Available Answers

1. 1.

   Fill in the blanks.

   1. The shape and size of a solid can be change when an external _______________ is applied.
   2. Atoms of certain elements combine together to form particles called _________________.
   3. Each ________________ is present in a fixed amount in a compound.
   4. The distance between the particles in matter is called _________________.
   5. The interparticle force of attraction is ________________ in liquids as compared to solid.
   6. A change that cannot be reversed is called an ________________ change.
   7. _________________ is a type of chemical change which produces heat energy used for both domestic and industrial purposes.
   8. _________________ is the process in which vapour on cooling change into liquid.
   9. Rusting of iron is a chemical change as a _________________ is formed.
   10. _________________ is the process by which the food that we eat is broken down into small molecules which can be easily absorbed.
   11. A _________________ is a pure substance that is formed when two or more elements chemical combine in a definite proportion by mass.
   12. Ozone is a __________________ molecule.
   13. Miscible liquids can be separated by the process of ___________________.
   14. __________________ is used to separate iron filings from sand and iodine.
   15. The technique of ___________________ is based on the principle of selective adsorption.
   16. An ___________________ cannot exist independently.
   17. When an atom of an element joins with another atom or atoms of the same element, a molecule an __________________ is formed.
   18. _________________, a compound when heated decomposes to give barium and nitrogen, both which are elements.
   19. Elements which possess valency 3 are called __________________.
   20. A __________________ is an arrangement of elements in the increasing order of their atomic number in a tabular format.
   21. ____________________ are the substances that are formed in a reaction.
   22. When sodium sulphate and barium chloride are mixed in an aqueous solution, a white precipitate of ___________________ is formed.
   23. The chemical reactions that take place in the presence of light are called __________________.
   24. Decomposition of potassium chlorate is accelerated in the presence of ___________________ (th) as a catalyst in the reaction.
   25. According to the law of conservation of mass, ___________________ can neither be created nor destroyed in a chemical reaction.
   26. Metals can bear a lot of strain and therefore have a high ___________________.
   27. The corrosion of iron is called ____________________.
   28. ___________________ is a hard non-metal.
   29. ___________________ is used to prepare teflon.
   30. Silicon is used to make silicon based polymers called _____________________.
   31. The process of formation of oxides is called ______________________.
   32. ___________________ is an essential component of proteins and amino acids.
   33. Nitrogen because of its inert nature dilutes the effect of oxygen present in the air and helps to control the rate of ___________________.
   34. In the laboratory, carbon dioxide is prepared by the action of ____________________ on ____________________ in Woulfe's bottle.
   35. Water cycle is also known as the _______________________.
2. 2.

   State whether the following statements are true (T) or false (F).

   1. Mass is the measure of quantity of matter contained in a substance.
   2. Solids have low density.
   3. Gases are highly compressible.
   4. The properties of a compound are different from those of its constituent elements.
   5. The particles in solids move away from each other and travel in all directions.
   6. Heat is released in an exothermic change.
   7. A change in mass of the substance occurs during a chemical change.
   8. Fusion is a process in which a liquid on cooling changes into solid.
   9. Sublimation is a physical change.
   10. Cooking of food s a physical change that is desirable, reversible and endothermic.
   11. The number ot atoms contained in a molecule of an element is called its atomicity.
   12. The constituents of a mixture are present in a definite ratio.
   13. Sugar solution is a homogenous mixture.
   14. An emulsion is a heterogenous mixture that consists of small solid particles suspended in a liquid.
   15. Alcohol and water are miscible liquids.
   16. The matter surrounding us is made up of atoms and molecules.
   17. An atom of oxygen can exist independently.
   18. When one atom of sodium combines with one atom of chlorine, a molecule of sodium chloride formed.
   19. A radical is capable of independent existence.
   20. The periodic table consists of eighteen groups and seven rows.
   21. A chemical change is also known as a chemical reaction.
   22. Nitrogen reacts with hydrogen under high pressure to form ammonia.
   23. An element is represented by a chemical formula and a compound is represented by a symbol.
   24. An arrow is placed between the reactants and the products to indicate the direction in which reaction is taking place.
   25. Methane burns in air to form carbon monoxide and water.
   26. Metals have high density.
   27. Corrosion of metals is a highly desirable process.
   28. Zinc is used to make dry cells and electrodes.
   29. lodine is used in photography in the form of silver iodide.
   30. Alloys of gold are used in X-ray tubes and as a shield against radiations.
   31. Air contains about 21% oxygen by volume.
   32. Oxidation involves the addition of oxygen to form oxide.
   33. Dry ice is used in refrigeration of food items.
   34. Carbon dioxide is removed from the atmosphere by respiration.
   35. Argon is used for welding metals.
3. 3.

   What is matter?
4. 4.

   Why solids cannot be compressed?
5. 5.

   Why do the molecules move freely in liquids?
6. 6.

   Give two examples of compressed gases. Also write their uses.