The four states of matter and particle motion
Grade 10 Science Worksheet
Circle the best answer, or write your answer on the line.
Bo heats 100 g of ice at −15 °C until it is liquid water at 0 °C. Ice warms at 2.09 J/g/°C; melting takes 334 J/g. How many joules?
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Energy added to 100 g of H₂O (computed from standard values)
energy added (kJ) temperature (°C) state 0 −20 ice 4.2 0 ice 20.9 0 ice and water 37.6 0 water 58.5 50 water 79.4 100 water 192.4 100 water and steam 305.4 100 steam From 79.4 to 192.4 kJ the temperature stays at 100 °C while the energy keeps rising. What does the energy do, Jun?
- It breaks the water molecules into separate hydrogen and oxygen atoms
- It speeds the molecules up, but the thermometer cannot read above 100 °C while boiling
- It pulls molecules apart into a gas, raising their potential energy, not their speed
Boiling the 100 g takes 226 kJ, but melting it took only 33.4 kJ. Why is boiling so much larger, Kira?
- Boiling separates molecules completely; melting only loosens their fixed pattern
- Water molecules become much heavier as steam, so each needs more energy to move
- Boiling also raises the temperature by 100 °C, which costs most of the extra energy
Compare energy per °C for liquid water and for ice in the table. What do you find, Luz?
- Ice takes more, because a solid is harder to heat than a liquid
- They take the same amount, because both are H₂O
- Water takes about twice as much: 0.42 kJ per °C against 0.21
At 300 K, H₂ (2.0 u) and O₂ (32.0 u) molecules are in one room. How do they compare, Milo?
- Same average kinetic energy; H₂ molecules move about 4 times faster
- O₂ has 16 times the kinetic energy because it is 16 times heavier than H₂
- H₂ has more kinetic energy because its molecules move faster
One gas is heated from 300 K to 600 K. What happens to the share of fast molecules, Noah?
- The slowest molecules disappear, so the ones left are fast
- A larger share moves faster than any given speed, though some stay slow
- The molecules speed up by the same amount, so the spread stays the same
A sealed balloon shrinks in a freezer. Using the particle model, why, Pia?
- Colder molecules hit the walls less often and less hard, so they push in less
- The molecules themselves shrink when they get cold, so they take up less room
- The cold air outside pushes harder on the balloon's walls than it did before
Water and ice at 0 °C (real data, CRC)
material density (g/cm³) liquid water 0.9998 ice 0.9167 A sealed bottle holds 1,000 g of water. It freezes. About how does its volume change, Ren?
- It shrinks by about 9%, since solids are denser than liquids are
- It grows by about 9%, from about 1,000 cm³ to about 1,091 cm³
- It stays near 1,000 cm³, since the mass is still 1,000 g
Water boils at about 95 °C in Denver, not 100 °C. Why, Tala?
- Gravity is weaker there, so the water is lighter and heats up sooner than elsewhere
- Denver has less oxygen, so the water burns at a lower temperature than at sea level
- Air pressure is lower there, so molecules escape the liquid at a lower temperature
Wet laundry dries at 20 °C, far below water's boiling point. Why, Zee?
- At 20 °C each molecule is fast enough to escape, so the cloth dries at once
- The cloth heats the water to 100 °C a little at a time, step by step
- A few fast surface molecules escape even though the average speed is low
