Atoms and Molecules — Science STD 9 — Question

Separate the following into physical and chemical changes:
Sublimation of a solid, Decomposition of water into hydrogen and oxygen by passing electric current, Formation of clouds, Making a fruit salad from raw fruits, Dissolving carbon dioxide in water.

State two observations which show that atom is not indivisible.

What is a stethoscope? Name the principle on which a stethoscope works.

What valencies will be shown by the elements A, B, C, D and E having atomic numbers 2, 4, 8, 10, and 13 respectively.

State two characteristics of matter demonstrated by:
Brownian motion.

Which of the following are physical changes and which are chemical changes?
Burning of candle wax, Melting of candle wax, Mixing of iron filings and sand, Burning of wood, Breaking a piece of chalk, Burning a piece of paper, Cutting a piece of paper.

How much work is done when a force of 2N moves a body through a distance of 10cm in the direction of force?

Bus X travels a distance of 360km in 5 hours whereas bus Y travels a distance of 476km in 7 hours. Which bus travels faster?

What do you understand by the term ‘acceleration due to gravity of earth'?

When water is heated to a temperature x, it gets converted into steam at temperature x by a process called R. And when steam at temperature x is cooled, it gets reconverted in to water at the same temperature x by a process called S.

1. How much is the value of x in Kelvin?
2. What is the process R called?
3. What is the name of the energy absorbed during the process R?
4. What is process S known as?
5. What is the name of energy released during the process S known as?