P6 - Molecules and Matter Flashcards
What is a boiling point?
temperature at which a pure substance boils or condenses
What is Boyle’s law?
for a fixed mass of gas at constant temperature, its pressure multiplied by its volume is constant
What is density?
mass per unit volume of a substance
What is freezing point?
the temperature at which a pure substance freezes
What is internal energy?
The energy of the particles of a substance due to their individual motion and positions
What is latent heat?
the energy transferred to or from a substance when it changes state
What is melting point?
The temperature at which a pure substance melts
What is physical change?
a change in which no new substances are produced
What is pressure?
force per unit cross-sectional area for a force acting on a surface at right angles to the surface. The unit for pressure is the pascal (Pa) or newton per square metre (N/m²)
What is specific latent heat of fusion Lf?
energy required to change 1kg of a substance from a solid to a liquid with no change in temperature
What is specific latent heat of vaporisation Lv?
energy required to change 1kg of a substance from a liquid to a gas with no change in temperature
A block of aluminium occupies a volume of 16cm³ and has a mass of 20.5g. What is the density?
1.3g/cm³
Calculate the volume of a chemical that has a mass of 3g and a density of 3g/cm³
1cm³
Gold has a density of 19g/cm³, Silver has a density of 10g/cm³. An Olympic medal has a volume of 80cm³. Which medal has the greatest mass?
Gold = 1520g
Silver = 800g
Gold medal has a greater mass
What is a solid?
A solid is a substance with a fixed shape and volume, it is more dense than gases and liquids. it cannot flow, It’s particles can only vibrate. It cannot be compressed. It’s particles are very close together and are fixed in a rigid arrangement
What is a liquid?
A liquid is a substance with no fixed shape but with a fixed volume, they are less dense than a solid but more dense than a gas. They can flow. They cannot be compressed. It’s particles are close together but are not fixed in a rigid arrangement, they are free to move
What is a gas?
A gas is a substance with no fixed shape or volume, it is less dense than solids and liquids and it can flow. It can be compressed. It’s particles are far apart.
What is the change from solid to liquid called?
melting
What is the change from liquid to solid called?
solidification
What is the change from liquid to gas called?
vaporisation
What is the change from gas to liquid called?
condensing
What is the change from gas to solid called?
deposition
What is the change from solid to gas called?
sublimation
What is the difference between boiling and evaporating?
Boiling is when all the particles have enough energy to turn into gas, evaporation is when only the particles at the surface have enough energy to turn into a gas.
What is conservation of mass when changing state?
When changing state a substance’s mass will not change.
What can change the melting and boiling point of a substance?
Any impurities in a substance will affect the melting and boiling point of the substance?
Describe and explain a temperature-time graph of a substance being heated
In solids, the particles are arranged in a regular pattern and vibrate about fixed positions. As the solid is heated the particles begin to vibrate faster about the fixed positions. Therefore, temperature increases. As the temperature increases, the particles eventually gain enough energy to break up the regular structure and the solid melts. While the solid is melting, the heat energy supplied is sued to break the bonds in the solid not to make the particle move faster. Therefore the temperature stays constant until all the solid has melted. When the liquid is heated the particles gain energy and move faster. Therefore the temperature increases. As the temperature increases the particles eventually gain enough energy to move apart completely and the liquid boils. While the liquid is boiling, the heat energy supplied is used to overcome the forces between the particles in the liquid not to make the particles move faster. Therefore the temperature stays constant until all the liquid has turned to a gas. At this point the liquid has completely turned to a gas and any further heating will once again make the particles move faster.
What is internal energy?
Internal energy is the total kinetic and potential energy of all the particles that make up a system
What is kinetic energy?
Kinetic energy is the energy an object possesses by virtue of its movement
What is potential energy?
potential energy is the individual position of particles relative to each other
What is specific heat capacity?
the amount of energy needed to raise the temperature of each kg of substance by 1*C
What type of energy is increasing when an object is increasing in temperature?
kinetic energy because the particles are increasing in speed, therefore internal energy is also increasing
What type of energy is increasing when a substance is changing state?
potential energy because the particles are moving further apart, therefore internal energy is also increasing
Describe the method to calculate the density of a regularly shaped solid (such as a cube or cuboid)
1) Set the measuring scale to 0 and the units to grams
2) Measure the mass of the object using the measuring scale
3) Using a ruler, measure the length, width, and height of the object in cm
4) Multiply these length measurement together to find the volume
5) Calculate the density of the object by dividing the mass by the volume
Describe the method to calculate the density of an irregularly shaped solid (such as a sharp rock)
1) Set the measuring scale to 0 and the units to grams
2) Measure the mass of the object using the measuring scale
3) Fill a measuring cylinder half-full with water (there needs to be enough water to completely submerge the solid). Record the volume of water currently in the measuring cylinder
4) Gently place the object into the water within the measuring cylinder
5) Record the new volume within the measuring cylinder
6) subtract the original volume of water from the volume when the object is in the water to find the volume of the object
7) divide the mass by the volume to find the density
Describe how to find the density of a liquid
1) Set the measuring scale to 0 and the units to grams
2) Measure the mass of the empty measuring cylinder using the measuring scale
3) Pour the liquid into the measuring cylinder
4) measure the new mass of the measuring cylinder with water in it
5) subtract the mass of the empty measuring cylinder from the new mass of the measuring cylinder with water in it to find the mass of the water
6) measure the volume of water using the measuring cylinder
7) divide the mass by the volume to find the density
Why does the temperature of an object remain the same whilst it is changing state?
When an object is changing state, the temperature remains that same. This is because the energy is going towards breaking the bonds between the particles and increasing the distance between the particles, not increasing their movement (kinetic energy). this is called latent heat.
What is latent heat?
latent heat is the energy transferred to a substance when it is changing state
What is specific latent heat?
Specific latent heat is the energy required to change 1kg of a substance from 1 state to another without a change in temperature
What are the units of specific latent heat?
J/kg
What is specific latent heat of fusion?
The energy required to change 1kg of a substance from a solid to a liquid without a change in temperature
What is specific latent heat of vaporisation?
The energy required to change 1kg of a substance from a liquid to a gas without a change in temperature
What is the equation for specific latent heat?
Specific latent heat = energy / mass
State how a gas exerts pressure on a surface
A gas exerts pressure on a surface when the random motion of its particles collide with the surface
Describe how the pressure of a gas in a sealed container is affected by changing the temperature of the gas
As temperature increases, the gas particles gain more kinetic energy and therefore collide with each other and the container more frequently and with more force. This increases the gas pressure
What is the kinetic theory of matter?
kinetic theory of matter states that matter is composed of a large number of small particles that are on constant motion
in which direction does gas pressure act?
gas pressure acts in all direction equaly
What is Brownian motion?
Brownian motion is the random, uncontrolled movement of particles in a fluid as they constantly collide with other molecules
What evidence is there to support kinetic theory of matter?
Brownian motion
What causes gas pressure inside a balloon?
The gas particles inside a balloon move randomly. They collide with the wall of the balloon. This causes a force to be exerted on the wall of the balloon. This is the pressure that keeps the balloon inflated
What happens to the gas pressure if the gas volume is increased?
the pressure decreases
What happens to the gas pressure if the gas volume is decreased?
the pressure increases
What is the equation for boyle’s law?
Pressure x Volume = constant
What are the requirements for Boyle’s law?
The temperature and mass of the gas are constant
What type of graph tend is shown in this image?
Proportional
What type of trend is this graph showing?
constant
What type of trend is this graph showing?
linear
Explain how the can crushing experiment works
To begin with you place a small amount of water into the empty can. You then heat the can above a bunsen burner. This causes the water to evaporate and form water vapour, this water vapour forces the air out of the can. Therefore, only hot water vapour is in the can. This water vapour exerts a greater pressure on the inside of the can than liquid water would. When the can is quickly turned upside down into the ice bath, the water vapour condenses and forms liquid water (no air can enter the can as it was placed upside down). The pressure inside the can decreases massively and is now less that the air pressure outside. Therefore, the air pressure outside of the can crushes it
What is temperature?
Temperature is a measure of the average kinetic energy of its particles
Explain, in terms of particles, how evaporation causes the cooling of water
Evaporation happens when particles at the surface of a liquid gain enough energy to break the bonds between themselves and become a gas. Evaporation causes cooling because only the liquid particles with more energy (hotter) evaporate, leaving the particles with less energy (cooler) behind. Because the hotter particles have evaporated and are not in the water anymore, only the cooler particles are remaining, therefore the average temperature has decreased, meaning the water has cooled.
What are the 3 states of matter?
solid, liquid, gas
How does the mass change as a substance changes state?
The mass does not change
Which state of matter contains the most energy?
gas
Which state of matter contains the least energy?
solid
What is the freezing point of water?
0*C
What is the boiling point of water?
100*C
What happens to the gas pressure in a sealed container when it is heated and why?
The gas pressure increase. This is because as the temperature of the helium inside the balloon is increased, the helium particles would gain more kinetic energy. As a result the helium particles would move faster, increasing the random and uncontrollable motion of the particles. Therefore, the particles would collide with the inside surface of the balloon more often and with a greater force. This greater force is applied over the same area, causing the pressure exerted by the helium inside the balloon to increase.
How can you observe random motion of gas particles?
You can see how particles in a gas move about randomly by using a microscope to observe smoke particles in a smoke cell. The air particles collide with the smoke particles and cause them to move along unpredictable paths. This random motion is called Brownian motion
What happens the the temperature of a fixed mass of gas if it is compressed slowly and why?
If a fixed mass of gas is compressed, work must be done on it. If the gas is compressed slowly, energy is transferred, by heating, to the surroundings. So the internal energy store and the temperature of the gas do not change
What happens the the temperature of a fixed mass of gas if it is compressed quickly and why?
If a fixed mass of gas is compressed, work must be done on it. If the gas is compressed quickly, the work done on the gas increases the internal energy store and the temperature of the gas. This is because energy is not transferred quickly enough to the surroundings
How is pressure related to the volume of the gas?
the pressure is inversely proportional to volume of the gas ( p = constant / v)
What happens to gas pressure is the volume is reduced and why?
If the volume of a fixed mass of gas is reduced, the molecules have less space to move in so they don’t travel as far between collisions. So, the number of collisions per second increases. And so the total force per unit area (pressure) of the gas increases
