Particle Model
Identify the state of matter described: particles vibrate in place, are tightly packed, and the substance has a definite shape and volume.
Solid
What do we call the substance that dissolves in a solvent?
Solute.
What separation process uses evaporation and condensation to collect pure water from salt water (as in a solar still)?
Distillation (or solar still/desalination).
What term describes a liquid's resistance to flow (its thickness or thinness)?
Viscosity.
Write the formula that relates density, mass, and volume.
Density=Mass / Volume
List two key ideas from the Particle Model of Matter that explain why temperature affects particle motion.
e.g., "All substances are made of tiny particles" and "Particles are always in motion; increasing temperature increases motion."
Define a homogeneous mixture and give one everyday example.
Homogeneous mixture = appears uniform (e.g., salt water).
What is fractional distillation and why does it separate petroleum into different products?
Fractional distillation separates by different boiling/condensing points.
If you want oil in a pipeline to flow faster on a cold day, should you heat or cool the oil? Explain briefly.
Heat the oil (reduces viscosity).
If an object has mass 1932 g and volume 100 cm3, what is its density? (Show calculation.)
200 = ρ=1932 g/100 cm3=19.32 g/cm3
Give an example (not water) of a substance that can exist as a solid, liquid, and gas and name one change-of-state term for each transition.
What other examples can you think of?
water: melting/freezing, vaporization/condensation, sublimation (if applicable).
Explain why water is often called the "universal solvent."
Water's polarity allows it to attract many charged or polar solutes.
Outline the main steps used to separate gold from crushed ore (as described in the unit).
Mine/crush ore → mix with water to form suspension → add chemicals to dissolve desired metal → add another metal (e.g., zinc) to displace and recover the metal.
Two fluids: A flows at 10.5 mL/s, B at 11.3 mL/s through the same tube. Which fluid is less viscous and why?
Fluid B (11.3 mL/s) is less viscous because it flows faster.
Explain why ice floats on liquid water using particle and density ideas.
Ice has lower density than liquid water because frozen water has particles arranged with more space, so its average density is less and it floats.
Explain, using particle ideas, why solids do not flow but liquids do.
Solids: particles fixed in place; liquids: particles can move/slide past one another.
Describe three factors that affect the rate at which a solute dissolves in a solvent.
Agitation (stirring), temperature, pressure (and particle size).
Explain how distillation separates components of a liquid mixture in terms of boiling/condensing temperatures.
Components boil at different temperatures, vaporize and recondense separately.
Explain how temperature affects viscosity in liquids and contrast that with how temperature affects viscosity in gases.
Liquids: viscosity decreases as temperature increases; Gases: viscosity increases as temperature increases.
State Archimedes' Principle and use it to explain why a large steel ship can float.
Archimedes: the buoyant force equals the weight of displaced fluid; ship's hollow shape lowers its average density so the weight of water displaced equals ship's weight.
Describe sublimation in particle terms and give one real-world example.
Sublimation = direct solid→gas (e.g., dry ice / solid CO2).
What is a supersaturated solution? Describe how you could make one and name one observable sign that a solution is supersaturated.
Supersaturated = contains more solute than normally soluble at that temperature; make by heating solvent, dissolve extra solute, then cool slowly — crystals may form suddenly.
Describe the "desert tent" method of desalination and explain one advantage and one limitation.
Desert tent: uses solar heat to evaporate water, condense on a cover and collect — advantage: low cost; limitation: slow and requires strong sunlight.
Describe an industrial application where controlling viscosity is critical and explain how changing viscosity improves performance.
e.g., paint manufacturing — adjust solvent to change viscosity so paint spreads well but doesn't drip.
A rock in air weighs 1.55 N and appears to weigh 1.40 N when submerged in water. Calculate the buoyant force on the rock and explain what that value means.
Buoyant force = apparent weight loss = 1.55−1.40=0.15 N1.55−1.40=0.15 N; this is the upward force exerted by the water on the rock.