Extra

Question 1

The Law of conservation of matter

Answer 1

• Matter cannot be created or destroyed, it can only be converted from one form to another
• In a chemical equation, there should be equal numbers of atoms on each side of the equation
• Total mass of reactants should equal total mass of products

Question 2

Evidence of chemical reactions

Answer 2

• Light given off
• Gas given off (often seen as bubbles)
• Temperature change
• Colour change
• Precipitate formed

Question 3

Decomposition reaction

Answer 3

• Whenever a single substance breaks down into two or more new substances
• Often occurs when chemical substance is heated or gains energy from another source such as light

Question 4

Combination reaction

Answer 4

Happens whenever two or more substances combine to form a single new substance

Question 5

Precipitation reaction

Answer 5

• Most commonly seen as a reaction between two clear solutions to produce a solid product called a precipitate
• When the two solutions are mixed all the ions from both solutions combine to form new products
• If one or more of these combinations forms an insoluble product, a precipitate will form

Question 6

Allotropes

Answer 6

• Different forms non-metals exist in

- E.g. Oxygen gas or ozone, carbon as diamond or graphite

Question 7

Double replacement/displacement reaction

Answer 7

Metals swap partners

Question 8

Single replacement/displacement reaction

Answer 8

• Metal pushes out other element and takes its partner

- E.g. metal + acid (forms) salt + hydrogen

Question 9

Salt rules

Answer 9

Chloride salts
Sulfate salts 
Nitrate salts
Carbonate salts 
Phosphate salts
Halide salts
- Anything with a metal part and non-metal part are salts