Question

1. true or false - when zinc is immersed in hydrochloric acid, it produces hydrogen gas. this is a physical change. 2. the physical change from liquid to solid is known as what? a) freezing c) melting b) vaporization d) condensation 3. true or false - when a liquid changes into a solid, this is considered to be a chemical change. 4. when a liquid gains enough energy they become gases. what is the general term for this process? a) freezing c) condensation b) vaporization d) melting 5. true or false - conversion of gaseous nitrogen to liquid nitrogen is an example of a chemical change. 6. true or false - the physical change of melting ice is reversible. 7. true or false - when nails, screws, and bolts are prepared from a piece of iron, the composition of iron will change. 8. which of the following is an irreversible physical change? a) boiling water c) sharpening a pencil b) melting a piece of lead d) dissolving sugar in water 9. ______ solid to liquid. a) melting c) condensation b) freezing d) vaporization 10. jordan is hungry for popcorn. he grabs a bag from the cabinet and places it in the microwave. once it has stopped popping he opens the bag and finds lots of popped popcorn for him to enjoy. what type of change occur as popcorn is cooked? a) chemical change c) material change b) physical change d) no change

Explanation:

1. When zinc reacts with hydrochloric acid, it forms zinc chloride and hydrogen gas. This is a chemical change as new substances are formed.
2. The physical change from liquid to solid is freezing. Melting is solid to liquid, vaporization is liquid to gas, and condensation is gas to liquid.
3. When a liquid changes into a solid, it is a physical change (freezing). No new substances are formed.
4. When a liquid gains enough energy to become a gas, the general term is vaporization. Freezing is liquid to solid, condensation is gas to liquid, and melting is solid to liquid.
5. Conversion of gaseous nitrogen to liquid nitrogen is a physical change (condensation). No new substances are formed.
6. Melting ice (solid to liquid) is reversible (freezing liquid water to ice).
7. When nails, screws, and bolts are made from iron, it is a physical change (shaping). The composition of iron remains the same.
8. Sharpening a pencil is an irreversible physical change (the wood and graphite are removed and cannot be put back). Boiling water (reversible gas - liquid), melting lead (reversible solid - liquid), and dissolving sugar (reversible solution - separation) are reversible.
9. Solid to liquid is melting. Freezing is liquid to solid, condensation is gas to liquid, and vaporization is liquid to gas.
10. Popping popcorn involves a chemical change. The moisture inside the kernel turns to steam, building pressure. When the kernel pops, new substances (like changed starches) are formed.

Answer:

1. False
2. A. Freezing
3. False
4. B. Vaporization
5. False
6. True
7. False
8. C. Sharpening a pencil
9. A. Melting
10. A. Chemical change