P6- molecules and matter Flashcards
What is the formula for density?
mass over volume
What is the unit for density?
kg/m3
How do you measure the density of a liquid?
Volume- measuring cylinder
Mass- weighing scale
Density- formula
What happens to objects that have a lower density than the liquid they are submerged in?
They will float.
How many g/cm3 are in kg/m3?
1000.
What happens to the number of particles when a substance changes state and why is this?
It stays the same; the mass of the substance is the same before and after the change of state.
What do particles in a solid do?
Vibrate around a fixed position, meaning they have a fixed shape
What do particles in a liquid do?
They come in contact with one-another regularly-random
doesn’t have a fixed shape and it can therefore flow.
What do particles in a gas do?
far apart- moves randomly and much faster
density is much less
What state if matter has the least energy?
The solid state
What state of matter has the most energy?
gas
What is boiling
When a liquid becomes a gas when it reaches its boiling point.
what is evaporation
When a liquid becomes a gas when before it reaches its boiling point.
What can impurities do to a substance’s melting and boiling point?
Change them.
What is latent heat?
The energy that must be transferred to a substance, to change its state.
For a temperature against time graph, what does a flat line show?
The melting and boiling points of the substance in question
Does the temperature of the substance change when a change in state is happening?
No.
What is internal energy
It is the total kinetic energy and potential energy stores of the particles in a substance.
Why do particles, in a substance, have kinetic energy?
Due to their individual positions relative to each other
What happens when the temp. of a substance increases, in terms of internal energy and particles?
The energy increases of the particles, meaning that the internal energy increases.
What happens when the total kinetic energy- of the particles- increases?
The substance’s temperature increases
What happens to the potential energy, when a substance changes state?
The particle’s potential energy increases
For a solid, what type of force of attraction are there between the particles?
Strong ones.
What happens when a solid is heated in terms of particles
The particle’s energy stores increase, giving the particles more energy to vibrate more vigorously.
What are the forces of attraction like in a liquid?
They are weaker than in a solid
What do the forces of attraction in a liquid stop the particles from doing
Moving completely away from one-another.
What shows that the forces of attraction in a liquid are not as strong as in a solid
As the particles can move freely TO AN EXTENT.
What happens when a liquid is heated?
Some of its particles gain enough energy to break from the other particles and enter into a gas state.
What are the forces of attraction in a gas like and what does this mean?
Negligible, this means that the particles of gas are completely away from each other.
What happens when a gas is heated
Its particles have more kinetic energy transferred to them (from the thermal energy) and therefore move faster.
What two things do gases collide with, when in a container?
The walls of their container and each other.
What happens when the gas particles collide with things and what does this include?
They exert a force and this causes pressure in the container that they are held in.
What is latent heat of fusion?
energy required for a substance to change from a solid to a liquid state, without a change in temperature.
What happens to the latent heat of fusion if a substance changes from a gas to a liquid
It heats the surroundings/gets transferred to the surroundings.
What is the specific latent heat of fusion?
The energy required to change 1kg of a substance from a solid to a liquid, without a temperature change.
What is the latent heat of vaporization?
the amount of energy required to change from a liquid to a vapor without a temperature change.
What happens to the latent heat of vaporization if the substances changes from a gas to a liquid?
It heats the surroundings/is transferred to the surroundings
What is the specific latent heat of evaporation?
It is the energy required to change 1kg of a given liquid into a vapor, with not change in temperature.
What two pieces of apparatus can be used to measure the specific latent heat of fusion and vaporization?
A joulemeter and a heater.
What can a joulemeter and a heater be used for
Heater- melt or boil given weight of ice or water (and watch weight decrease)
joulemeter- how many joules it takes
How do particles in a gas move?
At high speeds, in random directions.
How many gas particle collisions are there every second?
Millions.
What is pressure?
It is the force per unit area.
What happens if the pressure of a gas in sealed container increases? Give two. (5.)
The gas particles move FASTER and COLLIDE with the container walls with MORE FORCE, meaning the PRESSURE will INCREASE further and there are more FREQUENT collisions with the wall per second, meaning the pressure will increase further.
as the temperature of a gas increases, the pressure of the gas…
….also increases.
How can it be proven that gas particles move about randomly?
By using a microscope to look at smoke cell
In a smoke cell, what causes the smoke particles to move about randomly?
Their collisions with the air particles.
What is the official name given to the random movement of particles?
Brownian Motion.
What is Boyle’s law?
constant= pressure times volume
So for a fixed mass of gas at constant temp., what is the formula
constant= pressure times volume
How is the movement of a smoke particle in a glass smoke cell random?
As the air particles push it around
For a fixed mass of gas, the number of gas molecules is ____
constant
If the temperature is _____, the average speed of the molecules is _____
constant
If the volume of a fixed gas at constant temp. is reduced, what happens to the gas pressure?
Increases
Why does the gas pressure increase when the volume of a fixed mass of gas at constant temp. is reduced?
space the molecules move in smaller- doesn’t travel as far between each impact
molecules hit surface more often- no. of impacts per second increases- total force of impacts per square metre of surface area (pressure) increases
What does the volume of a fixed mass of gas depend on?
its pressure and temperature
What can a gas be compressed or expanded by? What does it produce?
Pressure changes- produces a net force at RIGHT ANGLES to the wall of the container of the gas
What happens when gas is stored in a tube and a piston is pushed into the tube?
the volume of the air in the tube decreases as the air is increased. Pressure increases.
When compressing gas slowly, what happens?
Gas loses energy by heating its surrounds at the same rate as energy is transferred to it.
When pushing a piston, gas loses energy by heating its surrounds at the same rate as energy is transferred to it. What does this mean?
The internal energy store and the temperature of the gas do not change.
When pushing a piston, what happens if the compression did not happen slowly?
the work done on the gas would increase its internal energy store and its temperature
To push the piston into the tube, what must be done?
work must be done (i.e. energy transferred) by applying a force to the piston
work must be done (i.e. energy transferred) by applying a force to the piston. What does the applied force have to do?
Overcome the force that is caused by the pressure of the gas(air) enclosed in the tube
