Science - Lesson 4

To break or form chemical bonds, a chemical change is required.

A chemical change changes the identity of the substance

What are mixtures?

A mixture is a combination of two or more substances that are combined physically but not chemically.

Pure Substances

A pure substance is a substance that has definite physical and chemical properties such as appearance, melting point, and reactivity. No matter the amount of a pure substance you have, it will always have the same properties. This is because pure substances are made up of one type of particle.

How are compounds classified?

By their pH As Organic or Inorganic By their role in the body

Biochemicals are divided into four categories:

Carbohydrates Lipids Proteins Nucleic Acids

Examples of Pure substances

Copper Water

How can elements be classified?

Differences in physical and chemical properties allow us to classify elements.

Mixtures can be separated by Physical changes

EX: don't like mushrooms on your pizza, you can pick them off Ex" a Salt and Salt water mixture would need to be separated by heating mixture until the water evaporates and the salt is left behind.

What are the 3 major classes of matter?

Elements Compounds Mixtures

Colloids mixture

Falls somewhere between suspensions and solutions. The particles in a colloid are spread throughout a liquid or gas but do not settle out quickly. EX: Milk or gelatin

Metalloids

Have some properties of both metals and non metals

How can mixtures classified?

Heterogeneous Homogeneous

What can you use to test whether a compound is an acid or base?

Litmus paper Blue litmus paper turns red in the presence of an acid. Red litmus paper turns blue in the presence of a base.

How can matter be classified?

Matter is made up of basic "ingredients" known as atoms.

Pure Substances cannot be formed or broken down by physical changes

Melting, freezing, cutting or smashing do NOT change the identity of pure substances.

Elements are broadly classified into three groups?

Metals Non Metals Metalloids

Mixtures are made up of more than one type of particle

Mixtures are NOT pure substances Mixtures contain more than one type of substance. Mixures do NOT have definite properties EX: sand and salt poured into a single beaker

Metals

Shiny, conduct heat and electricity well and can be shaped into thin sheets and wires. (Aluminum)

Heterogeneous mixtures

a mixture that does not have a uniform composition.

Lipids

are biochemicals that store excess energy in the body and make up cell membranes. Ex: fats, oils and waxes

Non-Metals

are not shiny and do not conduct heat or electricity well (such as charcoal)

Atoms

are the smallest unit of an element that maintains the properties of that element. Atoms can be combined in different ways to produce different substances.

Carbohydrates

are used as a source of energy and include sugars, starches and fiber.

Compounds can be classified

as acidic, basic or neutral by measuring a special value known as pH.

Mixture

contains a variety of elements and compounds that are not chemically combined with each other.

Base compounds

have a pH value greater than 7 EX: Baking soda Bases have a slippery feel and a bitter taste.

Acid compounds

have a pH value less than 7 Ex: Vinegar Acids have a sharp, sour taste

Neutral compounds

have a pH value of 7 Ex: Pure water and salt Water and salt are formed when an acid and a base react.

Periodic Table

is a useful tool that can help you to identify elements that have similar properties.

Compound

is made up of different kinds of atoms chemically combined. Compounds have different properties from the elements that make them up.

Element

is made up of one or more of the same kind of atom chemically combined

Organic compounds are made by

living things called biochemicals

Suspension mixture

mixtures in which the particles of a material are spread throughout a liquid or gas but are too large to stay mixed without being stirred or shaken.

Solution mixture

on substance is dissolved in another substance. Many solutions are liquids but can also be gases or solids EX: tea Air is a gaseous solution Alloys such as brass and steel solid solutions

Proteins

one of the most abundant types of compounds in your body. They regulate chemical activities of the body and build and repair body structures.

Organic

refers to compounds that contain carbon and hydrogen Found in most foods AND can be found in synthetic goods such as gasoline which contains organic compounds octane and heptane.

Nucleic acids

such as DNA and RNA contain genetic information and help the body build proteins.

Homogeneous mixtures

the substances in this mixture is evenly spread throughout. Ex: Sugar Water