Why are sodium(Na) and potassium(K) in the same group on the periodic table?
They have similar reactivity.
They are both colorless.
They have similar atomic weights.
They are both hard and brittle.
The correct answer is:
They have similar reactivity.
A student cuts some fabric into two pieces. Is this change physical or chemical?
It is a physical change because the process is reversible.
It is a chemical change because there is no phase change.
It is a chemical change because the size changes.
It is a physical change because there is no reaction.
The correct answer is:
It is a physical change because there is no reaction.
How are chemical changes different from physical changes?
They are reversible.
They involve heat.
They include shifts in the phase of matter.
They form new substances.
The correct answer is:
They form new substances.
How does a balanced chemical equation demonstrate the Law of Conservation of Mass?
it shows that all compounds remain bonded after the reaction.
it shows that the properties of the elements stay the same after the reaction.
it shows that only physical changes follow the Law of Conservation of Mass.
it shows that no atoms have been gained or lost during the reaction.
The correct answer is:
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 a cup of water. Boil the water. Find the mass of the water that remains.
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 an apple. Cut the apple and remove the core. Find the mass of the remaining apple.
d.Find the mass of a raw egg. Cook the egg. Find the mass of the cooked egg.
The correct answer is:
a.Find the mass of a cup of water. Boil the water. Find the mass of the water that remains.
One molecule of bromine (Br2) and two molecules of potassium chloride (KCl) combine in a reaction. How many atoms are in the products?
Four
Six
Three
Two