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