Particle Model of Matter

Question 1

Describe the Arrangement of Particles in a Solid

Answer 1

-The particles are very close together and are arranged in a regular pattern. the bonds in solids are very strong.

-The particles vibrate but do not move from place to place. Solids are rigid

-Solids have a fixed shape and volume. They cannot be compressed.

Question 2

Describe the Arrangement of Particles in a Liquid

Answer 2

-The particles are close together but are not arranged in a pattern. The bonds in liquids are not very strong.

-The particles can move around each other. Liquids are not rigid.

-Liquids have a fixed volume but no fixed shape. They cannot be compressed.

Question 3

Describe the Arrangement of Particles in a Gas

Answer 3

-The particles are very far apart and are not arranged in a pattern. There are no bonds in gases.

-The particles move very rapidly. Gases are not rigid.

-Liquids have no fixed volume and no fixed shape. They can be compressed.

Question 4

Describe what is Meant by Density

Answer 4

-The density of a material tells us the mass in a given volume.

Question 5

Give the Calculation for Density

Answer 5

Density (Kg/m^3) = Mass (Kg) / Volume (m^3)

ρ = m / v

Question 6

Explain why the Density of Solids and Liquids is Greater than the Density of Gases

Answer 6

-In both solids and liquids, the particles are very close together. This means that in a given volume of solid or liquid, we have a lot of mass packed into a relatively small volume. So both solids and liquids have a high density.

-However, in a gas the particles are very far apart. This means that in a given volume of gas, we have a very small amount of mass in a relatively large volume. So gases have a low density

Question 7

Explain why Polystyrene Has a Low Density

Answer 7

-Although polystyrene is a solid, it has a relatively low density. This is because polystyrene is packed full of air-spaces.

-Gases have a low density so because polystyrene contains a lot of air, the overall density of polystyrene is low.

Question 8

Describe a Method to Find the Density of a Regular Shaped Object in the Density Required Practical

Answer 8

-First, measure the mass of the object by placing it on a top-pan balance.

-Then use a ruler to measure the length of the sides of the object. From this we can calculate the volume.

-To do so, multiply the length, width and height together.

-Finally, use the equation density = mass / volume to determine the density of the object.

Question 9

Describe a Method to Find the Density of an Irregular Shaped Object in the Density Required Practical

Answer 9

-First, measure the mass of the object by placing it on a top-pan balance.

-Then fill a Eureka can with water so that the water overflows from the spout. Once, water has stopped flowing from the spout, place a measuring cylinder under the spout.

-Next, gently place the object into the water. Some of the water should overflow from the Eureka can and enter the measuring cylinder.

-Read the number on the measuring cylinder at the point where the water has reached. This is the object’s volume.

-Finally, use the equation density = mass / volume to determine the density of the object.

Question 10

Why is it Important to Measure the Mass Before the Volume in the Density Required Practical

Answer 10

-If volume were measure first, some water in the Eureka can may be absorbed by the object if it has holes in. This would cause the mass to be wrong when placed on the balance.

-Therefore, by calculating volume first, we prevent any errors in our calculation.

Question 11

Why is it Important that the Water Overflows From the Eureka can Spout in the Density Required Practical

Answer 11

-To make sure that the water is right up to the spout, we fill the Eureka can to the point where water pours out of the spout (we do not collect this water).

-Now, when we immerse our object, we know that we have collected all of the displaced water.

Question 12

Why is it Important to Use a Measuring Cylinder and Not a Beaker in the Density Required Practical

Answer 12

-A measuring cylinder is designed to measure volume accurately. Scientists say that a measuring cylinder is volumetric.

-However, a beaker is not volumetric so a beaker can only give us an approximate volume.

Question 13

Describe a Method to Find the Density of a Liquid in the Density Required Practical

Answer 13

-Place a measuring cylinder on a top-pan balance and zero the balance.

-Pour 10ml of the liquid into the measuring cylinder and record the liquid’s mass.

-Pour another 10ml of the liquid into the measuring cylinder, repeating the process until the cylinder is full and recording the volume and mass each time.

-For each measurement, use the use equation density = mass / volume to determine the density.

-Finally, take an average of the calculated densities. This will give a value for the density of the liquid.

Question 14

Describe what is Meant by Internal Energy

Answer 14

-When particles are moving, they have kinetic energy. Gases have the most and solids have the least.

Particles also have forces between them. There are also bonds between the atoms in a molecule. The energy in forces and bonds is called potential energy.

-The kinetic energy of the particles added to the potential energy of the forces and bonds is called the internal energy.

Question 15

Describe the Kinetic Theory of Matter

Answer 15

-Kinetic theory of matter states that particles that gain internal energy (usually by heating) vibrate more due to having more kinetic energy.

-Solid particles will vibrate in place but not move due to strong bonds.

-Liquid particles will be able to move more but are still ‘generally’ in contact with other particles. This allows it to change its shape.

-Gas particles have enough potential energy to overcome their bonds and separate.

Question 16

State the Names Given to Different Changes in State

Answer 16

Solid to Liquid = Melting
Liquid to Gas = Evaporation
Gas to Liquid = Condensation
Liquid to Solid = Freezing
Solid to Gas = Sublimation

Question 17

Explain why Change of State Does Not Involve a Change in Mass

Answer 17

-Changes of state do not involve a change of mass because we are not adding or taking away any particles.

-We are simply changing the energy of the particles and how the particles are arranged.

Question 18

Explain why Changes of State are Physical, Not Chemical Processes

Answer 18

-In changes of state, no chemical reaction takes place.

-If we reverse the change of state, then the material recovers its original properties.

Question 19

Explain, in Terms of Particles, how Solids Change to Liquids and Liquids Change to Gases

Answer 19

-A solid is heated up. This increases internal kinetic energy and makes it hotter.

-When it hits its melting point, the internal potential energy increases instead of the internal kinetic energy. The temperature stays the same but it starts to break bonds and becomes a liquid.

-As a liquid, the internal kinetic energy increases again and the internal potential energy stays the same. The liquid gets hotter.

-When the liquid hits its boiling point, the internal potential energy increases, letting the particles split up. The temperature stays the same.

-As a gas, the internal kinetic energy increases again and the internal potential energy stays the same. The gas gets hotter.

Question 20

Explain why the Temperature Rises Before a Change in State

Answer 20

-We are putting thermal energy into the chemical. This is causing the particles to vibrate (solid) / move around (liquid) with a greater kinetic energy

-The temperature is a measure of the average kinetic energy of the particles.

-So because we are increasing the kinetic energy of the chemical, the temperature of the chemical is increasing.

Question 21

Explain why the Temperature Stops Rising During Changes in State

Answer 21

-When a substance changes state, the energy that we are putting in is not increasing the kinetic energy of the particles.

-Instead, the energy is used to weaken or break the forces of attraction between the particles.

-So during a change of state, the temperature of the substance does not increase.

Question 22

Describe what is Meant by Specific Heat Capacity

Answer 22

Specific Heat Capacity is the energy needed to change 1kg of an object by 1°C.

Question 23

Give the Calculation for Specific Heat Capacity

Answer 23

Specific Heat Capacity (J/kg °C) = Change in Thermal Energy (J) / ( Mass (kg) x Temperature Change (°C) )

Question 24

Describe what is Meant by Specific Latent Heat of Fusion

Answer 24

The specific latent heat of fusion is the energy required to change one kilogram of a substance from a solid to a liquid with no change in temperature.

-This applies when a substance is melted.

Question 25

Describe what is Meant by Specific Latent Heat of Vaporisation

Answer 25

-The specific latent heat of vaporisation is the energy required to change one kilogram of a substance from a liquid to a gas with no change in temperature.

-This applies when a substance boils.

Question 26

Give the Calculation for Specific Latent Heat

Answer 26

Specific Latent Heat (J/Kg) = Energy for Change of State (J) / Mass (Kg)

L = E / m

Question 27

Describe Brownian Motion

Answer 27

-Brownian motion is the random motion of tiny particles in fluids.

-Random means the unpredictable speed and direction of any one particle.

Question 28

Describe how Temperature is Related to the Average Energy in Kinetic Stores

Answer 28

-The particles in a gas are constantly moving with random directions and speeds. If you increase the temperature of a gas, you transfer energy into the kinetic energy stores of its particles.

-The temperature of a gas is related to the average energy in the kinetic stores of the particles in the gas. The higher the temperature, the higher the average energy.

-So as you increase the temperature of a gas the average speed of its particles increases. This is because the energy in the particles’ kinetic stores in 1/2mv^2.

Question 29

Describe the Guy-Lussac Law

Answer 29

-The Guy-Lussac law states that pressure is proportional to temperature.

-If kept in a container of constant volume, the pressure will change proportionally to the temperature.

Question 30

Describe Boyle’s Law

Answer 30

-Boyle’s law states that pressure is inversely proportional to volume.

-Pressure (Pa) x Volume (m^3) = Constant

Question 31

Explain how Colliding gas Particles Create Pressure

Answer 31

-As gas particles move about at high speeds, they bang into each other. When they collide with something, they exert a force (and so a pressure) on it.

-In a sealed container, the outward gas pressure is the total force exerted by all of the particles in the gas on a unit area of the walls.

Question 32

Describe how Changing Volume or Temperature can Affect Pressure in Gases

Answer 32

-Faster particles and more frequent collisions both lead to an increase in net force, and so gas pressure.

-Increasing temperature will increase the speed and so the pressure (if volume is kept constant).

-Alternatively, if temperature is constant, increasing the volume of a gas means the particles get more spread out and hit the walls of the container less often. The gas pressure decreases.

Question 33

Explain how a Change in Pressure can Cause a Change in Volume

Answer 33

-The pressure of a gas causes a net outwards force at right angles to the surface of its containers.

-There is also a force on the outside of the container due to the pressure of the gas around it.

-If a container can easily change its size, then any change in these pressures will cause the container to compress or expand, due to the overall force.

Question 34

Explain how Compressing a Gas is an Example of Work Done

Answer 34

-When we compress a gas, we have to apply a force.

-This means that we have carried out work on the gas.

Question 35

Explain how Doing Work on a Gas can Increase its Temperature

Answer 35

-When we compress a gas we do work on it. Doing work on a gas increases the internal energy of the particles.

-Because the particles now have a greater kinetic energy, the temperature of the gas increases.

-This explains why the end of a bicycle pump heats up when we inflate a tyre.