Curie: It is the traditional unit of radioactivity. It is defined as the quantity of a radioactive substance which undergoes 3.7 x 10¹⁰ disintegrations in one second. This is actually close to the activity of 1 g of radium 226. 1 curie = 3.7 x 10¹⁰ disintegrations per second.

Ozone contains three oxygen atoms and hence it is called homo triatomic molecule. Eg. O₃

It produces a white light which contains light of different colours. Sunlight is a composite light which consists of light of various colours or wave lengths.

The sound is produced by vibrations.

The SI unit of electric potential or potential difference is volt (V). The potential difference between two points is one volt, if one joule of work is done in moving one coulomb of charge from one point to another against the electric force.
1 volt = 1 joule/ 1 coulomb.

The temperature measured in relation to absolute zero using the kelvin scale is known as absolute temperature. It is also known as the thermodynamic temperature.

(i) In a chemical reaction, the atoms of the reacting molecules or elements are rearranged to form new molecules
(ii) Old chemical bonds between atoms are broken and new chemical bonds are formed.
(iii) Bond breaking absorbs energy where as bond formation releases energy

(i) Mass percentage = \(\frac{Mass \ of \ the\ solute}{Mass \ of \ the \ solute \ + \ Mass \ of \ the \ solvent}\) x 100
= \(\frac{60}{60+120}\) x 100
= \(\frac{60}{180}\) x 100
Mass percentage of solute = 33.33%
(ii) Mass by mass % of solvent
= 100 - [Mass by mass % of solute]
= 100 - 33.33
= 66.67

It is the substance added to the ore to reduce the fusion temperature and to remove the impurities. E.g. Calcium oxide (basic), Silica (acidic).

(i) Whenever an object or a person falls freely under the action of earth's gravitational force alone, it appears to have zero weight.
(ii) This state refers to "weightlessness"