Question

1. Differentiate between an atom and a molecule,
2. State major differences between a compound and a mixture.
3. What is valency? Give the valencies of the following: oxygen, hydrogen, sodium
4. Classify the following as elements and compounds: water, nitrogen, carbon, h
magnesium, aluminium oxide, calcium carbonate.
5. What are the two essential conditions for rusting? How does oiling of iron ob
7. What are crystals? How can the crystals of sodium chloride be prepared fro
c Short ansv
chlorine.
6. Why does the cut surface of brinjal turn brown?​

Answer 1

Answer:

1.refer to the attached file

2. Compound are substances which can be formed by chemically combining two or more elements. Mixtures are substances that are formed by physically mixing two or more substances.

3. Valency is the combining capacity of the atoms to form a molecule either with same or different elements is defined as valency.

oxygen=-2

hydrogen =+1

sodium =+1

magnesium =+2

chlorine =-2

4. elements:nitrogen,carbon,magnesium

compounds:water,hydrogen chloride,aluminium oxide,calcium carbonate

5. The iron reacts with water and oxygen to form hydrated iron(III) oxide, which we see as rust. Iron and steel rust when they come into contact with water and oxygen – both are needed for rusting to occur. Boiling the water removes the oxygen and the layer of oil prevents it from re-entering.

6. When potatoes, eggplant or apples are peeled or cut, certain enzymes are exposed to air. When an enzyme called polyphenol oxidase, also known as tyrosinase is exposed to oxygen, oxidation takes place, which leads to browning of the surfaces of these fruits.

7.crystal are the substance which contain the fixed amount of water in it

ex.

to prepare crystal of sodium chloride  

1. take NaCl in the beaker .

2. add water to it .

3. heat the solution of NaCl and water =evaporation

4. then you will obtain the crystal of NaCl

NaCl is also called common salt

Explanation:

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