Chemistry

Question 1

What is the equation for combustion?

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Answer 1

hydrocarbon+oxygen->carbon dioxide+water(+energy)

Question 2

What is the symbol for a carbonate?

Answer 2

CO

3

Question 3

What is the symbol for a sulphate?

Answer 3

SO

4

Question 4

What is the symbol for a nitrate?

Answer 4

NO

3

Question 5

What is the symbol for a chloride?

Answer 5

CI

Question 6

What is the symbol for a dioxide?

Answer 6

CO

Question 7

What are the three substances that must be present for combustion to occur?

Answer 7

1. fuel
2. heat
3. oxygen

Question 8

What is thermal decomposition?

Answer 8

Thermal decomposition. A reaction in which a substance is broken down into at least two other substances by heat is called thermal decomposition. If limewater is shaken with a sample of the gas produced, the limewater turns milky. This shows that the gas is carbon dioxide

Question 9

What is an example of a decomposition equation?

Answer 9

CuCO ——>CUO+CO
3 Heat 2

Copper carbonate—->copper oxide+carbon dioxide

In this reaction the color goes from green to black as copper carbonate is being heated strongly so the compound breaks into two and changes colour to black

Question 10

What was the name of the man and the model that atoms were first described?

Answer 10

It is called the dalton model. And some of the key points go as follows:

1. Everything on earth is made up of atoms
2. Atoms cannot be created or destroyed and are the same for a given element
3. Atoms combine in fixed proportions to form compounds

Question 11

What are the three magnetic metals?

Answer 11

1. Iron
2. Nickel
3. Cobalt

Question 12

What is an element?

Answer 12

An element is a substance made up of only one type of atom

Question 13

What are molecules in an element?

Answer 13

In an element with molecules the atoms are joined together, but there’s still only one type which makes them an element. An example of an element without molecules is sulfur and one with molecules could be oxygen ( as said in the symbol O2)

Question 14

What is a compound?

Answer 14

A compound is molecules of different atoms that are chemically joined together

Question 15

What is a mixture?

Answer 15

A mixture is a group of atoms that are mixed together but aren’t chemically joined like in a molecule (so they’re not a compound)

Question 16

What is a chemical reaction?

Answer 16

A chemical reaction involves chemicals (known as reactants) combining together or splitting apart to form one or more new substance (known as the products)

Question 17

What happens when a compound is synthesised (made)?

Answer 17

Elements combine into molecules

Question 18

Are the new compounds produced in a chemical reaction the same reactants just combined together?

Answer 18

No, new compounds that are produced in a chemical reaction are always different from the original elements(reactants)

Question 19

What is a prime example of a new compound?

Answer 19

A prime example of a compound is when sulfur reacts with iron to form iron sulfide. Since iron is magnetic, it reacts with sulfur to make iron sulfide, a brand new substance that isn’t magnetic at all.

Question 20

What is the equation for the sulfur and iron reaction?

Answer 20

Word equation:Iron+sulfur—>Iron sulfide. heat

Symbol equation: Fe+S—->FeS
heat

Question 21

Can compounds be restored back?

Answer 21

Compounds can be split up back to their original elements, but it will take a lot of energy to do it. Also, when elements undergo a chemical reaction the products will always have a chemical formula

Question 22

How do you differ between an ide or an ate in compounds?

Answer 22

You usually see ‘ide’ on the end of a compound if two different elements combine.

Question 23

What happens if two identical elements combine?

Answer 23

It is not a compound, the name doesn’t even change apart from a small number at the side of the symbol signifying the extra atoms present

Question 24

What do you call a line of elements going vertically down on the periodic table?

Answer 24

A group

Question 25

How many groups are there on the periodic table?

Answer 25

7(8 if you include group zero which contains the noble gases).

Question 26

What do you call a group of elements along a horizontal line?

Answer 26

Periods

Question 27

How many periods are there on the periodic table?

Answer 27

Seven

Question 28

How do you work out how reactive the metals are?

Answer 28

The reactive metals (which are in group 1 and 2) get more reactive as you go down the groups. The metals in the middle of the table that don’t have groups are known as transition metals so aren’t at all reactive but they exist so therefore are named.

Question 29

How do you find out the reactivity of non metals?

Answer 29

The non metals in the periodic table (which are groups 3,4,5,6 and 7) get less reactive as you go down the groups ( so the opposite of the reactive metals). The noble gases are not reactive so they are not placed in order of reactivity.

Question 30

What are the properties of metals?

Answer 30

1. Some metals are magnetic 2. Metals conduct electricity 3. Metals conduct heat 4. Metals are strong and tough 5. Metals are shiny when polished 6. Metals are sonorous (make a nice dong sound when hit) 7. Metals are malleable( easily shaped) 8. Metals are ductile( can be drawn into wires) 9. Metals have high melting and boiling points 10. Metals have high densities(how tightly the atoms are packed together) 11. Metals make alloys when mixed with other metals

Question 31

What are the properties of non metals?

Answer 31

1. Non metals can be found in the periodic table ( all of them except for hydrogen can be found on the right of the zigzag) 2. Non Metals are poor conductors of electricity. 3. Non Metals are poor conductors of heat. 4. Non Metals aren’t strong or hard wearing (they break easily because the forces between the particles are weak, so they’re really good insulators also) 5. Non Metals are dull(don’t reflect light) 6. Non Metals are brittle ( hard but liable to break easily) 7. Non metals have low melting and boiling points(because the forces on their particles are weak) 8. Non metals have low densities ( most of their particles are not packed into a certain place and some are inclined to float in the air like helium). 9. Non Metals are not magnetic

Question 32

What’s the equation for metals reacting with dilute acids?

Answer 32

Metal + acid —> salt +hydrogen | all acids contain hydrogen, so the hydrogen in the equation comes from the acid

Question 33

What happens to metals above hydrogen in the reactivity series when they react with acids?

Answer 33

The metals above hydrogen in the reactivity series will react with acids to make a salt and hydrogen

Question 34

What happens to metals below hydrogen in the reactivity serious compared to the ones above?

Answer 34

The metals below hydrogen in the reactivity series won’t react with acids

Question 35

What’s an example of metals reacting with acids?

Answer 35

Zinc+sulfuric acid>zinc sulfate+H Z + H2SO4-> ZnSO4 +H2 The zinc takes the place of the hydrogen as it’s more reactive than hydrogen

Question 36

What is the general equation for when oxides react with acids?

Answer 36

acid + metal oxide—> salt + water Examples: hydrochloric acid+copper oxide>copper chloride + water

Question 37

What happens when metals and non metals react with oxygen?

Answer 37

When metals react with oxygen they create metal oxides(eg: magnesium+oxygen> magnesium oxide) When non metals react with oxygen they make oxides(eg: sulfur +oxygen-> sulfur dioxide)

Question 38

What is the PH of metal oxides and non metal oxides?

Answer 38

Metal oxides are alkaline so they have a ph which is higher than 7, so they react with acids to make salt and water Non metal oxides are acidic, so they have a ph of less than 7, so they will react with alkalis to make salt and water (alkali + non metal oxide-> salt + water) Example: sodium hydroxide + silicon dioxide-> sodium silicate + water

Question 39

What is a displacement reaction?

Answer 39

A displacement reaction is where a more reactive metal or element displaces a less reactive metal or element from its compound in a reaction. For example, if chlorine is added to a solution of potassium bromide, the bromine is replaced by the chlorine forming potassium chloride. Bromine is formed at the same time and can be detected by its colour.

Question 40

Are there any other types of displacement reactions?

Answer 40

A neutralization reaction is when an acid and a base react to form water and a salt and involves the combination of H+ ions and OH- ions to generate water. The neutralization of a strong acid and strong base has a pH equal to 7. An example of this is when hydrogen and sodium hydroxide react (to make sodium chloride). The hydrogen in the hydrochloric acid is displaced by sodium from the sodium hydroxide ( the alkali) which in symbol form is NaCl

Question 41

What happens if you drop a strip of magnesium into a glass of copper sulfate?

Answer 41

The blue copper sulfate solution goes colourless and the copper coats the magnesium strip. Magnesium must be more reactive as magnesium sulfate + copper is formed ( copper is still there coating the magnesium but it was displaced in the solution reaction)