Empirical data collection and analysis form the backbone of evidence-based research. This guide covers step-by-step methods, real-world examples, and tools to gather and interpret data effectively. Ideal for researchers, students, and professionals aiming for accuracy and reliability in their studies.
Question (i):
Statement: Which of the following pairs of quantities may be measured in the same unit?
Options:
(a) Heat and temperature
(b) Temperature and area
(c) Heat and work
(d) Length and work
Correct Answer: (c) Heat and work
Explanation:
Heat and work are both forms of energy and are measured in joules (J) in the SI system.
Tips and Tricks:
- Always link the units to the physical quantities: energy is measured in joules.
- Remember that temperature is measured in kelvin (K), and length is measured in meters (m).
Question (ii):
Statement: In which unit we usually measure the energy present in food?
Options:
(a) Kilojoules
(b) Megajoules
(c) Calorie
(d) Joule
Correct Answer: (c) Calorie
Explanation:
The energy in food is commonly measured in calories or kilocalories, though joules can also be used.
Tips and Tricks:
- Remember: 1 calorie = 4.184 joules.
- Energy in food is rarely represented in kilojoules for daily usage.
Question (iii):
Statement: What prefix is used for 1012?
Options:
(a) Mega
(b) Pico
(c) Giga
(d) Tera
Correct Answer: (d) Tera
Explanation:
Giga is the prefix for 109, and Tera is the prefix for 1012. The question might have a typo in choices.
Tips and Tricks:
- Memorize the SI prefixes:
- 106: Mega
- 109: Giga
- 1012: Tera
Question (iv):
Statement: In SI, the unit of pressure is expressed in:
Options:
(a) Newton per metre
(b) Newton per metre square
(c) Joule
(d) Pascal
Correct Answer: (d) Pascal
Explanation:
Pressure is force per unit area. In SI, pressure is measured in pascals (Pa), where 1 Pa=1 N/m2
- Remember: Pressure=Force/Area
Question (v):
Statement: Which symbol is used for kilogram in SI units?
Options:
(a) K
(b) k
(c) kgm
(d) kg
Correct Answer: (d) kg
Explanation:
The SI unit of mass is the kilogram, denoted by “kg.”
Tips and Tricks:
- Avoid confusion with “K,” which is for kelvin (temperature).
Question (vi):
Statement: What does a mole represent?
Options:
(a) Number
(b) Mass
(c) Volume
(d) Length
Correct Answer: (a) Number
Explanation:
A mole represents 6.022×1023 (Avogadro’s number). It is a measure of quantity, not mass, volume, or length.
Tips and Tricks:
- Recall Avogadro’s number when dealing with moles.
Question (vii):
Statement: Which unit of volume should usually be used in chemistry?
Options:
(a) Millilitre
(b) Litre
(c) Cubic centimetre
(d) Cubic metre
Correct Answer: (c) Cubic centimetre
Explanation:
In chemistry, small volumes are often measured in cubic centimeters (cm³), which are equivalent to millilitres (mL).
Tips and Tricks:
Question (viii):
Statement: Express 0.00008400.0000840 in scientific notation:
Options:
(a) 8.40×10−3
(b) 8.40×10−4
(c) 8.40×10−5
(d) 7.40×10−4
Correct Answer: (c) 8.40×10−5
Explanation:
To convert to scientific notation:
- Move the decimal 5 places to the right, so 0.0000840=8.40×10−5
Tips and Tricks:
- Count the decimal places to determine the exponent.
Question (ix):
Statement: In SI, the prefix “nano” means:
Options:
(a) 103
(b) 10−6
(c) 10−9
(d) 1012
Correct Answer: (c) 10−9
Explanation:
Nano is the SI prefix for 10−9
Tips and Tricks:
- Memorize prefixes: micro (10−6), nano (10−9), pico (10−12)
Question (x):
Statement: 65∘Cis equivalent to:
Options:
(a) 85∘F
(b) 149∘F
(c) 180∘F
(d) −85∘F
Correct Answer: (b) 149∘F
Explanation:
Use the formula: ∘F=(∘C×95)+32
Substituting 65∘C
∘F=(65×95)+32=149∘F
Tips and Tricks:
- Remember the conversion formula for Celsius to Fahrenheit.
2. Questions for Short Answers
(i) What is consistency of results?
Answer:
Consistency of results means getting the same result when an experiment or measurement is repeated under the same conditions.
(ii) Why SI units are user-friendly?
Answer:
SI units are user-friendly because they are based on a decimal system, making calculations easier and more standardized worldwide.
(iii) Does systematic error affect accuracy?
Answer:
Yes, systematic errors affect accuracy because they cause measurements to consistently differ from the true value.
(iv) What is the reason behind a random error?
Answer:
Random errors occur due to unpredictable factors like slight changes in environmental conditions or limitations of measuring instruments.
(v) What is the difference between precision and accuracy?
Answer:
- Accuracy: How close a measurement is to the true value.
- Precision: How consistent repeated measurements are, even if they are not close to the true value.
(vi) Which other systems of measurements are used apart from SI units?
Answer:
Other systems include the Imperial System (used in the USA) and the CGS System (centimetre, gram, second).
(vii) Define metre.
Answer:
A metre is the SI unit of length, defined as the distance light travels in 1/299,792,4581/299,792,458 seconds in a vacuum.
(viii) Mention two benefits scientists get by using SI units.
Answer:
- SI units are used worldwide, making data and results easy to compare.
- They are based on fixed standards, ensuring accuracy and reliability.
3. Constructed Response Questions
(i) Compare the units in SI system with those in MKS system.
Answer:
The SI system includes all MKS units (metre, kilogram, second) but also adds more units for quantities like temperature (kelvin) and electric current (ampere). SI is a broader and more complete system.
(ii) What are five basic SI units used in chemistry?
Answer:
- Metre (m) – for length
- Kilogram (kg) – for mass
- Second (s) – for time
- Mole (mol) – for amount of substance
- Kelvin (K) – for temperature
(iii) Explain the three units derived for basic SI units.
Answer:
- Newton (N): Derived for force (1 N=1 kg⋅m/s2
- Pascal (Pa): Derived for pressure (1 Pa=1 N/m2
- Joule (J): Derived for energy (1 J=1 N⋅m1
(iv) Why do we prefer to use smaller units of mass and volume in chemistry?
Answer:
In chemistry, substances are measured in very small quantities. Using smaller units like grams (g) or millilitres (mL) makes the measurements easier and more practical.
(v) What difficulties do we expect to encounter if we use different units of measurement in daily life?
Answer:
Using different units can lead to confusion, incorrect calculations, and errors when converting between systems.
4. Descriptive Questions
(i) What are our indigenous units of measurement for mass, volume, and length?
Answer:
- Mass: Maund, seer
- Volume: Litre, pail
- Length: Cubit, hand span
(ii) Compare SI units with Imperial system of units.
Answer:
- SI units are based on the decimal system, while Imperial units are not.
- Example:
- SI unit of length is metre; Imperial unit is feet.
- SI unit of mass is kilogram; Imperial unit is pound.
(iii) How can you avoid systematic errors in your measurements?
Answer:
- Calibrate instruments properly.
- Avoid faulty equipment.
- Use proper measurement techniques.
(iv) How do taking measurements in SI units ensure safety and reliability?
Answer:
SI units are accurate and universally accepted, reducing chances of errors in measurements, which is crucial for safety and reliability in science and engineering.
(v) Can a student be both inaccurate and imprecise in his measurements?
Answer:
Yes, a student can be both inaccurate (far from the true value) and imprecise (measurements are inconsistent). This happens when both the method and tools used are incorrect.
5. Investigative Question
Elaborate the importance of using SI units in space exploration.
Answer:
Using SI units in space exploration is important because:
- They ensure uniformity in calculations and measurements across different countries and space agencies.
- SI units reduce the risk of errors in crucial missions where precision is vital.
- They simplify the sharing of data and collaboration in international projects.
