Chemical reactions

Question 1

State what is a chemical reaction is.

Answer 1

A chemical reaction is a change in which atoms are rearranged to make new substances

Question 2

Can chemical reactions be reversed?

Answer 2

Chemical reactions are not easily reversible.

Question 3

State four pieces of evidence that may suggest a chemical reaction is happening.

Answer 3

Chemical reaction signs:

1. see huge flames or tiny sparks
2. notice sweet smell or foul stink
3. feel the substances getting hotter or colder
4. hear a loud bang or gentle fizzing

Question 4

State 3 examples of useful products made in chemical reactions

Answer 4

Useful products made in chemical reactions:

1. Medicines, such as paracetamol
2. Fabrics, such as polyester
3. building materials, such as cement

Question 5

Name two examples of chemical reactions that are not useful

Answer 5

Chemical reactions that are not useful:

1. Rusting of cars, boats, bridges and bicycles.
2. Food rot

Question 6

Are physical changes reversible?

Answer 6

Yes, physical changes are reversible.

Question 7

Give examples of two types of physical change

Answer 7

Physical changes examples:

1. Melting chocolate
2. Boiling water

Question 8

Describe physical properties of metals

Answer 8

Metals are malleable, shiny

Question 9

Describe physical properties of non-metals

Answer 9

Non-metals are brittle, dull

Question 10

Name additional physical properties

Answer 10

Physical properties:
boiling points
melting points
how well it conducts heat and electricity

Question 11

Many elements, both metals and non-metals take part in reaction with oxygen. What are the new substances called?
Zinc (metal)
Sulfur (non-metal)

Answer 11

The new substances are called Oxides.
Zinc oxide
Sulfur dioxide

Question 12

Describe two differences between a metal oxide and a non-metal oxide

Answer 12

Metal oxide will be a solid at 20 degrees celucius and most are alkalis
Non-metal oxides are gases at 20 degrees celucius and most are acids

Question 13

Write the word equation for zinc and oxygen and sulfur and oxygen

Answer 13

zinc + oxygen = zinc oxide

sulfur + oxygen = sulfur dioxide

Question 14

Name the reactants and the products in zinc + oxygen = zinc oxide

Answer 14

reactants - zinc and oxygen

products - zinc oxide

Question 15

State what an oxidation reaction is

Answer 15

In an oxidation reaction, a substance reacts with oxygen to make one or more oxides

Question 16

Name the products in the reaction of a metal with an acid

Zinc + hydrochloric acid

Answer 16

Zinc + hydrochloric acid = Zinc chloride + hydrogen