5.01-5.22 Solids, Liquids, and Gases

degrees Celsius (°C)

Unit using the Celsius scale to measure temperature, which has 0°C based on water’s freezing point and 100°C based on water’s boiling point.

Kelvin (K)

SI unit for measuring temperature with the kelvin (absolute) temperature scale. It has the same magnitude as 1°C, i.e. 1K obtains an equal magnitude to 1°C.

Joule (J)

SI unit for measuring energy.

Kilogram (kg)

SI unit for measuring mass.

Kilograms/meters^3 (kg/㎥)

Unit for measuring density.

Meter (m)

Unit for measuring length.

Meters^2 (㎡)

Unit for measuring area.

Meters^3 (㎥)

Unit for measuring volume.

Meters/second (m/s)

Unit for measuring speed.

Meters/second^2 (㎨)

Unit for measuring acceleration.

Newton (N)

Unit for measuring force.

Pascal (Pa)

SI unit for measuring pressure.

Joules/kilogram degrees Celsius (J/kg°C)

Metric unit for measuring specific heat capacity.

Density definition

Degree of compactness of a substance, measured as the quantity of mass per unit volume of that substance.

Density formula

Density = Mass (kg or g)/Volume (㎥ or ㎤), measured in kg/㎥ or g/㎤

Displacement

Way of measuring the volume of an irregularly-shaped object by:


1. Putting a known volume of water in a measuring cylinder (V1).
2. Putting the irregularly-shaped object inside.
3. Measure the new volume (V2).
4. Object volume is the volume of water displaced, or V2-V1).

You can also use a Eureka can to calculate the volume of irregularly-shaped objects:


1. Fill the eureka can with water until the water level reaches just at/below the spout’s level.
2. Wait for all the excess water to drip out of the spout.
3. Once all the excess water drips out the spout and the water level is just underneath the spout’s hole, place an appropriately-sized graduated measuring cylinder underneath the eureka can so it can collect water that drips out.
4. Gently lower your object into the can (preferably with it suspended onto a thread/string to minimize splashing that will lead to inaccurate results for volume).
5. The volume of water that drips out of the eureka can’s spout should be equal to the volume of the irregularly-shaped object.

The density of the objects can be calculated by dividing their mass (recorded from an electronic balance) by their volume (determined from using any 1 of the above 2 methods).

Water displacement

When an object enters water, it pushes out water to make room for itself. The object pushes out/displaces (change the position of an object) a volume of water that is equal to its own volume.

Buoyancy

Ability of an object to float in a fluid medium.

Object density > Fluid medium density

Object sinks as upthrust < weight

Object density = Fluid medium density

Object is partially submerged or partially floating as upthrust = weight

Object density < Fluid medium density

Object floats as the upthrust > weight

Buoyant force/upthrust

Upward force exerted on an object partially or wholly immersed in a fluid.

Archimedes' principle

A body partially or wholly immersed in a fluid experiences an upthrust (buoyant force) equal to the weight of the fluid displaced by that object.

Directly proportional

When the ratio of 2 variables is constant, resulting in a linear graph that goes through the origin. As 1 variable increases, the other increases, as 1 variable decreases, the other decreases.

Inversely proportional

When the product of 2 variables is constant, resulting in a downward sloping curve graph. As 1 variable increases, the other decreases, as 1 variable decreases, the other increases. We can linearize an inversely proportional relationship by stating that one variable is directly proportional to the reciprocal of the other variable.

Extrapolate

To extend a graph, curve, or range of values by inferring unknown values form trends in the known data.

Interpolate

To estimate unknown values that fall between known values.

Pressure definition

The perpendicular force applied per unit of area.

Pressure formula

Pressure (Pa) = Force exerted onto object(s) (N) / Area of contact between objects (㎡).
P = F/A.

Pressure is measured in ___________, the SI unit for ____________. 1 _____________ is equal to 1 _________.

Pascals (Pa), pressure, Pascal, Newton/meter squared or N/㎡

Pressure is __________ to force.

proportional.

Pressure is ____________ to area.

Inversely proportional (or proportional to 1/Area).

Gas pressure

Pressure in gases caused by particles exerting forces as they collide with the container walls.

Gas particles continually travel in____________ motion until they _________ into other ___________ and/or ___________________ to _______________. They move ___________ and in every __________ at high _________.

linear, collide, particles, container walls, change direction, randomly, direction, speeds.

Atmospheric pressure > interior air pressure causes

implosion (e.g. aluminum can collapses inside itself or "implodes")

Atmospheric pressure < interior air pressure causes

Explosion (e.g. balloon explodes when there is too much air inside it).

Describe how pressure acts in fluids

Pressure in fluids act equally in all directions, as long as the fluid medium is at rest (not moving).

Fluids

States of matter that can flow, specifically liquids and gases.

Pressure (in fluids) is _____________ to depth.

proportional

Pressure (in fluids) is ______________ to height.

inversely proportional

Explain why pressure in liquids is proportional to depth and inversely proportional to height.

More depth (lower height) means more fluid mass is above this object so more weight/force is acting on this object at its current position, leading to higher pressure.

Pressure is ______________ to gravitational field strength. Explain why.

proportional; higher gravitational field strength means there is more weight and therefore more force acting on an object, hence increasing the pressure.

Pressure is ______________ to density of the fluid medium an object is submerged in. Explain why.

proportional; higher density of the fluid medium means the fluid medium has a larger mass, and therefore a larger weight as well as force acting on it, hence increasing the pressure.

Pressure in a fluid (Stevin's law) formula

Pressure (Pa) = height (m) * density (kg/㎥) * gravitational field strength (N/kg)
P = h𝝆g

Pressure difference in a fluid (Stevin's law) formula

Change in pressure (Pa) = change in height (m) * density (kg/㎥) * gravitational field strength (N/kg)
𝚫P = 𝚫h𝝆g

Atmospheric air pressure

Approximately 100 000Pa (101 325Pa to be exact), however this varies slightly from day to day.

The air pressure in our bodies through ______________ is similar to the _______________ air pressure, so we do not notice it.

ventilation, atmospheric

Water's density =

1000kg/㎥ or 1g/㎤

Total pressure acting on a body in a liquid =

Change in pressure due to being submerged in the liquid body + Atmospheric pressure

Total pressure acting on a body in the air/atmosphere =

height of object * density of atmosphere/air medium * gravitational field strength of object's location

Factors affecting gas pressure in a container

temperature, volume, and particle concentration

Brownian motion

Random motion of atoms/particles suspended in a fluid medium caused by miscellaneous collisions between the particles and atoms/molecules/particles found in their surroundings. It was first observed by Robert Brown when he studied pollen grains' random motion in water.

Kinetic theory of matter states that

1. Gas particles are in constant random motion.
2. The combined volume occupied by gas molecules in a container is negligible compared to the distance or space between them.
3. Particles exert no forces on one another unless they collide.
4. Collisions between particles are completely elastic (i.e. no transfer of kinetic energy occurs, the particles involved in collisions do not gain or lose any kinetic energy).
5. Average kinetic energy of particles is proportional to their temperature in Kelvins.
6. Molecules always have linear motion, they always move in straight lines before colliding with the container walls and/or other particles to change direction.
7. Collision duration is negligible between the time between collisions.

Gas pressure

Pressure exerted by gas particles due to the combined force they exert through their collisions with their container walls.

Particle concentration is ____________ to pressure.

proportional; more particles -> more collisions between particles and container walls -> more force -> more pressure.

Temperature is ______________ to pressure.

proportional; higher temperature -> more average kinetic energy for the particles -> particles move at faster speeds and have more frequent collisions between each other as well as container walls -> More force -> Increased pressure.

Temperature

A measure of average kinetic energy per molecule in a substance, usually measured in degrees Celsius, degrees Fahrenheit, or Kelvins.

Thermal energy

A type of energy, it's the total kinetic energy of the particles in a substance.

Temperature VS thermal energy

1. Temperature is a WAY OF MEASURING energy, but thermal energy is a TYPE of energy.
2. Temperature is a measure of AVERAGE kinetic energy per molecule in a substance whereas thermal energy is a measure of the TOTAL kinetic energy of the particles in a substance.

More particle motion indicates ________________________ and hence higher ____________ as well as higher ___________ of ________________.

more average kinetic energy, temperature, levels, thermal energy.

More atoms (a.k.a. higher ______________________) and higher ________________ leads to higher levels of _________________.

particle concentration, temperature, thermal energy

Gay-Lussac's experiment

1. Independent variable is temperature, dependent variable is pressure, control variables are volume and mass of gas. Investigating effect of temperature on pressure.
2. Set water bath to 90 degrees Celsius.
3. Put thermometer and gas flask in water bath.
4. Wait until the gas reaches equilibrium, or when temperature and pressure readings remain constant.
5. Record the pressure reading from a pressure gauge.
6. Repeat steps 2-5 for 80, 70, 60, 50, 40, 30, and 20 degrees Celsius.
7. Plot the results in a graph.

If we _____________ the graph from Gay-Lussac's experiment until the line intersects the x-axis (where pressure is _________kPa), we will find that the temperature is _____________________ degrees Celsius or ________ Kelvin. Pressure, however, is always __________________ as there ___________ be a negative force exerted by particles.

extrapolate, 0, -273.15, 0, nonnegative, cannot

Absolute zero

Lowest temperature theoretically attainable at which pressure is 0, it's equivalent to -273.15 degrees Celsius or zero Kelvin. At this stage, it's impossible to cool a gas further.

Molecular motion _____________ cease at absolute zero, molecules still ___________ with ________________ . They move EXTREMELY slowly at the slowest _______________ speed to an extent where their motion is ________________. The energy at absolute zero is ______________ and close to __________ as no _______ energy from molecular _________ is available for ___________ or __________ to other systems.

does not, vibrate, zero-point energy, possible, unobservable, minimal, nothing, thermal, motion, transfer, conversion

Zero-point energy

Vibrational energy molecules obtain even at absolute zero

Particle kinetic energy infinitesimally nears zero (or is ___________ equal to 0) -> Gas particles _______ colliding with container walls -> ________ Pressure

theoretically, stop, zero

Kelvin scale

Temperature scale using Kelvins (SI unit for temperature). Absolute zero is zero on the Kelvin scale and there are no negative temperatures in the Kelvin scale. It is more mathematically accurate and convenient for absolute temperature.

Don't say "degrees Kelvin" or write "°K", it is just said as "___________" and written as "___"

Kelvin, K

Kelvin scale = _____________ temperature scale because ...

absolute, it measures the absolute value of temperatures (non-negative magnitudes) and absolute zero is equivalent to zero Kelvin.

Celsius (centigrade) scale

Temperature scale using degrees Celsius as a unit. It's based on 0°C for water's freezing point and 100°C for water's boiling point.

The ____________ of each unit in the Celsius and Kelvin scale are ________, meaning that a change of 1°C is ___________ to a change of _______.

magnitude, equal, equal, 1K.

Kelvin to Celsius

Celsius = Kelvin - 273.15 (273 is accurate enough for IGCSE unless stated otherwise by the question).

Celsius to Kelvin

Kelvin = Celsius + 273.15 (273 is accurate enough for IGCSE unless stated otherwise by the question).

Temperature (IN KELVINS) =

Average kinetic energy of particles

Explain the relationship between temperature (IN KELVINS) and pressure.

Directly proportional. Higher temperature -> Higher average kinetic energy of particles -> Higher speed of particle motion -> More frequent collisions between particles and container walls -> More force exerted over the same container wall area -> Higher pressure.

Temperature in ____________ is _____________________ to pressure, when the … of gas is …, so their graph would be _________ and go through the __________ as their ___________ is constant. This means doubling the temperature in _____________ leads to ____________ average kinetic energy of particles (average … of particles also …), ______________ collisions with container walls, _____________ force, and hence also ___________ pressure.

Kelvins, directly proportional, volume, constant, linear, origin, ratio, Kelvins, doubled, speed, doubles, doubled, doubled, doubled

Gay-Lussac's Law

Law stating that the ratio between pressure and absolute temperature (in Kelvins) of a gas (whose volume and particle concentration is kept the same) is constant, because pressure and absolute temperature of a gas are directly proportional. In other words:
P1/T1 (initial pressure and temperature conditions) = P2/T2 (final pressure and temperature conditions).

Volume is ________________ to pressure

inversely proportional (pressure is proportional to 1/volume); larger volume -> more space for same amount of particles to move in -> less frequent collisions -> less force -> less pressure, smaller volume -> less space for same amount of particles to move in -> more frequent collisions -> more force -> more pressure

Boyle's law experiment

1. Independent variable = Pressure (kPa), dependent variable = volume (㎤), investigating the effect of pressure on volume.
2. Use air pump to increase pressure to at least 300kPa.
3. Wait until the gas reaches equilibrium, i.e. temperature stays constant.
4. Release the air pump/pressure until the Bourdon gauge reads 300kPa.
5. Record the volume of air in the tube by reading of the scale.
6. Repeat for each pressure reading.
7. Repeat the entire experiment once or twice or to calculate an average volume of air.
7. Plot the results, one graph for pressure against volume, and one for pressure against 1/volume.

Ways to improve experiment reliability

Take repeats, improves data reliability as averages can be calculated and anomalies are easier to notice.

Anomaly

A piece of data that does not follow the trend formed by other pieces of data, often due to experimental error.

Ways to improve accuracy.

1. Use mm instead of cm scale as there is better precision.
2. Have a pump to hold pressure to give more time to make a reading (Boyle's law experiment)
3. Use a spirit level to ensure your eye is level when the scale when reading it to avoid parallax error.
4. Read from the bottom of the meniscus.

Precision VS Accuracy

Accuracy refers to how close a measurement is to the true or accepted value. Precision refers to how close measurements of the same item are to each other, it reflects how reproducible measurements are, even if they are far from the accepted value and inaccurate.

Spirit level

Device made from a sealed glass tube partially filled with alcohol or another liquid, it contains an air bubble whose positionn reveals if a surface is perfectly level.

Parallax error

Incorrect reading on a measuring instrument by viewing it from different angles to create a perspective of the object's positional shift.

Systemic error

Consistent, repeatable error associated with faulty equipment or a flawed experiment design.

Meniscus

Curve in surface of molecular substance (especially water) when it touches another material.

Boyle's law

Law stating that under constant temperature and mass of gas, the volume of a gas and its pressure are inversely proportional, meaning they have a constant product. In other wards P1V1 (initial pressure and volume situation) = P2V2 (final pressure and volume situation).

In Boyle's law, because temperature is ___________, particles have the ________ average kinetic energy and move at the same __________________. Gas compression therefore leads to _________ space and __________ for particles to move in, so particles hit ____________ walls _________ hard but ___________ often due to _________ collisions. This __________ force and __________ area of contact leads to _________ gas pressure.

constant, same, average speed, less, area, container, equally, more, more, increased, decreased, increased

Atmospheres(atm)

Unit of pressure equal to air/atmospheric pressure at sea level

1 atm =

101325 Pa

Energy efficiency equation

Efficiency = (Useful energy output/Total energy output) * 100%

Specific heat capacity

Amount of heat/thermal energy required to change the temperature of the unit mass of a given substance (usually 1kg) by a given amount (usually 1°C or 1K).

Specific heat capacity practical

1. Use scale to find mass of block/object.
2. Insert thermometer and immersion heater into respective holes in the block. You can optionally drop a small amount of oil or vaseline into the thermometer hole to improve the thermal contact between the thermometer and block.
3. Allow thermometer to reach thermal equilibrium (no temperature difference/changes between the system and their surroundings), then write down the initial temperature (T1).
4. Set up the circuit to measure energy input into the heater.
5. Turn on the power and allow the block to heat up until the Joulemeter reaches its maximum reading of 9999J, then turn off the power.
6. Even though the heater is switched off, heat will still be coming from the inside of the heater to the heated object/block. You’ll therefore notice that the temperature continues to rise for a short time. Record the highest temperature reached (T2).
7. Calculate the material’s specific heat capacity:

𝚫Q = mc𝚫T → c = (𝚫Q)/(m𝚫T)

Water’s specific heat capacity

4200J/kg°C or 4.2J/g°C

Change in thermal energy formula

Change in thermal energy (J) = mass (kg) * specific heat capacity (J*kg/°C or J*kg/K) * change in temperature (°C or K)
𝚫Q = mc𝚫T or E = mc𝚫T

Matter

Substance made from various types of particles that occupies physical space and has inertia.

Inertia

Physical force that keeps something stationary in the same position, or causes something moving to move in the same direction, unless an external force is applied.

Phase (a.k.a. state)

A physically distinctive form of matter, e.g. solids, liquids, gases, plasma.