Practicals

Question 1

What are the factors that affect rate of diffusion?

Answer 1

Concentration, temperature, size and shape of molecules, distance

Question 2

If concentration is the independent variable, what are the control variables?

Answer 2

Temperature, surface area (if solid reactent), volume of liquids used

Question 3

If temperature is the independent variable, what are the control variables?

Answer 3

Concentration and volume of liquids, surface area of solids

Question 4

What piece of equipment do I need to include if temperature is a control variable?

Answer 4

Thermometer

Question 5

Risks and control measures associated with HCl or NaOH

Answer 5

Corrosive, Irritant, wear gloves, lab coat and goggles

Question 6

What piece of equipment do I need to include if volume is a control variable?

Answer 6

Measuring cylinder or pipette

Question 7

How is agar made pink?

Answer 7

It is made with NaOH and phenolphthalein

Question 8

How do I work out a rate of diffusion?

Answer 8

1 ÷ time taken

Question 9

On a graph with a line of best fit, which data point is the most unreliable?

Answer 9

The one furthest from the line of best fit

Question 10

How is surface area controlled in expreiments using agar shapes?

Answer 10

Make sure the shapes are the same size, cut using same cutter, or cut to measure using a ruler

Question 11

If water baths are used…

Answer 11

Allow time for the baths/other substances to heat up before starting the experiment

Question 12

All methods in a rate of diffusion experiment require a..

Answer 12

Stopwatch

Question 13

Phenolphthalein turns pink in the presences of..

Answer 13

Bases

Question 14

Investigations into rate of diffusion can be extended by..

Answer 14

Using different substances/size molecules, or by using a broader range of initial independent variables

Question 15

If surface area is increased…

Answer 15

Rate of diffusion increases

Question 16

The height of an error bar is usually

Answer 16

Double the standard deviation of the values obtained for a given data point

Question 17

A common mistake in the graphs given in question 5 is..

Answer 17

Line of best fit it drawn dot-to-dot, no units given on one/both of the axes

Question 18

A common mistake in the methods given in question 5 is..

Answer 18

No repeats (can’t find an average value/identify anomolies)

Question 19

If an anomoly is identified it must be..

Answer 19

Circled and not included in the average value calculation

Question 20

Values chosen for the independent variable should be..

Answer 20

Evenly spread out and ideally cover a broad range of initial conditions

Question 21

True or false, the conclusion given in question 5 could be correct?

Answer 21

True, but if it is there is always something wrong or missing from how it was obtained

Question 22

Bar charts should be used when..

Answer 22

The independent variable is qualitative or discrete quantitative

Question 23

What is the distance between the burner and beaker in this practical?

Answer 23

Usually 1.5 cm

Question 24

Why does the conical flask have a black mark at the bottom?

Answer 24

Because the soot from the incomplete combusion touches the base of the flask

Question 25

What is the risk assessment when using a bunsen burner?

Answer 25

Can cause burns. To prevent, turn off whilst not in use

Question 26

How can the practical be extended?

Answer 26

By using lipids or oils instead of fuels

Question 27

What type of foods can be used in this practical?

Answer 27

Carbohydrates

Question 28

Why do we use carbohydrates?

Answer 28

Can be ignited

Question 29

How do we find the avarage heat energy per gram of food used?

Answer 29

heat energy gained by the water / change in mass of the food

Question 30

Why do we use a lid on the calorimeter?

Answer 30

To reduce heat loss

Question 31

What is the formula for heat energy?

Answer 31

Q = Mc ∆ T

Question 32

Why should the water be stirred throughout a calorimeter practical?

Answer 32

To make sure there is an even heat distribution

Question 33

Why should you wait after the fuel/food is extinguished before reading the final temp?

Answer 33

Because the temperature will continue to rise for a few moments after the flame has gone out

Question 34

Why do we surround the expiriment with a shield?

Answer 34

To block any wind draughts that could effect the flame or heat distribution

Question 35

What is repeatability

Answer 35

Repeating the experiment and getting the same/similar results

Question 36

What is reproducibility

Answer 36

Another person/team performs the same investigation and gets the same/similar results

Question 37

Filament lamp graph shows

Answer 37

As voltage increase, the gradient decreases (it's a non-ohmic conductor) ## Footnote As the filament gets hotter, the resistance increases

Question 38

How does an LDR (light-dependant resistor) work?

Answer 38

As the ambient light increases, the resistance decreases

Question 39

How can you ensure that the distance between a filament lamp and LDR doesn't change between readings?

Answer 39

Clamp the lamp at a fixed height and place the LDR underneath it

Question 40

Why does changing the distance between the lamp and LDR affect the resistance

Answer 40

The light from the lamp would decrease as the LDR is moved further away, which would increase resistance

Question 41

How do thermistors work?

Answer 41

As the ambient temperature increases, the resistance decreases

Question 42

What is sampling used for?

Answer 42

Used to study disruption of plants in a particular habitat, a small portion of the habitat is studied carefully

Question 43

What is the significance of random sampling ?

Answer 43

Random sampling prevents bias, allows for the sample to be representative of the population

Question 44

How can a random sample be collected?

Answer 44

Take samples at regular distance across the habitat, or use a computer to generate random numbers to plot co-ordinates on a map to use GPS system to find the exact position in the habitat at which to take samples

Question 45

When is it best to use line transects?

Answer 45

For large habitats or for going along the edge of footpaths

Question 46

How do line transects work?

Answer 46

Long tape measure is stretched across the habitat and plants touching the tape measure are recorded at regular intervals

Question 47

When is it best to use quadrats?

Answer 47

For smaller habitats

Question 48

What are the two types of quadrats?

Answer 48

Gridded and open

Question 49

How are quadrats used?

Answer 49

Square frame is placed at the randomly selected areas of the habitat, positioning the quadrat correctly you can count numbers of each plant you can either count everything in or touching in the quadrat or only organisms completely in the quadrat

Question 50

What are point frames?

Answer 50

Frames with a number of long needles, frame is lowered into an open quadrat and any plants touching the needles are recorded. If you have a frame with 10 needles you have to move it ten times in each quadrat tp give 100 readings.

Question 51

How are point frames used?

Answer 51

Each plant recorded as touching the needle will have 1% cover, so you can estimate the percentage cover of each plant from the results

Question 52

What are limiting factors?

Answer 52

A factor that limits the rate of reaction

Question 53

What is aeration?

Answer 53

Introducing air into the soil

Question 54

What is the importance of aeration?

Answer 54

Allows plants to respire, also for microorganisms to respire as these are needed to decompose organic matter and for nitrifiction of the soil , to help plants to absorb water and nutrients , to help prevent toxins forming in the soil and to also to help prevent plants from contracting diseases

Question 55

How are T-tests used?

Answer 55

T-testing determines if there is satistically significant difference between two data sets

Question 56

How does over-harvesting affect plant growth?

Answer 56

It depletes the soil of nutrients, making it difficult for plants to grow

Question 57

How are chi-squared tests used?

Answer 57

Chi-squared testing determines if there is a significant difference between the obsevered and expected data