• Compound is a substance formed by the chemical combination of two or more elements. – Ex. Citric acid – found in oranges and lemons – is a compound that is made of the elements carbon (C), hydrogen (H) and oxygen (O) citric acid is written as = C 6 H 8 O 7 What are compounds?
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Compound is a substance formed by the chemical combination of two or more elements. –Ex. Citric acid – found in oranges and lemons – is a compound that.
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• Compound is a substance formed by the chemical combination of two or more elements.
– Ex. Citric acid – found in oranges and lemons – is a compound that is made of the elements carbon (C), hydrogen (H) and oxygen (O)
• Surface area - Increased surface area increases reaction rate because more particles on the surface of a solid come into contact with the particles of another substance.
• Temperature - At higher temperatures, the average speed of particles is greater, particles collide more often, and collisions with more energy are more likely to break chemical bonds.
What can affect the rate of a chemical reaction? (cont)
During a chemical reaction, bonds are broken and atoms are rearranged to form new substances. Energy involved in chemical reactions is either stored in bonds or released.
• All matter is composed of tiny particles called atoms.
• The first model of the atoms was a solid sphere. Today’s model has a central nucleus with the protons and neutrons and an electron cloud surrounding it.
Lesson 1: Atoms
Lesson 2: Elements
• An element is a pure substance that cannot be broken down into any simpler substances. All atoms of the same element have the same number of protons.
• An element’s atomic number tells how many protons its atoms contain and its average atomic mass tells the average mass of its atoms.
• Elements are arranged on the periodic table according to their atomic numbers.
Lesson 3: Compounds
• Atoms of different elements can combine to form compounds.
• Ionic bonds usually involve the transfer of electrons from a metal atom to a nonmetal atom. A chemical bond that forms when atoms of nonmetals share electrons is called a covalent bond.
Lesson 4: Chemical Reactions and Energy
• In chemical reactions, energy is either absorbed or released. Energy is released in exothermic reactions. Energy is absorbed in endothermic reactions.
A. atom
B. electron
C. neutron
D. proton
Which term describes a neutral particle that exists in the nucleus of an atom?