Week 3 – For 9th Std

udita ogale 9th Std posts, Whatsapp Posts,

I. Video: Firemen lifting car with water

We have studied about the Newtons law of action and reaction.

Observe the video. Why is the car flying in the air? Identify which is the action force and which is the reaction force.

II. Mixed Qs

1. Derive the formula for pressure = Depth x density x g
2. Derive formula Buoyancy force = Weight of liquid
3. What is the difference and significance of G and g?
4. What is electro negativity?
5. What are polar covalent bonds?
6. What is oxidation state?
7. Find oxidation state of iron in FeO, Fe2O3 and Fe3O4. Find oxidation state of sulphur in SO–radical.
8. Write examples of ionic bond

III. Archimedes Principle

Revise and study Archimedes Principle. Then try to solve the following problems:

  1. A wooden block 10 x 10 x 10 cm is floating on water. Its 8 cm part is inside the water and 2 cm above. Calculate density of the wooden block.
  2. An iron cube weighing 100 gm is kept on the block. Will the block sink or float? How much part will now be submerged under water?
  3. A wooden block 10 x 10 x 10 cm is floating on a mixture of water and oil. It sinks in the oil and floats in the water. Its 6 cm part is inside water and 4 cm inside oil. Density of oil = 0.6 g/cc. Find the density of the block.
  4. A hollow 10cm x 10cm x 10cm box is made out of metal sheet. (without top lid)
    Mass of the the metal box = 200g. Will it float on water? Why?
    If yes, how much part of the box will be above the water surface?
    And maximum how many grams of sand can it carry without sinking?

IV. Respiration and Circulation

Measure your pulse rate = Number of heartbeats in one minute.
Also measure your rate of breathing = How many times you breathe in one minute.

Jump up and down continuously for 1 minute.
Now measure your pulse rate and breathing rate again.

What do you observe? Explain.

V. Activity – Heating Sugar

Do this in presence of your parents ONLY.

Take some sugar in a spoon with a sufficiently long handle. Heat it on the gas flame. (Parents please ensure the SAFETY). Observe. Do you observe yellowish-brown liquid?

Heat it for some more time. What do you observe? Explain.

Photos of activities done by young experimenters

You must have noticed that first we get yellowish liquid. Then it starts turning brown. On heating further, we get black coloured carbon.

It is a surprising fact that tasty and beautiful white-coloured sugar is made up of black-coloured carbon! This is a chemical change.

See the video below –
Observe that carbon in elemental form takes up much more space. So, when sugar gets converted to carbon, it spills over. Also observe that the carbon formed in the spoon can also burn.