Working Scientifically

Question 1

What is a hazard?

Answer 1

Something that could potentially cause harm

Question 2

If data is repeatable and reproducible, it’s…

Answer 2

Reliable and scientists are more likely to have confidence in it.

Question 3

How do you check repeatability?

Answer 3

You need to repeat the readings and check that the results are similar. You need to repeat each reading at least three times.

Question 4

How do you ensure your results are reproducible?

Answer 4

You can cross check them (by looking across the row) by taking a second set of readings with another instrument (or a different observer)

Question 5

Really accurate results are results that are…

Answer 5

Really close to the true answer

Question 6

What does the accuracy of your results usually depend on?

Answer 6

Your method - you need to ensure you are measuring the right thing and that you don’t miss anything that should be included in the measurements. E.g. if you were estimating the volume of an irregularly shaped object, you wouldn’t measure the sides with a ruler but you would measure the volume using a eureka can as you wouldn’t miss any gaps this way= more accurate.

Question 7

What does it mean if your
results are precise?

Answer 7

When the data is all really CLOSE to the mean (average) of your repeatable results (i.e. not spread out). You would have a table with columns and at the bottom of each column there would be a mean for that column and if that mean was 13 for example and the three results in that column were 12, 14, and 13 then data is precise.

Question 8

What is resolution?

Answer 8

The smallest change a measuring instrument can detect (a ruler might have a resolution of 1cm).

Question 9

The more sensitive an instrument is…

Answer 9

The greater resolution it has

Question 10

How is equipment calibrated(marked with a scale of readings/made sure it is in the right measurements/ensuring that it is working properly) ?

Answer 10

By measuring a known value. If there is a difference between the measured and known value of an object, this means there is something wrong with the equipment and you can use this to correct the inaccuracy of the equipment.

Question 11

How can you reduce the effect of RANDOM ERRORS (unpredictable differences caused by things like human errors in measuring .e.g. reading between two points on a ruler as it is an estimate)?

Answer 11

By taking repeat readings and finding the mean. This will make results more precise.

Question 12

If a measurement is wrong by the same amount every time, what is it called?

Answer 12

A SYSTEMATIC ERROR. (e.g. if you measured from the very end of your ruler instead of from the 0 cm mark every time then all of your measurements would be a bit too small). If you repeat the experiment in the exact same way and calculate a mean but there is still a Systematic error then this won’t correct the systematic error.

Question 13

What is a ZERO ERROR?

Answer 13

It is when a SYSTEMATIC ERROR is caused by using equipment that isn’t zeroed properly. (e.g. if an electronic balance always reads 1 gram before you put anything on it then all of your measurements will be 1 gram too heavy).

Question 14

How do you compensate for SYSTEMATIC ERRORs if you know about them?

Answer 14

e.g. if your electronic balance always reads 1 gram before you put anything on it then you just subtract 1 gram from all of your results.

Question 15

What is an anomalous result?

Answer 15

A result that doesn’t fit in with the rest at all. You ignore anomalous results when processing your results (i.e. calculating a mean)

Question 16

How do you calculate mean/average?

Answer 16

Add all the data values together and divide by total number of values in sample. Ignore anomalous results when calculating mean.

Question 17

How do you find mode (most common number)?

Answer 17

=value that occurs the most in your set of results. Ignore anomalous results when calculating the mode.

Question 18

How do you find median (middle number)?

Answer 18

Writing your results in numerical order and finding the middle number. Ignore anomalous results when calculating the median.

Question 19

In any calculation, you should round to the… number of significant figures given (s.f.) in the question?

Answer 19

Lowest

Question 20

What do you have to remember after writing down an answer that has been rounded?

Answer 20

To write down how many significant figures you’ve rounded to after your answer.

Question 21

If your calculation has multiple steps, what do you have to do?

Answer 21

Only round the final answer, or it won’t be as accurate.
Density=0.24g/0.715cm^3=0.33566=0.34g/cm^3m(2.s.f)
Smallest s.f. is 2.

Question 22

If your data comes in categories/is categoric, what chart do you use?
This happens when the independent variables come in distinct categories (solid, liquid, gas).

Answer 22

A bar chart

Question 23

You can also use a bar chart when…

Answer 23

Your independent variable is discrete (the data can be counted in chunks, where there’s no in-between value, eg. number of protons is discrete because you can’t have half a proton)

Question 24

Bar chart golden rules:

Answer 24

-Scale needs to be linear=there should be equal values for each division (only a scale on y-axis)
-Remember to include units
-Label both axis
-Give graph a title
-If you’ve got more than one set of data then include a key
-Draw it nice and big (covering at least half of the graph paper)
-Leave a gap between different categories
-Bars should be equal in width
Dependent variable on y-axis and independent variable on x-axis

Question 25

If your data is continuous, how do you present the data?
Continuous data happens when both variables are continuous (numerical data that can have any value within a range, e.g length, volume, temperature- you can have 0.5 degrees celsius or 0.7 degrees celsius)

Answer 25

Plotting a graph

Question 26

The rules for plotting a graph:

Answer 26

-Use the biggest data values you’ve got to draw a sensible scale on your axes
-Have a title
-The dependent variable goes on the y-axis (dependent on y, vertical one)
-The independent variable goes on the x-axis (horizontal one)
-To plot points, use a sharp pencil and make neat little crosses (don’t do blobs and don’t smudge)
-If you’re asked to draw a line (or curve) of best fit, draw line through or as near to as many points as possible, ignoring any anomalous results. Don’t join the crosses up.
-Curve of best fit is always a curve and line of best fit is a straight line
-Draw it nice and big (covering at least half of the graph paper)
-Remember to include units on both axes

Question 27

How do you calculate gradient?

Answer 27

gradient=change in y/change in x

Remember it has to be change in variables and can’t just be them straight up.
Remember, if the line is going downwards it will have a negative change in y but if it is going upwards it will have a positive change in y.

Question 28

The units of the gradient are…

Answer 28

(units of y)/(units of x)

Question 29

How do you find the gradient of a curve at a certain point?

Answer 29

Draw a tangent (straight line that touches the curve at that point, but doesn’t cross it) to the curve at that point. Then just find the gradient of the tangent by marking two clear points on the tangent and then use the equation to calculate gradient.

Question 30

Graphs show the relationship between two variables. What are the three types of correlation (relationship) between variables?

Answer 30

-Positive correlation- as one variable increases the other increases (points are close together in an upward line)
-Inverse (negative) correlation- as one variable increases the other decreases (points are close together in a downward line)
-No correlation- no relationship between the two variables (points are all spread out)

Question 31

Just because there’s correlation, it doesn’t mean the change in one variable is…

Answer 31

causing the change in the other- there might be other factors involved

Question 32

(S.I. units you’ll see in Physics) What are the standard units (S.I. units) for quantities of:
-mass
-length
-time
-Temperature

Answer 32

mass= kilogram, kg
length= metre, m
time= second, s
Temperature= kelvin, K

Question 33

Here are the prefixes that can be placed in front of base units (e.g.metres) to tell you how much larger or smaller they are:
-tera(T)
-giga(G)
-mega(M)
-kilo(k)
-deci(d)
-centi(c)
-milli(m)
-micro(μ)
-nano(n)
What are their multiple of units?

Answer 33

-tera(T)= 10^12
-giga(G)=10^9
-mega(M)=1000000 (10^6)
-kilo(k)=1000
-deci(d)=0.1
-centi(c)=0.01
-milli(m)=0.001
-micro(μ)=0.000001 (10^-6)
-nano(n)= 10^-9
Giga and Nano are basically inverses.
Mega and Micro are basically inverses.
THESE ARE NOT CONVERSION FACTORS, they just tell you how much of something there is.

Question 34

What is a conversion factor?

Answer 34

What number you multiply or divide by to get from the original number to the new number.
e.g. the conversion factor to get from metres to kilometres is dividing by 1000.

Question 35

What are the two rules when using conversion factors?

Answer 35

-To get from a bigger unit (like m) to a smaller unit (like cm), you MULTIPLY by the conversion factor.
-To get from a smaller unit (like g) to a bigger unit (like kg), you DIVIDE by the conversion factor.

Question 36

Here are some conversions that’ll be useful for PHYSICS:

Answer 36

-Mass can have units of kg and g.
kg to g= x 1000
g to kg= /1000
-Energy can have units of J and kJ.
kJ to J= x 1000
J to kJ= /1000
-Volume can have units of m^3 and cm^3.
m^3 to cm^3= x 1000000
cm^3 to m^3= /1000000
-Density can have units of kg/m^3 and g/cm^3.
kg/m^3 to g/cm^3= /1000
g/cm^3 to kg/m^3= x1000

Question 37

What do you have to do when using equations/formulae?

Answer 37

Always check that the values you substitute into the equation/formula have the right units. e.g. an equation might use metres as the distance unit but you may have distance in centimetres so you’ll have to convert the cm into m before you put it into the equation.

Question 38

To make sure your units are correct, it helps to…

Answer 38

write down the units on each line of your calculation.

Question 39

How do you draw conclusions from an investigation?

Answer 39

You look at your data and say what PATTERN or RELATIONSHIP you see between the DEPENDENT and INDEPENDENT variables. You need to use your RESULTS to back up your conclusion (the voltage across the bulb was 9V higher with a current of 12A compared to a current of 6A). Lastly, you need to REFER back to the original HYPOTHESIS and say whether the data SUPPORTS it or NOT. (the hypothesis for this experiment might have been that a higher current through the BULB would INCREASE the voltage across the bulb, if so then the data supports this)

Question 40

What do you have to remember when writing a conclusion?

Answer 40

That your conclusions matches the data you’ve got and doesn’t GO ANY FURTHER- you can’t conclude that the voltage across any circuit component will be higher for a larger current if you have only investigated voltage across a bulb- the results might be completely different. Ensure you only talk about the bulb in this case and not all of the possible circuit components, explicitly state ‘bulb’.

Question 41

Correlation doesn’t mean…

Answer 41

Cause

Question 42

There are three possible reasons for correlation:
-Chance
-Linked by a 3rd variable
-Cause

Answer 42

-Chance= Two things can show a correlation (link) purely due to chance.
-Linked by a 3rd variable= It may look as if a change in one variable is causing a change in the other, but it isn’t- a third variable links the two things (shark attacks increase when it’s hotter, it’s not the temperature that increases shark attacks it’s number of people in water)
-Cause=Sometimes a change in one variable does CAUSE a change in the other. You can only conclude that a correlation is due to CAUSE when you’ve CONTROLLED ALL THE VARIABLES that could, just could, be affecting the result.

Question 43

What is the equation for calculating uncertainty of a mean result?

Answer 43

Uncertainty=range/2

Question 44

The larger the range means the less ____ your results are and the more _____ there will be in your results.

Answer 44

Precise and uncertainty

Question 45

What is the symbol for uncertainty?

Answer 45

±

The uncertainty of a mean will look like:
Mean (e.g. 2.00) ± uncertainty (0.015m/s)

Question 46

How do you reduce uncertainty?

Answer 46

Measuring a greater amount of something. (e.g. in a speed experiment, measuring the distance travelled over a LONGER PERIOD of time compared to a shorter period will reduce the % uncertainty in your results.

Question 47

What is an evaluation?

Answer 47

A critical analysis of the whole investigation.

Question 48

In an evaluation, you should comment on:

Answer 48

-Method (was it valid? were all the other variables controlled to make it a fair test?)
-Quality of results (enough evidence to reach a valid conclusion?were they repeatable, reproducible, accurate and precise?)
-Anomalous results (were there any? if not then say so? if there were try to explain them- caused by errors in measurement? comment on the level of uncertainty in results too)
-State how confident you are that your conclusion is correct
-Any changes/suggestions to improve the quality of results (eg. taking more measurements at narrower intervals could give more accurate result)- when giving suggestions make sure you state why you think it would make the results better i.e. make them more accurate or precise?
-Possibly make predictions on other experiments based on your conclusion.