Energy in Reactions: Heat, Light and Everyday Chemistry

Section A: Exothermic Reactions

Question 1mcq

A reaction that releases heat is called:

A.Endothermic reaction

B.Displacement reaction only

C.Exothermic reaction

D.Precipitation reaction only

Question 2mcq

Which is an exothermic process?

A.Melting of ice

B.Thermal decomposition of limestone

C.Photosynthesis

D.Burning of natural gas

Question 3mcq

Respiration is considered exothermic because:

A.Energy is released from glucose

B.Oxygen is produced as a product

C.Energy is absorbed to make glucose

D.No chemical reaction occurs

Question 4mcq

If the temperature of a reaction mixture rises, the reaction is likely:

A.Endothermic

B.Only physical

C.Impossible

D.Exothermic

Question 5mcq

Why is combustion usually exothermic?

A.It always absorbs sunlight

B.It releases energy when substances react with oxygen

C.It produces no new substance

D.It breaks water using electricity

Question 6mcq

Which equation represents an exothermic reaction?

A.

2AgCl + light \rightarrow 2Ag + Cl_2

B.

CaCO_3 + heat \rightarrow CaO + CO_2

C.

6CO_2+6H_2O+light\rightarrow C_6H_{12}O_6+6O_2

D.

CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O + heat

Section B: Endothermic Reactions

Question 7mcq

A reaction that absorbs energy is called:

A.Neutral reaction

B.Endothermic reaction

C.Exothermic reaction

D.Combination only

Question 8mcq

Photosynthesis is endothermic because it:

A.Does not involve any chemical change

B.Absorbs light energy

C.Releases heat like burning

D.Forms a precipitate

Question 9mcq

If a reaction mixture becomes cooler, this suggests the reaction may be:

A.Always oxidation only

B.Always precipitation

C.Exothermic

D.Endothermic

Question 10mcq

Which is an example of thermal decomposition?

A.

CaO+H_2O\rightarrow Ca(OH)_2+heat

B.

Zn+CuSO_4\rightarrow ZnSO_4+Cu

C.

2H_2+O_2\rightarrow2H_2O

D.

CaCO_3 \xrightarrow{heat} CaO + CO_2

Question 11mcq

Why is cooking food generally linked to energy change?

A.Heat causes chemical changes in food substances

B.Food only changes shape without any chemical effect

C.Cooking removes all products

D.No energy is involved

Question 12mcq

Which observation best supports an endothermic reaction?

A.The container becomes hot

B.The container feels colder during the reaction

C.Light is emitted strongly

D.A flame is produced