Conservation of Mass
In any chemical reaction in a closed system, this statement accurately compares the total mass of the products to the total mass of the reactants.
What is "they are equal"?
If you remove a piece from a ball of wax, this characteristic property remains completely unchanged even though its mass decreases.
What is the melting point (or density/color)?
This term describes an insoluble solid that forms and settles at the bottom when two clear liquids react chemically.
What is a precipitate?
When designing an experiment to determine what causes a change in properties, this is the maximum number of independent variables you should change at a time.
What is one?
If 1 gram of sugar is completely dissolved in 10 grams of water, this will be the total mass of the resulting solution.
What is 11 grams?
To identify an unknown pure metal object regardless of its size or shape, you can calculate this ratio of its mass to its volume.
What is density?
Name two distinct pieces of evidence observed when zinc was dropped into hydrochloric acid that proved a chemical reaction occurred.
What are temperature increase (feeling warmer), gas production (filling the balloon), or size reduction of an insoluble metal?
Experiments must be designed so that other scientists can perform them under identical conditions and get consistent results. This term describes this requirement.
What is repeatable (or replicable)?
Jay mixed 10.2 grams of one liquid with 7.6 grams of another. Even though a solid precipitate formed, the scale read exactly 17.8 grams because of this principle.
What is the Law of Conservation of Mass (or atoms rearranged without changing total mass)?
Liquid 1 and Liquid 2 are both colorless with a density of 0.79 g/mL, but Liquid 1 boils at 56°C while Liquid 2 boils at 78°C. This states whether they are the same substance.
What is "they are different substances" (because their boiling points differ)?
During a phase change, molecules speed up or slow down. During a chemical reaction, this fundamental atomic process occurs instead.
What is the breaking and forming of chemical bonds (or rearranging atoms into new molecules)?
Changing multiple variables at once in a single experiment causes this specific problem when analyzing the data.
What is "you cannot determine which variable caused the observed change"?
When mixing two liquids in an open beaker, a student notices bubbling, and the total mass on the scale decreases. This is the primary reason for the mass loss.
What is gas escaping into the air from an open system?
Testing just one physical property may not identify an unknown metal because of this key scientific reason.
What is "different substances can share some of the same properties"?
When sugar (white) reacts with a white powder to form a yellow powder, this describes the relationship between the atoms in the reactants and the product.
What is "the yellow powder contains the exact same kinds of atoms, recombined into new molecules"?
This type of experimental setup prevents gas from escaping into the room, making it possible to measure total mass accurately before and after a reaction.
What is a closed system?
True or False: Matter can be destroyed in an open system when a chemical reaction produces a gas. Explain why.
What is False? (Matter is never destroyed; gas atoms simply escape into the surrounding environment.)
Increasing a sample of ice from 10 grams to 100 grams changes these two measurements while leaving its melting point untouched.
What are mass and volume?
A student claims that warming liquid water into steam is a chemical reaction because it absorbed heat and created gas. This refutes the claim.
What is "it is a phase change because the molecules ($H_2O$) remain unchanged, only their spacing and speed changed"?
$1000 Clue: In a Claim-Evidence-Reasoning (CER) response explaining why two liquids are different, the measured boiling points (56°C vs 78°C) represent this part of the framework.
What is the Evidence?