## Some Basic concepts in Chemistry

# Uncertainty in Measurement, S.I Units, Precision and Accuracy and Significant Figures

**Derived S.I units :**

(i) Area = length × length

= meter × meter = meter^{2} = m^{2}

(ii) Volume = length × breadth × height

= m × m × m = m^{3}

(iii) Speed = distance / time = meter / sec = ms^{−1}

(iv) \tt Acceleration = \frac{Change \ in \ velocity \ (m \ sec^{-1})}{Time \ \left(sec\right)}

(v) Force = mass (kg) × acceleration (m sec^{−2})

= kg ms^{−2} = newton (N)

(vi) \tt Pressure = \frac{force \left(kg \ m \ sec^{-2}\right)}{Area \ \left(m^{2}\right)}

kg m^{−1} s^{−2} = pascal (pa)

**Scientific notation :**

0.0000187 = 1.87 × 10^{−5}

120789 = 1.20789 × 10^{5}

N^{1} = N × 10^{n}

n = exponent (+ve or −ve and is integer)

N = any suitable number (usually between 1 to 9)

### Part1: View the Topic in this Video from 0:12 to 6:46

### Part2: View the Topic in this Video from 0:20 to 9:39

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1. Precision = Individual value − arithmetic mean value

2. Accuracy = Mean value − true value

3. °F = \tt\frac{9}{5}(°C) + 32

4. K = °C + 273.15