1 a chemical is any substance that has definite, indefinite composition. changes in chemicals or chemical reactions take place only in test tubes, all around us.
2. the type and arrangement of particles, crystals in a sample of matter determine the properties of the matter. most of the matter you encounter is in one of numerous, three states of matter.
3. the characteristics of a solid include fixed, variable volume and shape. particles that make up solids are held loosely, tightly in a flexible, rigid structure, so the particles can vibrate only slightly, flow past each other.
4. liquids have a fixed, variable volume but a fixed, variable shape. this situation occurs because particles in a liquid are held tightly, loosely and can, cannot slip past each other.
5. gases have fixed, variable volume and fixed, variable shape. gas particles may move apart to fill any container they occupy. this behavior occurs because gas particles are close together, far apart and are attracted, not strongly attracted to one another.
6. physical, chemical changes are changes in which the identity of a substance does not change. thus the changes of state are physical, chemical changes.
7. in a physical, chemical change, the identities of substances change and new substances form.
8. in the word equation hydrogen + oxygen + heat → water, hydrogen is a reactant, product, and water is a reactant, product.

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Accepted Answer

### Question 1
# Brief Explanations:
- For the first blank, a chemical has a definite composition (by definition of a chemical substance).
- For the second blank, chemical reactions occur all around us, not just in test tubes (e.g., rusting, digestion).
# Answer:
1. definite; all around us

### Question 2
# Brief Explanations:
- The type and arrangement of particles (not crystals, as crystals are a type of solid structure) determine matter's properties.
- Matter is commonly in three states: solid, liquid, gas (not numerous as a general classification for common states).
# Answer:
2. particles; three

### Question 3
# Brief Explanations:
- Solids have fixed volume and shape.
- Solid particles are held tightly in a rigid structure (not loose or flexible), and can only vibrate slightly (not flow past each other, which is liquid behavior).
# Answer:
3. fixed; tightly; rigid; vibrate only slightly

### Question 4
# Brief Explanations:
- Liquids have fixed volume (they don't expand/contract to fill a container) but variable shape (they take the shape of their container).
- Liquid particles are held loosely (compared to solids) and can slip past each other (allowing them to flow).
# Answer:
4. fixed; variable; loosely; can

### Question 5
# Brief Explanations:
- Gases have variable volume (they expand to fill their container) and variable shape (they match the container's shape).
- Gas particles are far apart (not close together like solids/liquids) and not strongly attracted (so they move freely).
# Answer:
5. variable; variable; far apart; not strongly attracted

### Question 6
# Brief Explanations:
- Physical changes are those where the substance's identity doesn't change (e.g., melting ice).
- Changes of state (like melting, freezing, vaporization) are physical changes because the substance remains the same (e.g., water in ice, liquid, gas is still H₂O).
# Answer:
6. Physical; physical

### Question 7
# Brief Explanations:
- Chemical changes involve a change in substance identity and new substances forming (e.g., burning wood to form ash and gas). Physical changes don't change identity.
# Answer:
7. chemical

### Question 8
# Brief Explanations:
- In a chemical equation, reactants are on the left (what reacts) and products on the right (what is formed). So hydrogen is a reactant, water is a product.
# Answer:
8. reactant; product

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