Grade 8 Science: Matter in Chemistry

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Questions and Answers

Which of the following best defines an element?

A pure kind of matter that can be broken down into simpler substances

A substance formed by the chemical combination of two or more elements

A pure kind of matter that cannot be broken down into simpler substances by ordinary chemical means (correct)

The smallest particle of a compound that can take part in chemical reactions

What is the composition of water (H2O) according to the text?

Oxygen and Nitrogen in a ratio of 2:1 by weight

Hydrogen and Oxygen in a ratio of 1:8 by weight

Hydrogen and Oxygen in a ratio of 2:1 by weight (correct)

Hydrogen and Nitrogen in a ratio of 1:8 by weight

What is the mass of an electron compared to a hydrogen atom?

Equal to the mass of a hydrogen atom

Twice the mass of a hydrogen atom

1/1837 times the mass of a hydrogen atom (correct)

10 times the mass of a hydrogen atom

How are compounds different from elements?

Elements are made up of similar kinds of atoms, while compounds are formed by the chemical combination of two or more elements Signup and view all the answers

What is the charge of a neutron?

Neutral Signup and view all the answers

What is the mass of an electron in terms of atomic mass unit (amu)?

1/1837 amu Signup and view all the answers

In an electrically neutral atom, what is the relationship between the number of protons and electrons?

Number of protons is equal to electrons Signup and view all the answers

What is the unit of measuring electric charge?

Coulomb Signup and view all the answers

What property do electrons and protons possess in terms of charge?

Electrons carry negative charge, protons carry positive charge Signup and view all the answers

What is the atomic number of an element defined as?

Number of protons only Signup and view all the answers

What is an element defined as in chemistry?

A pure form of matter that cannot be broken down by ordinary chemical means Signup and view all the answers

What are compounds formed by?

The chemical combination of two or more elements in a fixed proportion Signup and view all the answers

What are atoms composed of?

Electrons, protons, and neutrons Signup and view all the answers

What is the mass relationship between an electron and a hydrogen atom?

Mass of an electron is 1/1837 times the mass of a hydrogen atom Signup and view all the answers

What is the charge of an electron?

Negative charge Signup and view all the answers

Which subatomic particle is located in the nucleus of an atom?

Neutron Signup and view all the answers

What is the mass of a neutron compared to a hydrogen atom?

Equal Signup and view all the answers

What is the atomic mass of Boron (B) based on the given information?

11 Signup and view all the answers

How is the electric charge in an atom neutralized?

By balancing the positive charge of protons with the negative charge of electrons Signup and view all the answers

What property allows for the electrically neutral state of an atom?

Balance of protons and electrons Signup and view all the answers

Study Notes

Definition of an Element

An element is a pure substance that cannot be broken down into simpler substances by chemical means.
Elements are defined in chemistry as substances consisting entirely of one type of atom.

Composition of Water (H2O)

Water is composed of two hydrogen (H) atoms and one oxygen (O) atom.

Mass of an Electron

The mass of an electron is significantly smaller compared to a hydrogen atom, specifically approximately 1/1836 of the mass of a hydrogen atom.

Differences Between Compounds and Elements

Compounds are substances formed when two or more different elements chemically bond, while elements are pure substances made of only one kind of atom.

Charge of a Neutron

A neutron carries no electric charge, making it neutral.

Mass of an Electron in Atomic Mass Units (amu)

The mass of an electron is about 0.00055 amu.

Protons and Electrons in a Neutral Atom

In an electrically neutral atom, the number of protons equals the number of electrons, balancing the overall charge.

Unit of Measuring Electric Charge

The coulomb (C) is the standard unit for measuring electric charge.

Charge Properties of Electrons and Protons

Electrons possess a negative charge, while protons have a positive charge, resulting in opposite electrical properties.

Atomic Number Definition

The atomic number of an element is defined as the number of protons in its nucleus, which determines the element's identity.

Composition of Atoms

Atoms are composed of three main subatomic particles: protons, neutrons, and electrons.

Mass Relationship Between Electron and Hydrogen Atom

An electron's mass is negligible when compared to the mass of a hydrogen atom, emphasizing the dominance of protons and neutrons in atomic mass.

Charge of an Electron

An electron carries a negative electric charge.

Subatomic Particles in the Nucleus

Protons and neutrons are located in the nucleus of an atom, while electrons orbit around the nucleus.

Mass of a Neutron Compared to Hydrogen Atom

A neutron has a mass roughly equal to that of a proton, approximately the same as a hydrogen atom.

Atomic Mass of Boron (B)

The atomic mass of Boron is approximately 10.81 amu.

Neutralizing Electric Charge in an Atom

The electric charge in an atom is neutralized by having equal numbers of protons (positive charge) and electrons (negative charge).

Property of Electrically Neutral Atoms

The balance between protons and electrons allows for the neutral state of an atom, leading to its stability.

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Description

Explore the concept of matter in chemistry with this quiz designed for Grade 8 students. Learn about elements, their characteristics, and how they make up the world around us.