Which one of the following statements is correct?

• Covalent bonds are directional

• Ionic bonds are directional

• Both covalent and ionic bonds are directional

• Both covalent and ionic bonds are non-directional

When one strikes a safety match, the first step is:

• burning of sulphur

• decomposition of potassium chlorate into potassium chloride and oxygen

• conversion of a small amount of red phosphorus into white phosphorus

• burning of glue and starch

The LPG cooking gas contains propane and butane as the constituents. A sulphur containing compound is added to the LPG, because:

• it lowers the cost of production

• it enhances the efficiency of LPG

• it facilitates easy detection of leakage of the gas

• it assists in liquefying hydrocarbons

The genetic material of bacteria is found in:

• nucleus

• cytoplasm

• cell membrane

• ribosome

A horse and a donkey can breed to produce mule which is an infertile animal. The infertility is because horse and donkey belong to different:

• class

• order

• species

• genus

A plant having yellow leaves with dead spots has the deficiency of:

• Potassium

• Magnesium

• Nitrate

• Phosphate

7.

Fluoride toothpaste is sometimes recommended because fluoride:

• prevents plaque formation

• hardens the enamel of the tooth

• kills pathogenic bacteria

• prevents tooth ache

Along a streamline flow of fluid:

• the velocity of all fluid particles at a given instant is constant

• the speed of a fluid particle remains constant

• the velocity of all fluid particles crossing a given position is constant

• the velocity of a fluid particle remains constant

How is the kinetic energy of a moving object affected if the net work done on it is positive?

• Decreases

• Increases

• Remains constant

• Becomes zero

A particle is executing simple harmonic motion. Which one of the following statements about the acceleration of the oscillating particle is true?

• It is always in the opposite direction to velocity

• It is proportional to the frequency of oscillation

• It is minimum when the speed is maximum

• It decreases as the potential energy increases