1 .Explain the nature of molecules in solids, liquids and gases .
2 .Explain the law of conservation of mass with an example.
3 .Give the main differences between physical changes and chemical changes.
4 .Explain the energy changes in a chemical change.
5 .What happens to the intermolecular force of attraction between the molecules in a change of state of solid to liquid?
6 .List the main postulates to the kinetic molecular theory of matter.
7 . Differentiate between cohesive force and adhesive force.
8. What does the laws of conservation of mass States?
9. Complete this word equations.
i. magnesium + ____________
= magnesium oxide
ii. _________ + hydrogen = ammonia
iii. barium chloride + sodium sulphate =_____________ +_________
10 . Matter is neither _______ nor________ during a chemical reaction.
11 . The law that state that the mass of a products equals the mass of reactants in a chemical reaction.
12. Write the characteristics of physical changes and chemical changes.
13. What is an endothermic changes.
14. What is an exothermic changes.
15. When a solid is heated , its molecule gain ______ energy.
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Answers
Explanation:
1) In solids, molecules are very tightly packed and close to each other. In liquids, molecules are not tightly pack and is a bit free. In Gas, molecules are totally free and can move freely.
2) According to the law of conservation of mass, mass of reactants before a reaction is equal to the mass of product after the reaction.
Ex- 56 g of HCL and 44g of Sodim is taken and reaction took place. So, the product formed(Salt) mass will be same as 100g
3) In Physical change, only rearrangement of molecules take place. No new substance is formed but in chemical reactions new molecules are formed with new substances.
4) Sorry, I don't know
5) Intermolecular force of attraction decreases when a solid changes to liquid.
6) Sorry, I don't know
7) Sorry...
8) It states that mass can neither be created nor be destroyed.
9) i) oxygen
ii) Nitrogen
iii) Sorry
10) created;destroyed
11) Law of conservation of mass
12) Physical change:-
i. No new substances are formed
ii. Molecules remain same
iii. It is reversible in many cases.
Chemical change:-
i. Totally new substance is formed
ii. New molecules are formed
iii. It is irreversible
13) In endothermic changes, heat is absorbed.
14)In exothermic, heat is released
15) kinetic
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