Evidence of a Chemical Change

Front

Chemical Change Noun

---

[kem-i-kuhl cheynj]

Back

Chemical Change

---

A process where one or more new substances are formed with different properties, and which is not easily reversed.

---

Example: When hydrochloric acid is added to iron powder, a chemical change occurs, producing gas bubbles as evidence that a new substance has been formed.

Front

Chemical Reaction Noun

---

[kem-i-kuhl ree-ak-shun]

Back

Chemical Reaction

---

A process that involves the rearrangement of molecular or ionic structures, resulting in the formation of new substances.

---

Example: Methane (CH₄) and oxygen (O₂) molecules rearrange their atoms to form new substances, carbon dioxide (CO₂) and water (H₂O), which is a chemical reaction.

Front

Reactants Noun

---

[ree-ak-tuhnts]

Back

Reactants

---

The starting substances in a chemical reaction that are consumed during the process to form new substances called products.

---

Example: The image labels the starting substances in a chemical reaction, methane (CH4) and oxygen (O2), as the 'Reactants' before they are transformed into new products.

Front

Products Noun

---

[prod-uhkts]

Back

Products

---

The new substances that are formed as the result of a chemical reaction between the initial starting materials.

---

Example: In a chemical reaction, the starting materials (reactants) rearrange to form new substances, which are called the products (carbon dioxide and water).

Front

Precipitate Noun

---

[pri-sip-i-teyt]

Back

Precipitate

---

An insoluble solid that emerges from a liquid solution during a chemical reaction, often settling at the bottom.

---

Example: This image shows that when some solutions are mixed, a new solid substance, called a precipitate, can form. This is evidence of a chemical change.

Front

Physical Change Noun

---

[fiz-i-kuhl cheynj]

Back

Physical Change

---

A change affecting the form of a substance, such as its state or shape, but not its chemical composition.

---

Example: This diagram shows how a substance can change its state (solid, liquid, gas) through processes like melting or freezing without changing its chemical identity.