Properties of matter
What is the difference between an element and a compound?
An element is a pure substance made of only one type of atom, like oxygen or gold. A compound is a substance made of two or more different elements that are chemically bonded, like water (H₂O) or salt (NaCl).
What does the atomic number of element represent?
The atomic number represents the number of protons in an atom of an element.
What are the three main parts of an atom?
The three main parts of an atom are protons, neutrons, and electrons.
How does reactivity change as you move down group 1 (Alkali metals) on the periodic table?
Reactivity increases as you move down Group 1 (alkali metals) on the periodic table. This is because the outer electron is farther from the nucleus and more easily lost.
What is the main difference between a physical and chemical change?
The main difference is that a physical change doesn't create a new substance, while a chemical change forms a new substance.
How can you separate the components of a mixture?
You can separate the components of a mixture using methods like filtration, distillation, magnetism, or evaporation, depending on the properties of the substances in the mixture.
How is the atomic mass different from the atomic number?
The atomic number is the number of protons in an atom, while the atomic mass is the total number of protons and neutrons in an atom.
How is a negative ion formed?
A negative ion is formed when an atom gains one or more electrons.
What is the trend in reactivity as you move down group 17 (halogens)?
Reactivity decreases as you move down Group 17 (halogens) on the periodic table. This is because the atoms get larger, making it harder to gain an electron.
What happens to the temperature during an exothermic reaction? Why does this happen?
In an exothermic reaction, the temperature increases because the reaction releases heat to the surroundings.
What is an example of a compound and how is it formed?
An example of a compound is water (H₂O). It is formed when two hydrogen atoms chemically bond with one oxygen atom.
How is a positive ion formed?
A positive ion is formed when an atom loses one or more electrons.
What is the difference between a neutral atom and an ion?
A neutral atom has an equal number of protons and electrons, so it has no charge. An ion has either gained or lost electrons, resulting in a positive or negative charge.
Why are noble gases non-reactive?
Noble gases are non-reactive because they have a full set of valence electrons, making them stable and unlikely to bond with other elements.
Which type of reaction absorbs heat from the surroundings? Exothermic or endothermic?
An endothermic reaction absorbs heat from the surroundings.
Can a mixture be separated by chemical means? Why or why not?
No, a mixture cannot be separated by chemical means because its components are not chemically bonded. They are only physically combined, so methods like filtration or distillation are used to separate them.
What do elements in the same group of the periodic table have in common?
Elements in the same group of the periodic table have similar chemical properties and the same number of valence electrons.
How can an ion be identified and what is its charge?
An ion is identified by its charge. A positive ion (cation) forms when an atom loses electrons, and a negative ion (anion) forms when an atom gains electrons.
How does the atomic size change as you move across a period in the period table?
As you move across a period in the periodic table, the atomic size decreases because the number of protons increases, pulling the electrons closer to the nucleus.
What is an example of an endothermic reactions and how does it differ from an exothermic reaction?
An example of an endothermic reaction is photosynthesis, where plants absorb heat (energy) from sunlight. It differs from an exothermic reaction, which releases heat, like burning wood.
What is the main characteristic of an element?
The main characteristic of an element is that it is made up of only one type of atom.
How do ions differ from neutral atoms?
Ions differ from neutral atoms because ions have a charge due to the loss or gain of electrons, while neutral atoms have an equal number of protons and electrons, resulting in no charge.
What determines the atomic number of an element?
The atomic number of an element is determined by the number of protons in its atom.
In which group of the periodic table do elements become more reactive as you move down the group?
Elements become more reactive as you move down Group 1 (alkali metals).
Is melting ice a physical or chemical change? explain your answer.
Melting ice is a physical change because it changes from solid to liquid without forming a new substance.