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?
A hot plate adds the same energy each minute, all of it melting ice at 0 °C. How many minutes will 100 g of ice take, Esme?
Under a microscope, specks of smoke in a sealed cell of still air jiggle in random directions. What explains this, Jun?
- Unseen air particles, moving fast in every direction, keep bumping the specks from different sides
- The specks swell and shrink as the air around them warms and cools, so they seem to jiggle about
- Air particles are at rest, and just the smoke specks have energy to move about on their own
- 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?
- Faster air particles spread out and some leave the open bottom, so the air inside is less dense
- Hot air particles move upward in a straight stream, so they carry the balloon up with them
- Heating creates extra air particles that fill the balloon and lift it, which is why it gets bigger
- Hot air particles become lighter than cold air particles, so the balloon floats up on a cushion of them
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: the volume rose each time the temperature rose, so it must have doubled
- No: the volume rose only from 537 mL to 573 mL, much less than double
- Yes: 40 °C is twice 20 °C, and 573 mL is more than twice 537 mL
- No: a gas should not change volume when its temperature changes
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?
- 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
- 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
Dry ice (solid carbon dioxide) shrinks in an open bowl and leaves no liquid. Which explanation fits the particle model, Ren?
- 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
- Its particles gain enough energy to leave the solid and spread out as a gas without forming a liquid
- A liquid forms first, but it evaporates too quickly for anyone to see it on the bottom of the bowl
Drops form on the outside of a cold glass of water. Which explanation fits the particle model, Tala?
- The cold glass creates new water particles from the air that touches it, which adds mass to the glass
- Cold particles from the glass spread into the air and freeze the water vapor into small drops there
- Water seeps through tiny holes in the glass from the inside, and the drops are the water that got through
- Water vapor particles in the air lose energy on the cold glass, slow down, and condense into a liquid
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
- The fastest water particles escape as vapor, so the average speed of the particles left behind drops
- Cold particles from the air move into the water and take the place of the warmer water particles
- Evaporating particles slow to a stop and keep their energy where they stopped, which chills the skin