5 Solids, liquids and gases - iGCSE Physics Edexcel

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5.1 use the following units: degree Celsius (°C), Kelvin (K), joule (J), kilogram (kg), kilogram/metre3 (kg/m3 ), metre (m), metre2 (m2 ), metre3 (m3 ), metre/second (m/s), metre/second2 (m/s2 ), newton (N) and pascal (Pa)
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Terms in this set (21)
5.1 use the following units: degree Celsius (°C), Kelvin (K), joule (J), kilogram (kg), kilogram/metre3 (kg/m3 ), metre (m), metre2 (m2 ), metre3 (m3 ), metre/second (m/s), metre/second2 (m/s2 ), newton (N) and pascal (Pa)
degree Celsius (°C)
Kelvin (K), joule (J)
kilogram (kg)
kilogram/meter3 (kg/m3)
meter (m)
meter2 (m2)
meter3 (m3)
meter/second (m/s), meter/second2 (m/s2)
newton (N)
pascal (Pa)
5.3 know and use the relationship between density, mass and volume: volume mass density = V
density = mass / volume
ρ = m / V
Image: 5.3 know and use the relationship between density, mass and volume: volume mass density = V
5.4 practical: investigate density using direct measurements of mass and volume
The density of an object can be found by measuring the mass and volume and applying the formula above to calculate the density
.
For a regular object use a ruler to measure the lengths needed to determine the volume.

For an irregular object submerge it in water and measure the displaced volume.

Measure the mass of either type of object using a measuring balance.
5.5 know and use the relationship between pressure, force and area: area force pressure = A
Pressure = force / area

P = F / A
Image: 5.5 know and use the relationship between pressure, force and area: area force pressure = A
5.6 understand how the pressure at a point in a gas or liquid at rest acts equally in all directions
Pressure in liquids acts equally in all directions as long as the liquid is not moving.
5.7 know and use the relationship for pressure difference: pressure difference = height × density × gravitational field strength p = h × ρ × g
pressure = height x density x gravitational field strength

P = h x ρ x g

Gravitational field strength=10
Pressure is in pascals (Pa) - where 1 Pa if the same as 1 N/m2.
Depth is in metres (m)
Density is in kg/m3
5.8P explain why heating a system will change the energy stored within the system and raise its temperature or produce changes of state
A substance must absorb heat energy so that it can melt or boil. The temperature of the substance does not change during melting, boiling or freezing, even though energy is still being transferred.

At higher temperatures particles have more energy. Some of this energy can be transmitted to other particles that are at a lower temperature. For example, in the gas state, when a fast moving particle collides with a slower moving particle, it transfers some of it's energy to the slower moving particle, increasing the speed of that particle.
Image: 5.8P explain why heating a system will change the energy stored within the system and raise its temperature or produce changes of state
5.9P describe the changes that occur when a solid melts to form a liquid, and when a liquid evaporates or boils to form a gas
MELTING:
- Particles gain kinetic energy and begin to vibrate faster

- The structure is gradually weakened and this expands the solid until particles begin to break free of the structure

- although the particles are still loosely connected they are able to move around.

- As more and more energy is added the particles have enough Kinetic Energy to overcome the attractions between particles and become a liquid

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BOILING:
Particles gain kinetic energy and begin to vibrate faster

- The structure is gradually weakened and this expands the liquid until the most energetic particles begin to break free of the structure and leave the surface as a gas

-As more and more energy is added the particles have enough Kinetic Energy to overcome the attractions between particles and become a gas with negligible attractive forces between particles
Image: 5.9P describe the changes that occur when a solid melts to form a liquid, and when a liquid evaporates or boils to form a gas
5.10P describe the arrangement and motion of particles in solids, liquids and gases
SOLIDS:
Tightly packed
Held in fixed pattern
Vibrate about fixed positions

LIQUIDS:
Tightly packed
Can slide over each other

GASES:
Very spread out
Move with rapid, random motion
Image: 5.10P describe the arrangement and motion of particles in solids, liquids and gases
5.11P practical: obtain a temperature-time graph to show the constant temperature during a change of state
- Fill a beaker with crushed ice and use a thermometer to measure the temperature.

- Use a Bunsen burner to heat the beaker of ice.

- Using a stopwatch, record the temperature and state of the water every 30 s.

- Continue until the water has been boiling for a minute.

- Plot a graph of temperature against time. You should see a constant temperature when the ice is melting, and the water is boiling.

(Graph will be drawn out in the opposite way to show steam being cooled)
Image: 5.11P practical: obtain a temperature-time graph to show the constant temperature during a change of state
5.12P know that specific heat capacity is the energy required to change the temperature of an object by one degree Celsius per kilogram of mass (J/kg °C)Specific heat capacity: - Amount of heat energy required to increase the temperature of 1kg of a substance by 10 - Unit: J/kg 0C5.13P use the equation: change in thermal energy = mass × specific heat capacity × change in temperature ΔQ = m × c × ΔT5.14P practical: investigate the specific heat capacity of materials including water and some solids- Use a mass balance to measure the mass of the insulating container. - Fill the container with water and measure the new mass. (Determine the mass of water by calculating the difference in masses) - Place a thermometer into the water and measure the initial temperature of the water - Place an electric emersion heater into the water connected to a power supply and connect an ammeter in series and voltmeter in parallel. Calculate the power using 𝑃=𝐼𝑉 - Switch on the heater and start a stopwatch to measure how long the heater has been on. - Switch off the heater and stopwatch after a rise of 10oC. Continue measuring the temperature and record the maximum value. - Measure the specific heat capacity using 𝑐 = 𝑚Δ𝑇 - Repeat the measurement 2 more times and calculate an average. To work out the specific heat capacity for a metal cylinder use the same method but with holes drilled in to fit the thermometer and emersion heater.Students should: 5.15 explain how molecules in a gas have random motion and that they exert a force and hence a pressure on the walls of a containerThe molecules in a gas move around randomly at high speeds As they do so, they collide with the surface of nearby walls. This exerts a force across the surface area of the walls.5.16 understand why there is an absolute zero of temperature which is -273 °CAt absolute zero the particles have no thermal energy or kinetic energy, so they cannot exert a force. Absolute zero = 0 Kelvin = -2730C5.17 describe the Kelvin scale of temperature and be able to convert between the Kelvin and Celsius scalesZero Kelvin is equal to absolute zero (-273 °C).5.18 understand why an increase in temperature results in an increase in the average speed of gas moleculesTemperature of a substance is the kinetic energy of the molecules. The kinetic energy of the gas particles increases and thus their average speed also increases.5.19 know that the Kelvin temperature of a gas is proportional to the average kinetic energy of its moleculesThe Kelvin temperature of a gas is proportional to the average kinetic energy of its molecules.5.20 explain, for a fixed amount of gas, the qualitative relationship between: • pressure and volume at constant temperature • pressure and Kelvin temperature at constant volumeAs you heat the gas, the kinetic energy of the particles increases, and thus so does their average speed. This means more collisions per second with the walls. This causes in the total pressure to rise. If the same number of particles is placed in a container of smaller volume they will hit the walls of the container more often. More collisions per second means that the particles are exerting a larger force on the wall over the same time, so pressure has increased.5.21 use the relationship between the pressure and Kelvin temperature of a fixed mass of gas at constant volume: P1 / T1 = P2 / T2P1 / T1 = P2 / T2 P=pressure T=temperature IN KELVIN5.22 use the relationship between the pressure and volume of a fixed mass of gas at constant temperature: p1v1 = p2v2P1V1=P2V2 P=pressure V=volume