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Science Yr8 > Chemical reactions > Flashcards

Chemical reactions Flashcards

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1
Q

List 3 key signs of a chemical reaction

A
  • A colour change.* A flame or explosion.* Reaction gets hot or cold by itself.* A gas is produced in the reaction without heating.* A solid is produced in the reaction without cooling.
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2
Q

What happens in a chemical reaction?

A

Some bonds are broken and others form to make new chemicals

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3
Q

What does not happen in a physical change?

A

No bonds are broken or formed

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4
Q

When balancing a chemical reaction, what must we not change?

A

The chemical formulae i.e. the “small” numbers cannot change

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5
Q

What do we mean by a balanced chemical reaction?

A

There are the same number of atoms of each element in the reactants and in the products e.g. if there are 2 oxygen atoms in the reactants, there must be 2 in the products

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6
Q

What is wrong with this balanced equation?

A

An = symbol is used instead of an arrow (the 2 in O2 should also be a subscript)

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7
Q

2Ca + O2 = 2CaO

A
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8
Q

How do you identify an exothermic reaction?

A

An increase in temperature as energy is transferred to the thermal store of the surroundings

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9
Q

How do you identify an endothermic reaction?

A

A decrease in temperature as energy is transferred from the thermal store of the surroundings.

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10
Q

What is oxidation?

A

When an element combines with oxygen to form a compound

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11
Q

What is combustion?

A

When a fuel rapidly reacts with oxygen transferring energy to the thermal store of the surroundings (high temperature)

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12
Q

Rusting would be an example of what type of chemical reaction?

A

Oxidation

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13
Q

Are metal oxides acidic or alkaline?

A

Alkaline e.g. sodium hydroxide is a drain cleaner

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14
Q

Are non-metal oxides acidic or alkaline?

A

Acidic

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15
Q

What happens when a compound combusts?

A

Each element in the compound forms an oxide

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16
Q

Methane is a hydrocarbon (it contains carbon and hydrogen), what products form when it combusts

A

Water (oxidation of hydrogen) and carbon dioxide (oxidation of carbon)

17
Q

What is thermal decomposition?

A

A compound is broken down by heat

18
Q

What is a test for carbon dioxide?

A

Bubble through limewater (the limewater turns cloudy)

19
Q

What happens in displacement?

A

A more reactive metal takes the place of a less reactive metal in a compound

20
Q

Why are alkali metals (group 1 elements) reactive?

A

They have 1 electron in their outer shell

21
Q

Why are halogens (group 7 elements) reactive?

A

They have 7 electrons in their outer shell

22
Q

Why are nobel gases not reactive?

A

They have a full outer shell

23
Q

If a less reactive metal is added to a salt solution containing a more reactive metal, what will happen?

A

Nothing (no reaction will occur)

24
Q

What do all acids have in common?

A

They contain hydrogen

25
Q

Complete the names of these common acids

A
26
Q

An acid releases what into solution

A

Hydrogen ions (positive)

27
Q

An alkali releases what into solution?

A

Hydroxide ions (negative)

28
Q

pH 0 is a strong…

A

Acid

29
Q

pH 14 is a strong…

A

Alkali

30
Q

What is neutralisation?

A

The hydrogen ions from an acid combine with the hydroxide ions from the alkali to form water

31
Q

Acid + alkali -> what are the products?

A

Salt + water

32
Q

Acid + Metal carbonate -> what are the products?

A

Salt + water + carbon dioxide

33
Q

What is a salt?

A

Hydrogen ions in an acid have been replaced by a metal

34
Q

What is a catalyst?

A

A chemical that speeds up a chemical reaction without being used up in the reaction.

35
Q

Give an example of a biological catalyst

A

Enzyme (lipase, amylase, carboydrase, protease)

36
Q

Catalysts ___________ the _________ barrier which ___________ the rate of reaction

A

Catalysts REDUCE the ENERGY barrier which INCREASES the rate of reaction

37
Q

Give 3 examples of diatomic elements (i.e. they hang around in pairs!)

A

Oxygen, Nitrogen, Hydrogen, any halogen (group 7 element)

38
Q

True/False - all combustion reactions are oxidation reactions

A

t

39
Q

Where on the periodic table are many catalysts found?

A

Transition metals

Science Yr8 (7 decks)

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