Exercise

Write two main differences between an element and a compound. 

The atomic numbers of four elements $\mathrm{P}, \mathrm{Q}, \mathrm{R}$ and $\mathrm{S}$ are $6,\mathrm{}8,\mathrm{}14$ and $16$ respectively. Out of these, the element known as metalloid is:

Which is the incorrect statement, when ammonium chloride is sublimated?

How are physical changes different from chemical changes? Give one example of each.

Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what condition do these grapes ferment? Is it a chemical or a physical change?

Formation of a new substance is the key to identify a physical reaction.

The picture below shows a man swinging an object in a uniform circular motion. A, B and C are three different points on the path of motion of the object.

What is the net displacement of the object after one complete swing?

The velocity-time graph of a ball moving on the surface of a floor is given below.

If the mass of the ball is $200 \mathrm{g}$, then the value of force on the ball is