43. which of the following is a chemical property of water at 4 degrees c?
a. its ability to decompose into hydrogen and oxygen
b. its temperature
c. its state
d. its color

44. what must be done to be certain that a chemical change has taken place?
a. check for the production of bubbles before and after the change.
b. demonstrate that a release of energy occurred after the change.
c. check the composition of the sample before and after the change.
d. demonstrate that energy was absorbed by the reactants after the change.

45. when paper turns yellow-brown upon exposure to sunlight, what type of change is likely taking place?
a. both a physical change and a chemical change
b. a physical change
c. neither a physical change nor a chemical change
d. a chemical change

46. which of the following indicates that a chemical change has happened during cooking?
a. energy is transferred from the stove to a pan.
b. bubbles form in boiling water.
c. the food darkens.
d. butter melts.

47. which of the following indicates that a physical change has taken place?
a. precipitate formation
b. fracture formation
c. gas production
d. energy transfer

48. which action changes the identity of the substance referenced?

Question

43. which of the following is a chemical property of water at 4 degrees c?
a. its ability to decompose into hydrogen and oxygen
b. its temperature
c. its state
d. its color

44. what must be done to be certain that a chemical change has taken place?
a. check for the production of bubbles before and after the change.
b. demonstrate that a release of energy occurred after the change.
c. check the composition of the sample before and after the change.
d. demonstrate that energy was absorbed by the reactants after the change.

45. when paper turns yellow-brown upon exposure to sunlight, what type of change is likely taking place?
a. both a physical change and a chemical change
b. a physical change
c. neither a physical change nor a chemical change
d. a chemical change

46. which of the following indicates that a chemical change has happened during cooking?
a. energy is transferred from the stove to a pan.
b. bubbles form in boiling water.
c. the food darkens.
d. butter melts.

47. which of the following indicates that a physical change has taken place?
a. precipitate formation
b. fracture formation
c. gas production
d. energy transfer

48. which action changes the identity of the substance referenced?

Accepted Answer

### Question 43
# Brief Explanations:
A chemical property is related to a substance's ability to undergo a chemical reaction. Decomposing into hydrogen and oxygen (option a) involves a chemical reaction (water breaking into its elements), while temperature (b), state (c), and color (d) are physical properties.
# Answer:
a. Its ability to decompose into hydrogen and oxygen

### Question 44
# Brief Explanations:
A chemical change involves a change in composition. Checking composition before and after (option c) confirms if new substances formed. Bubbles (a) could be physical (e.g., boiling), energy release/absorption (b, d) can happen in physical changes (like phase changes), so only checking composition works.
# Answer:
c. Check the composition of the sample before and after the change.

### Question 45
# Brief Explanations:
Paper turning yellow - brown in sunlight is a chemical change because the paper's chemical structure is altered (due to reactions with light, like oxidation of lignin in paper), forming new substances. Physical changes don't change chemical identity, so it's a chemical change (option d).
# Answer:
d. a chemical change

### Question 46
# Brief Explanations:
Food darkening during cooking (like browning) involves chemical reactions (e.g., Maillard reaction) forming new substances. Energy transfer (a) is physical, boiling water bubbles (b) are physical (phase change), and melting butter (d) is physical (phase change). So option c is correct.
# Answer:
c. The food darkens.

### Question 47
# Brief Explanations:
Fracture formation (option b) is a physical change as it only changes the shape/structure of the substance without forming new substances. Precipitate (a), gas production (c) are signs of chemical changes, and energy transfer (d) can be in physical or chemical changes but isn't a sign of physical change itself.
# Answer:
b. fracture formation

### Question 48 (Incomplete, but assuming typical context)
If we assume common options (e.g., burning wood, vs. melting ice), a chemical change (like burning) changes the substance's identity. For example, if options were like "Burning a log" (chemical, changes to ash, CO₂ etc.) vs. "Melting ice" (physical). But since the question is incomplete, if we consider the pattern, actions like chemical reactions (e.g., reacting a substance) change identity, while physical actions (like cutting, melting) don't. If we had to guess with typical options, an action like "Burning sugar" would change its identity (chemical change), while "Cutting a piece of metal" (physical) wouldn't. But since the question is incomplete, we can note that a chemical change (involving reaction, decomposition, etc.) changes the substance's identity, while physical changes (like phase change, shape change) do not.

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Explanation:

Question 43

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Question 44