10 Questions
Which of the following is an example of a physical change?
Melting of ice
What is the chemical equation for the reaction of hydrogen gas with oxygen gas to produce water?
2H$_2$ + O$_2$ → 2H$_2$O
What is the word equation for the reaction of sodium with iodine to produce sodium iodide?
Sodium + Iodine → Sodium Iodide
Identify the type of reaction that occurs when hydrogen gas reacts with iodine gas to produce hydrogen iodide?
Synthesis
To balance a chemical equation, what should be done to the reactant side of the equation?
Add or remove coefficients
What is the difference between a physical change and a chemical change?
A physical change is a change in which the substance changes form but not composition, whereas a chemical change is a change in which the substance changes composition.
Write the word equation for the reaction of hydrogen gas with oxygen gas to produce water.
Hydrogen + Oxygen → Water
What is the chemical formula for sodium iodide?
NaI
What is the purpose of balancing a chemical equation?
To ensure that the number of atoms of each element is the same on both the reactant and product sides of the equation.
Write the chemical equation for the reaction of sodium with iodine to produce sodium iodide.
2Na + I₂ → 2NaI
Study Notes
Chemical Equations and Reactions
- A chemical equation is a written representation of a chemical reaction, using chemical formulas and symbols.
- Chemical reactions involve a change in the chemical composition of substances, resulting in new substances with different properties.
- Chemical reactions can be represented in two ways: word equations and chemical equations.
Word Equations
- A word equation is a written representation of a chemical reaction, using words to describe the reactants and products.
- Example: Hydrogen gas reacts with oxygen gas to form water.
Chemical Equations
- A chemical equation is a written representation of a chemical reaction, using chemical formulas and symbols.
- Chemical equations follow the law of conservation of mass, which states that matter cannot be created or destroyed during a chemical reaction.
- Chemical equations use the following symbols: -, →, ( ), and numbers in front of formulas (coefficients) to indicate the number of molecules of each reactant or product.
Physical and Chemical Changes
- A physical change is a change in the state or appearance of a substance, but not its chemical composition.
- Examples of physical changes: melting, boiling, freezing, condensation.
- A chemical change is a change in the chemical composition of a substance, resulting in new substances with different properties.
- Examples of chemical changes: burning, rusting, decomposition.
Balancing Chemical Equations
- A balanced chemical equation has the same number of atoms of each element on both the reactant and product sides.
- To balance a chemical equation, coefficients are added in front of formulas to indicate the number of molecules of each reactant or product.
- Example: 2H2 + O2 → 2H2O
Simple Ions and Atoms
- Common ions and atoms used in chemical equations: hydrogen (H), oxygen (O), sodium (Na), iodine (I).
- These ions and atoms are used to represent simple chemical reactions and equations.
Test your knowledge on word and chemical equations, physical and chemical changes, and balancing chemical equations with simple ions and atoms like hydrogen, oxygen, sodium, and iodine in this quiz designed for 8th-grade students.
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