1A2 Experiments and the Scientific Method

Question 1

Define:

Standard units of measurement

Answer 1

An internationally recognized system for scientific measurements.

Also called SI Units, this common language consists of base units for different kinds of measurement.

For example, the base unit for length is the meter (m).

Question 2

List out the 7 base units of the standard units of measurement.

Answer 2

• meter (m): length
• seconds (s): time
• kilogram (kg): mass
• Ampere (A): electrical current
• Kelvin (K): temperature
• mole (mol): amount of matter
• candela (Cd): luminosity

Additional SI units are generally combinations of a base unit and a prefix that indicates a magnitude of ten.

For example, a centimeter is 1/100th of a meter.

Question 3

Why do scientists use standard units in scientific measurements?

Answer 3

To ensure consistency and global understanding.

Standard units allow scientists around the world to communicate findings clearly and consistently without the risk of misinterpretation due to unit differences.

For example, scientists worldwide use kilograms as a measurement of mass to avoid confusion when comparing data.

Question 4

Define:

Unit conversion

Answer 4

The process of converting a value to another unit.

This involves mulitplying or dividing the original value by a conversion factor, or a pre-defined ratio that compares the two units of measurement.

For example, an American scientist may want to convert their data from meters to miles, since Americans are not as familiar with the length of a meter.

Question 5

What are common errors in unit conversion?

Answer 5

• Rounding errors
• Incorrect conversion factors
• Inconsistent units

Using consistent conversion factors ensures calculations align with scientific standards.

For example, using the wrong conversion factor when converting kilometers to miles will result in an incorrect answer.

Question 6

What are significant figures?

Answer 6

The digits in a measurement that reflect its accuracy and precision.

Significant figures indicate the precision of a measurement, with more digits showing greater accuracy and detail.

Question 7

What are the rules for determining significant figures?

Answer 7

• All non-zero digits are significant.
• All zeros in between non-zero digits are significant.
• All zeros before the first non-zero digit are NOT significant.
• All zeros to the right of non-zero digits with decimals are significant.
• All zeros after a non-zero non-decimal number are NOT significant.

These rules help determine how much precision is present in a measurement.

Question 8

How do you round significant figures?

Answer 8

If the next digit is 5 or higher, round up.

For example, when rounding 3.456 to two significant figures, the third digit (6) is 5 or greater, so you round up the second digit (5) to 6, resulting in 3.5. Rounding ensures the result reflects the measurement’s precision.

Question 9

How many significant figures are in the number 12,564,000?

Answer 9

5

Non-zero digits (1, 2, 5, 6, and 4) are significant, but trailing zeros are not unless there is a decimal (e.g., 12,564,000.0).

Question 10

What is standard notation?

Answer 10

The most common way to express numbers.

Standard notation is used by most people when communicating the size of a number.

For example, 20,000 and 4,700,000 are written in standard notation.

Question 11

What is scientific notation?

Answer 11

A way to express very large or small numbers using a coefficient and an exponent.

Scientific notation simplifies the writing of numbers that are too large or small to be practical for regular use.

Question 12

Describe the format of scientific notation.

Answer 12

a x 10^x

a is a coefficient that has an absolute value between 1 and 10. x represents a power of ten, either negative or positive.

Question 13

How do you convert a small number to scientific notation?

Answer 13

1. Move the decimal to the right until the absolute value of the number is between 1 and 10.
2. Count the number of places that the decimal moved.
3. Use the negative value of the number from step 2 as the exponent in the power of ten.

Converting a small number to scientific notation results in a negative exponent. This represents the decimal moving to the right.

Question 14

How do you convert a large number to scientific notation?

Answer 14

1. Move the decimal to the left until the absolute value of the number is between 1 and 10.
2. Count the number of places that the decimal moved.
3. Use the positive value of the number from step 2 as the exponent in the power of ten.

Converting a large number to scientific notation results in a positive exponent. This represents the decimal moving to the left.

Question 15

How do you convert from scientific notation to standard notation?

Answer 15

Remove the 10^x, then move the decimal x times to the right (if positive) or left (if negative).

Example: 2.304 x 10⁻⁷ becomes 0.0000002304. Moving the decimal to the left makes the number smaller.

Question 16

How do you convert standard notation to scientific notation?

Answer 16

Move the decimal point to get a number between 1 and 10, then multiply by 10 raised to the appropriate power.

Example: 56,000,000 becomes 5.6 x 10⁷. The exponent represents how many places the decimal point was moved to the left.

Question 17

What is the difference between accuracy and precision?

Answer 17

• Accuracy refers to how close a measurement is to the true value.
• Precision refers to the consistency of measurements.

You can have high precision without accuracy and vice versa.

Question 18

What does reliability in research describe?

Answer 18

The ability to repeat study results under the same conditions.

A study with high reliability produces consistent results each time, regardless of when or who conducts it.

Question 19

How are reliability and validity different in research?

Answer 19

• Reliability refers to consistency.
• Validity refers to accuracy.

A study can be reliable without being valid, but if a study is valid, it is often reliable.

Question 20

How many significant figures are in the number 12.0000?

Answer 20

6

The zeros after the decimal point are significant because they show the precision of the measurement.

Question 21

How many significant figures are in the number 0.00004?

Answer 21

1

Only the non-zero digit (4) counts as significant. Leading zeros do not contribute to precision.

Question 22

Define:

Random error

Answer 22

It refers to unpredictable variations in measurements that occur due to small, uncontrollable factors.

For example, if you’re measuring the length of an object with a ruler, slight differences in how you align the ruler each time could cause random errors in your measurements. Over time, this would lead to small fluctuations between trials.

Question 23

How can errors be reduced?

Answer 23

• Increasing sample size
• Taking multiple measurements
• Calibrating equipment
• Using randomized samples

These strategies help minimize both random and systematic errors improving the overall reliability and validity of results.

Question 24

What type of error causes predictable bias in measurements?

Answer 24

Systematic error

For example, a faulty scale always reading 2 kg heavier introduces bias.

Question 25

A researcher **observes** that their data points **cluster tightly** together but are consistently far from the true value. What does this indicate?

Answer 25

High precision, low accuracy. ## Footnote For instance, repeatedly measuring a length as 10.5cm when the true value is 12cm demonstrates precision without accuracy.

Question 26

What **visual aid** is best for showing percentages in a dataset?

Answer 26

Pie chart ## Footnote For example, a pie chart can *represent* how much sales have been made across different product categories in a month.

Question 27

# Fill in the blank: Data **presented** in rows and columns is called a \_\_\_\_\_\_.

Answer 27

Table ## Footnote Tables organize information into rows and columns, making it easier to read and compare data.

Question 28

# Fill in the blanks. The x-axis runs \_\_\_\_\_\_ , while the y-axis runs \_\_\_\_\_\_.

Answer 28

horizontally; vertically ## Footnote The orientation of these axes helps in visualizing relationships between variables. For example, in a graph tracking speed, time (x-axis) influences speed (y-axis).

Question 29

What **graph** best shows trends or patterns over time?

Answer 29

Line graph ## Footnote Line graphs highlight trends, such as how temperature changes hourly or sales grow monthly.

Question 30

What role does **proper calibration** play in measurements?

Answer 30

It helps **prevent** systematic errors. ## Footnote Regular calibration ensures measurement instruments stay accurate and provides consistency across different experiments.

Question 31

When should you **use** a pie chart versus a bar graph?

Answer 31

* Pie charts for *proportions*. * Bar graphs for *comparisons*. ## Footnote *Pie charts* are best for showing proportions within a whole, while [*bar graphs*](https://study.com/academy/lesson/interpreting-pie-charts-and-bar-graphs.html) are better for comparing individual values across categories.

Question 32

Why are axis labels **important** in graphs?

Answer 32

To clearly **identify** the variables being represented. ## Footnote For instance, labeling the **x-axis** as “Time (hours)” and the **y-axis** as “Temperature (°C)” helps avoid misinterpretation.

Question 33

# True or False: Tables are the **best** method for analyzing trends over time.

Answer 33

False ## Footnote Line graphs are better for **visualizing trends**, like temperature changes over a week, while tables are used to display raw data.

Question 34

What is the **difference** between qualitative and quantitative research?

Answer 34

* Qualitative research uses **descriptive** data. * Quantitative research uses **numerical** data. ## Footnote *Qualitative research* gathers descriptive data, like teacher stories on challenges and rewards. *Quantitative research* measures numerical data, like test scores before and after a new teaching method.

Question 35

What is the **dependent variable** (DV) in an experiment?

Answer 35

The variable **measured**. ## Footnote The dependent variable is the variable that you **measure** in the experiment to observe how it was **affected** by changes made to the independent variable. If you change the temperature to see how it affects a liquid's rate of evaporation, the **rate of evaporation** is the dependent variable.

Question 36

What is the **independent variable** (IV) in an experiment?

Answer 36

The variable **manipulated**. ## Footnote The independent variable is the variable that you **manipulate** to observe *its effect on the dependent variable*. For example, if you change the temperature to see how it affects a liquid's rate of evaporation, the **temperature** is the independent variable.

Question 37

# True or False: A dependent variable **changes** in response to the independent variable.

Answer 37

True ## Footnote For example, in an experiment testing fertilizer effects, plant growth (dependent) changes with the amount of fertilizer (independent).

Question 38

What is a **constant** in an experiment?

Answer 38

A factor that remains **unchanged** throughout the experiment. ## Footnote Constants are crucial for ensuring that any observed changes are due to the independent variable rather than other factors. For example, in a plant growth experiment, the amount of *water* and *soil type* should remain constant.

Question 39

What are **confounding variables**?

Answer 39

**Unexpected factors** that might influence the relationship between the independent and dependent variables. ## Footnote Confounding variables can skew results if not controlled. For example, in a study about exercise and weight loss, diet would be a confounding variable if not controlled for.

Question 40

What is the **main purpose** of a control group in an experiment?

Answer 40

To provide a **baseline** for comparing **results**. ## Footnote The main purpose is to provide a **standard** for comparison by not receiving the experimental treatment. This helps identify if changes in the experimental group are due to the treatment rather than other factors.

Question 41

Why is random sampling **important** in research?

Answer 41

To **reduce bias** and **improve the validity** of results. ## Footnote Random sampling ensures every individual in a population has an equal chance of being selected. For example, *randomly selecting* students from a school ensures **fair representation** in a survey on study habits, as it avoids over-representing or under-representing any specific group.

Question 42

# Fill in the blank. In a study, researchers **track** the performance of two groups of employees—one that follows a new training program and another that doesn’t—and compare their productivity levels over three months. This is an example of a/an \_\_\_\_\_\_\_\_ study.

Answer 42

experimental ## Footnote This represents an experimental study because the researchers **actively manipulate** one variable (the training program) to see its effect on the outcome (productivity). Experimental studies are used to establish *cause-and-effect relationships*.

Question 43

What is a **positive correlation** between two variables?

Answer 43

A **relationship** where as one variable increases, the other also increases. ## Footnote For instance, the amount of study time and exam scores often show a positive correlation: *studying more* typically results in *higher scores*.

Question 44

# Fill in the blank. Scientists are investigating the relationship between **physical activity levels** and **stress reduction**. They gather data by surveying a large group of people about their exercise habits and perceived stress levels over the past year without influencing their behavior. This is an example of a/an \_\_\_\_\_\_\_\_ study.

Answer 44

observational ## Footnote This represents an observational study because the researchers **passively observe** and collect data on naturally occurring variables (*dietary habits and heart health*) without any manipulation.

Question 45

# Fill in the blank. Predicting values within the **range** of observed data is called \_\_\_\_\_\_\_\_.

Answer 45

Interpolation ## Footnote For example, *estimating* a temperature reading at 15°C when data is available for 10°C and 20°C.

Question 46

What is **extrapolation**?

Answer 46

It is predicting values **beyond** the observed range. ## Footnote For instance, using past population data to **forecast** future growth trends.

Question 47

Why is it **important** to calculate **percent error** in an experiment?

Answer 47

To **measure** how accurate the results are compared to the expected value. ## Footnote For example, if the expected value is 50g and the measured value is 48g, the percent error quantifies the deviation as **4%**.

Question 48

A scale consistently shows that an empty container has a mass of 5 grams. What must be done before adding anything to the container?

Answer 48

**Calibrate** the scale so that the container has a mass of 0 grams. ## Footnote Otherwise, whatever you add to the container will register as 5 grams heavier than it truly is. Calibration fixes **systematic errors**, ensuring accuracy for all subsequent measurements.

Question 49

# Fill in the blanks. The **range** of a dataset represents the difference between the \_\_\_\_\_\_\_ and \_\_\_\_\_\_\_ values.

Answer 49

highest; lowest ## Footnote The range provides a simple measure of data spread. For example, in the dataset **[3, 7, 10, 15]**, the range is 15 - 3 = **12**.

Question 50

# Fill in the blank: **Dimensional analysis** ensures \_\_\_\_ \_\_\_\_\_\_\_.

Answer 50

unit consistency ## Footnote For example, converting 5 km/h to m/s ensures accurate comparison of speeds across different units.

Question 51

How do scientists **draw conclusions** from data?

Answer 51

By summarizing the evidence collecting and **making a statement that confirms or refutes** their hypothesis. ## Footnote Scientists will look at the evidence that was collected, analyze patterns or trends, then compare to their original hypothesis. Then, scientists will make inferences in order to explain their results.