States of Matter
A student leaves a glass of ice water on her desk. When she returns, she sees drops of water on the outside of the glass. What caused this?
Condensation: water vapor cooled and turned into liquid on the glass
A student drops a rock, a piece of wood, and a lily pad into water. Which will float and why?
Wood and lily pad float because their density is less than water.
A mixture of sand and iron filings is given. What is the fastest way to separate them?
Use a magnet to attract the iron filings.
A balloon is weighed before and after it is filled with air. Why is the second measurement greater?
Air has mass even though particles are too small to see.
A teacher wears gloves to pick up a hot metal pan. Why are gloves needed?
The metal pan conducts thermal energy, so gloves insulate and protect from burns.
Which change requires more energy: melting ice, boiling water, or condensation? Explain.
Boiling requires the most energy because particles must separate completely into gas.
A student classifies a sphere using a triple beam balance. Why is measuring mass useful in describing matter?
Mass is measurable and helps compare substances regardless of shape/size.
A student stirs salt into water until it is invisible. What happened to the salt particles?
They dissolved and spread evenly among the water particles.
Julia squeezes a bottle of air and a bottle of water. The air-filled bottle is easier to squeeze. Why?
Air particles are far apart and compressible; water particles are close together and not easily compressed.
A student mixes cereal with warm water and stirs with a magnet. What property is being tested, and what result would show iron is present?
Magnetism; iron in cereal would stick to the magnet.
A pan of water is boiling. Predict what would happen if you poured a large cup of cold water into the pan and explain why.
Boiling would stop because the temperature drops until the added water heats up.
A student has three unknown objects. Describe how you could test relative density, solubility, and magnetism to help identify them.
Test float/sink in water, try dissolving in water, and check with a magnet.
Students measure 25g of sugar and stir it into 580g of water. What is the total mass of the solution?
605g; mass is conserved.
Perfume is sprayed on one side of a room. Explain why it can be smelled across the room.
Gas particles spread out and move in all directions (diffusion).
A student stirs four powders into water and records:
1. floated
2. sank
3. sank but cloudy
4. dissolved and water changed color
Which formed a solution?
The powder that dissolved and made the water change color.
Compare evaporation and condensation at the particle level. How do particles behave in each?
In evaporation, fast-moving particles escape into gas; in condensation, particles lose energy and cluster into liquid.
Students test six materials in a circuit. Some complete the circuit, some do not. Which property are they testing, and how do they know?
Electrical conductivity; conductors complete the circuit and make the buzzer sound.
A student mixes salt and pepper. Both are the same size. How could they be separated most effectively?
Add water to dissolve salt, filter out pepper, then evaporate the water.
Students add food coloring to a beaker of water. It spreads out evenly without stirring. What does this show about particles?
Particles are in constant motion, causing mixing and spreading.
A student heats water on a hot plate until boiling. What would happen to the particle motion if the water kept heating?
Particles would move faster and escape as gas; kinetic energy increases.
Dry ice left out in a bowl changes directly into gas. What is this process called, and how does it show that matter changes states without disappearing?
Sublimation; matter changes from solid to gas, proving matter is conserved.
A student is asked to compare conductors and insulators of thermal and electrical energy. Give one example of each and explain why the difference matters.
Conductor: copper (lets energy flow). Insulator: rubber (blocks energy). Important for safety and correct material use.
A student claims, 'The sugar disappeared when I stirred it into the water. Use conservation of matter to explain why this is incorrect.
The sugar is still there as dissolved particles; it did not disappear—mass is conserved.
Design an investigation to prove that matter is made up of particles too small to see. Be specific about steps and observations.
Weigh a balloon before/after filling, or observe diffusion of food coloring in water as evidence of invisible particles.
A sealed bottle of soda is opened and bubbles escape. Explain what happens using the particle model of matter and conservation of mass.
Gas particles were trapped under pressure; they escape but mass is still conserved in the system.