Which element has the same number of valence electrons as bromine (Br)?
A. krypton (Kr)
B. potassium (K)
C. chlorine (Cl)
D. selenium (Se)
C. chlorine (Cl)
Bot
Why are sodium (Na) and potassium (K) in the same group on the periodic table?
A. They have similar reactivity.
B. They are both hard and brittle.
C. They are both colorless.
D. They have similar atomic weights.
A. They have similar reactivity.
Bot.
A student cuts some fabric into two pieces. Is this change physical or chemical?
A. It is a physical change because there is no reaction.
B. It is a physical change because the process is reversible.
C. It is a chemical change because the size changes.
D. It is a chemical change because there is no phase change.
A. It is a physical change because there is no reaction.
How are chemical changes different from physical changes?
A. They are reversible.
B. They form new substances.
C. They involve heat.
D. They include shifts in the phase of matter.
B. They form new substances.
How does a balanced chemical equation demonstrate the Law of Conservation of Mass?
A. it shows that only physical changes follow the Law of Conservation of Mass
B. it shows that no atoms have been gained or lost during the reaction
C. it shows that all compounds remain bonded after the reaction
D. it shows that the properties of the elements stay the same after the reaction
B. it shows that no atoms have been gained or lost during the reaction
Which procedure could be used to demonstrate that matter is conserved during a physical change?
A. Find the mass of an apple. Cut the apple and remove the core. Find the mass of the remaining apple.
B. Find the mass of a piece of ice. Let the ice melt. Find the mass of the liquid water.
C. Find the mass of a raw egg. Cook the egg. Find the mass of the cooked egg.
D. Find the mass of a cup of water. Boil the water. Find the mass of the water that remains.