Grade 10 Chemistry Unit

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Chapter 5 Chemicals in Action What is chemistry? Chemistry is the study of matter, its properties and its changes or transformations. Matter is anything that takes up space and has mass. All types of matter have physical and chemical properties. Physical properties include: state at room temperature (solid, liquid or gas), temperature, colour, odour, lustre, solubility and melting and boiling points. Chemical properties include how matter reacts with: air (oxygen),acids, bases, and water

5.1 Chemicals and chemical Change   There are many different types of matter that make up our world: Pure substance – all the particles that make up this matter are the same, as a result this matter has constant properties e.g. pure water is a clear colourless substance that freezes at 0 C and boils at 100 C. a) Pure substances can be classified as: Elements – cannot be broken down into a simpler substance because they are made of only 1 kind of atom e.g. gold, oxygen, and mercury. These elements can be identified by a chemical symbol found on the periodic table (Au, O, Hg). Some elements consist of molecules, which are formed when 2 or more atoms join together; for example oxygen (O) occurs in nature as pairs of oxygen atoms or molecules of oxygen (O2)

Compounds – contain 2 or more different elements in a fixed proportion Compounds – contain 2 or more different elements in a fixed proportion. Compounds can be identified with chemical formulas e.g. carbon dioxide (formula CO2) is a compound. Each molecule of carbon dioxide is made of 1 atom of carbon and 2 atoms of oxygen. Other examples of compounds are water (H2O), sodium chloride (NaCl or salt), and ammonia (NH3).

2) Another type of matter is a mixture 2)     Another type of matter is a mixture. Mixtures are made of 2 or more pure substances and can be separated by some physical method e.g. filtering, evaporation, and magnet. E.g. salt water with sand in it. The sand can be filtered with filter paper and the salt can be separated from the water by evaporating the water.   Mixtures can be classified as:

Solutions – a mixture where one pure substance is dissolved in another pure substance e.g. salt in water, oxygen in air, copper in a brass loonies. Homogeneous mixtures – a mixture that has 2 pure substances but appears to be only 1 pure substance e.g. Kool-Aid is a mixture of flavour crystals, sugar and water Heterogeneous mixture – a mixture that has 2 or more pure substances that can be seen as separate parts or layers e.g. pizza is made of cheeses tomato sauce and pepperoni

Matter Pure Substance Mixture Element Compound Solution Heterogeneous Homogeneous

Properties of Matter A physical change is a change in the size or form of a substance, which does not change the chemical properties of the substance e.g. boiling water, or dissolving sugar in water. A chemical change occurs when a substance changes into a new substance with different chemical properties e.g. iron rusting or burning charcoal. The starting materials in a chemical change are called reactants and the new materials made are called products. Iron + oxygen makes rust or iron (III) oxide   Fe + O2 makes Fe2O3 Reactants Products

Chemical Tests How are chemical changes useful? Chemical changes can be used to make a new substance or identify an unknown substance. There are 4 chemical tests that can be used to identify an unknown colourless gas: 1)      Oxygen Gas – a glowing splint bursts into flames 2)     Hydrogen Gas – a lit splint will cause a small explosion or pop sound 3)     Carbon dioxide Gas – a chemical called limewater will turn from colourless to white if exposed to carbon dioxide 4) Water Vapour (Gas) – cobalt chloride paper will change from blue to pink

POP!! Hydrogen Test Oxygen Test

Assignment Homework : Questions 1-3 pg 175

Periodic Table – an organized arrangement of elements that help us to explain and predict physical and chemical properties. The periodic table is generally arranges with metals toward the left side and the nonmetals towards the right side. One exception is hydrogen (H). Although it is located on the top left hand side of the periodic table it behaves mostly as a non-metal.

Chemical Families – elements have been grouped in columns or families Chemical Families – elements have been grouped in columns or families. Chemical families are groups of elements in the same vertical column that have similar physical and chemical properties. 1)      Alkali metals (group 1) – include lithium (li) , sodium (Na), and potassium (K) and all are shiny, silvery metals. They form compounds that are white solids and very soluble in water 2)     Alkaline Earth Metals (group 2) – include magnesium (Mg), calcium (Ca), and barium (Ba) and all are shiny , silvery metals, but they form compounds that are not soluble in water

3)     Halogens (group 17) – include fluorine (F), chlorine (Cl), and bromine (Br) and are all poisonous elements that react easily with sodium and all other alkali metals. 4) Noble Gases (group 18) – include helium (He), and neon (Ne) and do not form compounds. The other term for the noble gases is inert gases. Inert means does not react.

Elements and Atomic Structure What are atoms made of? The Bohr-Rutherford model of the atom suggests that atoms are made of 3 types of subatomic particles 1)      protons – heavy positively charged particles that are found in a dense positive core of the atom called the nucleus. The number of protons equals the atomic # of the element on the periodic table

2)     Neutrons – neutral particles that have the same mass as a proton and are also found in the nucleus. The number of neutrons in an atom can vary. (atomic mass – atomic # on the periodic table)

3)Electrons – negatively charged particles with almost no mass that circle the nucleus at different energy levels, also called orbits or shells. Since atoms are electrically neutral that number of electrons equals the number of protons

The key to understanding the formation of compounds is to understand the arrangements of electrons around the nucleus. The farther away an electron is from the nucleus the more likely it is to be involved in a chemical change. The electrons in the outer orbit (valence electrons) are involved in bonding atoms together to form compounds.

Bohr diagrams are used to represent the arrangement of electrons in various orbits of an atom 35 17 Or Cl

nucleus 1st energy level 2nd energy level 3rd energy level

Atomic Symbols     A full atomic symbol includes the symbol of the element with the atomic number at the bottom left corner and the mass number at the top left corner.     Copy Atomic Symbol Here 84 Kr 36

Consider what might happen to the charge of a neutral atom if the outer orbit of electrons are decreased or increased in number. When this occurs the atom becomes a charged particle called an ion. Ion’s can be positively charged, which is called a cation (caused by a loss of electrons from the outer orbit) or negatively charged, which is called an anion (caused by a gain of electrons in the outer orbit).

magnesium lost 2 electrons Mg Symbol of a Magnesium Atom Metal Atoms to Ions Mg 2+ Symbol of a Magnesium Ion Notice 2+ means magnesium lost 2 electrons Mg Atom 12p+ 2e- 8e- Mg Ion 12p+ 2e- 8e- Ne 2e- 8e- Magnesium atom Magnesium Ion by losing 2 electrons becomes To be like Its nearest Noble Gas

sulfur gained 2 electrons Symbol of a Sulfur Atom Nonmetal Atoms to Ions S 2- Symbol of a Sulfide Ion Notice 2- means sulfur gained 2 electrons And the name changed S Atom 16p+ 6e- 2e- 8e- Ar Atom 18p+ 8e- 2e- S Ion 16p+ 8e- 2e- Its nearest Noble Gas Sulphur atom To be like becomes Sulphide ion

Chloride gained 1 electrons Cl Symbol of a Chlorine Atom Nonmetal Atoms to Ions Cl 1- Symbol of a Chloride Ion Notice 1- means Chloride gained 1 electrons And the name changed S Atom 16p+ 6e- 2e- 8e- Ar Atom 18p+ 8e- 2e- S Ion 16p+ 8e- 2e- Its nearest Noble Gas Sulphur atom To be like becomes Sulphide ion

Homework : Activity 5.7 :Ionic Charges and Chemical Families (Use BLM 5.7a-c) Worksheet – Simple Ions