Suppose 10 atoms of carbon (C) react with 20 atoms of oxygen (O) to form 10 molecules of carbon dioxide (CO2). According to the law of conservation of matter, how many atoms are present in this reaction?(1 point)
Responses
20
20
10
10
15
15
30
30
Which procedure could be used to demonstrate that matter is conserved during a chemical change or reaction?(1 point)
Responses
Find the mass of a piece of paper. Tear the paper into smaller pieces. Find the mass of the pieces.
Find the mass of a piece of paper. Tear the paper into smaller pieces. Find the mass of the pieces.
Find the mass of an acid and a base. Combine them to produce water and a salt. Find the mass of the water and salt.
Find the mass of an acid and a base. Combine them to produce water and a salt. Find the mass of the water and salt.
Find the mass of a stick of butter. Heat the butter until it melts. Find the mass of the melted butter.
Find the mass of a stick of butter. Heat the butter until it melts. Find the mass of the melted butter.
Find the mass of a log. Burn the log until it turns to ash and smoke. Find the mass of the ash.
Find the mass of a log. Burn the log until it turns to ash and smoke. Find the mass of the ash.
What is always true according to the Law of Conservation of Matter?(1 point)
Responses
Atoms can be rearranged during a chemical reaction but cannot be added or taken away.
Atoms can be rearranged during a chemical reaction but cannot be added or taken away.
The total number of molecules before and after a chemical reaction stays the same.
The total number of molecules before and after a chemical reaction stays the same.
Atoms created during a chemical reaction must have the same mass as the atoms in the reactants.
Atoms created during a chemical reaction must have the same mass as the atoms in the reactants.
New molecules cannot be formed from the reactants during a chemical reaction.
Atoms can be rearranged during a chemical reaction but cannot be added or taken away.
A student combines two liquids in a beaker. She observes that the mass of the combined liquid is less than the mass of the two separate liquids. The student claims that this observation shows that matter is not conserved in chemical reactions. Which statement explains why the student’s claim is incorrect?(1 point)
Responses
The reaction did not change the physical properties of the liquids.
The reaction did not change the physical properties of the liquids.
The reaction produced a gas that escaped the beaker.
The reaction produced a gas that escaped the beaker.
The product contained fewer atoms than the reactants.
The product contained fewer atoms than the reactants.
The combined liquid was warmer than the two separate liquids.
The reaction produced a gas that escaped the beaker.
What does a hieroglyphic writing system use instead of alphabetic letters?
(1 point)
Responses
cuneiform shapes
cuneiform shapes
drawings or symbols
drawings or symbols
a numerical code
a numerical code
papyrus scrolls
drawings or symbols
What made the Egyptian lunar calendar difficult to use?
(1 point)
Responses
Days were different lengths in different seasons.
Days were different lengths in different seasons.
Each year had a different number of days.
Each year had a different number of days.
It was based on a star that appeared every three years.
It was based on a star that appeared every three years.
Only educated Egyptians could understand it