Diversity In Living Organisms — Science STD 9 — Question

What are conducting elements of xylem?

A bus decreases its speed from 80km/h⁻¹ to 60km/h⁻¹ in 5s. Find the acceleration of the bus.

Explain the term ‘pitch’ of a sound. On what factor does the ‘pitch’ of a sound depend?

Classify the following materials as homogeneous mixtures and heterogeneous mixtures:
Soda-water, Wood, Air, Soil, Vinegar, Alcohol and water mixture, Petrol and water mixture, Chalk and water mixture, Sugar and water mixture, Copper sulphate solution.

What do the following abbreviation stand for?

1. O
2. 2O
3. O₂
4. 3O₂

What is the mass of 5 moles of sodium carbonate (Na₂CO₃)?
(Atomic masses: Na = 23u; C = 12u; O = 16u)

A car is moving on a level road. If the driver turns off the engine of the car, the car’s speed decreases gradually and ultimately it comes to a stop. A student says that two forces act on the car which bring it to a stop. What could these forces be? Which of these two forces contributes more to slow down and stop the car?

Explain the formation of (i) sodium ion, and (ii) chloride ion, form their respective atoms giving the number of protons and number of electrons in each one of them. What is the reason for positive charge on a sodium ion and a negative charge on a chloride ion?

What is the number of valence electrons in:

1. Sodium ion, Na⁺
2. Oxide ion, O^2-