Distance travelled (d) = 400 km
Time taken (t) = 5 hour
Average Speed (s) = \(\frac{d}{t}=\frac{400}{5}=80\) 
Average Speed = 80 kmph (or) Km/hr.

PHOTOSYNTHESIS:
Plants manufacture food by a process called photosynthesis. During photosynthesis, carbon-dioxide from the air and water from the soil react in the presence of sunlight and chlorophyll to produce food.
\(\text { Carbon-di-oxide }+\text { water } \underset{\text { Chlorophyll }}{\stackrel{\text { Sunlight }}{\longrightarrow}} \text { food }+\text { oxygen }\) 
RESPIRATIO IN ANIMAL :
When we breathe in air, the oxygen present in the air reacts chemically with digested food within the body to produce carbon-di-oxide gas, water vapour and energy.
Food + Oxygen  Carbon-di-oxide + Water + Energy
(i) carbon-di-oxide formed during respiration dissolves in the blood and is exhaled out of the body through the lungs.
(ii) Plants release oxygen during photosynthesis which is much more than the oxygen consumed by the plants, during respiration.
(iii) Thus, the balance of O₂ & CO₂ in air is maintained.

We get electricity from thermal power, hydel power, tidal power wind power, solar power etc as sources of electricity
Thermal Power stations:
In thermal power stations, the thermal energy generated by burning coal, diesel or gas is used to produce steam. The steam is used to rotate the turbine. While the turbine rotates, the coil of wire kept between the electromagnet rotates. Due to electro magnetic induction electricity is produced. Here heat energy is converted into electrical energy.
Hydel power stations:
In hydel power stations, the turbine is made to rotate by the flow of water from dams to produce electricity. Here kinetic energy is converted into electrical energy. Hydel stations have long economic lives and low operating cost.
Atomic power stations:
In atomic power stations, nuclear energy is used to boil water. Here the steam is used to rotate the turbine. As a result, electricity is produced. Atomic power stations are also called as nuclear power stations. Here nuclear energy is converted into mechanical energy and then electrical energy.
Wind Mills:
In wind mills, wind energy is used to rotate the turbine to produce electricity. Here kinetic energy is converted into electrical energy.

(i) Computers are used in various fields.
(ii) In textile shop it is used for billing.
(iii) Computers are used to control large and small machines.
(iv) Computers are most important educational tools for teachers and learners.
(v) In Railways it is useful to book tickets and for other purposes.
(vi) It is also used in banks, ATM's, Post offices and in many places.
(vii) We can save many data and convert it into information.

FUNCTIONS OF THE ROOT:
i) The root fixes the plant to the soil.
ii) Absorbs water and minerals from the soil.
iii) Stores food in some plants like Carrot and beetroot
FUNCTIONS OF THE STEM:
i) The stem supports the branches, leaves, flowers and fruits.
ii) Transports Water and minerals from roots to upper aerial plant parts.
iii) Transports the prepared food from leaves to other parts through stem.
iv) Stores food as in the case of sugarcane

Linear motion - A coconut falling from a tree
Curvilinear motion - A car driving around a curve
Self rotatory motion - Motion of the wheel in a cart
Circular motion - Athlete running around a track
Oscillatory motion - Swinging of a pendulum
Irregular motion - Movement of people in a bazaar

When there is a change of position of an object with respect to time then it is called motion.
Types of motion:
a) Based on path:
i) Linear motion - a person walking on a straight path
ii) Curvilinear motion - throwing ball
iii) Circular motion - swirling stone tied to the rope
iv) Rotatory motion - a rotating top
v) Oscillatory motion - pendulum of clock
vi) Zig zag (or) Irregular motion - the motion of a bee
b) Based on duration:
i) period motion - movement of hour hand of a clock
ii) Non-periodic  - motion flapping of a flag in wind
c) Based on speed:
9) Uniform motion -  motion of a train at a constant speed
ii) Non-uniform motion - a vehicle moves in different speed

To protect from the skin dry due to over heat.

a) melting of wax and
d) Solidification of the molten wax can be reversed.
Burning of candle is a physical / reversible change. That is,
\(\text { Solid wax } \underset{\text { Cooling }}{\stackrel{\text { Heating }}{\rightleftarrows}} \text { molten wax }\)

Many of us expect that diameter of hole will decrease, but actually as the diameter of ring increases diameter of hole will also increase.

(i) The rib cage is made up of 12 pairs of curved, flat rib bones.
(ii) It protects the delicate vital organs such as heart and lungs.

(i) Cell is the basic structural and functional unit of every living organism.
(ii) cell is self sufficient to carryout all the fundamental and essential functions of an organism.
(iii) Without cell there is no life, So cells are called as building blocks of life.

They are exposed to harsh weather conditions, dust, pollution, heat and cold. So, they can have an adverse effect on their health. Hence, they weak a mask on duty.

(i) Germination of a seed can take more days. Because, it is a slow change.
(ii) "Changes which take place over a long period of time are known as slow changes".

Silver is not used to make electric wires because it is expensive.

The molecules in the solid move faster and vibrate when heating. Spread apart and occupy more space. So solid expands when heated.

(i) The atoms of a gas never stop moving.
(ii) They are not affected by gravity.
(iii) They spread out in order to occupy the available space.

The eye has three main parts namely cornea, iris and pupil

The skeletal system consists of bones, cartilages and joints. It provides a framework for the body.

Cytoplasm is called as "Area of movement"

Plant cell,Animal cell and most of fungi.

(i) Cell membrane
(ii) Cytoplasm
(iii) Nuclecus are the essential components of a cell.

Our earth surrounded by a huge envelope of air is called 'Atmosphere'. Five layers of atmosphere are:
(i) Troposphere
(ii) Stratosphere
(iii) Mesosphere
(iv) Ionosphere
(v) Exosphere

If we remove the fish from the aquarium and keep it in a dark place with green plants,
(i) they can't have sunlight and
(ii) have no CO₂ from the water produced by fish as they breathe.
(iii) Simply say, there is no possibility for photosynthesis to make their food.

When solute is dissolved in a solvent it forms a solution.
Solute + Solvent ⟶ Solution

On strong heating, cane sugar chars to almost pure carbon giving the smell of 'Burnt sugar'.
(i) Initial change - Physical change - melting
(ii) Final change - Chemical change - charring

Plants decaying is a chemical change.

Simple circuit is there in a torch light.

K₁, K₂  should be closed.

(i) The measurement of warmness or coldness of a substance is known as its Temperature.
(ii) SI unit of temperature is kelvin

The tail of the bird helps to change the direction of the movements.

We have to separate mixture,
(i) to remoe impurities
(ii) to separate useful components
(iii) to get a highty pure form substance

Husk or fine dust particles cdnbe separated from rice by the method 'winnowing"

The area where a particular organism actually lives is called its habitat.

Based on habitat, plant are classified as
i) aquatic plants
ii) terrestrial plants.

Charles Babbage and Augusta Ada Lovelace are the pioneers of computer.

We should not wash the fruits and vegetables after cutting because they lose some of their nutrients and thus their nutritional value gets reduced.

c. Flash card

1 millimetre < 1 centimetre < 1 Metre < 1 kilometre.

1.  Millimetre
2.  Second
3. Error
4. Time
5. Mass
6. Average
7. Length
8. Odometer
9. Tape
10. Litre