1) The chemical reactions are used in ..............

2) The mass of 2 molecules of sodium hydroxide equals .......... gm.{knowing that the atomic mass of sodium (23), hydrogen (1) and oxygen (16)}.

3) The chemical reaction causes ..........

4) The bright magnesium ribbon changes into a white powder of ....... when it burns in air.

5) On applying the law of constant ratios on the following reaction: 2Mg + O2 -------- 2MgO

7) Which of the following is considered a balanced chemical equation? ....

8) Direct combination reaction takes place between ...........

9) Ammonia combines with conc. HCl producing ....... of ammonium chloride.

10) The ....... equation verifies the law of conservation of matter.

11) Increasing the ratio of ...... gas in the atmosphere leads to increasing the air temperature.

12) The gases that cause building corrosion are ..............

13) The gases that affect the nervous system and the eye are ............

14) All these gases are acidic gases except ........

15) The substances resulted from burning of coal and cellulose fibers cause ........

16) A force is an effect that ..........

17) When you kick a static ball with your foot, a force acts on the ball which changes the ..........

18) Fundamental forces in nature are ..........

19) The amount of earth's gravitational pull on the object is ..........

20) An object's weight on the earth's surface is related to the ........ forces.

21) The work done to lift an object upwards increases by increasing ..........