Compounds and Mixtures

Compounds and Mixtures Unit 15

Compounds • compound: substance made up of two or more elements chemically combined • most of the matter making up the earth is composed of compounds • ex. water is a compound made up of the elements hydrogen and oxygen sugar is a compound made up of the elements carbon, hydrogen, and oxygen

Compounds • the properties of a compound are very different from the properties of the elements that form it • example: • sodium is a metal that burns easily • chlorine is a poisonous gas • they combine to form sodium chloride or table salt

Compounds • compounds are formed as the result of a chemical change • the elements combine to form a new substance with new properties • a chemical change is also required to break a compound down

Molecules • molecule: smallest part of a substance that has all the properties of the substance • a substance is any element or compound

Molecules • some elements occur as diatomic molecules • a diatomic molecule has two atoms of the same element joined together • most gases form diatomic molecules • ex. oxygen, hydrogen

Molecules • all molecules of a particular substance contain the same combination of atoms • ex. any molecule of water contains two atoms of hydrogen and one atom of oxygen

Mixtures • mixture: two or more substances that have been mixed together but not chemically combined

Mixtures • the substances in a mixture keep their own properties • the substances in a mixture can be present in any amount • a mixture can be separated by physical means

Mixtures • salt water is an example of a mixture • the salt and the water can be separated by the process of evaporation • another method that can be used to separate mixtures is filtering

Compounds & Mixtures

Ionic Bonds • neutral atoms have equal numbers of protons and electrons • when an atom gains or loses electrons, it becomes an ion • ion: an atom with an electric charge

Ionic Bonds • if a neutral atom gains electrons, it becomes a negative ion • if a neutral atom loses electrons, it becomes a positive ion

Ionic Bonds • ionic bond: bond formed between atoms that have gained and lost electrons • these two atoms have opposite electrical charges and are attracted to each other

Crystals • a crystal is a solid that contains ions arranged in a regular pattern called a crystal lattice • crystal lattice: ions arranged in a regular pattern • there are six basic types of crystal lattices

Covalent Bonds • most atoms do not have a complete outer energy level of electrons • atoms complete their outer energy levels by gaining, losing, or sharing electrons • ionic bonds are formed from the gaining or losing of electrons

Covalent Bonds • covalent bond: bond formed when atoms share electrons • both ionic bonds and covalent bonds result in atoms with complete outer energy levels

Covalent Bonds • atoms joined by covalent bonds remain electrically neutral

Ionic and Covalent Compounds

Organic Compounds • organic compounds contain the element carbon • organic compound: compound containing carbon • carbon dioxide is an inorganic compound that contains carbon

Organic Compounds • organic chemistry: study of organic compounds • about 95% of all known substances are organic compounds

Organic Compounds • carbon atoms have four electrons in their outer energy levels • carbon atoms can join other atoms in single, double, or triple covalent bonds • these types of bonds allow many different organic compounds to be formed

Organic Compounds • structural formula: molecular model of an organic compound • this helps because carbon atoms can form many different structures

Compounds needed by Living Things • all living things need certain organic compounds to stay alive

Compounds needed by Living Things • carbohydrates: sugars and starches • carbohydrates are an organism’s main source of energy • carbohydrates are made up of carbon, hydrogen, and oxygen • good sources of carbohydrates include: cereals, grains, vegetables, and fruits

Compounds needed by Living Things • lipids: fats and oils • fats and oils are lipids that store energy for an organism to use at a later time • good sources of lipids include butter, meat, cheese, and nuts

Compounds needed by Living Things • cholesterol is a lipid found in animal fat • too much cholesterol may form fatty deposits on the walls of blood vessels • this may interfere with the flow of blood throughout the body

Compounds needed by Living Things • proteins: compounds needed to build and repair the body • amino acids: building blocks of protein • amino acids contain carbon, hydrogen, oxygen, and nitrogen • amino acids join together to form long chains of proteins

Compounds needed by Living Things • milk, fish, eggs, and beans are good sources of protein • foods such as fish and beans provide the body with the amino acids it needs

Compounds and Mixtures