HS CHEMISTRY QUESTIONS I

1. Which of the following statements about the kinetic theory of matter is NOT TRUE?

• A. Particles are always in motion or vibration.

• B. In gases, particles are moving faster than those in liquids.

• C. The more energy that is added, the greater the speed of particles.

• D. Gases have high densities because the particles are widely separated.

Answer explanation

In gases, the distance between molecules, whether monatomic or polyatomic, is very large compared with the size of the molecules; thus gases have a low density and are highly compressible

2. Which statement about the boxes P, Q, and R is correct?

• A. Box P contains two compounds and box R contains two elements.

• B. Box P contains two elements and box Q. contains a mixture.

• C. Box P contains two elements and Box Q contains one compound.

• D. Box Q contains two compounds and Box R contains a mixture.

Answer explanation

Elements are pure substances which are composed of only one type of atom. Compound are substances which are formed by two or more different types of elements that are united chemically in fixed proportions.

3. The diagram is a particle model of a substance.

What would the particle model become when it is fully cooled?

• 
• 
• 
• 

Answer explanation

When a gas is cooled, the particles stop moving around as quickly and form a liquid. As a result, there is a phase shift.

4. A measuring cylinder contains 20 cm³ of water initially. When a stone with a mass of 60 g was placed into the measuring cylinder, the water level rose to 45 cm³ as shown in the diagram.

What is the density of the stone?

• A. 417 kg /m³

• B. 1333  kg /m³

• C. 2400 kg /m³

• D. 3000 kg /m³

Answer explanation

V = 45 - 20 = 25 cm³

D = m/v = 60g / 25cm³= 2.4 g/cm³

Convert g/cm³ --> kg/m³

2.4 g/cm³ x 1000 = 2,400 kg/m³

5. The diagram below shows a container of volume 1 liter is divided by a piston into two equal parts X and Y. The amount of air in X is doubled of that in Y.

 

What is the direction of force due to the pressure difference acting on the piston?

                        

                        

• A. Toward left  

• B. Toward right

•      C. Random direction  

•   D. The piston will not move

Answer explanation

The pressure (P) the gas exerts on the piston is equal to the force (F) with which it pushes up on the piston divided by the surface area (A) of the piston.

6. If a metal sphere is heated by Bunsen burner, which of the following quantities will increase?

(1) volume             (2) density             (3) mass

• A. (1)  only       

• B. (1) and (3) only

• C. (2) and (3) only

•     D. (1), (2) and (3)

Answer explanation

 Volume increases due to thermal expansion.

Mass remains unchanged because it is related to the amount of particles.

As mass remains unchanged but volume increases, density of it decreases

6a. Which of the following is NOT true about a physical change?

• A. Energy is not required.      

• B. It is a reversible change

• C. No new substance is formed.

• D. Changing of phase takes place

Answer explanation

In the case of physical changes, energy is used in phase change whereas, in chemical change, energy is involved in breaking and making bonds.

7. Which of the following statements must be true?

 (1) When liquid changes its state to solid, its volume decreases.

(2) When gas changes its state to liquid, its volume decreases.

(3) When solid changes its state to liquid, the particles can move more freely.

• A. (1) only            

• B. (1) and (2) only 

• C. (1) and (3) only

• D. (2) and (3) only

Answer explanation

It is not always true. When water changes to ice, its volume increases.

When water becomes a solid, the hydrogen bonds between the water molecules cause them to form a crystal lattice structure containing multiple empty spaces. The increased space in the crystal lattice structure of solid water results in a larger volume.

Study the diagram below and answer questions         

7a. A ball of naphthalene sublimes to become smaller in size.

Which of the following represents the correct change in state?

• A. Liquid to solid state      

• B. Solid to liquid state

• C. Solid to gaseous state

• D. Gaseous to solid state

Answer explanation

Sublimation is the conversion of a substance from the solid to the gaseous state without its becoming liquid.

Study the diagram below and answer questions         

8.The change in the state of matter from question 7 has taken place due to change in _______________ of particles of naphthalene.

• A. mass    

•   B. type

• C. size     

• D. movement    

Answer explanation

Sublimation is the conversion of a substance from the solid to the gaseous state without its becoming liquid.