WorksheetsDid a Chemical Reaction Take Place
Total questions: 25
Worksheet time: 1hrs 18mins
An experiment is performed in which a crystalline substance is added to a beaker filled with room temperature water. The following observations were made:
A. The crystals dissolve
B. A precipitate is formed
C. The bottom of the beaker feels warm to touch
D. Bubbles begin to form within the water
Which observations are evidence that a chemical reaction took place?
A
B
B and C
B, C, and D
When vinegar and baking soda are combined, bubbles begin to form. How are the formation of bubbles evidence of a chemical reaction?
Bubbles occur when there is a physical change.
There was no chemical reaction because there was not a color change.
Bubbles indicate the formation of a gas as a new product.
You need soap to form proper bubbles.
Four students performed four different investigations by combining different substances. Their results are shown in the table above. In which experiment did a chemical reaction take place, and how do you know?
In Experiment 1, a chemical reaction took place. Evidence for this is the production of bubbles, indicating a new substance was formed.
In Experiment 2, a chemical reaction took place. Evidence for this is the amount of the solution increased, indicating more product.
In Experiment 3, a chemical reaction took place. Evidence for this is the dissolving of the crystals, indicating the crystals took a long time to disappeared.
In Experiment 4, a chemical reaction took place. Evidence for this is the solid remains a solid.
Hydrogen and oxygen react to form water. At an atomic level, how do we know that a chemical reaction has occurred?
A. Hydrogen molecules are negative, and oxygen positive.
B. For every oxygen atom., two hydrogen atoms are needed.
C. The hydrogen and oxygen atoms regroup into a new molecule.
D. Oxygen atoms are much larger than hydrogen atoms.
A chemical reaction occurs that involves combining 1 atom of zinc with 2 atoms hydrogen and 2 atoms of chlorine. After the reaction, how many atoms of each element will there be?
1 zinc, 2 hydrogen, 2 chlorine
2 zinc, 2 hydrogen, 2 chlorine
2 zinc, 1 hydrogen, 2 chlorine
2 zinc, 1 hydrogen, 2 chlorine
Which of the following is the best description of the results of a chemical reaction?
The substance seems to disappear after dissolving in water.
The substance changes from liquid to solid at a low temperature.
A new substance with different properties is formed.
The reaction can be reversed to get back the original substance.
During a chemical reaction, substances (called reactants) are combined to form new substances (called products). Which of the following accurately describes the reactants and the products of a chemical reaction?
The products contain a different number of atoms than the reactants but have the same properties.
The number of atoms and the properties are the same in the reactants and the products.
The products contain the same number of atoms as the reactants but have different properties.
The number of atoms and the properties are different in the reactants and the products
C6H12O6
The student inferred that a chemical reaction occurred. What evidence supports this inference?
The zinc metal remained silver-colored and shiny
The student observed that the temperature changed from 25 •C to 23 •C when the solutions were combined and that a white substance rapidly formed and settled to the bottom of the container. What most likely happened to produce these results?
Which of the following BEST describes a chemical reaction?
A compound is crushed into a fine powder.
Atoms break apart into even smaller particles.
Existing electron bonds break and new bonds form.
Molecules move faster until they fly apart from each other
In a ___________change, a substance changes into a different substance.
Physical
Chemical
Which of these is NOT a sign that a chemical change has occurred?
A loss of transparency
An unexpected color change
A temperature change
The formation of a precipitate
The Law of Conservation of Mass states
that matter exists in all states and reacts the same
that matter can only be changed into new substances by introducing a catalyst
that matter exists in the same state throughout any chemical change
that matter cannot be created or destroyed and that the mass of the products must equal the mass of the reactants
a copper penny turning greenish after a few years.
Physical change
Chemical change
Which of the following IS a physical change?
Getting a haircut
Rusty metal
sour milk
A compound
___________________ are the elements or compounds that leave (are formed in) a chemical reaction.
Polymers
Bonds
Reactants
Products
The mass of all the reactants must equal the mass of all the products. Matter is neither created nor destroyed.
chemical reaction
chemical formula
law of conservation of mass
product
The process by which one or more substances change to produce one or more different substances is
chemical reaction
reactant
subscript
coefficient
What are the products of the chemical reaction pictured?
CH4 and CO2
CH4 and O2
CO2 and H2O
O2 and H2O
