Particles are tightly packed in a regular pattern

Particles vibrate together, keeping its shape and position

Retains a fixed volume and shape

Does not flow easily

Particles are loosely bonded with gaps between them.

Particles vibrate and slide past one another.

Takes shape of its container.

Flows easily

Particles are completely separated

Particles are free to move.

Takes shape of its container

Flows easily.

In solids, the particles are close together because they are bonded in fixed positions.

In liquids, the particles are attached together but are not as rigorously held together as particles in solids.

In gases, the molecules are completely unattached so the space between particles can be far and wide.

As mentioned before, particles in solids are in fixed positions, while particles in liquids and gases are more free.

A higher temperature results in faster motion which leads to more pressure. Therefore, the higher the temperature of gas, the more pressure of the gas at constant volume.

Imagine you've got a sealed container containing gas. When thugs particles move, they hit the sides of the container; this creates pressure on the container. The pressure of the gas depends on how often and how hard the molecules are colliding with the inside of the container.

Bromine is a brown, strongly smelling gas. You can use it to demonstrate diffusion in gases.

Fill half a glass jar full of bromine gas, and the other half full of air - separate the gases with a glass plate.

When you remove the glass plate, you'll see the brown bromine gas slowly diffusing through the air.

The random motion of the particles means that the bromine will eventually diffuse right through the air.

Particles in both liquids and gases move randomly. This is called Brownian motion. They do this because they are bombarded by the other moving particles in the fluid. Larger particles can be moved by the light, fast-moving molecules.

Most commonly used measurement of temperature s the Celsius Scale. The units of this scale are degrees Celsius.

This graph shows the temperature change as you supply heat energy to a solid. You'll have the same curve when cooling a gas until it becomes a solid. Note that when it comes to cooling, energy will be lost from the substance to its surroundings, instead of being gained - this is why the cooling curve won't be a mirror image.

As you heat a solid, its temperature rises until it reaches its melting point. As more energy is supplied, the solid melts and the temperature doesn't change. It is now a liquid.

When you supply heat energy to a liquid, its temperature will rise until it reaches its boiling point. As the liquid vaporises, its temperature doesn't change. It is now gas. Heating a gas will increase its temperature.

Melting point is the temperature at which solid and liquid phases are in equilibrium, whereas boiling point is the temperature at which the vapour pressure of a liquid is equal to the external pressure.

For pure water, the boiling point is 100°C at one atmosphere of pressure and the melting point is 0°C at one atmosphere of pressure.

- Occurs at a fixed temperature

- Relatively fast process

- Takes place throughout the liquid

- Bubbles are formed

- Temperature remains constant

- External thermal energy source required

- Occurs at any temperature

- Relatively slow process

- Takes place at the surface only

- No bubbles

- Temperature may change

- Heat from surroundings is enough

Condensation is when a gas changes to a liquid.

As a gas loses heat energy, they also lose kinetic energy, causing them to move slower. Their intermolecular forces of attraction become more significant, pulling the molecules together and allowing them to form weak bonds until they form a liquid.

Solidification or freezing is when a liquid changes to a solid.

As liquids lose energy, their molecules slow down and form more intermolecular bonds with one another. They becomes locked in place and thus they form a solid.

Explain evaporation in terms of the escape of more-energetic molecules from the surface of a liquid

Evaporation occurs when there are particles in a liquid that move faster, so fast that if they are near the surface they have enough energy to escape and become a gas.

During evaporation, the more energetic particles escape from the surface leaving the less energetic ones behind.

When water evaporates, it takes some thermal energy from whatever it has been on, resulting in that thing being cooler. Faster particles escape first, so slower particles are left behind, this means the temperature is lower than before.

Temperature: a higher temperature means that the particles have more energy to escape, resulting in a faster rate of evaporation.

Surface area: a bigger surface area, more of the molecules are at the surface, allowing them to escape.

Air flow: air flow picks up molecules at the surface before they can become liquid again. The higher rate of air flow, the faster the evaporation.

Describe qualitatively, in terms of molecules, the effect on the pressure of a gas of:

- a change of temperature at constant volume

- a change of volume at constant temperature

A higher temperature means the gas molecules move faster and have more collisions.

As the gas molecules will collide with the surface of their container more and at a higher speed, the total force they apply on the container will increase. Pressure is the force applied on a surface per unit area, so the gas pressure increases. Note that this is true when the volume is constant - if the volume increases, then the molecules have to travel further to hit the container, reducing the number of collisions. This could nullify the effect of the temperature on pressure.

The opposite is true when the temperature falls at a constant volume - molecules move slower, so fewer collisions and the collisions are less forceful, so the pressure falls.

When matter is heated, its particles gain energy, which is exerted as kinetic energy.

In solids, the particles vibrate harder and faster, creating more space between the particles, causing them to expand. This is most visible in metals. This process is thermal expansion.

In liquids, the particles move around faster, weakening the intermolecular forces of attractions, and are thus held less closely together. The liquid expands.

In gases, particles move faster as they are heated. If they are heated under constant pressure, the gas particles collide harder with the container surfaces, forcing them out, and allowing the gas in a gas syringe. This can e seen when warming the gas in a gas syringe. If gases are heated at a constant volume, however, they don't expand - the gas pressure simply increases.

Note that the cooling down of substances tend to have the opposite effect - the particles loose kinetic energy, come closer together and thus contract.

When considering thermal expansion, gases expand the most, followed by liquids and solids expand the least. This is because gases have the weakest intermolecular forces of attraction, allowing their molecules to move the furthest apart and solids have the strangest intermolecular forces, limiting the range of motion of the particles.

We often use hot water to warm up the lid of a jar. This expands the lid making it easier to move.

Liquid in thermometers expand and contract as the temperature changes. The volume of the liquid at a given temperature is how we read the temperature of a thermometer.

Overhead cables have to be slack so that on cold days when they contract, they won't snap or detach.

- these are found on most large bridges. They look like two metal combs, their teeth interlocking, and have the small gaps between each other. When heat causes the bridge to expand, the two sides of the expansion joint move towards each other. As the temperature cools, they gradually retract. This gives the bridge room for expansion and contraction, preventing the cracking/deformation of the bridge. The expansion joints have interlocking 'teeth' because this minimises the bump that motorcyclists feel as they ride over it.

Bimetal thermostats have a bimetallic strip. This is a strip in which there are two metals, with different coefficients of linear expansion, placed side by side. Therefore, when the strips warm up, one of the metals linearly expand more than the other, causing the bimetallic strip to bend.

When it becomes hot enough, the strip bends enough to close the circuit, and the air conditioner turns on, cooling down the room. Once the room has reached the desired temperature, the strip slowly unbends, opening the circuit and turning off the air conditioner. The same mechanism can be used for heaters - when it is warm, the strip bends away from the circuit, and as it grows colder, the strip straightens out until it closes the circuit and the heater can turn on again.

When you adjust the temperature on a thermostat, you're adjusting how far the bimetal strip has to bend/straighten out to close the gap.

Liquids: mercury, alcohol

thermocouple

thermocouple

Change in electrical resistance

Sensitivity is the property in a thermometer defined as the change in property per unit degree.

Range is the property in a thermometer defined as the lowest temperature measured to the highest temperature.

Linearity is the property in a thermometer defined as the same distance between all degree intervals.

A thermocouple consists of a mechanical junction of two dissimilar metals. This junction generates a small electrical potential. The value of which depends upon the temperature of the junction. Thus with calibration, and an appropriate choice of metals, one can obtain a thermometer for the desired temperature range.

The bigger the temperature difference between the two junctions, the greater the electric current.

Advantages of Thermocouples:

- Measures rapidly changing temperatures

- Measures higher temperatures

- Sensitive

- Can be read and logged in a computer

To be able to measure temperature easily we require fixed points. Two common fixed points are the melting and boiling points of water. These are 0°C and 100°C respectively.

Sensitivity is the property in a thermometer defined as the change in property per unit degree.

Range is the property in a thermometer defined as the lowest temperature measured to the highest temperature.

Linearity is the property in a thermometer defined as the same distance between all degree intervals.

In the case of a liquid-in0glass thermometer, it monitors volume of the liquid. Any device that includes a substance that changes uniformly with temperature can be calibrated and be made into a useful thermometer. The volume of the liquid and hence the length of the liquid column changes uniformly with temperature.

- Silver

- Copper

- Aluminium

- Brass

- Iron

- Lead

- Mercury

- Glass

- Wood

- Water

- Cork

- Cotton wool

- Air

- Plastic

Wax method:

- Take rods of different materials with the same dimensions and attach a drawing pin to the end of each using the same mass of wax.

- Using a container with four rubber-lined holes in the side. Insert the rods through the holes, pushing them in the same amount. Fill the container with boiling water and start the stopwatch. - Time how long it takes the drawing pin to fall off each rod and compare the times. The rod that allowed the pin to fall off the fastest is the best conductor.

According to the kinetic theory, all materials are made up of tiny, moving particles. In solids, these particles tend to vibrate around a fixed spot.

When you apply heat energy to these particles, they tend to vibrate more vigorously.

This heat energy can be transferred from one end of the material to the other, because the particles with more energy collide with the adjacent particles, causing them to vibrate harder and so forth.

In other words, the particles with more thermal energy pass on their energy to the particles surrounding them, causing the heat to spread from the hotter regions to the colder regions of the material.

Convection occurs when particles with more heat energy move and take the place of particles with less heat energy. Because this process requires the movement of particles, it can only occur in liquids and gases.

It is more efficient than conduction and requires less energy than radiation, so most of the heat is transferred by convection in liquids and gases.

As liquid or gas gains heat energy, its particles move faster, causing the space between them to increase. Therefore, the density of the liquid or gas also decreases.

That means that the less dense parts of the liquid or gas will have a lower mass per unit volume, making them lighter and causing them to rise to the top while the colder parts sink.

If the source of the heat energy is at the bottom of the container, like when you boil water on a stove then the colder part that sank to the bottom will soon become the hotter part and that will rise, and so on.

This process is convection.