solids liquids and gases

Question 1

Density definition

Answer 1

The mass per unit volume of a material

Question 2

density and mass corrilation

Answer 2

low density materials typically have a low mass
high density materials have a high mass

Question 3

gas molecules

Answer 3

Gases, for examples, are less dense than solids because the molecules are more spread out (same mass, over a larger volume)

Question 4

units for density

Answer 4

g/cm3

Question 5

practical: investigate density using direct measurements of mass and volume for a regular object

Answer 5

Independent variable = Type of shape / volume
Dependent variable = Mass of the object

1. • Place the object on a digital balance and note down its mass
2. • Use either the ruler,Vernier calipers or micrometer to measure the object’s dimensions (width, height, length, radius) – the apparatus will depend on the size of the object
3. • Repeat these measurements and take an average of these readings before calculating the density

• Ensure the digital balance is set to zero before taking measurements of mass
• Ensure to take repeat readings and calculate an average to keep this error to a minimum

Question 6

practical: investigate density using direct measurements of mass and volume for a irregular object

Answer 6

• Independent variable = Different irregular shapes / mass
  Dependent variable = Volume of displaced water

1. • Place the object on a digital balance and note down its mass
2. Fill the eureka can with water up to a point just below the spout
3. Place an empty measuring cylinder below its spout
4. Carefully lower the object into the eureka can - water is displaced
   from the eureka can via the spout into a measuring cylinder;
   the volume of water displaced is equivalent to the volume of
   the object
5. Measure the volume of the displaced water in the measuring cylinder
6. Repeat these measurements and take an average before calculating the density

• determine the volume of water displaced into the
  measuring cylinder by observing the scale at the bottom of
  the meniscus, at eye level to avoid parallax error:
• Place the irregular object in the displacement can carefully, as dropping it from a height might cause water to splash which will lead to an incorrect volume reading

Question 7

pressure definition

Answer 7

The concentration of a force or the force per unit area

Question 8

force and area correlation

Answer 8

Pressure is the action of a force over an area; if a force is spread over a large area it
will result in a smaller pressure whereas if the force acts over only a small area it will
result in a larger pressure

Question 9

untis for pressure

Answer 9

N/cm2
pascals
,

Question 10

understand how the pressure at a point in a gas or liquid at rest acts equally in all directions

Answer 10

When an object is immersed in a fluid, the fluid will exert pressure, squeezing the object

The pressure exerted on objects in fluids creates forces against surfaces

These forces act at 90 degrees (at right angles) to the surface

The amount of pressure exerted increases with depth:

The force from the pressure is exerted evenly across the whole surface of an object in a liquid, and in all directions

Question 11

solid

Answer 11

The molecules are very close together and arranged in a regular pattern
The molecules vibrate about fixed positions

A definite shape (they are rigid)
A definite volume

Question 12

liquid

Answer 12

• The molecules are still close together (no gaps) but are no longer arranged in a regular pattern
  The molecules are able to slide past each other

No definite shape – they are able to flow and will take the shape of a container
A definite volume

Question 13

gasses

Answer 13

• The molecules are widely separated - about 10 times further apart in each direction
  The molecules move about randomly at high speeds

Gases are highly compressible, this is because:
There are large gaps between the particles
It is easier to push the particles closer together than in solids or liquids

Question 14

what happens from soild to liquid

Answer 14

When a solid melts to form a liquid the strong bonds between the particles holding
them in fixed positions are broken - new weaker bonds now form between the
particles, but these allow the particles to move freely over one another

Question 15

liquid evaporates or boils to form a gas

Answer 15

When a liquid evaporates or boils to form a gas the bonds between the particles
holding them close together in the liquid state are broken - enabling the particles to
break free and so move freely from one another

Question 16

effect of temp

Answer 16

Heating - increasing the kinetic energy of its particles

This increase in kinetic energy (and therefore energy stored in the system) can:

• Cause the temperature of the system to increase
• produce a change of state (solid to liquid or liquid to gas)
  The higher the temperature, t
• the higher the average kinetic energy of the molecules and vice versa
  This means they move around faster

Question 17

practical: obtain a temperature - time graph to show the constant temperature during a change of state

Answer 17

Fill an insulated beaker with crushed ice straight from the freezer
- Place the ice cubes in the beaker (it should be about half full)
- Place the thermometer in the beaker
- Place the beaker on the tripod and gauze and slowly start to heat it using the bunsen burner
- As the beaker is heated, take regular temperature measurements (e.g. at one minute intervals)
Continue this whilst the substance changes state (from solid to liquid)

• Ensure the thermometer is held vertically in the beaker
• Ensure there are enough ice cubes to surround the
  thermometer in the beaker, and only begin the experiment when the temperature is below 0
• with crushed ice straight from the freezer

Question 18

specific heat capacitty definition

Answer 18

The specific heat capacity of a substance is the amount of thermal energy (in Joules)
required to raise the temperature of 1 kg of that substance by 1 °C

Question 19

Different substances have different specific heat capacities

Answer 19

If a substance has a low specific heat capacity, it heats up and cools down quickly (ie. it takes less energy to change its temperature)

If a substance has a high specific heat capacity, it heats up and cools down slowly (ie. it takes more energy to change its temperature)

Question 20

5.11P practical: obtain a temperature - time graph to show the constant temperature
during a change of state

Answer 20

Fill an insulated beaker with crushed ice straight from the freezer
o Insert a heater, thermometer and stirrer into the crushed ice
o Switch on the stirrer and heater and start a stopwatch - record the initial
temperature of the ice
o At frequent intervals e.g. every 15 seconds record the temperature and
continue until the ice has completely melted into water
o Plot a graph of temperature against time

Question 21

how to make the practical investigate the specific heat capacity of materials including water and some solids experiment for fare

Answer 21

The value obtained will be higher than the official value (4,200 J/kg °C) because some
thermal energy will be transferred to the surroundings by conduction, convection or
radiation - this can be reduced by increased use of insulation around the container
* To increase reliability - repeat the experiment, check for anomalous results, discard
them if present and then calculate a mean value for the specific heat capacity

Question 22

ABSOLUTE 0 temp

Answer 22

• Eventually it reaches a point where the particles stop vibrating; it no longer has any thermal energy and cannot be cooled any more - this temperature is -273 °C and is called absolute zero

Question 23

5.14P practical: investigate the specific heat capacity of materials including water and some solids

Answer 23

Use an electronic balance to measure the mass of an empty polystyrene container
then add water and measure the mass again; the difference in mass is the mass of the
water in the container
* Add a heater, stirrer and thermometer to
the water and then cover with a lid to
reduce heat loss
* Record the initial temperature
* Connect the heater to a power supply,
start a timer and simultaneously switch on
the current to the heater and stirrer
Record the reading on the ammeter and the supply voltage
* Heat the water until its temperature has risen approximately 15 °C then
simultaneously switch off the current to the heater and stirrer, record the maximum
temperature of the water, stop the timer and record the time that the water has
been heated

Question 24

what are the molecules in gas like

Answer 24

Molecules in a gas are in constant random motion at high speeds

Molecules in a gas are in constant random motion and so collide frequently with the walls of the container - their collisions exert a force on the surface area of the

Question 25

to converts from decress c to k (kelvins)

Answer 25

• from C to K –> +273
  from k to C –> minus 273

Question 26

whay does an increase of temp do to gas molecuels

Answer 26

• As you increase the temperature of a gas, the kinetic energy of the gas particles
  increases and therefore their average speed also increases