Science MCQ (1 Marks)

This is a physical change as there is not any new substance formed having different chemical composition and properties. Only the state of the substance is changed during the process and it can be reversed.

Chemical property.

Atom is the basic unit of matter which cannot be broken down into independent particles

Bathroom fittings are plated with chromium to prevent rusting or corrosion. Metal objects made of iron and steel are usually electroplated with chromium.

Zinc.

In a periodic change, the events are repeated after regular intervals like day and night. In the given example, no such change is taking place.
When the two solutions are mixed, we cannot conclude it is a chemical change as no precipitate formation, no evolution of gas, no change in temperature, nor any other indication of a chemical change is seen. Thus the reaction can be considered to be reversible and, the change will be physical.

Rust is a general term for a series of iron oxides, usually, red oxides, formed by the reaction of iron with oxygen in the presence of water or air moisture.
So the presence of impure water and oxygen are required to form rust from metal iron.

Hydrogen and oxygen combine together to form water is a chemical change. When a new substance is formed the change is called a chemical change.

All the above.

When iron is in contact with water and oxygen, it rusts. If salt is present, for example in seawater or salt spray, the iron tends to rust more quickly, as a result of chemical reactions.

The process of forming large crystals of pure substances from their solutions is known as Crystallization. The principle of crystallization is concerned with the thermodynamic conditions of crystallization and the kinetics of crystal nucleation and growth. Crystallization is the physical transformation of a liquid solution or gas to a crystal which is a solid with an ordered internal arrangement of molecules, ions or atoms.

Magnesium oxide.

When carbon dioxide is passed through lime water, it turns milky due to formation of white precipitate in form of calcium carbonate.

Here, all the statements are correct. Hence,

Layer of zinc is applied on iron surface in galvanization process to save it from rusting.

Cooking of vegetables involves many chemical changes.

An explosion of a cracker is a chemical change because the explosive reactants are transformed into gaseous products along with heat, light, and sound which cannot be reversed.

When milk converts in curd the process is irreversible and a new substance with different properties is formed hence it is an example of a chemical change.

No new substances are formed when wax melts. This is a physical change. However, if the wax burns, it is a chemical change. The question here is associated with melting, and so the answer is 'physical' change.

Milk into curd and germination of seeds both are chemical changes. Hence,

Adding salt to water makes it salty. This is a physical change because the original substances can be recovered by evaporation. In a chemical change, substances cannot be recovered.

The boiling of water is not a chemical change. If it boils for more time it changes to vapour state which is a physical change.
Whereas boiling of egg, burning of paper and cloth involves both physical and chemical change. The burning of paper and cloth forms ash.

Chemical change.

This is a physical change as there is not any new substance formed having different chemical composition and properties. Only the state of the substance is changed during the process and it can be reversed.

Dissolving sugar in water in water is usually considered to be a physical change, in this process there is no new chemical species form.

Sugar dissolving in water is a physical change because in this change no new substance is formed and the process is reversible.

Salt in water speeds up the reaction. This is because lots of dissociated ions are present in salt. As salt is a strong electrolyte and hence this tremendously accelerates corrosion in saltwater.

Cooking a vegetable.

Chemical reaction may accompany change in colour, evolution of heat and gas etc.

Iron gate does not need to be protected from sun. Paints cannot avoid dust.
To prevent rusting of Iron Gate, we do paint on it. Painting makes it beautiful.

The process of forming large crystals of pure substances from their solutions is known as Crystallization.

Cutting a log of wood in small pieces is a physical change. Burning of wood, Ripening of fruit, Cooking of food are chemical changes because a new substance is formed in them and they are not reversible.

Both physical change.

physical change.

Stretching of rubber band is a physical change.

Composition of the iron pillar make it resistant of rusting.
It has not rusted after such a long period.

Milky.

Cutting of log of wood into pieces is a physical change.

Mixing salt or common salt with water results in a change in its physical state. Sugar and salt are solids. When added to water, they get dissolved and we can not see the solid particles anymore. But this does not change the nature of these substances, that is, no new substances are formed during the process. So, the dissolution of salt or sugar in water is a physical change.

Cutting a log of wood in small pieces is a physical change . Burning of wood, Ripening of fruit, Cooking of food are chemical changes because a new substance is formed in them and they are not reversible.

Chemical change.

The burning of wood in the presence of oxygen produces ash. In this example, wood and oxygen undergo a chemical change to produce ash. The properties of ash are very different from wood or oxygen.

Chemical change does not forms new substance. There are two types of changes in matter namely physical and chemical change. Physical change is accompanied with change in physical properties of substances. This means they do not result in formation of new substances.