Core Chemistry Concepts and Calculations

Posted on Apr 26, 2025 in Chemistry

Fundamental Chemistry Definitions

Which statement best defines chemistry?
The science that studies the connections between the properties of matter and the particles that compose that matter.
Where can we find chemicals?
Everywhere.
Which statement most resembles a scientific theory?
A gas is composed of small particles in constant motion.
According to scientific methods, what is a Law?
A short statement that summarizes a large number of observations.

Measurements and Calculations

Significant Figures

How many significant figures are in each number?

  • A = 58.32: 4
  • B = 0.00250: 3
  • C = 2.7 x 103: 2
  • D = 0.500: 3
  • F = 2100: 2 (assuming trailing zeros are not significant)

Scientific Notation

Express the number 0.000042 in scientific notation:

4.2 x 10-5

Calculations with Significant Figures

Perform the following operation to the correct number of significant digits: 65.2 x 0.025 x (11.5 – 8.25)
5.4
Perform the multiplication to the correct number of significant figures: 65.2 x 0.0015 x 12.02
1.2

Unit Conversion

Convert 76 cm to m:

0.76 m

Density Calculations

An object has a mass of 23.4 g and displaces 9.7 mL of water. Determine its density in grams per milliliter (g/mL).
2.4 g/mL
What is the volume in liters (L) of 321 g of a liquid with a density of 0.84 g/mL?
0.38 L
A 40 g stone is dropped into a graduated cylinder containing 80 mL of pure water. The water level rises to 100 mL. Calculate the density of the stone in g/mL.
2 g/mL

Energy and Temperature

Temperature Concepts

What does the average kinetic energy of particles represent?
It relates to the temperature of a substance.
What does temperature measure?
How hot or cold a substance is.

Specific Heat Capacity

Is specific heat capacity defined as the amount of energy required to change the temperature of 1 kg of material by 1 °C?
Yes, that is the definition.
The specific heat capacity of water is 4180 J/(kg·°C). What is the amount of heat gained by 50 kg of water when heated from 30°C to 80°C?
10,450 kJ
The temperature of a lead fishing weight rises from 26°C to 38°C as it absorbs 11.3 J of heat. What is the specific heat if it weighs 7.4 g?
0.13 J/(g·°C)

Temperature Conversion

Convert -25°C to Kelvin (K):

248 K

Thermodynamics

Classify each change as exothermic or endothermic:

  • Wood burning in fire: Exothermic
  • Ice melting: Endothermic

Matter and Its Properties

Physical vs. Chemical Properties

Classify each property as physical or chemical:

  • The explosiveness of hydrogen gas: Chemical
  • The bronze color of copper: Physical
  • The shining appearance of silver: Physical
  • The ability of dry ice to change directly from solid to gas (sublimation): Physical

Classification of Matter

Classify each substance:

  • Mercury in a thermometer: Element (Pure Substance)
  • Air: Homogeneous Mixture
  • Noodle soup: Heterogeneous Mixture
  • Sugar: Compound (Pure Substance)