1. If you dissolve 5 grams of salt in 100 grams of water, what will be the total mass of the resulting saltwater mixture?
- A. Exactly 100 grams, because the salt disappears.
- B. Slightly more than 100 grams, but less than 105 grams.
- C. Exactly 105 grams.
- D. Less than 100 grams, because some water evaporates.
2. Why is dissolving a spoonful of sugar in water considered a physical change?
- A. Because the sugar is still present, just in a different form.
- B. Because the process creates bubbles and a new gas.
- C. Because the water's temperature changes significantly.
- D. Because the sugar can never be separated from the water again.
3. A student makes a powdered drink by mixing a packet of powder into a pitcher of water. The powder dissolves completely. Which statement provides the best evidence that the powder did not disappear?
- A. The water becomes colored and tastes sweet.
- B. The pitcher feels heavier than before.
- C. The volume of the liquid in the pitcher increases slightly.
- D. The mixture needs to be stirred for a long time.
4. Which of the following best describes the particles of a substance, like sugar, after it has fully dissolved in water?
- A. They are gone.
- B. They are invisible and spread out.
- C. They are clumped together at the bottom.
- D. They have transformed into water particles.
5. When sugar is stirred into hot tea until it is no longer visible, what has happened to the sugar?
- A. It has melted and turned into a liquid.
- B. It has been chemically destroyed by the heat.
- C. It has broken down into invisible particles that have spread throughout the tea.
- D. It has evaporated from the cup along with the water vapor.
6. Which of the following is an observation made at the macroscopic scale?
- A. A water molecule vibrating.
- B. A mixture appearing clear.
- C. An ion breaking free from a solid crystal.
- D. Solute particles swimming away.
7. If you mix a fine powder with water and the resulting mixture remains cloudy, what does this imply about the powder's particles at the nanoscale?
- A. The particles have all broken free and are mixed evenly with the liquid's particles.
- B. The particles are still in clumps large enough to block the passage of light.
- C. The particles have all settled at the bottom, making the top of the liquid clear.
- D. The particles have undergone a chemical change to form an entirely new substance.
8. What does the term "nanoscale" refer to when scientists study a process like dissolving?
- A. The observable changes in volume and temperature that we can measure directly.
- B. The level of individual atoms and molecules, which are too small to be seen with the naked eye.
- C. The speed at which a solid completely mixes into a liquid.
- D. The final color and clarity of the mixture after it has settled.
9. When a solid like sugar dissolves in water, what is happening to the sugar particles at the nanoscale?
- A. They are chemically destroyed by the water particles.
- B. They break away from the solid crystal and mix in between the water particles.
- C. They sink to the bottom of the container and become transparent.
- D. They are converted into heat energy, warming up the water.
10. Why does a solution of salt in water appear clear at the macroscopic level?
- A. The salt particles have transformed into a transparent gas.
- B. The salt has chemically reacted to become a new substance that is invisible.
- C. The individual salt particles are so small and are spread so evenly throughout the water that they no longer block or scatter light in a visible way.
- D. The water particles change their structure to hide the salt particles from view.