Science Class 7th

281. The changes that cannot be reversed are called

A) Reversible changes

B) Chemical change

C) Physical change

D) Irreversible change

282. Boiled egg is an

A) Physical change

B) Irreversible change

C) Option A is correct

D) None of these

283. Majority of the physical changes are

A) Irreversible

B) Reversible

C) Chemical

D) None of these

284. Majority of the chemical changes are

A) Reversible

B) Irreversible

C) Option B is correct

D) None of these

285. Photosynthesis, Respiration, rusting of iron and digestion of food are

A) Physical changes

B) Chemical changes

C) Irreversible changes

D) Both B & C

286. Hydrocarbons are compounds that are made up of only hydrogen and carbon.

A) Inorganic

B) Chemicals

C) Organic

D) None of these

287. Hydrocarbon burn in air producing

A) CO2

B) Water

C) Energy

D) All of them are correct

288. Plastic is prepared from the petroleum by the process called

A) Polyether

B) Polymerization

C) Chemical process

D) None of these

289. Vegetable oil is converted into solid for fat by a process called

A) Hydrogenation

B) Polymerization

C) Polythene

D) None of the above

290. The process of hydrogenation take place at

A) 300-350 degree

B) 250-300 degree

C) 400 degree

D) None of these

291. Polythene is

A) Monomer

B) Polymer

C) Element

D) Fertilizer

292. Thermal energy transfer between objects in different ways.

A) Two

B) Three

C) Four

D) Five

293. ____Occurs when thermal energy is transferred between two objects that are touching each other.

A) Conduction

B) Convection

C) Radiation

D) None of these

294. Occurs only in liquids and gases.

A) Conductor

B) Convection

C) Radiation

D) None of these

295. Convection cannot take place in _____

A) Liquid

B) Solid

C) Gas

D) Air

296. Coastal breeze is produced by

A) Conduction

B) Radiation

C) Convection

D) None of these

297. Sun heat reaches us through a mode of transfer called

A) Convection

B) Conduction

C) Radiation

D) None of these

298. The heat in the metal rod flows by the process of

A) Radiation

B) Conduction

C) Convection

D) Magnetization

299. The process of heat transfer from a hotter place to a colder place by actual movement of the particles of the medium is known as :

A) Convection

B) Conduction

C) Radiation

D) Evaporation

300. Black or dark colour clothes are worn in cold climates because these are :

A) Good reflector

B) Good reflector and poor absorber

C) Poor absorber

D) Poor reflector and good absorber