T 20 UN
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After the class, students will be able to:
To identify the SI units
To identify the significant figures in calculation To use scientific notation to express very small and very large numbers
To use Factor label method to solve problems in a particular situation
WHAT IS CHEMISTRY?
WHAT IS MATTER?
Matter = anything that has mass and occupies space
ATOMS – smallest distinctive unit in a sample of matter
MOLECULES – larger units of 2 or more atoms. EOS
PROPERTIES OF MATTER
Physical property: characteristic displayed by a sample of matter without undergoing any change in its composition
Chemical property: characteristics displayed as a result of change in composition
PHYSICAL AND CHEMICAL CHANGES
Physical Change: changes in appearance but not in composition
(same substance before and after)
e.g., melting of ice in the winter ice (solid) → water (liquid)
Chemical Change: changes resulting in altered composition and/or molecular structure (different substance before and after) e.g., electric current pass through water
Water → H2 gas + O2 gas
UNITS OF MEASUREMENT
SI BASE UNITS
Scientists worldwide use common measurement units called the
International System of Units (SI)
Name of units
Symbol of unit
distance x distance
m/s or ms-1
m/s2 or ms-2
mass x acceleration
COMMON SI PREFIXES
COMMON UNITS IN
• The SI unit for length, the meter (m), is too large for most laboratory purposes.
• More convenient units are the centimeter
(cm) and the millimeter (mm).
1 m = 100 cm = 1000 mm
1 cm = 10 mm
•Volume is a derived unit with dimensions of (length)3.
•SI unit for volume is the cubic meter, m3.
•Volume units typically use the Liters base
•Very convenient for measuring the volume of irregularly shaped containers MEASURING VOLUME - CONT
Regularly shaped objects can use a variant of the volume unit … cubic distance units Some volume equivalents: 1 m3
1 cm3 =
1 mm3 =
1 L = 1000 mL
1 mL = 1000 µL
• The base unit for measuring mass is the kilogram (kg)
• However, gram (g) is a more convenient unit for laboratory measurements
1 kilogram = 1000 gram
Temperature is a measure of the intensity of heat.
The Celsius scale is the temperature scale in general scientific use.
The SI unit of temperature is the kelvin
The conversion of kelvin to degree
Celcius and Celcius to Fahrenheit are given by these mathematical equations
K = °C + 273.15
°F = (1.8 x °C) + 32
The density of an object is its mass per unit volume,
where d is the density, m is the mass, and V is the volume. • The SI unit of density is kilogram per cubic meter (kg/m3).
• Typically, density is in units of g/L (g/dm3) or g/mL (g/cm3).
PRECISION AND ACCURACY IN
• Precision refers to how closely individual scientific measurements agree with one another. • Accuracy refers to the closeness of the average of a set of scientific measurements to the “correct” or “most probable” value.
• Sampling errors occur when a group of scientific measurements do not represent the entire population of the variable being studied.
PRECISION AND ACCURACY ILLUSTRATED
• All digits in a number that are known with certainty plus the first uncertain digit.
• The more significant digits obtained, the better the precision of a measurement.
• The concept of significant figures applies only to measurements.
An exact number is a number that arises when you count items or when you define a…