Chapter 21: Experimental Design

Question 1

What is a hypothesis?

Answer 1

It is a statement based on a specific idea and which can be tested experimentally. It is a prediction of what is expected to happen when a hypothesis is tested in a laboratory.

Question 2

What are the three variables?

Answer 2

Independent, dependent, controlled

Question 3

What is an independent variable?

Answer 3

It is the parameter that you change

Question 4

What is a dependent variable?

Answer 4

It is the parameter that you measure

Question 5

What is a controlled variable?

Answer 5

It is the things that you must keep the same

Question 6

Why are controlled variables important?

Answer 6

They keep the experiment fair, so the results will be accurate.

Question 7

What can you use to measure time?( list two)

Answer 7

Stopwatch and stopclock

Question 8

How long is one minute in seconds?

Answer 8

1 minute= 60 seconds

Question 9

What can you use to measure temperature?

Answer 9

Thermometer( Can be digital)

Question 10

What is the unit of temperature?

Answer 10

It is degrees Celsius(°C)

Question 11

What can you use to measure mass?

Answer 11

Digital balance

Question 12

Does the digital balance have to be tared before being used?

Answer 12

Yes

Question 13

How many grams are in 1 kilogram?

Answer 13

1000 grams

Question 14

How can you measure the volume of liquids?
(List three)

Answer 14

Burettes, pipettes, and measuring cylinder

Question 15

What is the most accurate way of measuring a fixed volume of liquid?

Answer 15

Pipettes

Question 16

What is the most accurate way of measuring a variable volume of liquid?

Answer 16

Burettes

Question 17

What is the least accurate way of measuring a volume of liquid?

Answer 17

Measuring cylinders

Question 18

How can you measure the volume of gases?

Answer 18

A gas syringe

Question 19

What does it mean when data is accurate?

Answer 19

When data is accurate, it means it is close to the true value

Question 20

What does it mean when data is precise?

Answer 20

When data is precise, the values obtained are close to each other

Question 21

Experiment: Get the density of an eraser

Actual density of an eraser:1.5g/mol

Your values:
Experiment 1: 1.45 g/mol
Experiment 2: 1.43 g/mol
Experiment 3: 1.51 g/mol
Experiment 4: 1.50 g/mol
Experiment 5: 1.52 g/mol

Is this precise or accurate?

Answer 21

It is both precise and accurate

Question 22

Experiment: Get the density of an eraser

Actual density of an eraser:1.5g/mol

Your values:
Experiment 1: 2.11g/mol
Experiment 2: 2.12g/mol
Experiment 3: 2.13g/mol
Experiment 4: 2.14g/mol
Experiment 5: 2.15g/mol

Is this precise or accurate?

Answer 22

It is precise but not accurate

Question 23

Experiment: Get the density of an eraser

Actual density of an eraser:1.5g/mol

Your values:
Experiment 1: 1.5g/mol
Experiment 2: 1.59g/mol

Is this precise or accurate?

Answer 23

It is accurate but not precise

Question 24

What are the two types of errors?

Answer 24

Random errors and systematic errors

Question 25

What are random errors?

Answer 25

They are small errors that can be reduced by repeating the experiment multiple times, ignoring an anomalous point, and calculating the average.

Question 26

What is an anomalous data?

Answer 26

It is when data differs from other normal values

Question 27

What is systematic error?

Answer 27

It is a major error where you need to restart your experiment.

Question 28

What is filtration used to separate?

Answer 28

An insoluble solid from a liquid

Question 29

When you use filtration on rocks and water, the rocks stay up and the water goes through the funnel.

Which is the filtrate and which is the residue?

Answer 29

Filtrate: Water
Residue:Rocks

Question 30

What is evaporation used to separate?

Answer 30

A soluble solid from a solution

Question 31

What is crystallization?

Answer 31

It is a process used to obtain salt crystal using a water bath

Question 32

What are the types of distillation?

Answer 32

Simple distillation and fractional distillation

Question 33

What is simple distillation used to separate?

Answer 33

It is used to separate a solvent form a solution

Question 34

What is fractional distillation used to seperate?

Answer 34

It is used to separate miscible liquids according to their boiling points

Question 35

What is chromatography?

Answer 35

It is a method to separate and identify colored and colorless solutes depending on their solubility in solvents.

Question 36

What do we use to write the baseline?

Answer 36

A graphite pencil

Question 37

Should the water be placed under, above, or on the baseline?

Answer 37

It should be under to prevent the solutes from dissolving in the solvent and getting diluted

Question 38

What should we do if the solvent is a volatile liquid?

Answer 38

We should cover the jar to stop the solvent from evaporating

Question 39

Why do we use locating agents?

Answer 39

Locating agents make the invisible and colorless spots visible when being sprayed on the chromatogram.

Question 40

What do insoluble solutes do in chromatography?

Answer 40

They stay on the starting line

Question 41

How do we know if a substance is pure using chromatography?

Answer 41

We can know if a substance is pure depending on how many spots there are.

1 spot= pure
2 or more= not pure

Question 42

What is the formula for Rf?

Answer 42

Rf= distance traveled by solute/ distance traveled by solvent