Section 7 - Matter

Question 1

What is density?

Answer 1

How much space a substance takes up compared to its mass.

Question 2

What is the equation for density?

Answer 2

ρ=m/V

ρ = Density
m = Mass
V = Volume

Question 3

What makes an object float?

Answer 3

If its average density is less than the fluid’s density it will float. This is because the object is pushed above the fluid because the object’s weight will have displaced in a smaller area, preventing it from sinking.

Question 4

How can a liquid’s density be worked out?

Answer 4

By measuring a set volumes mass and using the density calculation.

Question 5

How can a solid’s density be worked out?

Answer 5

By measuring its mass, and how much liquid is displaced in a displacement can as its volume, density can be worked out using the density formula.

Question 6

What is kinetic theory? How does it describe particle?

Answer 6

A method of explaining particles, where the particles making up matter are tiny balls with lots of forces between them. The way matter behaves can be explained with how the balls move and the forces between them.

Question 7

What are the three states of matter?

Answer 7

Solid, liquid and gas.

Question 8

How are the particles in a solid described, according to kinetic theory?

Answer 8

Close together in fixed regular arrangements due to strong forces of attraction, the particles don’t have much kinetic energy so they can only vibrate around fixed positions.

Question 9

How are the particles in a liquid described, according to kinetic theory?

Answer 9

Close together in irregular arrangements due to weaker forces of attraction, the particles have some kinetic energy so they can move over one another easily in random directions at low speeds.

Question 10

How are the particles in a gas described, according to kinetic theory?

Answer 10

Randomly, there are almost no forces of attraction between particles so they move at high speeds in random directions.

Question 11

What is it called when a solid becomes a liquid?

Answer 11

Melting.

Question 12

What is it called when a liquid becomes a solid?

Answer 12

Freezing.

Question 13

What is it called when a liquid becomes a gas?

Answer 13

Evaporating.

Question 14

What is it called when a gas becomes a liquid?

Answer 14

Condensing.

Question 15

What is it called when either a solid becomes a gas or a gas becomes a solid?

Answer 15

Subliming.

Question 16

How does density normally change with state.

Answer 16

Solids are more dense than liquids and liquids are more dense than gasses.

Question 17

What is specific heat capacity?

Answer 17

The energy required to raise the temperature of 1kg of a substance by 1°C

Question 18

What is specific latent heat?

Answer 18

The energy required to change the state of 1kg of a substance without changing its temperature.

Question 19

What is the formula for specific heat capacity?

Answer 19

ΔQ=m×c×Δθ
ΔQ = Change in Thermal Energy
m = Mass
c = Specific Heat Capacity
Δθ = Temperature Change

Question 20

What is the formula for specific latent heat?

Answer 20

Q=m×L
Q = Thermal Energy
m = Mass
L = Specific Latent Heat

Question 21

How is gas pressure explained by kinetic theory?

Answer 21

Particles in a gas take up very little space, most of a gas is empty space. And because gas particles move about randomly at very high speeds they often collide with one another and whatever else is in the way, upon colliding with something they exert a force. In a sealed container, the outwards gas pressure is the total net force exerted by all of the particles in a gas per unit area of the container walls.

Question 22

How does temperature affect gas pressure and why?

Answer 22

The speed of the particles in a gas depends on the temperature of the gas, so in higher temperatures, the particles move quicker than in the same gas at a lower temperature. Because the particles are moving at higher speeds, they collide with things more, exerting force more often. Additionally, the force exerted in each collision also increases at higher temperatures. This means the net force on the container walls also increases, meaning that the pressure increases with higher temperatures.

Question 23

How does volume affect gas pressure and why?

Answer 23

Increasing a gas’s volume means the particles are more spread out, so they must travel further before colliding with either another particle or the container walls, so they collide less often. With fewer collisions, the net force acting on the container walls decreases and so the pressure decreases in larger volumes.

Question 24

How is the relationship between gas volume and pressure in a sealed container displayed? What does this mean?

Answer 24

P₁V₁=P₂V₂
P₁ = Pressure 1
V₁ = Volume 1
P₂ = Pressure 2
V₂ = Volume 2
This means that pressure and volume are inversely proportional, so when volume increases, pressure must decrease.

Question 25

What is absolute zero?

Answer 25

The coldest anything can be, -273°C, the particles of the substance have so little kinetic energy that they are practically still.

Question 26

What is the Kelvin scale?

Answer 26

A scale of measuring temperature, it starts at 0K or absolute zero, an increase of 1°C is also an increase of 1K.

Question 27

How do you convert between Celsius and kelvins?

Answer 27

To convert from Celsius to kelvins add 273.

To convert from kelvins to Celsius subtract 273.

Question 28

How does pressure cause a change in the volume of a container without a fixed volume?

Answer 28

A container without a fixed volume, like a balloon, only has a constant volume when the external (inward) and internal (outward) pressures are equal. So by increasing the internal pressure of the container, such as by heating it, the container’s volume will increase to decrease its internal pressure to the point that it is equal to the external pressure again.

Question 29

How does doing work on a gas affect its temperature? Why?

Answer 29

Doing work on a gas can increase its internal energy (or its thermal energy store), which increases its temperature.

Question 30

Why do objects stretch, compress or bend?

Answer 30

They have more than one force acting on them in opposing directions in a way that means that the object is unable to move because of the forces.

Question 31

Describe the forces required to bend an object.

Answer 31

A single pushing force acting towards the middle of an object with another pushing force acting on either side of it from the opposite side of the object.

Question 32

Describe the forces required to compress an object.

Answer 32

Two pushing forces acting on the object from opposite sides of the object.

Question 33

Describe the forces required to stretch an object.

Answer 33

Two pulling forces acting on the object from opposite sides of the object.

Question 34

What does it mean if an object has distorted elastically?

Answer 34

The object will return to its original shape and length after the forces causing it to distort have been removed.

Question 35

What does it mean if an object has been inelastically distorted?

Answer 35

The object cannot return to its original shape and length after the forces causing it to distort have been removed.

Question 36

What is the elastic limit?

Answer 36

the point at which an object stops distorting elastically and begins to deform inelastically.

Question 37

What causes work to be done on an object?

Answer 37

When forces distort an object and the energy is transferred to elastic potential energy.

Question 38

What happens to the energy of forces distorting an object in elastic distortion?

Answer 38

All the energy is transferred to the objects elastic potential energy store.

Question 39

What is the relationship between extension and force in elastic distortion?

Answer 39

The extension of the stretched object is directly proportional to the force applied, so there is a linear relationship between the two.

Question 40

What is the equation for the relationship between force and extension in elastic distortion?

Answer 40

F=k×x
F = Force
k = The Spring Constant
x = Extension

Question 41

What is the spring constant?

Answer 41

A material’s unique relationship between distortion and the force required to distort it.

Question 42

What is the limit of proportionality?

Answer 42

The point at which the relationship between an object’s extension and the force applied to distort it goes from a linear relationship to a non-linear relationship.

Question 43

How is work done calculated for linear relationships?

Answer 43

E=½×k×x²
E = Energy Transferred in Distortion
k = The Spring Constant
x = Extension

Question 44

What is pressure?

Answer 44

The force applied to an object’s surface per unit area.

Question 45

What is the equation for pressure?

Answer 45

P=F÷A
P = Pressure
F = Force
A = Area

Question 46

What is the equation for fluid pressure?

Answer 46

P=h×ρ×g
P = Pressure
h = Height of column or the depth of the object
ρ = Density of the liquid
g = Gravitational field strength

Question 47

Why does a fluid’s density affect its pressure?

Answer 47

Density in liquids is constant throughout, so in a denser liquid, at a given depth, there are more particles able to collide, this means that there is a greater pressure.

Question 48

Why does an object’s depth affect the pressure it experiences in a fluid?

Answer 48

The deeper an object is in the fluid, the more fluid there is above it. The fluid acts down on the object due to gravity so the object experiences a greater force the deeper it is.

Question 49

What is upthrust?

Answer 49

A force exerted on an object by a fluid it is either partially or completely submerged in which pushes it up/

Question 50

Why do objects in a fluid experience upthrust?

Answer 50

When an object is in a fluid, it displaces a volume of the fluid equal to the volume of the object submerged. Additionally, the fluid exerts pressure on the object from all sides wherever it is submerged and since pressure increases with depth, the pressure acting on the bottom of the object is greater than the pressure acting on the top of the object, so since the force exerted on the bottom of the object is larger the object is pushed up.

Question 51

Why does an object float or sink?

Answer 51

If the upthrust acting on an object is equal to its weight, the object will float. If the upthrust is less than the object’s weight it will sink. This means that whether an object floats or not in a liquid depends on its density, if the object is less dense than the fluid it will float, if it is denser then it will sink.

Question 52

How does atmospheric pressure vary with height? Why?

Answer 52

As altitude increases, pressure decreases. This is because as altitude increases, the atmosphere’s density decreases, so there are fewer air particles to collide with and so pressure decreases.