Question:
What are elements?
Answer:
Elements are substances that cannot be chemically broken down into simpler substances. So an element is made up of only one kind of atoms. For example, silver is an element which is made up of only silver atoms. Eiements are the building blocks of all matter.
Is Matter Around Us Pure?
Q 1.
What is the general name of the process by which tea-leaves are separated from prepared tea ?
Q 2.
How much water should be added to 15 grams of salt to obtain 15 per cent salt solution ?
Q 3.
Classify the following as physical or chemical changes :
(i) Cooking of food
Q 4.
Name one pair of liquids which can be separated by using a separating funnel.
Q 5.
Name one pair of substances whose mixture can be separated by fractional distillation.
Q 6.
Define Brownian movement in colloids.
Q 7.
Calculate the mass of glucouse and mass of water required to make 200g of 25% solution of glucouse.
Q 8.
Give two reasons for supposing that water is a compound and not a mixture.
Q 9.
What type of magnet is fitted on a crane to separate scrap iron objects from a heap of waste materials in factories ?
Q 10.
Name the property of one of the constituents which can be used to separate a mixture of salt and iodine
Q 11.
What are non-aqueous solutions?
Q 12.
What is saturated solution? Explain with an example.
Q 13.
To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293K. Find its concentration at this temperature.
Q 14.
Name a non-metal which is a good conductor of electricity.
Q 15.
Name the property :
(a) which allows metals to be hammered into thin sheets.
(b)
Q 16.
What is meant by saying that metals are malleable and ductile ?
Q 17.
What is the concentration of a solution which contains 16 g of urea in 120 g of solution ?
Q 18.
Name the process which can be used to separate a mixture of salt solution and sand.
Q 19.
Which technique can be used to detect and identify traces of poison present in the stomach wash of a person ?
Q 20.
State the differences between compounds and mixtures.
Q 21.
How are sol, solution and suspension different from each other?
Q 22.
Which of the two will scatter light: soap solution or sugar solution ? Why ?
Q 23.
How much water should be mixed with 12 mL of alcohol so as to obtain 12 % alcohol solution ?
Q 24.
Name the process you would use to separate ammonium chloride from a mixture of sodium chloride and ammonium chloride.
Q 25.
Name the property of any one of the components which can be used for separating the following mixture : Salt and Camphor
Q 26.
Name the source from which nitrogen and oxygen are obtained on a large scale.
Q 27.
How is cream separated from milk ?
Q 28.
What are different categories of pure substance?
Q 30.
What is an unsaturated solution?
Q 31.
What are different ways to separate solid mixtures?
Q 32.
Who used the term 'element' first time?
Q 33.
Identify the following as mixture or compound.
(i) blood
(ii) common salt
(iii) sugar
(iv) brass
Q 34.
Give examples of liquids that are
(i) completely miscible
(ii) partially miscible
(iii) practically immiscible
Q 35.
State whether the following statement is true or false : Milk is a pure substance.
Q 36.
What is the general name of the materials which contain at least two pure substances and show the properties of their constituents ?
Q 37.
Name the process you would use to separate a mixture of anthracene and copper sulphate ?
Q 38.
Name the process by which the various gases of the air are separated.
Q 39.
Name any two solid substances whose mixture can be separated by sublimation.
Q 40.
Name the process which is used in milk dairies to separate cream from milk.
Q 41.
What are the characteristics of mixture?
Q 42.
Explain with an example what is a colloid?
Q 43.
Which of the following is a mixture ?Salt, Air, Water, Alum, Sugar
Q 44.
How will you separate a mixture of chalk powder and water ?
Q 45.
How will you separate iron pins from sand ?
Q 46.
What are the kinds of mixture?
Q 47.
List the points of differences between homogeneous and heterogeneous mixtures.
Q 48.
What is a compound? Give an example.
Q 49.
What is a solution? What are the properties of a solution?
Q 50.
What is meant by solute and solvent?
