Matter in Our Surroundings — Science STD 9 — Question

Explain why, a cricket player moves his hands backwards while catching a fast cricket ball.

While diluting a solution of salt in water, a student by mistake added acetone (boiling point 56°C). What technique can be employed to get back the acetone? Justify your choice.

How will you separate water from mustard oil?

The substance X normally exists in a physical state which can flow easily but does not fill its vessel completely. It also turns anhydrous copper sulphate blue. When substance X is cooled excessively, it changes into a substance Y which has a fixed shape as well as a fixed volume. If, however, the substance X is heated strongly, it changes into a substance Z which has neither a fixed shape nor a fixed volume.

1. Name the substances (i) X (ii) Y and (iii) Z.
2. What is the process of conversion of X into Y known as?
3. At which temperature X gets converted into Y?
4. What is the process of conversion of X into Z known as?
5. At which temperature X gets converted into Z?

Compare the three types of meristems.

Potassium chlorate decomposes, on heating, to form potassium chloride and oxygen. When 24.5g of potassium chlorate is decomposed completely, then 14.9g of potassium chloride is formed. Calculate the mass of oxygen formed. Which law of chemical combination have you used in solving this problem?

If a sprinter runs a distance of 100 metres in 9.83 seconds, calculate his average speed in km/h.