Question

State whether each of the following is a physical or a chemical property: (a) Manganese bubbles in acid. (b) Silver is malleable. (c) Calcium turns dark in air. (d) Carbon grinds to a powder.

Short answer

(a) Chemical; (b) Physical; (c) Chemical; (d) Physical.

Step-by-step solution

Define Physical and Chemical Properties

A physical property is an attribute of a substance that can be observed or measured without changing its composition, such as color, melting point, or electrical conductivity. A chemical property involves the ability of a substance to undergo a specific chemical change.

Evaluate Manganese Bubbles in Acid

When manganese bubbles in acid, this interaction indicates a chemical reaction between manganese and the acid, likely producing gas as a product. Therefore, this is a chemical property.

Evaluate Silver is Malleable

Malleability, the ability of a material to be deformed under compressive stress (such as hammering or rolling), is a physical property. It does not involve a chemical change in the composition of silver.

Evaluate Calcium Turns Dark in Air

When calcium turns dark in air, it interacts chemically with oxygen or other substances in the air, often forming a compound like calcium oxide. This is a chemical reaction, indicating a chemical property.

Evaluate Carbon Grinds to a Powder

Grinding carbon into a powder involves a physical change – changing the size and form of the material without altering the chemical structure of carbon. This is a physical property.

Key concepts

Chemical Reaction

When you think of a chemical reaction, imagine a process where substances interact and undergo a transformation to make something new. In a chemical reaction, the original substances, known as reactants, change into different substances called products. These reactions can often be observed through various signals such as:

• Formation of gas (like bubbles in a liquid)
• Color change
• Temperature change

For example, when manganese bubbles in acid, it's not just fizzing for fun. It's participating in a chemical reaction where it might be producing a gas as a result of interacting with the acid. Thus, this bubbling indicates a chemical property.

Physical Change

Physical changes are like transformations that only affect the form or appearance of a substance but not the kind of substance it is. Think of it as a makeover – the outside might change, but the inside stays the same. During a physical change:

• Substances may change state (like ice melting into water)
• The size or shape of the material may be altered
• No new substances are formed

When carbon is ground into a powder, it undergoes a physical change. The particles become smaller, but it's still carbon. There are no new materials created, which makes it a physical property rather than a chemical one.

Malleability

Malleability is a fascinating physical property of metals. It describes how a material can be reshaped without breaking. Imagine a piece of metal being hammered or rolled into thin sheets. If it can handle that kind of stress without cracking – congratulations, it's malleable! Malleability is useful for many industrial applications where flexibility in shape is crucial. For example, silver is known for its malleability, allowing it to be crafted into intricate jewelry or components without altering its chemical makeup.

Substance Composition

The composition of a substance refers to the types of atoms it contains and their arrangement. This composition is like a molecular recipe that defines what the substance is. When evaluating whether a property is physical or chemical, consider whether the composition changes:

• In physical changes, the composition remains the same.
• In chemical changes, the composition changes leading to new substances.

For example, when calcium turns dark in air, it interacts with oxygen to form calcium oxide. This is a chemical change because the original composition of calcium changes, showcasing a chemical property.