Question

Identify each of the following as a physical or chemical property of a candle: a. The candle is \(20 \mathrm{~cm}\) high with a diameter of \(3 \mathrm{~cm}\). b. The candle burns. c. The wax of the candle softens on a hot day. d. The candle is blue.

Short answer

a. Physical, b. Chemical, c. Physical, d. Physical

Step-by-step solution

- Determine the property type for part (a)

Part (a) states that the candle is 20 cm high with a diameter of 3 cm. These are measurements of the candle's size, which are characteristics that do not change the substance itself. Therefore, this is a physical property.

- Determine the property type for part (b)

Part (b) states that the candle burns. Burning involves a chemical reaction where the candle's wax reacts with oxygen to produce new substances (carbon dioxide, water, and other compounds). Hence, this is a chemical property.

- Determine the property type for part (c)

Part (c) describes the wax of the candle softening on a hot day. Softening due to heat is a change in the state of matter from solid to a more pliable form without altering the chemical composition. This is a physical property.

- Determine the property type for part (d)

Part (d) states that the candle is blue. Color is an observable characteristic that does not involve a change in the substance's chemical makeup. Thus, this is a physical property.

Key concepts

chemical properties of substances

Chemical properties of a substance describe how it interacts with other substances to form new compounds. These properties involve a transformation that changes the substance's chemical structure. When something burns, rusts, tarnishes, or decomposes, these actions are chemical reactions.

For example, when the candle burns (part b in the exercise), it doesn't just melt. It reacts with oxygen in the air to produce gases like carbon dioxide and water vapor. This means the original candle wax turns into completely new substances.

Chemical properties include:

• Reactivity with other chemicals
• Flammability
• Acidity or basicity
• Oxidation states

Understanding chemical properties is essential for predicting how substances will behave in different environments or conditions.

physical properties of substances

Physical properties can be observed and measured without changing the substance's chemical identity. These properties include characteristics such as color, size, density, and state (solid, liquid, gas).

In the exercise, parts a, c, and d highlight physical properties. The height and diameter of the candle (part a) and the fact that the candle is blue (part d) are attributes that don't change the chemical makeup of the candle. When the wax softens on a hot day (part c), it still remains wax—only its state or form changes.

Key physical properties include:

• Color
• Density
• Conductivity
• Melting and boiling points

Recognizing physical properties helps us classify and compare different substances without altering their chemical composition.

state of matter changes

The state of matter change refers to the transition between solid, liquid, and gas. These changes occur due to variations in temperature or pressure but do not involve making or breaking chemical bonds.

In the exercise, when the candle wax softens on a hot day (part c), it undergoes a physical change from solid to a more malleable state. This is a perfect example of a state change caused by heat. The wax remains chemically the same even though its appearance and texture might change.

Common state changes include:

• Melting (solid to liquid)
• Freezing (liquid to solid)
• Evaporation (liquid to gas)
• Condensation (gas to liquid)

Understanding these changes is a fundamental part of physical science and helps explain everyday phenomena, like why ice melts in your drink or how water vapor forms clouds.