Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Matter is anything that has mass and takes up space, composed of tiny particles called atoms.
An Element is a pure substance consisting of only one type of atom. It cannot be broken down into simpler substances by chemical means. Examples include Gold () and Oxygen ().
A Compound is a substance formed when two or more different elements are chemically bonded together in a fixed ratio. For example, Water () always contains two Hydrogen atoms for every one Oxygen atom.
A Mixture consists of two or more substances that are physically combined but not chemically bonded. They can be separated by physical methods like filtration or evaporation.
Homogeneous Mixtures (Solutions) have a uniform composition throughout, such as salt water ().
Heterogeneous Mixtures have a non-uniform composition where individual components are visible, such as a mixture of sand and iron filings.
The Law of Conservation of Mass states that mass is neither created nor destroyed during a chemical reaction. The total mass of the reactants must equal the total mass of the products: .
📐Formulae
💡Examples
Problem 1:
Determine the number of atoms of each element present in a molecule of Sulfuric Acid, which has the chemical formula .
Solution:
There are atoms of Hydrogen (), atom of Sulfur (), and atoms of Oxygen ().
Explanation:
In the formula , the subscripts indicate the number of atoms for the preceding element. No subscript after '' implies a value of . Total atoms = .
Problem 2:
Identify if the following is an element, compound, or mixture: A bowl of cereal with milk.
Solution:
Heterogeneous Mixture
Explanation:
The cereal and milk are physically combined but not chemically bonded. You can distinguish the different parts (the cereal pieces and the liquid milk), and their ratio can vary, making it a heterogeneous mixture.
Problem 3:
If of Magnesium () reacts completely with of Oxygen () to form Magnesium Oxide (), what is the mass of the product formed?
Solution:
of
Explanation:
According to the Law of Conservation of Mass, the mass of the reactants must equal the mass of the products. Therefore: .