Chemical reactions Flashcards
How can you identify a chemical change?
- Change in temperature
- Seeing bubbles being produced (gas formation)
- Permanent colour change
- A new solid is formed (precipitate)
- Energy (heat or light) is produced or absorbed
How to determine the type of salt from a neutralisation reaction?
Base + acid
- Sodium Hydroxide + Sulfuric acid = Sodium sulfate
- Magnesium oxide + Hydrochloric acid = Magnesium chloride
- Sodium oxide + Acetic acid = Sodium acetate
- Copper(II) oxide + nitric acid = Copper(II) nitrate
How to write a chemical formula?
- Use chemical symbols
- If a compound contains more of any element, put the number next to it.
E.g Na_2 = Two sodium atoms, SO_4 = one sulfur atom, four oxygen atoms.
What are acid-base reactions?
- Reaction between an acid and a base is called neutralisation.
- An acid-base mixture is not as acidic or basic as the individual starting solutions.
What are fossil fuels made of?
- Fossil fuels are made of hydrocarbons - carbon compounds made of carbon and hydrogen atoms.
What are fossil fuels?
- Generic term for non-renewable energy sources such as coal, coal products, natural gas, derived gas, crude oil, petroleum products, and non-renewable waste.
What are products?
Are what you end up with after the reaction. They are written after the arrow.
What are reactants?
Reactants are what you start with before the reaction. They are written before the arrow.
What are the properties of a base?
- Feel slippery
- Taste bitter
- Corrosive
- Can conduct electricity (Think alkaline batteries.)
- Do not react with metals.
- Turns red litmus paper blue.
- pH value > 7
What are the properties of an acid?
- Tastes sour
- Conduct electricity
- Corrosive, which means they break down certain substances.
- Many acids can corrode fabric, skin, and paper.
- Some acids react strongly with metals.
- Turns blue litmus paper red.
- pH value < 7
What happens during a chemical reaction?
- Atoms involved rearrange to create a new substance.
- Atoms are not created nor destroyed; they simply rearrange.
What happens during the combustion of fossil fuels?
- The carbon compound in the fossil fuels reacts with oxygen in the presence of a heat source to form carbon dioxide (CO_2) and water.
E.g. Methane (natural gas) + oxygen -> Carbon dioxide + water
- CH_4 + O_2 -> CO_2 + H_2O
What is a base?
- A base is a solution that has an excess of OH ions.
- Another word for a base is alkali.
- Bases are substances that can accept hydrogen ions.
What is a chemical change?
- Something new, that was not there before, is formed.
- Chemical structure of the substances has been rearranged.
What is a combustion reaction?
- Combustion = Burning.
- Three things needed for combustion: Fuel, heat, and oxygen.
- If one is removed, the fire goes out.
- When fuel burns, it releases thermal energy (heat).
Used to heat our homes, power most cars, generate electricity.
What is a compound?
- A pure substance made of the same type of molecules which are made of several types of atoms.
What is a mixture?
- A substance made of several types of elements and/or compounds which are mixed (not joined by bonds).
What is a molecule?
- A particle made up of several atoms that are bonded together.
What is a physical change?
- Involves a change in state.
- Nothing new is formed.
- Are easily reversible.
What is a precipitation reaction?
- Substances in solution are mixed and form an insoluble product.
- This insoluble product is called a precipitate and can be seen as a solid that has formed in the reaction mixture.
What is an acid?
- A solution that has an excess of H+ ions. It comes from the Latin word acidus that means “Sharp” or “Sour.”
- The more H+ ions, the more acidic the solution.
What is an atom?
- The smallest particle of a chemical substance.
What is an element?
- A substance that consists of only one type of atom.
What is the neutralisation equation?
- acid + base (alkali) -> chemical salt + water.
What is the pH scale?
- pH is the measure of how acidic a substance is.
- Ranges from 0-14.
- Acidic solutions = pH < 7.
- pH 0 is very acidic.
- pH 7 is neutral (Pure water = pH 7).
- Basic solutions have pH values above 7.
Why does one use chemical formulae?
- For a molecule/compound, we use the chemical symbols of elements it contains to write down its formulae.
