Ch. 2 CHEMISTRY. Matter: has mass and takes up space Mass: quantity of matter an object has.
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Transcript of Ch. 2 CHEMISTRY. Matter: has mass and takes up space Mass: quantity of matter an object has.
Ch. 2
CHEMISTRY
Matter: has mass and takes up space
Mass: quantity of matter an object has.
Elements: pure substances that can not be broken down. Each has its own chemical symbol. We find elements arranged on the periodic table of elements.
*90% of all living things contain the elements O, C, H, and N.
Atoms: Simplest particle of an element.
• Molecules: simplest part of a substance
Atoms:– Nucleus: core of atom
• Proton: positive electrical charge• Neutron: no charge
*Atomic Number: number of protons
electron
neutron
proton
• Electrons: negative charge particles that orbit in shells around nucleus.
– Electrons are the same number as protons.
• Compound: 2 or more elements combined together.
• Ex: Water = H2O
–The subscript shows the number of atoms of each element. (2= 2 hydrogens)
• Chemical Reaction: atoms become rearrange, and new bonds form. A new substance is made.
Bonds: energy that holds compounds together
• Covalent bonds are: 2 atoms that share 1 or more pairs of electrons. Usually between non metals– Ex: water
• Ionic: formed by electrical attraction between . No actual sharing takes place. Usually between metals. – Ex: Salt = NaCl
Energy• Energy is the ability to do work or cause
change.
• State of matter: are solid, liquid and gas.
– Reactant: is involved in the chemical reaction.– Product: is the product that is formed by the
reaction.
• Energy for our bodies are provided mainly by sugars from the foods we eat. These sugars are broken down by chemical reactions that produce the energy.
• Exergonic energy: is the release of energy.
• Endergonic energy: absorption of the energy.
• Catalysts: reduce the energy needed for the reaction to occur.– Enzymes: catalysts that are used in living
things
• There is a constant flow of energy in all living things. Most reactions deal with
movement of electrons.
• Many reactions involve a transfer of electrons called Oxidation-Reduction, or Redox reactions.
– Oxidation is the loss of electrons– Reduction is the gain of electrons
• Most systems in anything living involve water, or some combination of substances dissolved in water.
• Solutions: 1 or more substances dissolved in another substance.
– Solute: dissolved in solution. In smaller amount
– Solvent: substance in which solute is dissolved
– Concentrated: amount of solute in the solution
– Saturated: no more solute can be dissolved.
* Aqueous solutions: water is the solvent
• Mixture: 2 or more substances that have variable composition.
– Homogeneous: the same through out.
ex: milk– Heterogeneous: different through out.
» Ex: rocky road ice cream
• Dissociation is the breaking apart of the water molecule into 2 ions of opposite charge.– Acids= have a greater number of hydronium (H)
ions. 0-7 on pH scale– Base (alkali) have a greater number of hydroxide
ions (OH) 7-14 on pH scale
• pH is the way of measuring H or OH ions. It stands for Potential Hydrogen
– Buffers are substances use to neutralize
• Physical properties and changes describe what is observed by the senses and the changes in appearance only. The substance remains the same.– Ex: color, shape, mass, density
• Chemical Properties and Changes describe how a substance reacts with other substances and the new substances that are formed.– Ex. Rust, baking