Chemical and Physical Changes Quiz

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Questions and Answers

What distinguishes a chemical change from a physical change?

Chemical changes are reversible.

Chemical changes involve breaking or forming bonds. (correct)

Physical changes create new substances.

Physical changes result in a color change.

Which of the following is a physical change?

Burning wood.

Mixing vinegar and baking soda.

Rust forming on iron.

Dissolving sugar in water. (correct)

Which of the following indicators is most likely to signify a chemical change?

The color of the substance stays the same.

The substance remains unchanged.

A solid forms from mixing two liquids. (correct)

The substance becomes colder.

What is the correct name for the compound formed when sodium and chlorine react?

Sodium Chloride Signup and view all the answers

What do the reactants represent in a chemical reaction?

Substances present at the beginning of the reaction. Signup and view all the answers

How should the state of matter be indicated in a chemical equation?

By adding the state symbols next to each reactant and product. Signup and view all the answers

Which of the following is true regarding the conservation of mass in a chemical reaction?

Mass remains constant throughout the reaction. Signup and view all the answers

What is a word equation?

A description of a chemical reaction using only names of reactants and products. Signup and view all the answers

What does the conservation of mass state about reactants and products in a chemical reaction?

The total mass of the reactants is equal to the total mass of the products. Signup and view all the answers

Which of the following scenarios would violate the principle of conservation of mass?

A gas escapes from an open container during a reaction. Signup and view all the answers

What role do coefficients play in balancing a chemical equation?

They represent the number of molecules of each reactant and product. Signup and view all the answers

In the reaction C + Cl2 → CCl4, how can you balance the equation correctly?

By adding a coefficient of 2 to Cl2. Signup and view all the answers

Why can subscripts not be altered when balancing chemical equations?

Changing subscripts alters the identity of the compounds involved. Signup and view all the answers

If 2.5g of Copper reacts with 3g of oxygen and produces 5.5g of copper sulfide, what can you infer?

Mass is conserved during the reaction. Signup and view all the answers

What happens when experiments require materials to be dissolved or evaporated?

They can potentially result in apparent mass loss. Signup and view all the answers

Which statement describes the concept of balancing a chemical equation?

It involves changing the coefficients to equalize the number of atoms. Signup and view all the answers

Study Notes

Physical Changes

Physical changes alter appearance but do not form or break chemical bonds.
A new substance is not created.
Examples include melting ice, mixing salt and water, and crumpling paper.

Chemical Changes

Chemical changes create new substances by forming or breaking chemical bonds.
These changes are irreversible.
Indicators of chemical change: fire, temperature changes, explosions, odors, color changes, bubbling/fizzing.

Three Golden Rules of Chemical Reactions

Chemical reactions are typically irreversible.
They create new substances.
They involve an energy change.

Naming Compounds

Rule 1: When two elements combine (e.g., metal + non-metal), the ending is usually "-ide" (e.g., Sodium Chloride).
Rule 2: When three or more elements combine, if one is oxygen, the ending is "-ate" (e.g., Copper Sulphate).
The metal's name comes first, followed by the non-metal with the changed ending.

Metals and Non-metals with Oxygen

When metals combine with oxygen, the compound is named with the metal first, followed by the nonmetal ending changed to "-ate".
Example: Copper Sulphate

Reactants and Products

Reactants: The substances at the start of a reaction.
Products: The new substances formed during the reaction.
Atoms in reactants are rearranged to form products.

Word Equations

Word equations describe reactions using names of substances, not chemical formulas or symbols.
An example is: Copper + Oxygen → Copper Oxide.
The arrow indicates the direction of the reaction.

State Symbols

State symbols indicate the physical state of reactants and products.
Symbols:
- Solid (s)
- Liquid (l)
- Gas (g)
- Aqueous solution (aq)
Example: Hydrogen (g) + oxygen (g) → water (l)

Conservation of Mass

Mass remains constant in a chemical reaction: reactants' mass equals products' mass.
Atoms are rearranged, not created or destroyed.
Example: 2.5 g copper + 3 g oxygen → 5.5 g copper oxide

Balancing Chemical Equations

No atoms are created or destroyed during a chemical reaction.
Balancing involves adjusting coefficients (numbers in front of formulas) to make the number of each atom the same on both sides of the equation.
Subscripts (small numbers below elements) cannot be changed.
Example: C + 2Cl₂ → CCl₄ (balanced)

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Description

Test your understanding of chemical and physical changes with this quiz. Learn about the properties of substances, how chemical reactions differ from physical changes, and the rules for naming compounds. Assess your knowledge of key concepts in chemistry!