Attraction and Repulsion
It is observed that when the ends of two magnets are brought near each other, they either pull towards or push away from each other. The pulling of magnets towards each other is termed as attraction and pushing away from each other is called repulsion.
When North pole of a magnet is brought near the more... 
Three states of water and their inter conversion
Similarly, water on heating to 100°C starts boiling and changes into steam.
This process is called vaporisation or Boiling. Also steam or water vapour on cooling change to liquid water and the process is called condensation.
You can see snow on mountains. Snow is a natural form of ice. Snow melts and the water flows down through the hills.
We observe in our surroundings that water from sea, lakes, ponds, plants, etc. water evaporates all the time (especially in summer), and the evaporated water goes into the air as water vapour.
A very common observation is formation of water droplets on a glass containing cold water or ice cubes. It happens because the water vapour present in the atmosphere changes (condenses) into water drops on coming in contact with the cool glass.
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Do You Know
Antarctica is the driest continent on the earth.
Rain on venues is made up of sulphuric acid and due to intense heat there, is evaporates before reaching the surface.
CLOUDS AND RAIN
The air around us is moist. It is because water keeps on evaporating from the water bodies such as lakes, rivers, sea etc. on the surface of earth. Though we cannot see the water vapours as they are invisible but we can always feel them. For e.g. on a hot and sticky day in summer, or on a cold foggy day of winters, we can feel the water vapours all around us.
The warm air holding more... 
COMPONENTS OF FOOD
The main components of foods are carbohydrates, protein, fats, vitamins andminerals. These are called nutrients.
Carbohydrates
Carbohydrates are also called energy giving food. It is the main sources of energy It is made up of carbon, hydrogen, and oxygen. There are three types of carbohydrates.
(a) Sugars: It is a simple carbohydrate having sweet taste. Sources of sugarare glucose, Sugarcane, milk and fruits; such as banana, apple, grapes, etc.
(b) Starch: It is a complex carbohydrate. It is a tasteless, colour less, white power. Sources of starch are : wheat, maize, potato and rice.
(c) Cellulose: It is present in plant cell wall. It is a complex carbohydrate.
Humans cannot digest cellulose.
Children, players and people who do manual work require more carbohydrates.
Protein
Protein helps in body growth and repairs the tissues so it is also called bodybuilding food. We get protein from milk, eggs, meat, fish and all kinds ofpulse.
Protein molecule is made of a large number of smaller molecules called aminoacid. The daily requirement of protein for adults is 1 gram per kilogram of thebody weight. When the body is building new tissue, more proteins are required, so growing children and pregnant lady more... 
Air Balloons
Properties of air
\[\to \]Air occupies space.
\[\to \]Air exerts pressure.
\[\to \]Air cannot be seen but it can be experienced.
The atmosphere extends upto 1000 km above the surface of Earth. However this air gets thinner and thinner as we go up. That is why mountaineers have to carry their own oxygen supply in oxygen in cylinders. Ninety nine percent of air is found up to a height of 30 km above the surface of Earth.
Composition of air
Air is a mixture of gases, water vapour and dust particles. Lavoisier was the first scientist to prove that air is a mixture of gases and not a compound.
He found that
(1) Air is a mixture of gases. Oxygen is the active part of air and make up about one fifth of air by volume.
(2) When certain substances are burnt in air, they combine with oxygen.
So air is a mixture and not a compound.
Composition of dry air. Dry air is without water vapour
| Gas | Percentage by volume |
| 1. Nitrogen 2. Oxygen 3. Rare gases (including 0.93% argon and0.018% neon) 4. Carbon dioxide 5. Impurities | 78.09 20.95 01.00 0.02 to 0.04 Variable |
\[=\frac{1}{2}\times BC\times AD\]
Observe the given figure,
\[\Delta \,ABC\] is a right angled triangle, right angled at B.
Area of \[\Delta \,ABC=\frac{1}{2}\,BC\times AB\]
For Example:
Find the perimeter and area of triangle ABC.
Sol: \[P=AB+BC+CA\] = 7 + 4 + 5 = 16 cm Base = BC, Height =AD
Area
\[=\frac{1}{2}\times BC\times AD\]
\[=\frac{1}{2}\times 4\times 3\]
\[=6c{{m}^{2}}\]
2. RECTANGLE
Area of rectangle \[ABCD=AB\times BC=l\times b\]
Perimeter of rectangle = sum of all sides
\[=l+b+l+b\] \[=2l+2b\] \[=2(l+b)\]
Diagonal (AC) of rectangle \[=\sqrt{{{l}^{2}}+{{b}^{2}}}\]
For example:
For the adjoining rectangle find:
(i) the perimeter;
(ii) the area.
Sol. Perimeter \[=2(l+b)\,=2(6+4)\,=2\times 10=20\,cm\] Area \[=l\times b=6\times 4=24\,c{{m}^{2}}\]
3. SQUARE
Perimeter of square ABCD with side \[a=4a\]
Area of square with side \[a={{a}^{2}}\]
Diagonal of square
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Fractions in the form of \[1\frac{1}{4}\] or \[2\frac{1}{2}\] are know as mixed fractions.
Let us represent mixed fraction by using figures.
EQUIVALENT FRACTIONS
Equivalent fractions represent same part of the whole.
For example \[\frac{1}{2}\,=\frac{2}{4}\,=\frac{3}{6}\,=\frac{4}{8}\,=\frac{5}{10}\]
We can find more equivalent fractions by multiplying or dividing the numerator and the denominator by the same number.
SIMPLEST FORM OF A FRACTION
A fraction is said to be in the simplest form (or lowest form) if its numerator and denominator have no common factor except 1.
The easiest way to find the simplest form of a fraction is to divide the numerator and denominator by their HCF.
For example: To reduce \[\frac{125}{225},\] find their HCF.
HCF of 125 and 225 =25
\[\therefore \,\,\,\,\,\,\frac{125}{225}\div \frac{25}{25}=\frac{5}{9}\] simplest form
To reduce \[\frac{36}{72}\]
H.C.F of 36 and 72 = 36
\[\therefore \,\,\,\,\,\frac{36}{72}\div \frac{36}{36}=\frac{1}{2}\] simplest form.
LIKE FRACTIONS
Fractions with the same denominator are called like fractions.
\[\frac{4}{13},\,\frac{3}{13},\,\frac{12}{13},\,\frac{9}{13}\] are examples of like fractions.
UNLIKE FRACTIONS
Fractions like \[\frac{1}{5},\,\frac{2}{3},\,\frac{3}{4}\] have different denominators are called unlike fractions.
Fraction on the number line
Let us draw a number line and mark \[\frac{3}{4}\] on it. \[\frac{3}{4}\] is greater than 0 and less that 1. As \[\frac{3}{4}\] means 3 part out of 4, we will divide the gap between 0 and 1 into four equal parts, and mark \[\frac{1}{4},\,\frac{2}{4},\,\frac{3}{4},\,\frac{4}{4}(=1)\] as shown below.
LINE SEGMENT
A line segment is a portion of a line with two fixed end points.
For example:
(i) An edge of a box.
(ii) 
This is a line segment named as AB and read as line segment AB.
INTERSECTING LINES
If two or more lines meet each other at one point then they are called intersecting lines.
AB and CD are intersecting lines and 0 is the point of intersection
PARALLEL LINES
If two or more lines do not meet each other, whenever they are extended, then they are called parallel lines.
AB is parallel to CD
CONCURRENT LINES
If three or more lines pass through a point, then they are called concurrent lines and the point through which these all lines pass is called point of concurrent.
TRANSVERSAL
A line which intersects two or more given lines at distinct points is called a transversal of the given lines.
For example
Here line \['\ell '\] is transversal of lines 'm' and 'n'
PERPENDICULAR LINES
Perpendicular lines are two lines that intersect each other at a right angle.
For example:
A line AB placed horizontally and line CD placed vertically to AB as shown in above figure.
ANGLES
Two rays with a common initial point form an angle.
The space within the arms of an angle, produced indefinitely, is called the interior of the angle.
The space outside the arms of an angle, produced indefinitely, is called the exterior of the angle.
Two angles which have a common arm, a common vertex, and lie on either side of the common arm are called adjacent angles.
Here \[\angle \,AOB\] and \[\angle \,BOC\] are adjacent angles.
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