2B2 Chemical and Physical Properties Flashcards
Differentiate the chemical and physical properties of matter, changes of matter, and the law of conservation of matter.
Define:
physical properties
Properties that describe observable characteristics without changing composition.
They include color, texture, shape, hardness, malleability, weight, and mass.
Define:
chemical properties
Properties that describe how a substance interacts with others to form new substances and require a reaction that changes composition.
They include reactivity, flammability, pH, corrosion, and conductivity.
What is reactivity?
A chemical property that describes how readily a substance undergoes chemical reactions.
For example, sodium reacts violently with water.
Why is malleability a physical property?
It describes a substance’s ability to deform under pressure without breaking and does not involve a chemical transformation.
It is a physical property of metals like gold and aluminum.
What are the two types of physical properties of matter?
- Intensive properties
- Extensive properties
What is the difference between intensive and extensive properties?
- Intensive properties: They do not change with quantity.
- Extensive properties: They depend on quantity.
Intensive properties include density, color, molecular weight, and temperature.
Extensive properties include mass, number of moles, and volume.
Why is temperature considered an intensive property?
It does not depend on the amount of matter in the sample.
A glass of water and an ocean can have the same temperature despite their difference in size.
True or False:
Freezing water is an intensive change.
True
The freezing point of water remains constant regardless of the sample size.
Why is mass an extensive property?
Mass depends on the amount of matter in a sample.
Larger samples have greater mass and viceversa.
What distinguishes physical changes from chemical changes?
- Physical changes: They do not alter the substance’s chemical composition.
- Chemical changes: They alter the substances chemical composition.
Physical changes include melting and freezing.
Chemical changes include rusting and burning.
Why is boiling water a physical change?
It changes the state of water from liquid to gas without altering the chemical composition.
The molecular structure (H2O) remains the same before and after boiling.
Why is boiling point a reliable intensive property?
It remains constant for a pure substance under the same conditions.
Boiling point helps identify substances due to its consistency.
Define:
a specific property
A property described as a ratio of mass and another property of matter.
It’s an intensive property that is on a ‘per unit mass’ basis.
Examples:
- Specific volume (v): ν = V / m where V is the volume and m is the mass.
- Specific heat (c): c = Q / (mΔT) where m is the mass and ΔT is the change in temperature.
What happens during a chemical change?
- There is rearrangement of atoms.
- Bonds are broken and new ones formed.
- New substances with new properties are formed.
Examples:
- Rusting iron: A new substance (iron oxide) is formed through the reaction of iron with oxygen and water.
- Burning wood: Wood is converted into ash, carbon dioxide, and water vapor.
True or False:
Melting ice is a chemical change.
False
Melting ice is a physical change, as it only alters the state from solid to liquid.
During melting, substances remain the same at the molecular level.
Why is burning a candle considered a chemical change?
It produces new substances, such as carbon dioxide and water vapor.
The wax undergoes combustion, changing its chemical composition.
What is a phase change?
The transition between states of matter (solid, liquid, gas).
Examples include melting, freezing, and vaporization.
Define:
the triple point
The temperature and pressure at which solid, liquid, and gas phases of a particular substance coexist in equilibrium.
It occurs under specific temperature and pressure conditions.
True or False:
Dissolving sugar in water is a chemical change.
False
Dissolving sugar is a physical change because the sugar can be recovered through evaporation.
Why is tearing paper considered a physical change?
Tearing only changes the shape and size of the paper, not its composition.
The chemical structure of cellulose in the teared paper remains unchanged.
What is the role of intensive and extensive properties in science?
They help:
- Categorize matter.
- Analyze the behavior of matter.
List four examples of chemical reactions.
- Combustion
- Synthesis
- Decomposition
- Replacement
Replacement reactions can be single or double.
In chemical reactions, what happens to atoms?
Atoms are broken apart, rearranged, or put together in new ways.
The mass of atoms before and after a reaction remains equal.
State the law of conservation of matter.
Matter can neither be created nor destroyed.
This law is essential in understanding chemical reactions and ensures the total mass remains constant before and after physical and chemical changes.
Who is credited with the modern form of the law of conservation of matter?
Antoine Lavoisier
Lavoisier’s work in the late 18th century helped establish this scientific law.
What theory was replaced by the law of conservation of matter?
The phlogiston theory.
The phlogiston theory incorrectly suggested that mass was destroyed during combustion.
Define:
matter
in the context of the law of conservation of matter.
Physical material that occupies space and possesses mass.
This definition is crucial for understanding the implications of the law.
What significant invention in the 17th century helped prove the conservation of matter?
The vacuum pump.
It allowed scientists to weigh gases and demonstrate that mass is transformed during combustion.
What are the modern exceptions to the law of conservation of matter?
Nuclear processes including fusion, fission, and matter-antimatter reactions.
In these processes, mass can be converted into energy and vice versa.
What is the significance of the law of conservation of mass in chemical reactions?
It allows for chemical reactions to be fully understood and quantified.
This understanding is vital for predicting the mass of products in reactions.
How does the combustion of methane illustrate the law of conservation of mass?
The balanced equation shows that mass is conserved during the reaction.
The equation CH4 + 2O2 → CO2 + 2H2O accurately represents the reaction.
What happens to the mass of gasoline after it is burned?
It is converted into carbon dioxide and water vapor.
This illustrates the law of conservation of matter in combustion reactions.
What happens to the mass of rusted metal compared to its original form?
It can have more mass due to the combination with oxygen.
Rust (iron oxide) contains extra oxygen atoms.
