Review Chapter-2

Atoms An atom is made up of protons, electrons and neutrons.protonselectronsneutrons The mass of an atom is found in the nucleus, since the neutrons and protons each weigh considerably more than the electrons orbiting it. The electrons can be removed or shared with other atoms without having a great impact on the mass of a chemical, and therefore it is through movement of electrons that chemical reactions take place. Of course, electrons could just happily spin off and completely leave the atom - it's not like they're part of the nucleus. However, the positive charge of the protons attracts the negatively chargedpositivechargenegatively electrons to it (since positive and negative charges attract each other). This keeps them spinning around the nucleus

Elements Consists of only one kind of atom Cannot be broken down into a simpler type of matter

Molecule A molecule consists of two or more atoms of the same element, or different elements, that are chemically bound together

Compounds A substance formed by bonding two or more elements in definite proportions. Can be broken down into a simpler elements

Mixtures Consists of two or more different elements and/or compounds physically intermingled Can be separated into its components

Types of Bonding Covalent – to share Ionic – to transfer

Water Neutral – 10 protons/10 electrons Polar –Oxygen (-) charge –Hydrogen (+) charge Covalent Bond

Water A water molecule can form (H+) hydrogen ion and a (OH-) hydroxide ion. If H+ = OH-, water If H+ > OH-, acid If OH- > H+, base

Acids acids produce H+ ions acids are proton donors

Properties of acids taste sour (don't taste them!)... react with bases to form salts and water

Examples: Acids citric acid (from certain fruits and veggies, notably citrus fruits) ascorbic acid (vitamin C, as from certain fruits) vinegar carbonic acid (for carbonation of soft drinks) lactic acid (in buttermilk)

Bases bases produce OH- ions bases are proton acceptors

Properties of bases taste bitter (don't taste them!) feel slippery or soapy react with acids to form salts and water

Examples: Bases detergents soap household ammonia

Cohesion/Adhesion Cohesion: (attraction btw molecules of same substances) –Water is attracted to other water. This is called cohesion. Adhesion: (attraction btw molecules of different substances) –Water can also be attracted to other materials. This is called adhesion.

Enzymes