Homework Practice

Printable assignment

Chemical Change Foundations

Section A: Signs of Chemical Change

Question 1mcq

Which observation is the strongest evidence that a chemical reaction has occurred?

A.The substance changes position

B.The substance is placed in a new container

C.A new substance is formed

D.The substance is cut into smaller pieces

Question 2mcq

Which of the following is usually a sign of chemical change?

A.Change in size only

B.Change in shape only

C.Change in place only

D.Evolution of a gas

Question 3mcq

In a chemical reaction, substances present before the reaction are called:

A.Reactants

B.Products

C.Catalysts only

D.Precipitates

Question 4mcq

2Mg + O_2 \rightarrow 2MgO

, the product is:

MgO

2Mg

only

O_2

Mg

Question 5mcq

Which everyday example is a chemical change?

A.Tearing of paper

B.Rusting of an iron nail

C.Dissolving sugar in water

D.Melting of ice

Question 6mcq

Why is melting of wax usually treated as a physical change, while burning of wax is a chemical change?

A.Burning changes only shape

B.Melting always releases oxygen

C.Both form exactly the same substance

D.Melting changes state, but burning forms new substances

Section B: Reactants, Products and Vocabulary

Question 7mcq

CaCO_3 \rightarrow CaO + CO_2

, which substances are products?

A.Only

CaCO_3

B.Only

CO_2

as a reactant

CaCO_3

and

CaO

CaO

and

CO_2

Question 8mcq

A solid formed when two aqueous solutions react is called a:

A.Catalyst

B.Solvent

C.Precipitate

D.Reactant only

Question 9mcq

When lead nitrate solution is mixed with potassium iodide solution, a yellow solid appears. This mainly shows:

A.Only filtration

B.Only evaporation

C.Only melting

D.Formation of a precipitate

Question 10mcq

Curd formation from milk is considered a chemical change because:

A.Milk becomes colder only

B.New substances with different taste and properties are formed

C.Milk only changes container

D.Milk is simply cut into pieces

Question 11mcq

Which change is most likely reversible and physical?

A.Freezing of water into ice

B.Cooking of an egg

C.Burning of paper

D.Rusting of iron

Question 12mcq

Which pair is correctly matched?

A.Precipitate — gas escaping

B.Reactant — substance formed after reaction

C.Product — substance present only before reaction

D.Gas evolution — bubbles seen during reaction