in their body are called multicellular organisms.

All human beings, plants and animals are multicellular organisms.

Nutrition

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

Nutrition is very important as the nutrients from the food consumed enables living

organisms to build their bodies and grow.

Nutrition helps to repair damaged parts and organs.

Nutrition also provides energy for carrying out various functions.

Autotrophs and Heterotrophs

Organisms that make food themselves are called autotrophs.

Plants are an example of autotrophs as they make their own food using carbon dioxide,

water and light energy.


Organisms that rely on others and usually take in ready-made food made by the

autotrophs are called heterotrophs.

Animals and human beings are an example of heterotrophs as they depend on plants in

many ways for their food.

Photosynthesis

Photosynthesis is the process of synthesis of food by green plants.

This process usually takes place in the leaves of plants.

The process requires chlorophyll (green coloured pigment), sunlight, carbon dioxide and

water.

Organelles

Organelles are tiny cellular structures inside a cell and perform specific functions that

are important for the cell.

They are found in the cytoplasm of a cell.

E.g. Chloroplast is the cell organelle that carries out photosynthesis.

Chloroplasts

The chloroplast is a type of organelle that exists in plants.

These organelles contain chlorophyll, the green coloured pigment that is responsible for

carrying out the process of photosynthesis in plants.

Chlorophyll

Chlorophyll is the pigment that is responsible for the synthesis of food in green plants.

This pigment green colour to its bearers and is abundantly found in leaves.

Chlorophyll is locked inside the chloroplast.

Process of Photosynthesis

The process of photosynthesis takes place in the leaves, the “food factory” of the plants.

Carbon dioxide is taken in through tiny pores on the leaves called stomata.

Water and minerals that are required for the process are transported to the leaves from the

roots through the stem.

Chlorophyll helps the leaves use the energy from the sunlight to prepare food using the

carbon dioxide, water and minerals.


Oxygen is released as a byproduct of this process.

The equation can be given as:

Nutrients Being Replenished in Soil

Nutrients

Plants absorb mineral nutrients from the soil in order to make their own food and for

other important processes.

Soils need to be enriched with nutrients such as nitrogen, phosphorus, potassium etc

regularly.

Only then can we grow plants and keep them healthy.

There are 17 most important nutrients for plants.

6 are called macronutrients and rest are called micronutrients.

Macronutrients are required in large quantities while micronutrients are required in very

small quantities.

Other Modes of Nutrition

Symbiotic Relationship

Organisms that live together and share their shelter and nutrients are said to be in

a symbiotic relationship.

Certain fungi live in the roots of trees.

The tree provides nutrients to the fungus and, in return, receives help from it to take up

water and nutrients from the soil.

This association works well for both the fungi and the tree.

Another most common example is of Rhizobium bacteria.

They reside in the root nodules of leguminous plants.

The bacteria provide a plant with nitrogen that they fix and in turn, they get shelter and

food from the plant.

Rhizobium

Rhizobium is a type of bacteria that convert atmospheric nitrogen into a soluble form that

can be utilised by plants (nitrogen fixation).

It usually resides in the roots of leguminous plants like peas, gram, moong etc and is

instrumental in providing these plants with a rich source of nitrogen.


Nitrogen Fixation

Nitrogen is an important nutrient required for soil and for plants.

However, nitrogen in the atmosphere is not easily accessible.

The process by which nitrogen is converted into a form that can be used by plants and

other living organisms is called nitrogen fixation.

Parasites

A parasite is a heterotroph that completely depends on another organism for its food.

The organism to which the parasite latches onto is called the host.

The host, in the process, is deprived of all nutrients for its own growth as they are

consumed by the parasite.

For example, Cuscuta (Amarbel) is a nongreen plant that takes readymade food from the

plant on which it is growing.

Saprotrophs

Organisms which rely on dead and decaying matter for their food are

called Saprotrophs.

This mode of nutrition is called saprotrophic nutrition.

For example, Fungi.

Fungi secrete digestive juices on the dead and decaying matter and convert it into a

solution.

Then they absorb the nutrients from it.

Insectivorous Plants

Plants that feed on insects are called Insectivorous plants.

These plants are green and carry out photosynthesis.

But they grow in nitrogen-deficient soils.

So, in order to get nitrogen, they feed on insects.

These insectivorous plants have their parts modified for attracting and catching insects.

For example, The pitcher plant, Venous flytrap

Did You Know?

Cactus Plants


Most of the photosynthesis takes place in the leaves of green plants.

However, in case of some desert plants, it takes place in their stem and even branches.

Cacti are found in the desert and their leaves are modified to spines to avoid loss of water

due to transpiration.

Therefore, their green stems enable them to carry out the process of photosynthesis.


Nutrition in Animals Class 7 Science - Chapter 2

Different Ways of Taking Food

Each species or type of organism has their own way of taking in food.

Bees and hummingbirds suck plant-nectars, infant of humans and some animals feed on

mother’s milk, Snakes such as python consume the animals upon which they prey.

Aquatic animals filter small food particles floating closeby and feed on them.

Digestion in Humans

The digestive tract and the associated glands together constitute the digestive system in

humans.

This constitutes the whole path along which food moves through the body, starting from

the mouth and ending at the anus.

Digestive tract includes the oesophagus, stomach, small intestine and large intestine.

Salivary glands, liver and pancreas are the major digestive glands.

Buccal Cavity

The buccal cavity is more commonly known as the mouth, and it is the beginning of the

digestive system for humans.

It consists of the tongue and teeth.

Teeth: Helps in chewing food and breaking down food into smaller particles.

Tongue: Fleshy muscular organ attached at the back to the floor of the buccal cavity.

Saliva is secreted in the mouth and helps in the break down of food.

Tongue

It is a muscular organ, fleshy in nature attached to the back of the base of the buccal

cavity.

It helps in mixing saliva with food while chewing and aids in swallowing.

The tongue possesses tastes buds that help us recognise different tastes.

Tooth Decay

Bacteria present in mouth break down the sugars present from the leftover food and

release acid.

These acids gradually damage the teeth and results in tooth decay.


Oesophagus or food pipe

The food that is swallowed, passes into the oesophagus.

It is a muscular tube, about 25 cm long, with a sphincter (valve/opening) at each end.

Its function is to transport food and fluid, after being swallowed, from the mouth to the

stomach.

Food is propelled down by as there in movement through the walls of the food pipe.

Stomach

It is a thick-walled bag-like structure.

It obtains food from the food pipe and opens into the small intestine towards the other

opening.

The inner lining of the stomach produces mucus, hydrochloric acid(HCl)and other

digestive juices.

Food is churned into semi-solid mass in the stomach.

Enzymes present in the gastric juice disintegrate the food.

Hydrochloric acid helps in partial digestion of proteins and also kills harmful bacteria.

Small Intestine

This is a highly coiled organ of 7.5 metres length.

It receives secretion from the liver and pancreas.

Complete digestion and absorption of food take place in the small intestine.

The inner walls of the intestine have finger-like outgrowth called villi.

Villi increase the surface area for absorption of food.

Each villus has a small network of blood vessels.

Absorbed food by villi is transferred to the body via blood vessels.

Large Intestine

It is wider and shorter than the small intestine.

It is 1.5m in length.

Absorption of water and salt from undigested food occurs in the large intestine.

Remaining waste matter is passed out through the rectum.

Time to time, faecal matter is removed through the anus (egestion).

Anus

The anus is the opening at the end of the human digestive tract.


The removal of faecal matter from the large intestine occurs through the anus and this

process is called egestion.

Saliva and Salivary glands

Three pairs of salivary glands are present around the mouth and they pour their secretion,

saliva, into the mouth by salivary ducts.

Saliva has mucous and salivary amylase.

Mucous helps in easy passage of food through the food pipe.

Salivary amylase is an enzyme responsible for breaking of starch content of food into

simpler sugars.

Gall Bladder

The gallbladder is a small pear-shaped organ present under the liver, on the right side of

the body.

It stores bile juice secreted by the liver.

Bile plays an important role in the digestion of fats.

Ingestion

The process of taking food into the body is called ingestion

Digestion

The breakdown of complex components of food into simpler substances is called

digestion.

Partial digestion takes place in the stomach and complete digestion takes place in the

intestine.

Absorption & Assimilation in Small Intestine

The digested food is taken up by the blood vessels lining the small intestine’s walls. This

phenomenon is referred to as absorption.

The inner walls of the small intestine have many finger-like outgrowths called villi.

The substances that are absorbed are transported through blood vessels to various organs

of the body where it is utilized to build complex substances like proteins essential for the

body. This is called assimilation.

Digestion in Grass Eating Animals

Digestive system in grass eating animals is different from that of humans.


These animals are chewing continuously even when they are not eating.

They swallow the grass very fast and store it in a chamber called Rumen.

In the rumen, the bacteria partially digest the food and now it is called as cud.

Later, cud reverts to the mouth and animal chews it again slowly.

This phenomenon is referred to as rumination and the animals are called as ruminants.

They also have very long small intestine which helps in complete digestion of cellulose,

the main component of grass.

Cud

Partially digested food, returned from rumen into the mouth, for further chewing is called

as cud.

Rumination

Rumination is the process by which the cattle regurgitates previously consumed feed

and masticates it a second time.

Feeding and Digestion in Amoeba

Amoeba

Amoeba is single-celled organism, microscopic in nature found in pond water.

Amoeba regularly changes its shape and position.

Process of Digestion in Amoeba

Amoeba captures the food particles with the help of pseudopodia. The process is called as

phagocytosis.

A food vacuole is thus created with the food material inside.

Digestive juices are produced into the food vacuole when it is moving through the

cytoplasm.

They act on the food and disintegrate it down into simpler substances and the digested

food is then absorbed.

Finally, the food vacuole opens to the outside and undigested food is released into

surrounding water.


Fibre to Fabric Class 7 Science Notes - Chapter 3

Fibres from Plants

Plant fibre is mainly composed of cellulose and cellulose fibres. These are most

commonly used to make paper and cloth.

Cellulose generates long, often highly lustrous fibres when prepared appropriately.

Plants including cotton, jute, flax and hemp are used to obtain plant fibres.

Jute

Jute fibre is obtained only from the stem of the jute plants. It is soft, shiny and long fibre

with a silky texture which is grown in rainy season.

Jute mainly grows in regions having alluvial soil which is found in the delta regions of

the Ganges and Brahmaputra rivers.

Basics of Fabric

Fibres

The finer part of the thread is referred to as fibre.

Fibre is a thread like structure that is spun into ropes, clothes and strings.

Fabrics are made from fibres obtained from natural or artificial sources. Example: rayon,

nylon, polyester, etc.

Fibre to Yarn to Fabric

Fabric consists of thin strands called yarn, which in turn consists of thinner strands called fibres.


Cotton and Its Processing

Cotton is obtained from cotton bolls which are directly from the surface of cotton seeds.

It is grown in black clayey soil with a warm climate.

The processing of cotton involves Ginning, Spinning, Weaving and Knitting.

Wool

Fibre from Animals

Wool

The natural animal fibre obtained from sheep, goat, yak, camel, etc.

All these animals have an outer covering of hair, which is shaved off to obtain wool

fibres.


Silk

Natural protein fibre is cultivated from the cocoon of mulberry silkworm larvae.

Wool from Animals

Wool comes from sheep, goat, yak and some other animals. These wool-yielding animals

bear hair on their body because hair keeps them warm and wool is derived from these

hairy fibres.

Wool is used to make various wool fabrics like woollen clothes, carpets, woollen

sweaters, saddle cloths etc.

Rearing and Breeding of Sheep for Wool

Rearing: It is a process of breeding, feeding and providing medical care to sheep. These animals

are kept since they produce one or more useful products for the human beings.

Breeding: Some special breeds of sheep are specially chosen to give birth to sheep which have

only soft under hair. This process of selecting parents for obtaining special characters in their

offspring is termed as ‘selective breeding’.

Mary Had a Little Lamb

Processing fibres into wool

The skin of the sheep is hairy having two types of fibres forming its fleece:

(i) the coarse beard hair

(ii) the fine soft under-hair near the skin is the fleece.

This fleece is the main source of fibres of wool.

The process of making fibre into wool follows a series of processes: Shearing → Scouring →

Sorting → Dyeing → Straightening, Rolling and Combing.

Occupational hazards of fibre production

Sometimes the sorters get infected by a bacterium, anthrax, which causes a fatal blood disease

called sorter’s disease.


Silk

Silk from Animals

Silk is a natural protein fibre which is obtained from silkworm and can be used as a

textile fibre.

The different types of silk are produced by different types of silkworms.

It can be differentiated on the basis of lustre and texture. Few examples are Kosa, tassar,

mooga, etc. They are produced by various types of silkmoths. One of the common types

is the mulberry silkmoth.

Development of Silk Moth

Sericulture

Rearing of silkworm to produce raw silk is called sericulture.

In this process, silkworms are reared at appropriate temperature and humidity to get silk

threads from cocoons.

Processing Silk Obtained from Cocoons

Cocoons are collected and left under the sun, or boiled for separating out the silk fibres.

After that reeling of silk is done, the process of unwinding silk from a cocoon.

Then, the spinning of silk fibres into threads is done.

The silk threads obtained are woven into desired clothes.


Natural Fibres vs. Synthetic Fibres

Natural Fibres

The naturally occurring fibres that humans derive from plants or animals are known as

natural fibres.

Animal fibres: These are the fibres that are acquired from animals. For example Wool,

silk etc.

Plant fibres: These are the ones that are obtained from plants. These fibres are extracted

from the plants to make fabrics.

Synthetic Fibres

Fibres that are made by humans using chemical substances are known as synthetic or

man-made fibres.

These are more durable than natural fibres.

For example:- Polyester, Nylon, Acrylic etc.


Heat Class 7 Science Notes - Chapter 4

Have you ever experienced feeling cold inside the house and warm in sun during winter? Also,

feeling hot inside as well as outside the house in the summer season? To protect ourselves from

the chilling cold we wear clothes made of wool. These woolen clothes are obtained from wool

yielding animals such as sheep, goat, yack, etc. Wearing light colored clothes during summer

will give us a feeling of coolness. To know if the object is hot or cold, and the degree of its

hotness, we will be studying this chapter. The measure of the intensity of heat present in a

substance is called temperature. It is measured with the use of a device called thermometer.

There are two types of thermometer viz Laboratory thermometer and clinical thermometer.

Below are a few differences between the two:

Laboratory thermometer Clinical thermometer

It is mainly used in labs for scientific purposes Used at hospitals, homes, etc.

Wide range and accurate Short range and Simple device

Few Important Questions

1. Why stainless steel pans are provided with copper bottoms? Explain.

2. What happens when one end of a wooden spoon is dipped in an ice cream cup?

3. Calculate and give the right answer: 1lt of water at 30°C is added to 1lt of water at 50°C.

What is the temperature of the mixture?

4. Which color clothes absorb more heat when compared to light colors?

5. What are conductors? Give one example.

6. What are insulators? Give an example.

7. Distinguish between the clinical thermometer and the laboratory thermometer.

8. How to determine the hotness of an object?

Thermometer: Clinical & Laboratory Thermometer Thermometer (thermos: hot; metron: measure) is the universal instrument used to measure temperature. Temperature and heat are two words which often confuses people. For example, how do you explain the hotness of an object? What is the measure or basis for that hotness? The answer to that is temperature. Heat is a form of energy and its unit is Joules. On the other hand, Temperature is the measure of that heat. Which means, if the heat is more, the temperature is more as well. But how do we measure temperature? We use a device called thermometer to measure the temperature of any object.

Temperature & Thermometer

By definition, the temperature is the measurable extent of hotness or coldness. It is a mathematical representation of heat. There are different units to measure temperature, like Celsius (˚C), Kelvin (K) and Fahrenheit (˚F).

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There are different types of thermometers according to the needs. For example, there are one set of thermometers which is used to measure body temperature while another set of thermometers to measure boiling point and freezing point during experiments. Here, we will discuss the two types of thermometers, namely, clinical thermometer and laboratory thermometer.

Properties of thermometric liquid

The liquid that is used in the thermometer needs to have some properties and they are listed below:

The liquid used should be visible.

The thermal expansion of the liquid must be uniform.

The freezing point of the liquid used must be low.

Clinical Thermometer

Clinical thermometers are meant for clinical purposes. It is developed for measuring the human body temperature. It is a long narrow glass tube with a bulb containing mercury at the end. The normal human body temperature is 37˚C; which can fluctuate between the ranges 35˚C to 42˚C. Hence, the clinical thermometers have the range 35˚C to 42˚C. The level of mercury tells our body temperature in ˚C. Since mercury is a toxic element, thus these thermometers have been replaced by digital thermometers nowadays.

Note: Clinical thermometers must be sterilized before use for the safe and clean check-up.

How to read a Thermometer?

The thermometer is washed with water at normal temperature.

It is given a few jerks. We notice that the jerks bring the level of mercury down.

We make sure that it falls below the 37⁰C mark or the 98⁰F mark, the normal human body temperature.


The thermometer is then kept under the tongue or under the arms in order to get the reading on the thermometer.

The thermometer is then held close to the eye as shown in figure 3 in order to see the correct reading.

The temperature difference indicated between two bigger marks is noted. Also, the number of division (shown by smaller marks) between these marks is noted. For e.g. the bigger mark reads 10 and the number of division is 5, then each division reads the value equal to 10/5 = 20

We note the value of the bigger mark that the mercury thread has crossed (which is 98 in the Fig.4 Example 1). Then the number of the division of the mercury thread has crossed is noted (3 in this case). Now, this value is multiplied by the value of one division (which is 0.2 in this case). Hence, the temperature reading is 98 + (3×2) = 98.6.

Laboratory Thermometer

Since clinical thermometers can’t be used to measure temperature other than the human body, we need a special type of thermometers for other purposes. A laboratory thermometer, which is colloquially known as the lab thermometer, is used for measuring temperatures other than the human body temperature. It ranges from -10˚C to 110˚C. Laboratory thermometers are designed for lab purposes such as checking boiling point, freezing point, or temperature of other substances. You can use a laboratory thermometer for checking the temperature of a solvent but not a clinical one.


Weather reporters also use maximum-minimum thermometers for measuring maximum

and minimum temperatures of a place.

Learn more about thermometers, heat energy and temperature.

Conductors And Insulators

We differentiate the elements around us on the basis of their physical properties such as

malleability, phase, texture, colour, polarity, solubility etc. But as we know, another very

important classification of elements is done on the basis of their conductivity of electric charge

i.e. conductors and insulators.

If we perform a simple experiment with a battery and a small LED bulb, we will notice that

when then the electric circuit between the battery and the bulb is completed using a plastic or a

cotton thread, the bulb doesn’t glow, whereas if we perform the same experiment with the help

of a metallic wire such as copper, the bulb starts to glow. This indicates that some of the

elements enable the transfer of charge from the battery to the bulbs, while others do not. The

basis of the classification of such elements is their electrical conductivity. Let us learn more

about conductors and insulators in this comprehensive article.

What are Conductors?

In simple terms, an electrical conductor is defined as materials that allow electricity to flow

through them easily. This property of conductors that allow them to conduct electricity is known

as conductivity.

The flow of electrons in a conductor is known as the electric current. The force required to make

that current flow through the conductor is known as voltage.

When a charge is transferred to such an element, it gets distributed across the entire surface of

the object, which results in the movement of electrons in the object. The charges transferred to

an electrical conductor distribute until the force of repulsion between electrons in areas of excess

electrons is decreased to the minimum value. When such an object is brought in contact with

another conductor, the charge gets transferred from the first conductor to the other until the

overall repulsion due to charge is minimized.

Metals, humans and Earth are all conductors. This is the reason why we get electric shocks!

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Examples of conductor

Graphite, the human body and the earth are good conductors of electricity. Some of the common

conductor examples include metals such as:

Copper

Gold

Iron

Conductors And Insulators Examples

What are Insulators?

Insulators are materials that hinder the free flow of electrons from one particle of the element to

another. If we transfer some amount of charge to such an element at any point, the charge

remains at the initial location and does not get distributed across the surface. The common

process of charging of such elements includes charging by rubbing (for some elements, with the

help of suitable materials) and charging by induction.

Examples of insulators

Some of the common insulator examples are given below:

Plastic

Wood

Glass

Differences Between Conductor and Insulators

Some key conductor and insulator differences are given in the table below.


Conductor Insulator

Materials that permit electricity or heat to pass through it

Materials that do not permit heat and electricity to pass through it

A few examples of a conductor are silver, aluminium and iron

A few examples of an insulator are paper, wood and rubber

The electrons move freely within the conductor

The electrons do not move freely within the insulator

The electric field exists on the surface but remains zero on the inside

The electric field doesn’t exist

Frequently Asked Questions on Conductors and Insulators Questions

Which of the following is the most conductive element?

1) Copper 2) Iron 3) Silicon 4) Silver

Silver is the most conductive element.

Why are metals a preferred choice of material for making electrical wires?

Metals are a preferred choice of material for making electrical wire because they are good

conductors of electricity.

The material that has a resistance of zero is known as a _____.?

Superconductor

What is a semiconductor?

A semiconductor is a material whose electrical conductivity falls between that of a conductor and

an insulator. Example, Germanium and Silicon

What is the purpose of lightning rods?

The purpose of a lightning rod is to protect structures from lightning damages by blocking the

surges and guiding their currents to the ground.


Which are the factors that affect the resistivity of a conductor?

The resistivity of a conductor depends on

Temperature

The material with which the conductor is made of


Acids, Bases and Salts Class 7 Science Chapter 5

Acids and Bases

Acids

Acids are substances that taste sour and are corrosive in nature.

It turns blue litmus paper to red.

These substances are chemically acidic in nature.E.g.:-orange juice, curd, vinegar,

hydrochloric acid etc.

Bases

Bases are substances that, in aqueous solution, are slippery to the touch and bitter in taste.

It turns red litmus paper to blue.

These substances are chemically basic in nature. Eg:- soap, ammonium hydroxide,

calcium hydroxide, etc

Neutralisation Reaction

When an acid and base react with each other to form a salt, water and heat then such

reaction is known as neutralisation reaction.

In this reaction, the acidic and basic nature of the acid and base respectively are

destroyed.

The reaction between hydrochloric acid and sodium hydroxide is a classic neutralisation

reaction where sodium chloride is formed.

HCl+NaOH→NaCl(salt)+H2O

Salts

Salts

Salt is the product formed from the neutralisation reaction of acids and bases.

In the reaction between hydrochloric acid and sodium hydroxide the salt formed is

sodium chloride.

HCl+NaOH→NaCl+H2O

Salt can be acidic, basic or neutral in nature.

Visual Indicators


Indicators

Substances which are used to test whether a substance is acidic or basic are called indicators.

Acidic Solution Basic Solution

Red litmus No change Turns blue

Blue litmus Turns red No change

Natural Indicators

Plants or plant parts contain useful chemicals that are used for testing an acidic or basic

property of a solution are termed as natural indicators. China Rose and turmeric are

examples of natural indicators.

Litmus

Litmus is a naturally occurring purple indicator which is extracted from lichens.

When added to an acidic solution, it turns red and when added to a basic solution, it turns

blue.

It is available in the form of a solution or as strips of paper known as litmus paper.

(A) Red litmus turns blue indicating a basic solution

(B) Blue litmus turns red indicating an acidic solution

Phenolphthalein

Phenolphthalein is an acid-base indicator which is colourless in acid solution but turns

pink to red as the solution becomes alkaline.

It is a synthetic indicator and is used for the neutralisation experiment.

Olfactory Indicators

Olfactory indicators are substances whose smell changes whether they are mixed with an

acidic or a basic solution.

Onion, clove oil and vanilla extract are examples of such indicators.

Visual Indicators


Visual Indicators are substances used to show visually (as by a change in colour) the

condition of a solution with respect to the presence of a particular material (as a free acid

or base).

Common examples are litmus, red cabbage, phenolphthalein, etc

Neutralization

Neutralisation in Daily Life

During indigestion, taking milk of magnesia (magnesium hydroxide) gives us relief as it

neutralizes the effect of excess acid produced inside the stomach.

The effect of ant sting which is caused by formic acid can be neutralized by rubbing

moist baking soda (basic in nature).

To ensure that plants can grow well, the soil is treated with either acids or bases

depending if it’s basic or acidic in nature.

Factory wastes, generally being acidic in nature can cause environmental damage, are

treated with basic substances before discharge.

Recap of Concepts

Safety Measures While Using Acids

When diluting acids, pour the acid into the water, NOT water into acid as this may cause

spattering of the acid.

Safety gloves are to be worn whenever working with acids or bases.

Uses and Applications

pH of Soil

Excessive use of chemical fertilisers changes the pH of the soil.

Plants do not grow well when the soil is either too acidic or too basic.

Hence substances are added to bring the pH at a neutral level.

Uses of Acids and Bases

Food preservation – Citric acid.

Aerated drinks – Carbonic acid.

Baking powder – Tartaric acid.

Cooking – Acetic acid(vinegar)


Manufacture of soaps – Sodium hydroxide.

Manufacture of bleaching powder – Calcium hydroxide

As a foaming agent in fire extinguishers – Aluminium hydroxide.

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Nutrition in Plants Class 7 Science - Chapter 1 7 Ch 1... · 2020. 4. 11. · E.g. Amoeba Organisms with more than one cell in their body are called multicellular organisms. All human