Grade Nine Science

Unit 1- Matter What is matter? Can matter change? Matter is anything that has mass and takes up space. Can matter change? Provide examples. (Snow melting, water boiling)

1.2 Properties of Matter What do we mean by the properties of an object? A property is simply a characteristic that we can use to describe something. There are physical properties and chemical properties.

1.2 Physical Properties of Matter A physical property does not involve a substance becoming a new substance. There are many types of physical properties that you may want to describe: Colour - red, green, blue…? Texture - smooth, fine, coarse…? Taste - sour, salty, sweet, …?

1.2 Other Physical Properties of Matter States of matter at room temperature solid, liquid, or gas. Hardness is the measure of the resistance of a solid to being scratched or dented. Malleable is the opposite of brittle. Glass and dried clay are examples of things that are brittle. Aluminum foil is malleable. Gold is malleable since it can be hammered into thin sheets.

1.2 Other Physical Properties of Matter Copper is ductile since it can be pulled into wires. Melting and boiling points. What is the boiling point of water? The melting point of ice? Crystal form. Example, salt. Solubility is the ability of a substance to dissolve in a solvent such as water. Salt is soluble while pepper is not.

1.2 Chemical Properties of Matter A chemical property describes the behaviour of a substance as it becomes a new substance. Combustibility describes the ability of a substance to react with oxygen to produce carbon dioxide, water and energy. If a substance is combustible or flammable, it will burn when exposed to a flame. A substance that will not burn is described as nonflammable. List some materials that are combustible. List some materials that are nonflammable.

1.2 Chemical Properties of Matter Reaction with acid. The ability of a substance to react with acid is a chemical property. Name some substances that react with acids such as vinegar. Would you drink acid? Look at the side of a Coke can.

Hand out WHMIS Table Assignment #1 Create a simple map of your home and indicate where you would have found products with some of the hazardous household product symbols that we have discussed.

1.5 Density Which is heavier: a 12 inch bar of gold or a pillow full of feathers? A 12 inch bar of gold weighs more than a pillow full of feathers even though the pillow takes up more space. Why? Gold is more dense. It has more matter per unit volume.

1.5 Density Density is the amount of matter per unit volume of that matter. Density(D) = Mass(m) / Volume(V) If you know any two of the three variables (D,m, or V), you can solve for the third. m = D x V V = m / D

Sample density question #1 If a rock has a mass of 49 g and occupies a volume of 7 cm3, what is the density? D = m / V = 49 g / 7 cm3 = 7.0 g/ cm3

Solve these sample density questions An object has a mass of 250 g and occupies a volume of 14.5 cm3, what is the density? A piece of wood occupies a volume of 46 cm3 and it has a mass of 100 g. What is the density of the wood? An unknown metal has a density of 2.6 g/cm3 and a mass of 15 g. How much volume does this piece of metal occupy? A sample of a particular liquid has a density of 6.85 kg/L and it occupies a volume of 3.4 L. How much does this particular sample weigh?

Answer to question #1 D = m / V = 250 g / 14.5 cm3 = 17.24 g/ cm3

Answer to question #2 D = m / V = 100g / 46 cm3 = 2.17 g/ cm3

Answer to question #3 D = m / V V = m / D = 15 g / 2.6 g/cm3

Answer to question #4 D = m / V M = D x V = 6.85 kg/L x 3.4 L ** Note that volume can be expressed as cm3, m3, ml or even L.

Approximate Densities of Some Common Materials Substance Den sity kg/m3 g/cm3 Gold 19300 19.3 Silver 10500 10.5 Aluminum 2700 2.7 Ice 920 .92 Wood (birch) 660 .66 Distilled Water 1000 1.0

Water is more dense than ice! Why is this so important? It means that ice floats in water instead of sinking. Think of the poor fish if this was the not the case. Why is ice less dense than water? When water freezes, it expands which means that the same mass of water is spread over a greater volume.

Homework Answer questions 2,3,4 on page 25 of the text.

Physical and Chemical Changes

A burning candle – what happens? As the candle burns, the wax melts ( a solid becomes a liquid), and then it hardens (a liquid becomes a solid). These are physical changes. The wax also combusts producing heat and light. This chemical change involves the wax becoming carbon dioxide, water and energy.

What is a physical change? In a physical change, the substance involved remains the same substance, even though it may change state or form. When candle wax melts, it is still wax. Changes of state – melting, boiling, freezing, condensation, and dissolving – are physical changes . Most physical changes are easy to reverse.

What is a chemical change? In a chemical change, the original substance is changed into one or more different substances that have different properties. As candle wax melts, some of the wax particles combine with oxygen to produce water vapour, carbon dioxide, heat and light.it is still wax. Chemical changes always involves the production of new substances. Examples include burning, cooking and rusting. Most chemical changes are difficult to reverse.

Clues That a Chemical Change Has Happened A colour appears. Heat or light is given off. Bubbles of gas are formed. A solid material forms in a liquid. The change is difficult to reverse.

Homework Answer questions 2 and 3 on page 30.

Corrosion

What is corrosion? Corrosion is the slow chemical change that occurs when a metal reacts with oxygen from the air. This chemical reaction forms a new substance called an oxide. Different kinds of corrosion: Rusting Aluminum corrosion Silver tarnish

Rusting Rusting is a chemical change that involves iron, oxygen from air and water, and salt or other minerals that may be in dissolved in the water. Where do we normally see rust? What can we do to prevent rust?

Aluminum Corrosion Aluminum has a chemical property similar to iron in that it reacts with oxygen to form an oxide. The aluminum oxide that forms is strong and it is unaffected by water.

Silver tarnish Unlike iron and aluminum, silver does not react with oxygen but it does react with sulphur. Sulphur is found in Mustard Eggs Acid rain Silver sulphide causes silver to develop a black coating. The black layer is annoying but it can be removed by polishing the silver.

Preventing Corrosion There are many ways to prevent corrosion: Painting metal prevents oxygen from getting at the metal Use plastics instead of steel Cathodic protection – using one metal to attract corrosion(oxygen) from another

Combustion In combustion, a substance reacts rapidly with oxygen and releases energy. The energy may be in the form of heat and light. Many substances can act as fuels. Eg. Wood, diesel oil, and kerosene

Combustion The Fire Triangle The fire triangle is a convenient way to remember the three components of any combustion reaction. Removing any one of these makes the triangle incomplete and puts out the fire. Oxygen Heat Fuel

Combustion Fossil Fuels Fossil fuels were formed from plants, animals, and micro-organisms that lived millions of years ago. Include coal, oil, natural gas and gasoline Fossil fuels are made up of hydrocarbons The main products of burning fossil fuels is carbon dioxide and water vapour

Combustion Fossil Fuels Hydrocarbon + oxygen => carbon dioxide + water reactants products

Combustion Pollution Under ideal conditions, the combustion of hydrocarbons produces only carbon dioxide and water. What happens if there is not enough oxygen or if the hydrocarbons are not pure? Carbon monoxide, sulphur dioxide, and nitrogen oxides may be produced. These are all pollutants.

Homework Answer questions 1-5 on page 39