Chemistry Year 8 2020

Question 1

What is Matter?

Answer 1

Everything around us that has mass and takes up space

Question 2

What happens in a physical change?

Answer 2

In a physical change, a substance changes in size, shape, state, or two substances are mixed together. No new substances are formed. So when a physical change occurs to a compound, the molecules change their position or motion. But the bonds that hold them together are not broken and so the same number and type of molecules remain after the change

Question 3

What happens in a chemical change?

Answer 3

In a chemical change gas, heat or light are often released, and the change usually can not be undone. A new substance is formed. During a chemical change, some of the chemical bonds between atoms are broken and new bonds are formed. This re-arrangement of atoms is what produces a new substance.

Question 4

Which subatomic particle is not found in the nucleus?

Answer 4

Electrons

Question 5

Which subatomic particle has no electrical charge?

Answer 5

Neutrons

Question 6

The mass of the neutron is approximately equal to the mass of the:

Answer 6

Proton

Question 7

Most of an atom’s volume is made up of:

Answer 7

Empty Space.

Question 8

Where is most of the mass of an atom located?

Answer 8

In the nucleus

Question 9

Overall, the nucleus has a ____________ electrical charge.

Answer 9

Positive

Question 10

What is a chemical element?

Answer 10

Elements are substances that are made up of just one type of atom. Each element has a unique set of characteristics that scientists refer to as properties.

Question 11

Calcium is an element. What type of atoms is it made out of?

Answer 11

Calcium atoms

Question 12

Each element has a unique set of ________ that determine how it looks and behaves.

Answer 12

Properties

Question 13

How many elements are there?

Answer 13

117

Question 14

How many elements naturally occur?

Answer 14

92.

Question 15

What is a chemical symbol for an element?

Answer 15

A chemical symbol is one or two letters, usually derived from the element they represent. For example, the chemical symbol for calcium is Ca. t is important to remember that the first letter of a symbol is always upper-case, and the second is always lower-case.

Question 16

How many types of atoms are there in an element?

Answer 16

one. Although the atoms within an element are always arranged in different ways.

Question 17

What is an element with a single atom called?

Answer 17

monatomic.

Question 18

What is a cluster of atoms called?

Answer 18

a molecule

Question 19

What is lattice?

Answer 19

lattices are a type of element, in which the atoms within it are composed in a grid-like structure.

Question 20

What are the physical properties of an element?

Answer 20

Physical properties include whether the element is solid, liquid or gas, its melting and boiling points, how well it conducts heat or electricity and if it can bend or whether it breaks if is applied.

Question 21

Describe any observations that indicate that a chemical change has occurred

Answer 21

change in colour
change in temperature
production of light or sound
the disappearance of a solid
formation of a new solid
formation of new gas – may be indicated by fizzing or a new odour

Question 22

What is the reactant in a chemical change?

Answer 22

A substance that takes part in and undergoes change during a reaction.

Question 23

What is the product in a chemical change?

Answer 23

Products are the substances formed from chemical reactions.

Question 24

How would you write a word equation for the following? When a strip of Magnesium is added to hydrochloric acid, magnesium chloride and hydrogen gas are formed.

Answer 24

Magnesium + hydrochloric acid -> magnesium chloride+ hydrogen gas.

Question 25

Describe the nucleus and electron shells of an atom

Answer 25

A nucleus is the centre of the atom. Protons and neutrons are found in this nucleus. The nucleus is surrounded by electron shells, these shells hold the electrons.

Question 26

Define the term atomic number

Answer 26

An atomic number refers to the number of protons within an atom.

Question 27

Define the term mass number

Answer 27

A mass number refers to the total number of protons, neutrons and electrons within an atom.

Question 28

How do you write the symbol for an atom?

Answer 28

The first one or two letters of the atom are placed on right while the mass number is displayed on the upper right, and the atomic number is displayed on the lower left.

Question 29

What is a chemical compound?

Answer 29

a substance formed from two or more elements chemically united in fixed proportions.

Question 30

Define the terms pure substance and mixture.

Answer 30

A pure substance is a substance that only contains one type of compound or one type of element. Whereas a mixture is a substance that contains two or more elements/compounds that are not chemically bonded.

Question 31

Describe how elements are arranged in the Periodic Table

Answer 31

The periodic table of elements arranges all of the known chemical elements in an informative array. Elements are arranged from left to right and top to bottom in order of increasing atomic number. Order generally coincides with increasing atomic mass. The rows are called periods.

Question 32

Which substances on the periodic table are metals, non-metals, and metalloids?

Answer 32

Metals. In the periodic table, you can see a stair-stepped line starting at Boron (B), atomic number 5, and going all the way down to Polonium (Po), atomic number 84. Except for Germanium (Ge) and Antimony (Sb), all the elements to the left of that line can be classified as metals. If this is hard to understand refer to the image in the science book.