The four states of matter and particle motion

Answer Key - Grade 10 Science Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   Ari turns 10 g of ice at −10 °C into steam at 100 °C. Specific heats: ice 2.09, water 4.18 J/g/°C. Melting 334 J/g, boiling 2260 J/g. Total joules?

   30,329 J
2. 2.

   Bo turns 5 g of ice at −20 °C into steam at 100 °C. Specific heats: ice 2.09, water 4.18 J/g/°C. Melting 334 J/g, boiling 2260 J/g. Total joules?

   15,269 J
3. 3.

   Esme turns 20 g of ice at −5 °C into steam at 100 °C. Specific heats: ice 2.09, water 4.18 J/g/°C. Melting 334 J/g, boiling 2260 J/g. Total joules?

   60,449 J
4. 4.

   10.0 g of steam and 10.0 g of boiling water, both at 100 °C, cool to 40 °C on skin. Steam condenses at 2260 J/g; water cools at 4.18 J/g/°C. Which releases more, Jun?

   • Steam, about 10 times as much: 22,600 J from condensing, 2,508 J from cooling
   • Steam, but just slightly more, because steam is a gas with a very low density here
   • The same, because both start at 100 °C and both end at 40 °C on the skin
5. 5.

   Kira drops 20.0 g of ice at 0 °C into 200 g of water at 25 °C. Melting takes 334 J/g; water 4.18 J/g/°C. What is the final temperature?

   • About 12.5 °C, the simple average of the two starting temperatures, 0 °C and 25 °C
   • About 22.7 °C, found by skipping the energy needed to melt the ice
   • About 15.5 °C, after the water melts the ice and warms the meltwater

6. Read this first

   Water and ice at 0 °C (real data, CRC)

   material	density (g/cm³)
   liquid water	0.9998
   ice	0.9167

7. 6.

   Milo says ice floats because ice molecules are lighter than liquid water molecules. Verdict?

   • No: ice floats because it is colder, so its molecules have less kinetic energy
   • Yes: a lower density means each ice molecule has less mass than a water molecule
   • No: the molecules are identical; ice's open pattern spreads them out, lowering density
8. 7.

   CO₂ at 50 atm and 300 K does not follow the ideal gas model well. Which reason fits the particle model, Pia?

   • The molecules are crowded, so their own volume and attractions matter
   • The molecules shrink at high pressure, which leaves them even more gaps
   • The molecules slow almost to a stop when the pressure gets that high
9. 8.

   NH₃ (17.0 u) and HCl (36.5 u) gases start from opposite ends of a long tube at one temperature. Where does white NH₄Cl form, Ren?

   • At the midpoint, since both gases carry the same average kinetic energy
   • Closer to the NH₃ end, since ammonia is the more reactive gas
   • Closer to the HCl end, since lighter NH₃ moves about 1.5 times as fast
10. 9.

    Why does sweating cool the body, Tala?

    • The fastest molecules escape, so the sweat left behind has lower average energy
    • Sweat soaks up cold from the surrounding air as it slowly evaporates off the skin
    • The molecules slow down together as they leave the skin, and that cools it down
11. 10.

    In a sealed jar at 25 °C, water and its vapor are in equilibrium. What does that mean, Zee?

    • Molecules evaporate and condense at equal rates, so amounts stay steady
    • Evaporation keeps running faster than condensation until the water is gone
    • Evaporation has stopped, so the jar holds just still water