Paper 1 Practicals

Question 1

What is SHC?

Answer 1

The amount of energy required to raise 1kg of a substance by 1 degrees C

Question 2

Describe a practical to determine the SHC of a material

Answer 2

-place a beaker on a scale and press the balance to zero
-add oil to beaker and record mass of oil from balance
-place a thermometer and immersion heater into the oil, reading the starting temp
- wrap beaker in insulating foam (reduces thermal energy transfer to surroundings)
-connect joulemeter to immersion heater, leave for 30 mins (allows temp to rise for accurate reading)
-read total number of joules passed into immersion heater and final temp on thermometer
-calculate SHC

Question 3

Specific heat capacity equation

Answer 3

SHC= energy
—————————————
mass x temp change

Question 4

SHC: What are sources of inaccuracy and solutions?

Answer 4

• thermal energy passing out of beaker into the air-> use insulator with less thermal conductivity
• not all thermal energy passes into oil-> ensure immersion heater is fully submerged in oil
• incorrect reading of thermometer-> use an electronic temperature probe
• thermal energy not spread through oil-> stir the oil

Question 5

Determine the effectiveness of thermal insulators.

Answer 5

• place a small beaker inside a larger beaker
• boil some water, transfer 80cm3 into the small beaker
• use a piece of cardboard as a lid for the large beaker (must have a hold for a thermometer
• record start temp + start stopwatch
• record temp every 3 mins, for 15 mins
  -Now, repeat the experiment with same volume of water, but with an insulating material surrounding the small beaker (in between 2 beakers)
• repeat with different types of insulating materials (polystyrene balls, cotton wool), using same mass.
• record results on a table

Question 6

Thermal insulators: what are the independent, dependant and control variables?

Answer 6

Independent: type of thermal insulator
Dependant: temperature of the water
Control: volume of water, mass of material, start temp of water

Question 7

Thermal insulators: what are the X and Y values on the graph?

Answer 7

X= time (mins)
Y= temperature (degrees C)

Question 8

Thermal insulators: what is the effect of the most insulating material in terms of temperature?

Answer 8

the water will cool down the most slowly

Question 9

Determine the effect of the thickness of thermal insulation

Answer 9

• start with a beaker of 80cm3 hot water
• measure temp every 3 mins for 15 mins
• repeat experiment but with 2 layers of newspaper wrapped around beaker
  -repeat 2 more times (one with 4 layers, 1 with 6 layers)
  -

Question 10

Thickness of thermal insulation: what are the independent, dependant and control variables?

Answer 10

Independent: layers of insulation
Dependant: temperature of water
Control: start temp of water, volume of water

Question 11

Thickness of thermal insulation: what is the conclusion of the experiment?

Answer 11

the more layers of insulation, the slower the water cools down (more layers are more effective insulator than less layers)

Question 12

Describe how to investigate how the length of a wire affects resistance in a circuit

Answer 12

• attach a wire to a metre ru;ler using tape
• connect the wire to a circuit using crocodile clips, one starting at 0cm, other starting at chosen distance ie 5cm (this distance is the distance connected to the wire)
• record the amps on the ammeter and the potential difference across the wire on the voltmeter
• ## move the crocodile clip further along the wire (ie to 10 cm), to increase the length of the wire. Record the results from the voltmeter and ammeter

Question 13

How does length of a wire affect resistance?

Answer 13

as the length of the wire increases, so does resistance (directly proportional)

Question 14

Resistance and length of wire: issues of the practical?

Answer 14

• small resistance at length of 0cm -> zero error (reading on measure instrument when value should be zero, systematic error.) MUST BE SUBTRACTED FROM each result. Caused by equipment (clip isn’t exactly at zero, resistance caused by clip+wire)

-if temp of wire increases, resistance automatically increases-> use low PD (keeps current low, reduces heating in wire) turn of current in between reading.

Question 15

I/V characteristics: resistor

Answer 15

• battery connected by wires to resistor, resistor in series with ammeter + variable resistor, parallel with voltmeter
• read PD on voltmeter, current on ammeter, record values into table
• adjust variable resistor
• record changed current and PD
  -repeat to get several readings
• switch direction of battery (get negative readings), record readings, change resistance on variable resistor, repeat experiment
• record data on a I/V graph

Question 16

I/V characteristics: what is the relationship between current and potential difference with a resistor? (graph)

Answer 16

They are directly proportional, passes through the origin
shows resistor= ohmic conductor, linear component
ONLY IF RESISTOR IS AT CONSTANT TEMP

Question 17

I/V characteristics: filament lamp

Answer 17

battery connected by wires to bulb, bulb in series with ammeter + variable resistor, parallel with voltmeter
- read PD on voltmeter, current on ammeter, record values into table
- adjust variable resistor
- record changed current and PD
-repeat to get several readings
- switch direction of battery (get negative readings), record readings, change resistance on variable resistor, repeat experiment
- record data on a I/V graph

Question 18

I/V characteristics: what is the relationship between current and potential difference with a filament lamp? (graph)

Answer 18

(looks like an f)
current is not proportional to PD
As current increases, temp of bulb increases, which causes resistance to increase (both negative and positive, both ways)
non linear component

Question 19

I/V characteristics: diode

Answer 19

battery connected by wires to diode, diode in series with milliammeter + variable resistor + extra resistor, parallel with voltmeter
(extra resistor as diode is easily damaged by high current, keeps current low, protects diode) (milliammeter for the low current (sensitive)

• read PD on voltmeter, current on milliammeter, record values into table
• adjust variable resistor
• record changed current and PD
  -repeat to get several readings
• switch direction of battery (get negative readings), record readings, change resistance on variable resistor, repeat experiment
• record data on a I/V graph

Question 20

I/V characteristics: what is the relationship between current and potential difference with a diode? (graph)

Answer 20

graph shaped like backwards, curvy ‘L’
Current is very low until positive readings, then once it starts increasing, increases very high very quickly
Little to no current in reverse direction, diode only allows current in one direction
It has a high resistance in 1 direction, and a very low resistance in the other

Question 21

What it the density equation?

Answer 21

Density= mass
————–
volume

Question 22

How do you determine a density of a regular object?

Answer 22

• determine the mass of the object using a balance
• use a ruler to measure the length of the side
• find the volume (length cubed)
• use equation (density = mass/volume) to calculate density

Question 23

How do you determine a density of an irregular object? (displacement)

Answer 23

• find mass of object using a balance
• fill a Eureka can with water
• now carefully lower object into water (can use a string), causes water to be displaces and flow out of the spout of the can
• measure volume of water displaced using measuring cylinder (volume of water= volume of object)
• use equation (density = mass/volume) to calculate density