Parallelogram : A parallelogram is a quadrilateral, in which both the pairs of opposite sides are parallel. The quadrilateral ABCD, drawn alongside, is a parallelogram; since, AB is parallel to DC and AD is parallel to BC i.e.

AB || DC and AD || BC. Also, in a parallelogram ABCD: (i) opposite sides are equal: i.e. AB = DC and AD = BC. (ii) opposite angles are equal: i.e. ∠ABC = ∠ADC and ∠BCD = ∠BAD (iii) diagonals bisect each other : i.e. OA = OC = 12 AC and OB = OD = 12 BD.

Some special types of Parallelograms (a) Rhombus : A rhombus is a parallelogram in which all its sides are equal.

∴In a rhombus ABCD : (i) opposite sides are parallel: i.e. AB||DC and AD||BC. (ii) all the sides are equal: i.e. AB = BC = CD = DA. (iii) opposite angles are…

Quadrilateral: A quadrilateral is a plane figure enclosed by four sides. It has four sides, four interior angles and four vertices.

In quadrilateral ABCD, shown alongside: (i) four sides are : AB, BC, CD and DA. (ii) four angles are : ∠ABC,∠BCD, ∠CDA and ∠DAB ; which are numbered∠1, ∠2, ∠3 and ∠4 respectively. (iii) four vertices are : A, B, C and D.

Diagonals of a Quadrilateral : The line segments joining the opposite vertices of a quadrilateral are called its diagonals.

The given figure shows a quadrilateral PQRS with diagonals PR and QS. Types of Quadrilaterals : 1. Trapezium: A trapezium is a quadrilateral in which one pair of opposite sides are parallel.

A.State whether the following statements are true or false.

1.Liquids have fi xed shape and volume.

2. The volume of liquid depends on the size of the particles.

3. The molecules of gases are in constant motion.

Name the following.

Name some oxides of Oxygen