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Year 8 Science Exam Semester 2 > 6.4 Chemical Reactions > Flashcards

6.4 Chemical Reactions Flashcards

1
Q

What is matter made up of?

A

Particles

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2
Q

What are the smallest particles called?

A

Atoms

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3
Q

What are atoms?

A

The smallest building blocks from which all substances are made

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4
Q

What shape are atoms?

A

They are hard spheres

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5
Q

What do atoms usually form?

A

They are rarely on their own and they cluster together to form molecules

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6
Q

What are The 5 principles of Daltons atomic theory of matter?

A

1) all matter is made up of tiny, hard, invisible particles called atoms
2) substances made up of one type of atom are called elements
3) the atoms of different elements can be distinguished by their different masses
4) atoms can combine to form new substances called molecules
5) atoms are not created or destroyed in a chemical change

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7
Q

In a pure substance, what are molecules like?

A

Molecules all have the same number of atoms and are identical in size and shape

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8
Q

When a chemical change occurs, what happens to the atoms?

A

They rearrange to form different combinations of atoms

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9
Q

What happens if atoms rearrange to form a new substance with a different colour?

A

A permanent colour change has occurred

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10
Q

What happens if atoms rearrange to form a gas?

A

You will see bubbles, smoke or smell new odour

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11
Q

What happens if atoms rearrange to form a solid?

A

A precipitate may occur

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12
Q

In a chemical change can the atoms be created or destroyed?

A

No they are never created or destroyed

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13
Q

What are the starting substances known as in a chemical reaction?

A

Reactants

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14
Q

What are the substances that are formed in chemical reactions.

A

Products

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15
Q

What do reactants rearrange to form?

A

Products

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16
Q

How are atoms in molecules and lattices held together?

A

They are held together by chemical bonds that store energy

17
Q

What are spontaneous reactions?

A

They are reactions that proceed by themselves

18
Q

What are the two types of spontaneous reactions?

A

First can obtain enough energy from the surroundings to start and continue
The other needs a kick start from an external energy supply but can then continue with the reaction

19
Q

What are non-spontaneous reactions?

A

Require and energy to be constantly added to it otherwise the reaction will stop

20
Q

Why do scientists use chemical equations?

A

Because it is clearer, faster and easier

21
Q

What replaces an equal sign in a reaction?

A

An arrow, there is no equal sign. The arrow means that the reactants have become the products

22
Q

What s the simplest was to write a chemical equation?

A

By using chemical names:
Hydrochloric acid (HCL) + Sodium Chloride (NaOH)
A word equation looks like this:
Hydrochloric acid + Sodium Hydroxide -> Sodium Chloride + Water

23
Q

What is a chemical equations?

A

Chemical name is now resolved with chemical formula

HCl + NaOH -> NaCl + H2O

24
Q

What is corrosion?

A

When metal reacts with oxygen

Most common type of corrosion is rust

25
Q

What makes some metals more likely to corrode?

A

Their chemical properties

26
Q

What is rusting?

A

The name giving to the corrosion of iron

Iron needs to react with oxygen or water to produce orange-brown compound iron (iii) oxide (Fe2O3)

27
Q

How can you prevent rusting?

A

Coating, galvanising and alloying

28
Q

Why do we using costing?

A

It is cheapest and simplest way to protect iron

Coating forms a barrier between iron and oxygen

29
Q

What happens if the barrier is removed in coating?

A

If coating is scratched or cracked the the barrier is removed and rusting will occur

30
Q

What do we use to coat iron?

A

Paint, plastic or other metals like chromium

31
Q

What is galvanising?

A

If iron is coated with zinc, it is good because even if it is scratched or cracked it will still protect

32
Q

What does zinc react easily with?

A

Oxygen but even when it is scratched, the zinc reacts with oxygen not iron

33
Q

What is iron is mixed with other metals?

A

The chemical and physical properties change. These mixtures are known as alloys

34
Q

Why is iron never used in its pure form?

A

Because it is too soft and undergoes corrosion quickly

35
Q

What is stainless steel made up of?

A

90% iron

10% chromium

Year 8 Science Exam Semester 2 (9 decks)

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