Elements

Q.

Which of the following materials fall in the category of a pure substance? (a) Ice (b) Milk (c) Iron (d) Hydrochloric acid (e) Calcium oxide (f) Mercury (g) Brick (h) Wood (i)Air

Q.

Non-metals are generally poor conductors of heat and electricity.

Say True or False.

1. True

2. False

Q. Who was the first scientist to use the term element?

1. J.J Thompson
2. Robert Boyle
3. Antoine Laurent Lavoisier
4. Neils Bohr

Q.

___tells us the number of atoms of each element in a compound.

Q. Two or more elements that are chemically bound together in a fixed ratio is know as a

1. Compound
2. Homogeneous Mixture
3. Mixture

Q.

Mercury is a liquid non-metal.

1. False

2. True

Q.

Is a compound homogeneous or heterogeneous?

Q.

Most of the elements exist in the solid state at room temperature.

1. True

2. False

Q.

Fill in the blanks with appropriate word. Small pieces of stone can be removed from rice by_____.

Q.

Classify elements based on their physical states.

Q.

List the properties of pure substance.

Q. The atoms or molecules of a solid are always arranged in a regular pattern . Do you agree ? Give reasons
Pls explain the question and answer in detail

Q.

Which amongst the following does not represent a polyatomic ion?

1. Chloride

2. Sulphate

3. Carbonate

4. Phosphate

Q.

Non-metals generally have low melting and boiling points.

1. True
2. False

Q. Arrange the molecules in the increasing order of molecular weight.

1. ${\mathrm{CO}}_{\mathrm{2\; <}}\mathrm{CaO\; <}{\mathrm{CaCO}}_{\mathrm{3\; <}}\mathrm{CO}$
2. ${\mathrm{CaCO}}_{\mathrm{3\; <}}\mathrm{CaO\; <}{\mathrm{CO}}_{\mathrm{2\; <}}\mathrm{CO}$
3. $\mathrm{CO\; <}{\mathrm{CO}}_{\mathrm{2\; <}}\mathrm{CaO\; <}{\mathrm{CaCO}}_3$
4. ${\mathrm{CO}}_2<\mathrm{CaO\; <}\mathrm{CO\; <}{\mathrm{CaCO}}_3$

Q.

An element is a substance which cannot be subdivided into two or more simpler substances by any physical or chemical means.

1. True
2. False

Q. The noble gas used in advertising signboards is ​ ​

1. Helium
2. Argon
3. Neon
4. Krypton

Q. What is the mass of sulphur that would react with 5 g of iron to form ferrous sulphide $\text{(FeS)}$?

1. 2.8

Q.

What are non-metals? Give any four examples.

Q.

Which one of the following may be termed as a pure substance?

1. Sodium chloride

2. Soft drink

3. Aerosol

4. Soil

Q.

How many oxygen atoms are present in 50g of $CaC{O}_3$?

1. 3.011 $\times$ ${10}^{23}$
2. 9.033 $\times$ ${10}^{23}$
3. 6.022 $\times$ ${10}^{23}$
4. 12.044 $\times$ ${10}^{23}$

Q.

1. A ____________________ represents one atom of an element.

Q.

What do the symbol $\mathrm{Z}$ represent?

Q.

Identify the monoatomic molecule from the following:

1. Ozone

2. Hydrogen

3. Nitrogen

4. Helium

Q.

How is matter classified on the basis of chemical constitution?

Q. discovery of fundamental particle

Q. Define : Elements

Q. method is used by the farmer to separate barley grains from its husk.

1. Winnowing
2. Handpicking
3. Sieving

Q. In sieving, components of a mixture are separated due to the difference in their .

1. textures
2. colours
3. sizes
4. weights

Q. What would happens if symbol are not used to represent elements?