Module 1 - Practical Skills Flashcards Preview

A Level Chemistry OCR A (2022) > Module 1 - Practical Skills > Flashcards

Flashcards in Module 1 - Practical Skills Deck (14)
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1
Q

When is a measurement valid?

A

When it measures what it is supposed to be measuring.

2
Q

When is a result accurate?

A

When it is close to the true value.

3
Q

What are precise results?

A

When repeat measurements are consistent/agree closely with each other.

4
Q

What is repeatability?

A

How precise repeated measurements are when they are taken by the same person, using the same equipment, under the same conditions.

5
Q

What is reproducibility?

A

How precise repeated measurement are when they are taken by different people, using different equipment.

6
Q

What is the uncertainty of a measurement?

A

The interval within which the true value is expected to lie.

7
Q

Define measurement error.

A

The difference between a measured value and the true value.

8
Q

What type of error is caused by results varying around the true value in an unpredictable way?

A

Random error.

9
Q

What is a systematic error?

A

A consistent difference between the measured values and true values.

10
Q

What does zero error mean?

A

A measuring instrument gives a false reading when the true value should be zero.

11
Q

Which variable is changed or selected by the investigator?

A

Independent variable.

12
Q

What is a dependant variable?

A

A variable that is measured every time the independent variable is changed.

13
Q

Define a fair test.

A

A test in which only the independent variable is allowed to affect the dependent variable.

14
Q

What are control variables?

A

Variables that should be kept constant to avoid them affect the dependent variable.