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Chemistry > Chemical change > Flashcards

Chemical change Flashcards

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1
Q

What is the law of conservation of mass?

A

Atoms are not created or destroyed in a chemical reaction

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2
Q

In the reaction carbon + oxygen  carbon dioxide, why does the mass decrease?

A

Atoms are being lost as a gas (carbon dioxide)

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3
Q

In the reaction magnesium + oxygen  magnesium oxide, why does the mass increase?

A

Atoms from a gas (oxygen) are being added

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4
Q

What is a symbol equation?

A

A chemical equation in which the chemicals are represented by formulae

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5
Q

What is a balanced equation?

A

A symbol equation where all the reactant atoms have become product atoms

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6
Q

What do “big numbers” in front of formulae tell us?

A

How many units of each formula there is in the balanced equation

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7
Q

Which numbers can be changed when balancing an equation?

A

Big numbers in front of formulae

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8
Q

How can you tell if an equation is balanced?

A

Equal numbers of atoms of each element on each side of the reaction arrow

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9
Q

Unit and symbol for mass?

A

Kilogram/kg (gram/g)

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10
Q

Unit and symbol for volume?

A

Cubic metres/m3 (cubic centimetres/cm3) (cubic decimetre/dm3)

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11
Q

What is concentration?

A

The amount of solute dissolved per unit volume of solvent

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12
Q

Unit and symbol for concentration (when using mass)?

A

Grams per cubic decimetre – g/dm3

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13
Q

What must particles do in order to have a chance to react?

A

Collide (with sufficient energy and in the correct orientation)

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14
Q

What is rate of reaction?

A

How quickly a reaction takes place

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15
Q

Units and symbols for rate?

A

Cubic centimetres per second (cm3/s) & grams per second (g/s)

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16
Q

How can you monitor rate of reaction?

A

How quickly a product is formed or a reactant is used

17
Q

How can you measure how quickly a product is formed?

A

Volume of gas per second using a gas syringe, change in mass

18
Q

How can you measure how quickly a reactant is used?

A

Change in mass

19
Q

What is turbidity?

A

Cloudiness

20
Q

How can you monitor changes in concentration to measure rate?

A

Changes in colour or turbidity (disappearing cross)

21
Q

How can you calculate relative rate from time taken?

A

relative rate = 1/time taken

22
Q

On a graph of concentration/mass/volume of gas against time, what is represented by the gradient?

A

rate of reaction

23
Q

What are the 5 factors that can alter the rate of reaction?

A

Temperature, surface area, pressure (gases), concentration and catalyst

24
Q

How does temperature affect rate of reaction?

A

Increasing temperature increases rate of reaction

25
Q

What needs to happen to collisions between particles to increase rate?

A

Increased frequency and/or increased energy

26
Q

How do particles behave at higher temperatures?

A

They move faster and collide more frequently

27
Q

What do particles have more of at higher temperatures?

A

Energy

28
Q

Which state of matter can we alter the pressure of?

A

Gases

29
Q

How does pressure affect rate of reaction?

A

Increasing pressure increases rate of reaction

30
Q

How are particles spaced at high pressure?

A

Closer together – more particles per unit volume.

31
Q

How does concentration affect rate of reaction?

A

Increasing concentration increases rate of reaction

32
Q

How are particles spaced at low concentration?

A

Further apart – fewer particles per unit volume.

33
Q

What effect does breaking solid matter into smaller bits have on surface area?

A

Increases surface area to volume ratio.

34
Q

How does surface area affect rate of reaction?

A

Increasing surface area increases rate of reaction

35
Q

Why does a larger surface area increase rate of reaction?

A

More particles at the surface and available for collisions

36
Q

What is activation energy?

A

The minimum energy with which particles must collide in order to react

37
Q

What is a catalyst?

A

A chemical that increases the rate of a reaction without being used up itself

38
Q

How do catalysts increase the rate of reaction?

A

By decreasing the activation energy

Chemistry (4 decks)

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