Solids, liquids and gases as moving particles
Grade 8 Science Worksheet - Challenge Me
Circle the best answer, or write your answer on the line.
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Melting test (example data)
trial mass of ice (g) minutes to melt A 400 8 B 100 2 All of the hot plate's energy goes into melting.
Each minute the hot plate adds the same energy, all of it melting ice at 0 °C. How many minutes will 200 g of ice take, Ari?
Each minute the hot plate adds the same energy, all of it melting ice at 0 °C. How many minutes will 600 g of ice take, Bo?
Under a microscope, specks of smoke in a sealed cell of still air jiggle in random directions. What explains this, Jun?
- Air particles are at rest, and just the smoke specks have energy to move about on their own
- The specks swell and shrink as the air around them warms and cools, so they seem to jiggle about
- Unseen air particles, moving fast in every direction, keep bumping the specks from different sides
- A steady breeze through the cell pushes the specks around, which makes them seem to jiggle at random
Air in a hot-air balloon is heated, and the balloon rises. Which explanation fits the particle model, Kira?
- Hot air particles become lighter than cold air particles, so the balloon floats up on a cushion of them
- Hot air particles move upward in a straight stream, so they carry the balloon up with them
- Faster air particles spread out and some leave the open bottom, so the air inside is less dense
- Heating creates extra air particles that fill the balloon and lift it, which is why it gets bigger
A hot metal spoon sits in cool water. After a few minutes both are at one temperature. What explains this, Luz?
- Cold flows from the water into the spoon until both are equally cool, much as water flows into a cup
- Faster spoon particles pass energy to slower water particles in collisions until the speeds match
- The spoon's particles stop moving and hand their energy over to the water particles around them
- Heat leaves the spoon until the spoon is cold, while the water stays at its first temperature
Gas in a flexible balloon (example data)
temperature (°C) volume (mL) 0 500 20 537 40 573 Milo says the gas volume doubles when the temperature doubles from 20 °C to 40 °C. Does the table support that?
- Yes: 40 °C is twice 20 °C, and 573 mL is more than twice 537 mL
- No: the volume rose only from 537 mL to 573 mL, much less than double
- Yes: the volume rose each time the temperature rose, so it must have doubled
- No: a gas should not change volume when its temperature changes
Dye test, three trials at each temperature (example data)
trial seconds at 50 °C seconds at 10 °C 1 38 95 2 45 110 3 41 90 Noah compares the dye times. Which statement do the data support?
- The 50 °C times range from 38 s to 45 s, so these data are too uneven to trust for a comparison
- Every 50 °C trial was faster than every 10 °C trial, a gap far larger than the spread within a group
- The 110 s trial is far from the others, so it should be thrown out before the two groups are compared
- The two sets of times overlap, so temperature made no real difference to the dye
Each beaker started with 200 mL of water. Pia compares the mass lost from open beakers in 24 hours. Which statement do the data support?
- The 10 °C losses range from 2 g to 4 g, so these data are too uneven to support any comparison
- The 4 g result is the odd one in its group, so it should be removed before the groups are compared
- Each 50 °C beaker lost more than any 10 °C beaker, a gap much larger than the spread within either group
- Evaporation depends on the beaker and not on the water temperature, so these data show nothing about the effect of warmth
Dry ice (solid carbon dioxide) shrinks in an open bowl and leaves no liquid. Which explanation fits the particle model, Ren?
- Its particles gain enough energy to leave the solid and spread out as a gas without forming a liquid
- Its particles shrink as the dry ice warms until they are far too small to see, so the solid vanishes
- Its particles are destroyed as the dry ice warms, so just the empty bowl is left behind in the room
- A liquid forms first, but it evaporates too quickly for anyone to see it on the bottom of the bowl
Wet skin feels cool as the water evaporates. Which explanation fits the particle model, Zee?
- Water particles shrink as they evaporate, and smaller particles are cooler than larger particles
- Evaporating particles slow to a stop and keep their energy where they stopped, which chills the skin
- Cold particles from the air move into the water and take the place of the warmer water particles
- The fastest water particles escape as vapor, so the average speed of the particles left behind drops