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Chemical Changes Flashcards

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1
Q

what is the difference between Chemical and Physical changes

A
  1. Physical changes have no new substances formed
  2. The changes can usually be reversed and get their constituents by using separation techniques
  3. Chemical changes occur when one or more substances are formed.
  4. The changes are not easily reversible and cannot get the reactants back very easily.
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2
Q

How do we represent Chemical reactions?

A
  1. Use word equations to show the substances that are involved in chemical reactions.
  2. A word equation includes the reactants used and the products formed in a chemical reaction.
  3. The reactants are on the left and the products are on the right side.
  4. They are connected by an arrow
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3
Q

What happens during a chemical change?

A

The atoms rearrange themselves to form products

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4
Q

Give me some some examples of word equations

A

Hydrogen + Oxygen = Water

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5
Q

What happened to the numer of atoms before and after the reaction?

A
  1. They remain the same.
  2. The mass of the reactants is also the same as the mass of the products.
  3. Mass is conserved
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6
Q

What are some types of chemical changes

A

Combustion, Thermal Decomposition, Oxidation and Neutralization

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7
Q

What are the properties of acids

A
  1. Sour taste
  2. May burn the skin.
  3. Turns blue litmus paper red.
  4. Reacts with alkalis , metals, and carbonates.
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8
Q

Give an example a of strong acid

A

Acid in car battery

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9
Q

Give an example of a strong alkali

A

Oven cleaner

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10
Q

What is the term salt used for?

A

‘Salt’ is a general term for a compound containing an element that is a metal.

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11
Q

What is the word equation that represents chemical reactions between acids and metals

A

acid + metal —–> salt + hydrogen

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12
Q

What can we do to test for hydrogen?

A
  1. Use a lighted splint and insert it in the test tube without it touching the solution
  2. It should extinguish with a pop sound
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13
Q

What is the word equation that represents chemical reactions between acids and carbonates

A

acid + carbonate ——-> salt + carbon dioxide + water

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14
Q

How can we test for carbon dioxide?

A
  1. Use limewater
  2. If white precipitate is formed, there is carbon dioxide
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15
Q

What are the ways we can determine the acidity or alkanity of a solution?

A

pH scale, litmus paper, universal indicator soloution.

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16
Q

What happenes when alkalis or acids come into contact with blue or red litmus paper.

A
  1. Acids turn blue litmus red
  2. Alkalis turn red litmus blue
17
Q

What are some applications of neutralisation

A
  1. Antacids (to neutralise excess gastric acid).
  2. Toothpaste (helps neutralise acids that cause tooth decay)
18
Q

State some of the ways chemical changes occur

A
  1. Mixing
  2. Heating
  3. Exposure to light
  4. Exposure to oxygen
  5. Using an electric current ( electroplating)
19
Q

How does the knowledge of chemical reactions help us in our daily lives.

A
  1. Cooking
  2. Respiration
  3. Decomposition (decay)
  4. Rusting
  5. Combustion
20
Q

What are the properties of Alkalis

A
  1. Have a bitter taste
  2. Soapy feel
  3. May burn the skin
  4. Turns red litmus paper blue.
  5. Reacts with acids to neutralise
21
Q

Give an example of a weak acids

A

Citric acid found in orange juice

22
Q

Give an example of a weak alkali

A

Baking soda

23
Q

What is Combustion

A
  1. It is a chemical substance that is heated in the presence of oxygen to form one or more new substances
  2. carbon + oxygen ———> carbon dioxide
  3. Heat and light is usually given out during combustion
24
Q

What is thermal decomposition

A
  1. Thermal decomposition is the process in which a substance breaks down into two or more substances upon heating
                                                   heat
  2. e.g. ( Calcium carbonate ————-> calcium oxide + carbon dioxide)
25
Q

What is oxidation

A
  1. When a substance gains oxidation it undergoes oxidation
26
Q

What is Neutralisation

A
  1. When an acid is mixed with an alkali
  2. acid + alkali ——-> salt + water

Sci (12 decks)

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