Pure substances and Mixtures Unit 1 Lesson 4

How can compounds be classified?

Compounds can be classified as acidic, basic, or neutral by measuring a special value known as pH. • Organic refers to compounds that contain carbon and hydrogen. • Compounds can be organic or inorganic. • Organic compounds made by living things are called biochemicals.

Substances

elements, compounds, and mixtures.

heterogeneous

A mixture is one that does not have a uniform composition.

What do elements, compounds, and mixtures have in common?​

Atoms

How can elements be classified?

Elements are broadly classified as metals, nonmetals, or metalloids. Each element has a place in an arrangement called the periodic table of the elements.

What are two types of heterogeneous mixtures?

Suspensions and colloids.

Chemical Chnges and Bonds

The chemical bonds that hold atoms together cannot be broken easily. To break or form chemical bonds, a chemical change is required. Individual atoms cannot be broken down into smaller parts by normal physical or chemical changes.​

What happens when a pure substance undergoes a chemical change?​

The chemical bonds that hold the atoms together are broken and a new substance is formed.

Pure substances

a substance with definite physical and chemical properties. Pure substances are made up of just one type of particle. Physical changes such as melting, freezing, cutting, or smashing do not change the identity of pure substances. When a pure substance undergoes a chemical change, it is no longer that same substance. Elements and Compounds are pure substances.

Colloids

a third type of mixture that falls somewhere between suspensions and solutions. colloid particles are small and do not settle out quickly, examples are milk and gelatin and look homogenous but we consider them to be heterogeneous.​

Mixture

contains a variety of elements and compounds that are not chemically combined with each other. Mixtures are not pure substances. Mixtures do not have a defined property because they do not have a defined chemical makeup. Mixtures can be separated by physical changes, although some mixtures are difficult to separate. Magnets, centrifuges, filters, and other materials can be used to separate mixtures.

Biochemicals

divided into four categories: carbohydrates, lipids, proteins, and nucleic acids.

Acids

have a pH value below 7. Acids tend to be sharp and sour an example is vinegar.

Bases

have pH values greater than 7. Bases have a slippery feel and a bitter taste.

Metalliods

have some properties of both metals and nonmetals. the metalloids lie between the metals and nonmetals in the periodic table.

Solution

homogenous mixture, one substance is dissolved into another, like tea.

Compound

made up of different kinds of atoms chemically combined. Compounds have different properties from the elements that make them up. Example: water because it is made up of two different kinds of atoms.

Element

made up of one or more of the same kind of atom chemically combined. Example: copper because made up off one atom.

homogenous

mixture has a uniform composition, an example of a homogenous is if you add sugar to a cup of water, the sugar dissolves. Each part of the sugar-water mixture has the same sweet taste.

Nonmetals

not shiny and do not conduct heat or electricity well. Nonmetals are at the right and are often shaded with a color different from that of the metals.

Neutral Compounds

pure water and table salt, have a pH value of 7. Water are salt form when acids and bases react.

Metals

shiny, conduct heat and electricity well, and can be shaped into thin sheets and wires. Metals start at the left and make up most of the elements in the periodic table.

Suspension

spread throughout a liquid or gas but are too large to stay mixed without being stirred or shaken. A suspension is a heterogenous mixture. Particles settle in suspensions.

Atoms

the smallest unit of an element that maintains the properties of that element

Litmus paper

used to test a ph level. Blue litmus paper turns red in the presence of an acid. Red litmus paper turns blue in the presence of a base.