1. an example of a physical property is ______
a. flammability
b. ability to rust
c. acidic
d. state of matter

2. a ______ is a type of change in which the form of matter is changed but one substance is not transformed into another.

3. physical changes are
a. reversible
b. irreversible
c. almost reversible
d. neither

4. which of the following does not represent a physical change in matter?
a. crumpling a sheet of paper
b. melting (unclear text, likely a substance)
c. the evaporation of water
d. burning wood

5. (true or false) physical changes do not change the chemical composition of a substance.

6. what must be added or removed to matter in order for a phase change to occur?

Question

1. an example of a physical property is ______
a. flammability
b. ability to rust
c. acidic
d. state of matter

2. a ______ is a type of change in which the form of matter is changed but one substance is not transformed into another.

3. physical changes are
a. reversible
b. irreversible
c. almost reversible
d. neither

4. which of the following does not represent a physical change in matter?
a. crumpling a sheet of paper
b. melting (unclear text, likely a substance)
c. the evaporation of water
d. burning wood

5. (true or false) physical changes do not change the chemical composition of a substance.

6. what must be added or removed to matter in order for a phase change to occur?

Accepted Answer

### Question 1
# Brief Explanations:
Physical properties are characteristics of a substance that can be observed or measured without changing its chemical composition.
- Option a (Flammability): This is a chemical property because it relates to how a substance reacts with oxygen to burn (a chemical change).
- Option b (Ability to rust): Rusting is a chemical reaction (oxidation of iron), so this is a chemical property.
- Option c (Acidity): Acidity involves chemical reactions (like how a substance donates protons), so it's a chemical property.
- Option d (State of matter): The state of matter (solid, liquid, gas) of a substance can be observed without changing its chemical identity (e.g., water as liquid or ice as solid is still H₂O). So this is a physical property.
# Answer:
d. State of matter

### Question 2
# Brief Explanations:
A physical change is a change in which the form or appearance of matter changes, but the chemical identity of the substance(s) remains the same (no new substance is formed). In a physical change, the atoms of matter are rearranged, but one substance does not transform into another (unlike chemical changes where new substances are formed). So the blank should be filled with "physical change".
# Answer:
physical change

### Question 3
# Brief Explanations:
Physical changes can often be reversed. For example, melting ice (physical change) can be reversed by freezing the water back into ice. Dissolving salt in water is a physical change and can be reversed by evaporating the water to get the salt back. While some physical changes might seem hard to reverse (like breaking a glass), many are reversible. Chemical changes are usually irreversible, but physical changes are mostly reversible.
- Option a (Reversible): Correct, as many physical changes (like phase changes, dissolving) can be reversed.
- Option b (Irreversible): Incorrect, this is more typical of chemical changes.
- Option c (Mostly reversible): While "mostly" is true, the best answer here is "reversible" as the core idea is that physical changes are generally reversible (unlike chemical which are not).
- Option d (Neither): Incorrect, since physical changes are reversible.
# Answer:
a. Reversible

### Question 4
# Brief Explanations:
Physical changes do not change the chemical composition of a substance. Chemical changes result in new substances.
- Option a (Crushing a sheet of paper): Only changes the shape/size of the paper, no new substance. Physical change.
- Option b (Melting paraffin wax): Changes from solid to liquid wax, still paraffin. Physical change.
- Option c (The evaporation of water): Water changes from liquid to gas, still H₂O. Physical change.
- Option d (Burning wood): Burning wood involves combustion, which produces new substances like carbon dioxide, ash, etc. This is a chemical change, so it does NOT represent a physical change.
# Answer:
d. Burning wood

### Question 5
# Brief Explanations:
Physical changes only affect the physical properties (like state, shape, size) of a substance, not its chemical composition. For example, melting ice (physical change) still has the same chemical formula (H₂O) before and after. So the statement "Physical changes do not change the chemical composition of a substance" is true.
# Answer:
True

### Question 6
# Brief Explanations:
For a chemical change to occur, energy (in the form of heat, light, electricity, etc.) is usually involved. Specifically, energy (often in the form of heat, but can also be light or electricity) must be added or removed (or a reactant like oxygen in combustion) to initiate a chemical reaction. The key factor is energy (or a reactant, but energy is a common trigger). So the answer is that energy (usually heat, but can be other forms like light, electricity) must be added or removed (or a reactant must be introduced) for a chemical change to occur. In many cases, heat is the most common - for example, burning requires heat, cooking requires heat, etc. But more generally, energy (in some form) must be involved (added or removed) to cause the atoms/molecules to rearrange into new substances.
# Answer:
Energy (usually in the form of heat, light, or electricity) must be added or removed (or a reactant must be introduced) for a chemical change to occur. (Commonly, heat is a key form of energy involved in many chemical changes, like combustion, cooking, etc.)

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