Composition, Elements, Compounds and Mixtures Chapter 3 Science Sec 1

30 Question-and-Answer style flashcards based on the lecture notes.

How are elements represented in the Periodic Table?

By chemical symbols, usually one or two letters with the first letter capitalized.

How many known elements are there?

118 elements.

What do groups refer to in the periodic table?

Vertical columns.

What do periods refer to in the periodic table?

Horizontal rows.

Name a metal and one of its typical properties mentioned.

Iron; grey solid, good conductor of heat and electricity, strong, hard, malleable, and magnetic.

What are the two broad categories of elements by properties?

Metals and non-metals.

What is a carbon allotrope mentioned as the hardest substance?

Diamond; a carbon allotrope, extremely hard and transparent.

What is Graphite and its notable properties?

Carbon in graphite form; black solid, smooth, strong, lightweight, and a good conductor of electricity.

What are the properties of iodine mentioned?

Black crystals; brown liquid that turns blue-black with starch; poisonous; used to test for starch.

What is water classified as chemically?

A compound formed from hydrogen and oxygen.

What is a compound?

A substance made up of two or more different elements chemically combined.

What defines a chemical reaction regarding energy?

Heat and sometimes light energy are given out or taken in.

What is an atom?

The smallest particle of an element that has the chemical properties of the element.

What is a molecule?

Two or more atoms chemically combined; can be of the same or different elements.

How is the number of atoms in a compound shown in formulas?

By subscripts, e.g., H2O has two hydrogen atoms.

What does a fixed mass ratio in a compound mean?

Elements combine in a fixed proportion by mass (e.g., NaCl 1:1 by mass).

Can compounds be separated by physical methods?

No; they require chemical methods such as heating or electrolysis, which involve energy.

What is a mixture?

A substance made of two or more substances that are mixed but not chemically combined.

What can mixtures be made of?

Elements, compounds, or both.

Do mixtures have fixed proportions?

No; the proportions of components can vary.

Give an example of a mixture from the notes.

Air (oxygen, nitrogen, carbon dioxide, noble gases) or milk.

What is a solution?

A homogeneous mixture where a solute dissolves in a solvent.

What is a solute?

The substance that dissolves in the solvent.

What is a solvent?

The substance that dissolves the solute.

What is a suspension?

A mixture where insoluble substances are suspended in a liquid or gas; they may settle; light cannot pass fully.

Name three methods to separate mixtures mentioned.

Magnetic separation, Filtration, Evaporation.

How does an element differ from a compound in terms of atoms?

An element is made of one type of atom; a compound contains two or more different elements chemically combined.

How does solubility typically respond to higher temperatures for many solutes?

Solubility usually increases with higher temperature; more solute can dissolve in hotter water.