always true, sometimes true , never true: chemical properties are observed only when a substance undergoes a chemical change
describe what happens during a chemical reaction
one or more substances change into one or more new substances
sometimes, always , rarely, never: a change in the composition of matter______occurs during a chemical reaction.
Which representation of a chemical reaction is correct?
a. products ———>reactants
list 4 possible clues to a chemical change
1. transfer of energy 2. a change in color 3. the production of a gas 4. the formation of a precipitate
true or false: if you observe a clue for a chemical change, you can be certain that a chemical change has taken place.
what is a precipitate
a solid that forms and settles out of a liquid mixture
during a reaction , the mass of the products is always equal to the mass of the __________
The law of conservation of matter states that in any physical change or chemical reaction, mass is neither ________ nor _________.
created , destroyed
is burning paper a physical change or a chemical change?
chemical change because the identity of the paper changes
what are the reactants in the above experiment
paper and oxygen
what are the products in the above experiment?
ash and gases
the ash produced when burning the paper has less mass that the original paper. was there a mass change that occurred? explain
mass was conserved ash and gases were produced and those also have mass. The total of the paper and oxygen equals the total mass of the ash and gases.
How does a chemical cahnge affect the composition of matter?
the composition of matter always changes during a chemical change
name 4 possible clues that a chemical change has taken place
a transfer of energy, a change in color, the production fo a gas, the formation of a precipitate
in a chemical reaction, how does the mass of the reactants compare with the mass of the products?
the mass of the products is always equal to the mass of the reactants
what is the main difference between physical changes and chemical changes?
in physical changes, the chemical composition of a substance does not change; in a chemical cahnge, the chemical composition of the reactants changes as one or more products form
classify the following changes as physical or chemical
a. water boils
b. milk turns sour
c. salt dissolves in water
d. a metal rusts
according to the law of conservation of mass, whne is mass conserved?
mass is conservec in every physical change or chemical reaction
what is a chemical property?
the ability of a substance to undergo a specific chemical change
one or more substances change into one or more new substances during _________?
a chemical reaction
a substance that is present at the start of the creation is called the _______
a substance that is produced during the reaction is called______
what is a precipitate?
a solid that forms when two liquids react
describe the law of conservation of matter
mass is conserved in any physical change or chemical change…neither created nor destroyed