Science Secondary 1 Final Examination

The formula of talcum powder was given in old textbooks as  $MgO.SiO_2.H_2O$  . What is the number of oxygen atoms in one molecule of talcum powder?

• 2

• 3

• 4

• 5

Which of the following correctly describes the behavior of particles in liquid soft drink?

• The particles are arranged in a regular manner.

• The particles are free to move and slide over another.

• The particles move freely at great speeds.

• The particles vibrate about in their fixed positions.

"At first, the particles of the substance were close together and moved randomly. They then became regularly arranged and vibrated in their fixed positions." This situation occurred when Andrew ....

• boiled a pot of soto

• froze a cup of tea

• dried wet trousers in the sun

• melted white sugar

"This state of water has the weakest forces of attraction between its particles." The state of water mentioned in the statement above is most likely to be ....

• liquid water

• ice

• snow

• water vapor

Ice and liquid water are similar because ....

• the particles have the same amount of energy

• they can be compressed

• they can take the shape on any container

• they consist of the same type of particles

Parker is constructing a ball-and-stick model of an atom using balls of different masses. Which of the following you expect to see in Parker's model of an atom?

• The lightest balls represent neutrons.

• The lightest balls represent electrons.

• The heaviest balls represent neutrons and electrons.

• The heaviest balls represent protons and electrons.

Which of the following statements about a ball-and-stick model of an ammonia molecule,

 $NH_3$  is not true?

• The ball-and-stick model shows how the nitrogen and hydrogen atoms are connected to one another in an ammonia molecule.

• The balls used to represent nitrogen and hydrogen atoms are different in color or size.

• There are three nitrogen atoms and one hydrogen atom.

• There are four balls to represent four atoms.

Which of the following is true about the chemical formulae of these compounds:  $Na_2SO_4$  , $K_2CO_3$  ,  $AgNO_3$  ?

• They all have the same mass number.

• They all contain carbon atoms.

• They all contain oxygen atoms.

• They all have the same number of electrons.

Which of the following information is not directly obtained from a chemical formula?

• Number of each type of atom in the molecule.

• Number of atoms in the molecule.

• Types of atoms in the molecule.

• Chemical properties of the molecule.

In a discussion, Adrean stated that the number of atoms in a molecule of water decreases when water turns into ice. What was wrong with Adrean's statement? The number of atoms in a molecule of water ....

• decreases only when water into water vapor

• is fixed whether it is in solid, liquid or gaseous form

• depends on the amount of water

• increases when water turns into ice