chemical recations

Question 1

what is a chemical recations ?

Answer 1

it is when 2 or more elements combine

Question 2

what is a word equation ?

Answer 2

a word equation shows the names of the substances in a re action.

Question 3

what does endothermic reactions do ?

Answer 3

they take in energy from their surrondings

Question 4

what is a balanced equation ?

Answer 4

A balanced equation gives more information about a chemical reaction because it includes the symbols and formulae of the substances involved. There are two steps in writing a balanced equation

Question 5

how do you write a balanced equation ?

Answer 5

replace the name of each substance with its symbol or formula
use numbers to balance the equation, if it is not already balanced.

Question 6

how does metal react with oxygen ?

Answer 6

Metals react with oxygen in the air to produce metal oxides. For example, magnesium reacts with oxygen to produce magnesium oxide when it is heated in air

Question 7

why do some compounds break down ?

Answer 7

Some compounds break down when heated, forming two or more products from one reactant. This type of reaction is called thermal decomposition.

Question 8

why does other metal carbonates decompose in the same way ?

Answer 8

Other metal carbonates decompose in the same way. Here are the equations that represent the thermal decomposition of calcium carbonate

Question 9

A catalyst is a substance that ?

Answer 9

speeds up reactions
is not used up during the reaction (its mass is the same at the start and end of the reaction)
is chemically unchanged after the reaction has finished

Question 10

why is it the very small amount of catalyst increases ?

Answer 10

Only a very small amount of catalyst is needed to increase the rate of the reaction between large amounts of reactants. Different catalysts are needed to catalyse different reactions.

Question 11

why does catalytic convert ?

Answer 11

A catalytic converter reduces the release of harmful gases from vehicles

Question 12

why is strong forces called bones ?

Answer 12

The atoms in a compound are chemically joined together by strong forces called bonds. This is why the properties of a compound are different from the elements it contains, and why you can only separate its elements using another chemical reaction. Separation methods like filtration and distillation will not do this.

Question 13

why is corrosive substance lower than 7 ?

Answer 13

Corrosive substance which has a pH lower than 7. Acidity is caused by a high concentration of hydrogen ions

Question 14

When methane burns in oxygen, carbon dioxide and water are made. Which is a reactant?

Answer 14

Oxygen

Question 15

Copper oxide and carbon dioxide are made when copper carbonate is heated strongly. Which is a product?

Answer 15

Copper oxide

Question 16

What name is given to the force that holds atoms together in a compound?

Answer 16

Chemical bonds hold atoms together in a compound. Gravity is a force that attracts two masses together

Question 17

What is another name for combustion?

Answer 17

Burning can also be described as combustion. Displacement reactions involve swapping elements in a reaction.

Question 18

Combustion reactions always release energy. What word can be used to describe them?

Answer 18

Exothermic

Question 19

Which of these is found in the fire triangle and is therefore essential for combustion?

Answer 19

Oxygen is essential for combustion

Question 20

What is a hydrocarbon?

Answer 20

Hydrocarbons contain hydrogen and carbon only. Most come from crude oil, but not all of them

Question 21

What is produced when a hydrocarbon fuel burns in a very good supply of oxygen?

Answer 21

Carbon dioxide and water are produced. Carbon and water may be produced when there is not enough oxygen.

Question 22

Which type of combustion releases the most energy?

Answer 22

Complete combustion releases the maximum amount of energy. Thermal decomposition is not the same as combustion.

Question 23

What name is given to a substance that speeds up a reaction without being used up or chemically changed?

Answer 23

A catalyst speeds up a reaction. A reducing agent removes oxygen from something

Question 24

Which of these is the smallest particle?

Answer 24

The smallest particle is an atom.

Question 25

Which of these is the correct symbol for magnesium?

Answer 25

The symbol for magnesium is Mg.

Question 26

Which statement about elements is correct?

Answer 26

Most elements are metals

Question 27

Where are the metals found in the periodic table?

Answer 27

Metals are found on the left of the periodic table.

Question 28

Which of the following is not a general property of metals?

Answer 28

A general property or metals is that they are not poor conductors of electricity.

Question 29

Which of the following is not a general property of non-metals?

Answer 29

A general property of non-metals is that they are not strong.

Question 30

An element sinks in water and makes ringing sound when hit. It is most likely to be

Answer 30

An element that sinks in water and makes a ringing sound when hit is most likely to be a metal.