Chemical reactions Flashcards

1
Q

How can you identify a chemical change?

A
  • 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
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2
Q

How to determine the type of salt from a neutralisation reaction?

A

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

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3
Q

How to write a chemical formula?

A
  • 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.

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4
Q

What are acid-base reactions?

A
  • 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.
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5
Q

What are fossil fuels made of?

A
  • Fossil fuels are made of hydrocarbons - carbon compounds made of carbon and hydrogen atoms.
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6
Q

What are fossil fuels?

A
  • Generic term for non-renewable energy sources such as coal, coal products, natural gas, derived gas, crude oil, petroleum products, and non-renewable waste.
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7
Q

What are products?

A

Are what you end up with after the reaction. They are written after the arrow.

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8
Q

What are reactants?

A

Reactants are what you start with before the reaction. They are written before the arrow.

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9
Q

What are the properties of a base?

A
  • Feel slippery
  • Taste bitter
  • Corrosive
  • Can conduct electricity (Think alkaline batteries.)
  • Do not react with metals.
  • Turns red litmus paper blue.
  • pH value > 7
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10
Q

What are the properties of an acid?

A
  • 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
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11
Q

What happens during a chemical reaction?

A
  • Atoms involved rearrange to create a new substance.
  • Atoms are not created nor destroyed; they simply rearrange.
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12
Q

What happens during the combustion of fossil fuels?

A
  • 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

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13
Q

What is a base?

A
  • 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.
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14
Q

What is a chemical change?

A
  • Something new, that was not there before, is formed.
  • Chemical structure of the substances has been rearranged.
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15
Q

What is a combustion reaction?

A
  • 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.

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16
Q

What is a compound?

A
  • A pure substance made of the same type of molecules which are made of several types of atoms.
17
Q

What is a mixture?

A
  • A substance made of several types of elements and/or compounds which are mixed (not joined by bonds).
18
Q

What is a molecule?

A
  • A particle made up of several atoms that are bonded together.
19
Q

What is a physical change?

A
  • Involves a change in state.
  • Nothing new is formed.
  • Are easily reversible.
20
Q

What is a precipitation reaction?

A
  • 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.
21
Q

What is an acid?

A
  • 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.
22
Q

What is an atom?

A
  • The smallest particle of a chemical substance.
23
Q

What is an element?

A
  • A substance that consists of only one type of atom.
24
Q

What is the neutralisation equation?

A
  • acid + base (alkali) -> chemical salt + water.
25
Q

What is the pH scale?

A
  • 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.
26
Q

Why does one use chemical formulae?

A
  • For a molecule/compound, we use the chemical symbols of elements it contains to write down its formulae.