States of Matter & Thermal Capacity Flashcards
All 41 cards in this deck
Describe the arrangement and movement of particles in a solid.
Closely packed in a fixed, regular arrangement; they vibrate about fixed positions.
Using the kinetic theory model, describe the movement of particles in a liquid.
They move around freely in random directions at various speeds, sliding past and colliding with each other.
Using the kinetic theory model, describe the arrangement and movement of particles in a gas.
Far apart with no fixed arrangement; they move randomly in all directions at high speeds and collide with each other.
What is the equation for density, including units?
density = mass ÷ volume, ρ = m ÷ V, in kg/m³ (mass in kg, volume in m³).
What do you multiply a density in g/cm³ by to convert it to kg/m³?
- e.g. 2.7 g/cm³ = 2700 kg/m³
Why is a substance usually denser as a solid than as a liquid?
Its particles are closer together and more tightly packed, so there are more particles per unit volume.
True or false? When water boils, the space between the particles increases and the density decreases.
True. Steam particles are much further apart than in water, so steam is less dense.
What are the steps to determine the density of a regular solid?
e.g. a rectangular metal block- Measure the mass on a balance.
- Measure length, width and height and multiply them to get the volume.
- Divide mass by volume to get the density.
What are the steps to determine the density of an irregular solid by displacement?
e.g. a glass marble- Find the mass of the marble on a balance.
- Note the water level in a measuring cylinder, add the marble so it is fully submerged, note the new level; the difference is the volume.
- Divide mass by volume.
What are the steps to determine the density of a liquid?
e.g. cooking oil- Measure the mass of the empty measuring cylinder.
- Pour in the liquid, read its volume and measure the new mass; mass of liquid = difference in masses.
- Divide the mass of the liquid by its volume.
Why can the displacement method not be used to find the volume of a piece of wood?
The density of wood is less than that of water, so it floats; less water is displaced than the volume of the wood.
What is sublimation?
A change of state from solid directly to gas (or gas directly to solid), without becoming a liquid.
What happens to the mass of a substance when it melts, boils, condenses or freezes?
Mass is conserved — it stays the same.
Why are changes of state physical changes rather than chemical changes?
They are reversible — the material recovers its original properties if the change is reversed, and no new substance is formed.
What does a flat (horizontal) section on a temperature–time heating graph show?
e.g. a plateau at 0 °C while ice is heatedA change of state is happening: the temperature stays constant while energy is supplied — here the ice is melting.
What two things can heating a system do?
Raise its temperature, or produce a change of state.
What happens to the particles of a substance when its temperature rises?
Their average kinetic energy increases, so they move or vibrate faster.
Why is the real temperature rise of an electrically heated object smaller than the value calculated from ΔQ = m × c × Δθ?
Not all the energy supplied stays in the object — some is transferred to the surroundings and to other parts of the apparatus.
Define specific heat capacity.
The energy needed to raise the temperature of 1 kg of a substance by 1 °C.
Define specific latent heat.
The energy needed to change the state of 1 kg of a substance, with no change in temperature.
What is the difference between specific latent heat of fusion and specific latent heat of vaporisation?
Fusion is for melting/freezing (solid ↔ liquid); vaporisation is for boiling/condensing (liquid ↔ gas).
True or false? Specific heat capacity and specific latent heat are both measured in J/kg °C.
False. Specific heat capacity is in J/kg °C; specific latent heat is in J/kg.
What is the equation linking change in thermal energy, mass, specific heat capacity and change in temperature?
ΔQ = m × c × Δθ, with ΔQ in J, m in kg, c in J/kg °C and Δθ in °C.
In a heating experiment, what equation gives the energy supplied by an electric heater from its power and the heating time?
E = P × t, with energy E in J, power P in W and time t in s.
What is the specific heat capacity of water?
4200 J/kg °C.
What is the equation for the thermal energy needed for a change of state?
Q = m × L, with Q in J, m in kg and specific latent heat L in J/kg.
True or false? In Q = m × L, m is the total mass of the substance present.
False. m is only the mass that actually changes state.
How does adding a lid reduce unwanted energy transfer from a container of hot water?
It stops hot vapour and warm air escaping from the surface, reducing energy transfer by evaporation and convection.
How does lagging reduce unwanted energy transfer from a container of hot water?
Lagging is a poor thermal conductor and traps air, so less energy is conducted to the surroundings.
Apart from the material used, what feature of an insulating layer reduces energy transfer?
Its thickness — thicker insulation transfers energy more slowly.
True or false? Insulating a hot object stops it transferring energy to the surroundings completely.
False. Insulation only slows the rate of energy transfer.
State the measurements needed to determine the specific heat capacity of water.
The mass of the water, the temperature rise (start and end temperatures), and the energy supplied by the heater (joulemeter reading).
Give two ways the apparatus can be adapted to improve the specific heat capacity of water experiment.
Any two: add a lid/cover, add lagging/insulation, add a stirrer, use a more sensitive thermometer, ensure the heater is fully submerged.
What are the steps to obtain a temperature–time graph for melting ice?
e.g. crushed ice in a beaker- Put crushed ice and a thermometer in a beaker and record the starting temperature.
- Heat gently and record the temperature every 30 s until well above 0 °C.
- Plot temperature against time — a plateau appears at 0 °C while the ice melts.
If water in the specific heat capacity experiment keeps being heated, what temperature does the graph level off at?
About 100 °C — the boiling point, where the water changes state instead of getting hotter.
When a substance is melting or boiling, why does its temperature stay the same even though energy is still being supplied?
The energy is used to overcome the bonds holding the particles together, so none goes into making the particles move faster and the temperature does not rise.
When a substance is condensing or freezing, why does its temperature stay the same?
As the particles bond together they give out energy, which stops the temperature dropping until all of the substance has changed state.
How do the forces of attraction between particles compare in solids, liquids and gases?
Strongest in solids, weaker in liquids, and very weak (negligible) in gases.
What is the internal energy of a substance?
The sum of the kinetic energy and the potential energy of all of its particles.
What volume in cm³ is equal to 1 ml?
1 cm³, so a measuring cylinder reading in ml gives the volume in cm³.
Which common substance is less dense as a solid than as a liquid?
Water: ice is less dense than liquid water, which is why ice floats.