Term 1 Chemistry

Question 1

define aqueous solution

Answer 1

A mixture in which a substance is dissolved in water

If a substance is in an aqueous solution, it is represented using the symbol (aq).

Question 2

define atom

Answer 2

The smallest particle of an element

An atom is made up of even smaller subatomic particles – protons, neutrons and electrons.

Question 3

define balanced

Answer 3

An equation with equal numbers of atoms of each element on either side

A balanced chemical equation follows the law of conservation of matter.

Question 4

define chemical bond

Answer 4

An attractive force that holds atoms together

A chemical bond can hold atoms together in a molecule or lattice.

Question 5

define chemical equation

Answer 5

A representation of how a chemical reaction rearranges atoms

A chemical equation can be represented in words, symbols, or diagrams.

Question 6

define chemical formula

Answer 6

A symbol that shows the chemical composition of a molecule or lattice

The chemical formula for water is H2O as each molecule has two hydrogen atoms and one oxygen atom.

Question 7

define chemical reaction

Answer 7

The re-arrangement of atoms to form one or more new substances

In a chemical reaction the number of each type of atom remains the same.

Question 8

define chemical symbol

Answer 8

One or two letters used to represent an element

The first letter of a chemical symbol is uppercase and the second letter is lowercase.

Question 9

define coefficient

Answer 9

A number placed before a formula in a chemical equation

A coefficient is placed before a formula, whereas a subscript is used within it.

Question 10

define compound

Answer 10

Two or more elements joined together by chemical bonds

e.g. The compound sodium chloride consists of sodium and chloride atoms chemically bonded together.

Question 11

define element

Answer 11

A substance made up of only one type of atom

e.g. Gold is an element in which every atom has 79 protons.

Question 12

Law of Conservation of Matter

Answer 12

The rule that the number of atoms in a chemical reaction remains the same

During all chemical reactions, the total number of atoms of each element doesn’t change.

Question 13

define molecule

Answer 13

A group of atoms bonded together

e.g. An oxygen gas molecule is made up of two oxygen atoms bonded together.

Question 14

define physical change

Answer 14

A change in matter that does not form new substances

Physical changes include breaking, mixing and changing the state of a substance.

Question 15

define product

Answer 15

A substance formed by a chemical reaction

In a chemical equation, the products are located to the right of the arrow.

Question 16

define reactant

Answer 16

A substance that reacts to form one or more new substances

In a chemical equation, the reactants are located to the left of the arrow.

Question 17

define reactive

Answer 17

Tending to take part in chemical reactions

Sodium is one of the most reactive elements in the periodic table.

Question 18

define state symbol

Answer 18

A symbol used to indicate the state of matter of a substance

e.g. The state symbol (s) is used for solids, (l) for liquids, (g) for gases, or (aq) for aqueous solutions.

Question 19

define subscript

Answer 19

A number used to show how many atoms of an element are present

e.g. The subscript 2 in H2O shows there are 2 hydrogen atoms present in water.

Question 20

define symbol equation

Answer 20

A chemical equation that uses chemical formulas to represent substances

e.g. A symbol equation would represent ammonium as the chemical formula NH₃.

Question 21

define unbalanced

Answer 21

An equation with an unequal number of atoms on either side

Unbalanced equations must be balanced so that they follow the law of conservation of matter.

Question 22

define word equation

Answer 22

A chemical equation that uses names to represent substances

A word equation would represent ammonium in an equation as the word ammonium.

Question 23

define atomic number

Answer 23

The number of protons in an atom

Each element has a unique atomic number. A hydrogen atom has 1 proton so its atomic number is 1.

Question 24

define charge

Answer 24

An electrical property of matter

A particle can have a positive charge, a negative charge or no charge (neutral).

Question 25

define electron

Answer 25

A very small subatomic particle with negative charge

Electrons are located outside the nucleus of an atom.

Question 26

define electron cloud model

Answer 26

A model of the atom in which electrons move freely

In the electron cloud model, electrons may be anywhere in the electron cloud at any time.

Question 27

define ion

Answer 27

An atom or molecule with a net charge

A neutral atom that gains an electron becomes a negative ion with a charge of –1.

Question 28

define isotope

Answer 28

A variation of an element with a certain number of neutrons in each atom

e.g. Carbon-14 is an isotope of carbon that has two more neutrons than the carbon-12 isotope.

Question 29

define mass number

Answer 29

The number of protons and neutrons in an atom

Atoms of an element can have more or less neutrons, changing their mass numbers.

Question 30

define net charge

Answer 30

The overall electrical charge of a particle

The net charge of an atom is the number of protons minus the number of electrons.

Question 31

define neutral particle

Answer 31

A particle with zero net charge

Neutrons are neutral. An atom is neutral when it has an equal number of protons and electrons.

Question 32

define neutron

Answer 32

A large subatomic particle with no charge

Neutrons are located in the nucleus of an atom.

Question 33

nucleus

Answer 33

The central part of an atom, with an overall positive charge

Nuclei are made up of positively charged protons and uncharged neutrons.

Question 34

define planetary model

Answer 34

A model of the atom in which electrons move in defined orbits

In the planetary model, electrons circle the nucleus like planets orbiting the Sun.

Question 35

define positive ion

Answer 35

An atom or molecule with a net positive charge

With more protons than electrons, these ions have an overall positive charge.

Question 36

define negative ion

Answer 36

An atom or molecule with a net negative charge

With more electrons than protons, these ions have an overall negative charge.

Question 37

define proton

Answer 37

A large subatomic particle with positive charge

Protons are located in the nucleus of an atom.

Question 38

define radiation

Answer 38

The energy or particles released during radioactive decay

The three main types of radiation are alpha particles, beta particles and gamma waves.

Question 39

define radioactive decay

Answer 39

The process of unstable atoms releasing radiation

Releasing radiation makes the atom’s nucleus more stable.

Question 40

define stable isotope

Answer 40

An isotope in which the nucleus is not likely to break apart

e.g. Carbon-12 is a stable isotope of carbon that has equal numbers of protons and neutrons.

Question 41

define subatomic particle

Answer 41

A particle of matter that is smaller than an atom

Protons, neutrons and electrons are types of subatomic particles.

Question 42

define unstable isotope

Answer 42

An isotope in which the nucleus is likely to break apart

Carbon-14 is an unstable isotope of carbon because it has too many neutrons in the nucleus.

Question 43

Describe the location of subatomic particles in an atom

Answer 43

Protons and neutrons are located in the densely packed nucleus at the centre of the atom. The nucleus is tiny compared to the size of the whole atom, which is mostly empty space.

Electrons are located in the empty space around the nucleus, randomly whizzing around.

Question 44

Compare the subatomic particles by their mass  and electrical charge

Answer 44

Protons
- Mass = 1
- Charge = positive

Neutrons
- Mass = 1
- Charge = neutral

Electrons
- Mass = 1/1840
- Charge = negative

Question 45

Describe how the number of protons determines an element’s atomic number

Answer 45

The number of protons is the same as the atomic number of the element. So as the number of protons increases by 1, so does the atomic number.

Question 46

Explain the relationship between protons and electrons in neutral atoms

Answer 46

In a neutral atom, the charges of protons and electrons are equal in size but opposite (positive or negative), they balance each other out. This means that the atom as a whole has an overall charge of zero.

Question 47

Describe the repulsion and attraction of charged particles

Answer 47

Opposite charges attract
Like charges repel

Question 48

Explain how the number of neutrons affects the mass number of an atom

Answer 48

Each time a neutron is added, the mass number increases by 1.

This is because the mass number is the total number of protons and neutrons in the nucleus.

Question 49

Describe how mass number relates to isotopes

Answer 49

Atoms of the same element with different mass numbers are known as isotopes. Different isotopes of an element are identified by their mass numbers – for example, as carbon-12 or carbon-14. Each isotope may be stable or unstable

Question 50

Compare types of radiation

Question 51

Explain how radioactive decay results in stable atoms

Answer 51

Unstable atoms release radiation in a process called radioactive decay. Releasing radiation makes the atom’s nucleus more stable.

Question 52

Describe what is a chemical reaction

Answer 52

A chemical reaction is the transformation of one or more substances into new substances.