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1.Sugar and salt are available in different sizes- as big blocks, small grains and powder. What are the properties retained by them in all these forms?
There is no difference in colour and taste. Along with this, there is no change in many of its properties like melting point, boiling point, chemical properties, density, solubility etc.

2.Even when salt and sugar are made invisibly small, do they retain their properties? How did you understand it?

In sugar solution and salt solution the particles become invisibly small. They retain their taste even they are changed into minute particles. Also there is no change in their chemical properties. Even if the substance is in any state it does not lose its properties. Experiment done to identify this.

a.If we heat sugar, sugarcandy, sugar powder etc. in dry test tubes we get carbon and water.

b.On heating sugar with con. sulphuric acid we get water, carbon dioxide, sulphur dioxide etc.

c.Dissolve sugar in dilute hydrochloric acid and heat it. Add a few drops of Benedict's solution and heat it. A red precipitate is formed. Repeat the experiment using sugar powder, sugarcandy etc. The same result is obtained. Glucose formed from the sugar converts the Cu²⁺ ions present in the Benedict solution into red Cu₂O.

3.Why do salt and sugarcandy show different qualities? Isn't it because of the difference in their tiny particles?

Salt and sugarcandy show different qualities because of the difference in their tiny particles.

Sugar contains only the same type of tiny particles of sugar. Hence sugar is a pure substance. Pure substance means that it is made of only the same kind of minute particles.

A molecule is the smallest particle having all the basic properties of a pure substance. All the molecules of a pure substance are alike.

4.Sugar solution is a mixture. Are its properties the same as that of the mixture in a bakery? What are the differences between them?

Mixture and sugar solution have different properties. We feel the same taste in every parts of a sugar solution. But we feel different tastes in various parts of the mixture. We can separately see the components of the mixture. But we cannot separately see the pure substances present in the sugar solution such as sugar and water. From this we can understand that there are two types of mixtures.

Homogeneous mixtures have uniform properties throughout the mixture. Heterogeneous mixture have different properties in different parts.

5.Many of the elements are in solid state. Which elements are found in liquid state and gaseous state?

Elements seen in liquid state - Mercury, bromine, caesium and francium.

Elements seen in gaseous state - Hydrogen, oxygen, nitrogen, chlorine.

Classify the elements mainly as metals and non metals.

Metals - Metals are defined as elements that form positive ions by losing electrons in a chemical reaction.

Non metals - Non metals are defined as elements that form negative ions by gaining electrons in a chemical reaction.

6.12H, 3C, 5 Al What does each of these indicate?

12H is the symbol of hydrogen and also it represents the 12 atoms of hydrogen. 3C is the symbol of carbon and also it represents the 3 atoms of carbon. 5 Al is the symbol of aluminium and also it represents the 5 atoms of aluminium.

7.How can you write the abbreviated form for five sodium atoms, two phosphorus atoms and fifteen nitrogen atoms?

(use the periodic table to find out the names and symbols).

Five Sodium atom - 5 Na

Two Phosphorus atom - 2 P

Fifteen Nitrogen atom -15 N

Is it interesting to know the way in which the elements get their name.

8.What are elements and compounds?

Pure substances which cannot be further divided into smaller substances are called elements. Compounds are pure substances formed by the combination of two or more elements.

9.What are the properties of mixtures?

Contain more than one component.

Quantities of components may vary.

Mixture shows the properties of its components.

10.What is known as heterogeneous mixture? Write an example.

When the different parts of a substance is different in properties it is said to be heterogenous.

Example: Milk

11.What is the qualitative and quantitative significance of symbol?

A symbol is not merely used as a sign of a chemical element. It also denotes one atom of that element as well as one atomic mass of an atom. Thus the symbol for Hydrogen, H represents one atom of Hydrogen. H also stands for one atomic mass of Hydrogen. A symbol is a short scientific mode of representing names of atoms of elements.