Quiz 1

Matter is defined as anything that has mass and takes up space.
Atoms are the fundamental building blocks of matter.
All substances possess characteristic properties that distinguish them from others.

Matter: Anything that has mass and occupies volume.
Atom: The smallest unit of an element that maintains its chemical identity.
Element: A pure substance that cannot be broken down into simpler substances. It consists of only one type of atom.
Compound: A substance formed from two or more elements that are chemically bonded together.
Mixture: A combination of two or more substances where each retains its individual properties.
Homogeneous Mixture: A mixture with uniform composition throughout.
Heterogeneous Mixture: A mixture where the individual substances are not uniformly distributed.
Physical Properties: Characteristics that can be observed or measured without changing the substance's identity.
Chemical Properties: Characteristics that describe a substance's ability to undergo changes that transform it into different substances.
Intensive Property: A property that does not depend on the amount of matter present.
Extensive Property: A property that depends on the amount of matter present.

Matter exists in many forms and has common properties:
- Volume: The amount of three-dimensional space an object occupies. It is a characteristic of all matter.
- Mass: A measure of the amount of matter in an object, determined using a balance.
General Definition: Matter is anything that has mass and takes up space.

Atoms: Considered the basic units of matter. They combine to form molecules.
Molecules: The smallest unit of a compound that retains all the properties of that compound. For instance, a water molecule (H₂O) consists of two hydrogen atoms bonded to one oxygen atom.

Properties help distinguish between substances and can include:
- Melting Point: The temperature at which a solid becomes a liquid.
- Boiling Point: The temperature at which a liquid turns to vapor.
- Density: Mass per unit volume (e.g., Water's density is approx. 1000 kg/m³ at 4°C).
Properties can be classified into:
- Intensive Properties: Such as boiling and melting points that remain consistent regardless of the sample size. For example, iron melts at 1538°C, whether in 20g or 20kg.
- Extensive Properties: Such as mass and volume, which depend on the amount of matter present.

Physical Property: Can be observed without changing the identity of the substance (e.g., boiling point, melting point).
Physical Change: Occurs when a substance undergoes a change that does not affect its chemical identity (e.g., melting, boiling).
States of Matter:
- Solid: Definite shape and volume; particles are closely packed and vibrate in place.
- Liquid: Definite volume but conforms to the shape of its container; particles are close but can move past one another.
- Gas: Neither definite shape nor volume; particles move rapidly and are far apart.
- Plasma: A state where electrons are lost from atoms, leading to charged particles.
Changes between these states (e.g., melting and boiling) are classified as physical changes because they do not alter the substance's chemical identity.

Chemical Property: Relates to the ability of a substance to undergo changes that transform it into different substances (e.g., combustion, oxidation).
Chemical Change (Reaction): A process where one or more substances are converted into different substances with distinct properties (e.g., burning charcoal produces carbon dioxide gas).
Reactants: The initial substances that undergo a chemical reaction;
Products: The new substances formed as a result of a chemical reaction.
Example: The burning of charcoal can be represented as:
ext{C} + ext{O}2 ightarrow ext{CO}2
The law of conservation of mass states that the total amount of matter remains constant during a reaction.

Changes in matter, whether physical or chemical, involve changes in energy (e.g., heat, light).
Conservation of Energy: The total amount of energy remains the same regardless of the changes; energy is not created or destroyed but changes form.
The boundaries between physical and chemical changes can sometimes be ambiguous—dissolving sugar in water may be viewed as a physical change, while dissolving table salt might be considered a chemical change.

Pure Substance: Has a fixed composition and is homogeneous. Can be classified as:
- Element: Cannot be broken down into simpler substances.
- Compound: Can be decomposed into simpler substances (e.g., water into hydrogen and oxygen).
Mixture: A physical combination of two or more substances that retain their individual properties. Can be classified into:
- Homogeneous Mixture: Uniform composition (e.g., sugar dissolved in water).
- Heterogeneous Mixture: Non-uniform composition (e.g., salad dressing).
Mixtures can often be separated by physical means, such as filtration or centrifugation.

Laboratory chemicals are generally treated as if they are pure, but they contain impurities.
Different grades of chemical purity are denoted, including those specified by the American Chemical Society (ACS), United States Pharmacopoeia (USP), and others. These grades indicate the level of purity and presence of impurities, which can significantly affect experimental results.

Understanding the properties of matter and the distinction between physical and chemical changes is crucial for any study in chemistry. Definitions and classification of matter, alongside its properties, form the fundamental knowledge that underpins chemical sciences.