Physical and Chemical Changes Test - 8

According to this question the correct option will be ‘A’ because Examples of physical change include changes in the size or shape of matter. Changes of state —for example, from solid to liquid or from liquid to gas —are also physical changes

According to this question the correct option will be ‘C’  because the examples of a physical change are folding of a paper sheet, melting of wax, freezing and boiling water, melting of ice, condensation, vaporization, magnetizing a compass needle, dissolving sugar in water, etc.

According to this question the correct option will be ‘C’ because  Physical changes are changes in which no new substance is formed, and the chemical composition stays the same. - change in state of matter, e.g. liquid to solid. - change in shape - change in size For example: - freezing water to make ice - molding clay - cutting wood or paper.

According to this question the correct option will be ‘B’ because Mass doesn't change in physical or chemical change. Physical change are changes that affect the form of a substance. Example is the change in the state of water from solid to liquid and to ice. Chemical change is a type of change that occurs when a substance is changed from one form to another form that cannot be reversed.

According to this question the correct option will be ‘D’  because chemical reaction we  probably know is the reaction between vinegar and baking soda. This reaction produces a gas called carbon dioxide. This gas can be used to put out a flame.

The brown colour of the apple after cutting is due to the chemical change of the enzymes.

When an apple is cut, oxygen is introduced into the injured plant tissue. When oxygen is present in the cells, polyphenol oxidase enzymes(PPO) in the chloroplasts rapidly oxidize phenolic compounds naturally present in the apple tissues to o-quinones, colourless precursors to brown coloured secondary products. o- quinones then produce the brown colour by reacting to form compounds with amino acids or proteins they self-assemble to make polymers.

Chemical changes involve chemical reactions and the creation of new products. Typically, a chemical change is irreversible.

Examples are:

Dropping sodium into water

combustion (burning) of wood

metabolism of food in the body

cooking an egg

digesting sugar with the amylase in saliva

baking a cake

electroplating a metal

explosion of fireworks

rotting bananas

grilling a hamburger

milk going sour

According to this question the correct option will be ‘A’  because Explosion of a Cracker is a chemical change . ⇒ In chemical change, chemical properties of substances are changed and a new substances are formed. ⇒ Explosive reactants [like nitrogen, carbon, sulphur etc] are transformed into gaseous products [like NO2,Co2,SO2] which are different from reactants along with liberation.

When a piece of magnesium ribbon is ignited, light and heat are produced.

When magnesium burns, it actually reacts with oxygen in the air and not with fire.

Magnesium reacts with oxygen to form a compound called magnesium oxide. 

The reaction is as follows:

\(2 M g+O_{2} \rightarrow 2 M g O+\) heat \(+\) light

Hence, the correct option is C.

A reversible change is a physical change that can be undone. 

A final substance can be converted back to the original substance without creating any new material.

An irreversible change is a permanent change that cannot be undone.

A. Hardening of cement is an irreversible change as we cannot reverse back to the original cement powder form once the cement hardens.

B. Freezing of ice-cream is reversible change as it can be reversed back by heating and it will convert to original form.

C. Opening of a door is reversible change as it can be reversed simply by closing the door 

D. Melting of chocolate is reversible change as it can be reversed by cooling the chocolate to its original form.

Option A is the correct answer.

According to this question the correct option will be ‘A’  because Petrol just changes its state from the liquid form to the gaseous form because of the presence of energy in the form of heat. A change of state is a reversible reaction and hence, this is a Physical change.

According to this question the correct option will be ‘A’ because  Boiling water is a physical change, as it rearranges molecules but does not affect the internal structures. Boiling water forces the water molecules away from each other as the liquid changes to vapor

According to this question the correct option will be ‘B’  because The ozone layer that protects us from harmful ultraviolet radiation continues to thin over populated areas of the world, a new study warns. Scientists say the layer is in better shape, however, over the North and South Poles.

Both expansion and contraction is used during the change.

The iron blade has a ring in which the wooden handle is fixed. The ring is slightly smaller in size than the wooden handle.The ring is heated and it becomes slightly larger in size (expands). The handle  fits into the ring. When the ring cools it contracts and tightly fits on the handle.

According to this question the correct option will be ‘B’  because Zinc serves as corrosion control or as a sacrificial anode. (Sacrificial anodes are highly active metals that are used to prevent a less active material surface from corroding.) When ductile iron pipe is coated with zinc, the zinc is consumed in place of the iron.