half-term 2- balancing equations, reactions

Question 1

diatomic elements

Answer 1

always come in pairs

Question 2

list the 7 diatomic elements

Answer 2

Hydrogen
Nitrogen
Oxygen
Fluorine 
Chlorine
Bromine
Iodine

Question 3

what do chemical reaction involve?

Answer 3

changes as bonds are made and broken

Question 4

exothermic reaction

Answer 4

releases energy

Question 5

three examples of exothermic reactions

Answer 5

• combustion
• respiration
• neutralisation

Question 6

endothermic reaction

Answer 6

takes place in energy

Question 7

two examples of endothermic reactions

Answer 7

• photosynthesis

- thermal decomposition

Question 8

two changes of state for endothermic reactions

Answer 8

• melting

- boiling

Question 9

two changes of state for exothermic reactions

Answer 9

• freezing

- condensing

Question 10

surroundings

Answer 10

everything else

Question 11

reactants

Answer 11

starting materials in a chemical reaction

Question 12

products

Answer 12

substance that is formed as the result of a chemical reaction

Question 13

complete combustion

Answer 13

Combustion is said to be “complete” when the reaction produces a minimal number of products

Question 14

in an energy profile what is the pattern for an exothermic graph?

Answer 14

up to down

Question 15

in an energy profile what is the pattern for an endothermic graph?

Answer 15

down to up

Question 16

chemical reaction

Answer 16

• not easily reversible

- make new substances and products

Question 17

physical reaction

Answer 17

• reversible reaction

- no new products are made

Question 18

signs of chemical reactions

Answer 18

• change in colour
• change in temperature
• bubbles