Which is an example of chemical change?
a. Water freezes
b. Wood is cut
c. Bread is baked
d. Wire is bent
c. Bread is baked.
100
What is the Law of Conservation of Mass?
The law that says that during chemical reactions, matter cannot be created or destroyed, only rearranged.
100
What is the process by which one or more substances change to produce one or more different substances?
A chemical reaction
200
What charge do electrons have?
A negative charge.
200
What are rows and columns in the periodic table called?
Periods and groups or families.
200
Which is not a clue that could indicate a chemical change?
a. Change in color
b. Change in shape
c. Change in energy
d. Change in odor
b. change in shape
200
Atoms are never ________ or _______ in a chemical reaction.
Lost or gained.
200
What is a combination of chemical symbols and numbers to represent a substance?
A chemical formula.
300
An atom has an atomic mass of 23 and atomic number 11. The number of protons are_________.
12
300
What does atomic number and atomic mass represent?
Atomic Number-The number of protons and electrons. Atomic mass-The combined mass of the protons and neutrons.
300
What happens to energy in exothermic chemical reaction?
Energy is released.
300
Every atom in the reactants becomes part of the ________.
Products.
300
What is a representation of a chemical reaction that uses symbols to show the relationship between the reactants and the products?
A chemical equation.
400
The element X has 2 valence electrons. It is a____________.
Metal.
400
The elements characterized as nonmetals are located in the periodic table at the
(1) far left; (2) bottom; (3) center; (4) top right
4
400
What is the reactivity of elements in groups 1 & 2.Very reactive.
Very reactive.
400
A chemical equation must show the same numbers and kinds of atoms on both sides of the ________.
Arrow.
400
What is a substance or molecule that participates in a chemical reaction?
A reactant.
500
.Which of the following descriptions apply to the nucleus?
a. Positively charged
b. Mostly empty space
c. Small
d. Dense
a., c. and d
500
The elements in the present Periodic Table are arranged according to their (1) atomic numbers; (2) atomic masses; (3) mass numbers; (4) oxidation state
1. Atomic Numbers
500
What is the coefficient needed for Al when the equation Al + Cl2 = AlCl3 is balanced?
2
500
A ________ equation illustrates the law of conservation of mass.
Balanced.
500
What is the substance that forms in a chemical reaction?