Understanding Chemical Changes

• Chemical changes are explored, focusing on how they occur and are depicted through equations
• Plants usually grow from seeds over weeks, but chemical gardens can grow in a single day
• Chemical gardens are created by mixing different chemicals

Chemical Changes as a Result of Interactions

• Chemical changes can be identified and represented differently
• Rusting occurs when iron reacts with air, causing a shiny key chain to become dull and rusty
• Changes are classified as physical or chemical
• Physical changes, like dissolving sugar or evaporation, are reversible and don't create new substances
• Chemical changes are usually irreversible and result from chemical interactions
• Chemical changes occur when matter interacts with heat, light, or electricity, or when different kinds of matter interact
• Energy, as heat or light, can be absorbed or released during a chemical change
• Word equations represent chemical changes
• Word equations include reactants on the left, products on the right, and conditions required for the reaction

Chemical Reactions

• Carbon and oxygen react when burning charcoal, converting chemical energy to heat, and light energy
• Products in chemical reactions have different properties than reactants
• The formation of plastic showcases chemical changes

Key Differences

• Physical changes do not form new substances, while chemical changes do
• Physical change product properties are the same as reactants, chemical change product properties are different
• Physical changes are reversible, chemical changes are usually irreversible
• Heat or light can be taken in or given out during a chemical reaction
• Reactants and products are used in a word equation to represent a chemical reaction.

Types of Chemical Changes

• Fireworks produce bright, colorful lights through chemical reactions when compounds are burned
• Light sticks show chemical change when chemicals mix
• Light sticks contain two chemicals separated by a casing, and a smaller, thinner tube
• Bending the light stick breaks the inner tube, releasing the chemical and causing a reaction that gives off light

Mixing Substances

• Mixing baking soda with liquids leads to chemical changes
• Baking soda reacts with stains
• Cleaning coffee or tea-stained cups involves using a baking soda paste, where the paste and stains react, removing stains

Matter and Heat

• Cooking an egg involves a chemical change
• Raw eggs are liquid, heat causes changes, solidifying the egg white and yolk

Irreversibility

• Chemical changes are irreversible
• Introducing heat interacts with different substances, causing change

Rubber Tyres

• Charles Goodyear accidentally mixed natural rubber with sulfur on a hot stove in 1839
• The result was heat-resistant rubber commonly used in vehicle tires

Thermal Decomposition

• Sugar heated turns into carbon and water vapor; is known as thermal decomposition
• Thermal decomposition is a chemical change caused by heat breaking substances into simpler forms
• Production of glass relies on thermal decomposition of limestone (calcium carbonate) into calcium oxide and carbon dioxide

Matter and Oxygen

• Matter also interacts with oxygen
• Exposing bikes and chains to the environment results in rust because they are made of iron or steel
• The iron or steel then slowly reacts with oxygen in the presence of moisture, rusting the metal, this process is called "oxidation"
• Oxidation is a process where a substance reacts with oxygen
• Oxidation reactions also occur duing combustion and cellular respiration

Combustion (Burning)

• When cooking, natural gas burns in oxygen, that releases heat, which is used to cook the food
• The combination of natural gas with oxygen is considered "combustion"
• Combustion combines a substance with oxygen in the presence of heat resulting in new substances
• Combustion involves the burning of fuels e.g. coal, natural gas, petrol & diesel
• Combustion usually release lots of high amounts of heat
• The energy released by combustion can be used for cooking, transport and generating electrical energy in power stations

Complete Combustion

• When there is lots of oxygen complete combustion occurs
• In car engines, oxygen burns which creates carbon dioxide and water vapour
• Besides fuels, other examples of combustion are the burning of carbon and sulfur
• Coal and oil contain sulfur and when they burn, combustion is a result
• Sulfur burning produces a colorless and pungent gas with a choking smell

Sulfur Dioxide

• Burning of sulfur produces sulfur dioxide which results in air pollutants
• Sulfur dioxide is an air pollutant and contributes to acid rain

Cellular Respiration

• Movement and survival requires energy
• Cellular respiration is a very important oxidation reaction in the cells of living things to get energy from food
• Living cells of plants and animals take in oxygen which releases the energy stored in glucose
• In cellular respiration, chemical energy in glucose turns into different energy types
• Glucose and oxygen react in the cell to form carbon dioxide and water, plus energy

Matter and Light

• Light interacts with matter and causes chemical changes.
• These chemical changes are found in: photosynthesis and creating x-ray film

Photosynthesis

• Photosynthesis is a very important process where living things survive
• Photo means 'light' while synthesis means 'to make'
• Photosynthesis is a process in which food is made in green plants in the presence of light
• Plants utilize energy from sunlight and make food in leaves
• Photosynthesis is a chemical change, and needs reactants; carbon dioxide, water. It requires sunlight and chlorophyll to make glucose and oxygen

X-Ray Film

• X-ray sensitive to x-rays
• X-ray similar to light rays
• X-ray film includes chemicals that coat their thin layer
• Chemicals contain silver bromide crystals which converts to silver by X-rays and light
• Using X-rays can observe body's internal structures such as bone etc

Matter and Electricity

• Sending electric current through a substance causes chemical changes produced during: electrolysis and electroplating

Electrolysis

• Substances break down substances when they interact with electric current, this process is called electrolysis
• Electrolysis chemically decomposes substances when sending an electric current through it

Electroplating

• To make various coins and trophies seem more beautiful, a thin layer of metal coats them
• It can also prevent rusting
• During an electrical current passing through a substance it coats metal, this is called electroplating

Acids and Matter

• Chemical reactions occur when matter interacts with other matter
• Thermal decomposition is a chemical change that occurs when matter interacts with heat.
• Rusting, combustion, and cellular respiration are chemical changes that occur when matter interacts with oxygen.
• Photosynthesis and X-ray film processing are chemical changes that occur when matter interacts with light.
• Electrolysis and electroplating are chemical changes that occur when matter interacts with electricity.

Reactions between Matter

• Antacids used by doctors for gastric pains
• Too much fluids with hydrochloric acid can lead to stomach aches
• Antacids have hydrochloric acids to form harmless products that provide relief

Acids

• Acids found in living things
• Some acids found in citrus fruits such as lemons etc
• Other type of acids are used in industries for purposes

Acids react with Metals

• Using acids, decorative patterns can be carved in metal
• This technique relies on metal reaction (copper etc)
• During acid etching, metal interacts with acid and produce hydrogen gas

Acids react with carbonates

• Baking includes reactants such as acid with carbonate which makes carbon dioxide
• In bread making, carbon dioxide is trapped as air bubbles which results in the dough rising while baked

Alkalis

• Alkalis are in many things around us
• A presence of an alkali make solution taste bitter
• Alkali usually found in detergents and soaps

Neutralization

• Acid is formed when bacteria is on food partials, this leads to tooth decay so brush regularly with toothpaste
• toothpaste has alkalis
• Alkalis react with acid in our teeth produces results in salt and water etc, which neutralized, tooth decay prevented

Indicators

• Most alkalis/acids are colourless
• Indicators will give the colours solutions, which can test alkaline
• Indicator is a substance that test if the solution being tested are acidic or alkaline

Litmus Paper

• The litmus paper test solutions on alkaline and acid

Acidity VS Alkalinity

• Acidity and Alkalinity tested using universal indicator
• Strengths can go throught colour change
• Indicators includes: blue litmus paper,red litmus paper,universal indicator etc

Movement of Atoms during Chemical Reactions

• Experiment: a small piece of sodium metal was measured along with chlorine gas after that, the sodium was heated and inserted into the flask which contains the chlorine gas
• The mass of both reactants (reactants was found to be consistant)
• In conclusion, mass of reactants and mass of products always equal

Atoms

• Atoms cannot be destroyed
• Only chemical reactinos make atoms rearrange the reactants
• Example of sulfur oxygen combine to form sulfur dioxide etc

Lavoisier

• Lavoisier discovered that although the states can change of matter in chemical reaction, the mass does not and stays the same

Beneficial and Harmful

• Chemical changes and their impact on people

Global Climate

• Ozone depletion and the green house effect
• Human actions are a major risk for climate change etc
• Examples of pollutions in the air in atmosphere
• Oxides, gases, etc

Air Pollutants

• Burning and combustion
• Releasing air pollutions in atmosphere
• Rusting cause a loss of finite natural resources
• Rusting occurs when metal interacts with other matters

Natural Resources

• Wastage of food supply and resources
• Burning releases air pollutions which is harmful