P6 - Molecules and Matter

Question 1

What is the formula for density

Answer 1

Density (g/cm cubed ) = mass(g)/ volume (cm cubed)

Question 2

A block of wood has a density of 0.8 g/cm3. The block measures
30 cm x 10 cm x 10 cm. Calculate the mass of the block of wood in kg.

Answer 2

0.8 = mass /3000

0.8 × 3000 = mass
2400 g = mass

Question 3

How would you determine the voloume of an irregular object ?

Answer 3

Fill a measuring cylinder so that there is enough water to cover the object when it is placed inside the cylinder. Take the reading of the volume.
Carefully lower the object into the cylinder.
Take the new reading of the volume. Subtract the original reading to obtain the volume of the object.

Question 4

Explain the difference in density between the different states of matter in terms of the arrangement of atoms and molecules

Answer 4

Solid - compact, rigid, jose mourinho defence
Liquid - are close ,no regular arrangement, darians sisters bunda
Gas -well separated with no regular arrangement

Question 5

What is density?

Answer 5

Mass per unit volume of a substance

Question 6

How do you measure the density of a solid object or a liquid?

Answer 6

Measure its mass and its volume, then use the density equation p = m/v

Question 7

What happen to objects when they have a lower density than water (i.e., <1000kg/m3)

Answer 7

They float in water

Question 8

Steam machines are used to sterilise kitchen work surfaces.
The latent heat of vaporisation for water is 2.26x10^6 J/kg. Calculate the energy needed to change 60 g of water into steam.

Using the formula (thermal energy for a change of state = mass x specific latent heat)

Answer 8

0.06 kg x 2.26 x 10^6 = 135600 joules

Question 9

Give one reason why the temperature of the solder joint remains constant as the liquid solder becomes solid.

Answer 9

the solid actually loses some energy when these molecules escape. This keeps the temperature from rising beyond the boiling point. As heat energy is added, more molecules escape, and the temperature remains relatively constant.

Question 10

what is the process called from a gas to a solid

Answer 10

Deposition

Question 11

what is the process called from a solid to a gas ?

Answer 11

Sublimation

Question 12

what is the process called from a gas to a liquid

Answer 12

Condensation

Question 13

What is boiling point?

Answer 13

The temperature at which a pure substance boils or condenses

Question 14

What is freezing point?

Answer 14

The temperature at which a pure substance freezes

Question 15

What is internal energy?

Answer 15

The energy of the particles of a substance due to their individual motion and positions

Question 16

What is latent heat?

Answer 16

The energy needed for a substance to change state but not the tempreture.

Question 17

What is the melting point?

Answer 17

The temperature at which a pure substance melts or freezes (solidifies)

Question 18

What is physical change?

Answer 18

A change in which no new substances are produced

Question 19

What is pressure and the unit?

Answer 19

force per unit cross-sectional area for a force acting on a surface at right angles to the surface. The unit of pressure is the pascal (Pa) or newton per square metre (N/m2)

Question 20

What is specific latent heat of fusion Lf?

Answer 20

energy needed to melt or freeze 1 kg of a substance with no change of temperature

Question 21

What is specific latent heat of vaporisation Lv?

Answer 21

energy needed to evaporate or condense 1 kg of a substance with no change of temperature.

Question 22

What is Boyles law?

Answer 22

Boyle’s law is a gas law, stating that the pressure and volume of a gas have an inverse relationship. If volume increases, then pressure decreases

Question 23

What is the change of state when wax turns from a solid to a liquid

Answer 23

It is melting

Question 24

What is the change of state when a gas turning back into a liquid?

Answer 24

Condensation

Question 25

What is the change of state when frozen CO2 (dry ice) turns directly to a gas?

Answer 25

Sublimation

Question 26

What is the change of state when liquid wax turns back into a solid?

Answer 26

It is Freezing

Question 27

What is Brownian motion?

Answer 27

The random movement of particles in a fluid

Question 28

What is the equation for Internal Energy?

Answer 28

Internal Energy = Potenial Energy + Kinetic Energy

Question 29

On a Graph of Tempreture/Time, what does the Potential Energy represent?

Answer 29

The straight line, were the Tempreture doesn’t change and it is going the process of changing states so is breaking down the bonds instead of kinetic energy.

Question 30

On a Graph of Tempreture/Time, what does the Kinetic Energy represent?

Answer 30

A incline or decline line, the Tempreture does change and there is no change of state but the kinetic energy is increasing.

Question 31

What is the equation to find out pressure?

Answer 31

Pressure = force/area

Question 32

What is a Pure Substance?

Answer 32

A substance that contains only one type of atom or molecule.

Question 33

What is the equation for changes of state?

Answer 33

E = ml

Thermal energy supplied to, or lost by the body = the mass of the body x specific latent heat

Question 34

What is the internal energy of a substance?

Answer 34

The combined energy of the kinetic and potential energy of the particles in the substance (or system)

Question 35

What is the equation for internal energy?

Answer 35

Internal energy = potential energy + kinetic energy (kJ)

Question 36

What is Specific Latent Heat?

Answer 36

The amount of energy required to change the state of one kilogram of the substance with no change in temperature.

Question 37

What is Specific Heat Capacity?

Answer 37

The amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius.