Working Scientifically (Chem)

Question 1

precision vs accuracy

Answer 1

precision: spread around the mean
accurate: how close to the true value

Question 2

we repeat experiments to…

Answer 2

check and eliminate anomalies
check repeatability/reproducability of experiment

Question 3

how to make experiments more accurate

Answer 3

use equipment with more increments/better resolution
use burette instead of measuring cylinder
control more variables (eg insulation - temperature changes)

Question 4

validity

Answer 4

suitability of the procedure to answer the question being asked

Question 5

reproducible

Answer 5

when experiment is repeated by another person using different equipment and the same results are obtained

Question 6

random error (and how to fix)

Answer 6

error in measurement caused by factors that vary from one measurement to another

effect can be reduced by repeating and calculating the mean

Question 7

systematic error

Answer 7

an error that occurs in the same way each measurement, causing values to vary by a consistent amount each time
eg: methods of observation, instrument used, temperature

to avoid, repeat using different techniques/equipment

Question 8

gas tests

Answer 8

oxygen: glowing splint held in a test tube -> splint relights

hydrogen: lighted splint held in a test tube -> squeaky pop

carbon dioxide: gas bubbles through limewater -> turns cloudy/milky white

chlorine: damp litmus paper held in test tube -> paper bleaches

Question 9

when to use bar chart

Answer 9

discrete,categoric data